Transforming non-readily removable chlorides in waste-to-energy ash to chlorellestadite for reducing chloride and heavy metal release, and co 2 curing of treated waste-to-energy ash

Abstract

A process for the treatment of a waste-to-energy (WTE) ash, which includes soluble and insoluble chlorides and one or more heavy metals, from municipal waste incineration is described. The process reduces chloride and heavy metal release by transforming the non- readily removable chlorides in waste-to-energy ash into chlorellestadite, potentially enabling their use within cementitious systems. A carbonated chlorellestadite is also described for use in cementitious materials with enhanced strength and a lower CO2 footprint.

Description

TRANSFORMING NON-READILY REMOVABLE CHLORIDES IN WASTE-TO-ENERGY ASH TO CHLORELLESTADITE FOR REDUCING CHLORIDE AND HEAVY METAL RELEASE, AND CO2CURING OF TREATED WASTE-TO-ENERGY ASHRELATED APPLICATION

[0001] The present patent document claims the benefit of and priority to U.S. ProvisionalPatent Application No. 63 / 614,816, which was filed on December 26, 2023, and is hereby incorporated by reference in its entirety.STATEMENT OF FEDERALLY FUNDED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under DE-AR0001401 awarded by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy. The government has certain rights in the invention.TECHNICAL FIELD

[0003] The present disclosure is related generally to a treatment method for waste-to- energy ash, and more specifically to upcycling of waste-to-energy ash for use in cementitious materials by transforming non-readily removable chlorides to chlorellestadite. The present disclosure is also related to a carbonated chlorellestadite for use with cementitious materials.BACKGROUND

[0004] Sustainably sourced development minerals are vital to meeting the demand for low- carbon construction materials. A potential waste material that can be a low-carbon construction material for cementitious systems is waste-to-energy (WTE) ash, a by-product of waste incineration. However, WTE ash contains chloride-bearing species and heavy metals, which can promote steel reinforcement corrosion and present long-term leaching risks, restricting its use with cementitious materials. It would be advantageous to overcome theselimitations preventing the use of WTE ash with cement-based materials, enabling their use with cementitious systems.

[0005] Further, concrete accounts for a significant portion of total greenhouse gas emissions, and 6-8 percent of these emissions can be directly attributed to cement production. Therefore, there is a strong push towards reducing emissions associated with cement production to decarbonize concrete.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The embodiments may be better understood with reference to the following drawing(s) and description. The components in the figures are not necessarily to scale.Moreover, in the figures, like-referenced numerals designate corresponding parts throughout the different views.

[0007] FIG. 1 is a flow chart showing exemplary steps of the ash treatment process.

[0008] FIG. 2 is a schematic illustration showing exemplary steps of an example treatment of a waste-to-energy (WTE) ash.

[0009] FIG. 3A shows Cl concentration remain in each exemplary ash 1, ash 2, ash 3, and ash 4 after each step 0, 1, 2, 3, and 4 defined in FIG. 2.

[0010] FIG. 3B shows Cl concentration remain in the residual filtrates of ash 2 and ash 3 obtained after each step 1, 3, and 4 defined in FIG. 2.

[0011] FIG. 4A shows Cl release from treated and untreated ash 2 and ash 3.

[0012] FIG. 4B shows Zn release from treated and untreated ash 2 and ash 3.

[0013] FIG. 4C shows the kinetics of cement hydration in the presence of treated and untreated ash 2 (10% replacement).

[0014] FIG. 4D shows the kinetics of cement hydration in the presence of treated and untreated ash 3 (10% replacement).

[0015] FIG. 5A shows Pb concentration in exemplary ash 1, ash 2, ash 3, and ash 4 after each step 0, 1, 2, 3, and 4 defined in FIG. 2.

[0016] FIG. 5B shows Pb mobility in treated and untreated ash 1, ash 2, ash 3, and ash 4.

[0017] FIG. 6A shows the crystalline constituents of ash 1 matrix identified via X-rayDiffraction.

[0018] FIG. 6B shows the proportions of crystalline constituents in the ash 1 matrix obtained from Rietveld refinement of powder diffraction patterns shown in FIG. 6A.

[0019] FIG. 6C shows the concentration of phases that disappear during ash treatment of ash 1.

[0020] FIG. 6D shows the concentration of phases that form during ash treatment of ash 1.

[0021] FIG. 7A shows the crystalline constituents of ash 2 matrix identified via X-rayDiffraction.

[0022] FIG. 7B shows the proportions of crystalline constituents in the ash 2 matrix obtained from Rietveld refinement of powder diffraction patterns shown in FIG. 7A.

[0023] FIG. 7C shows the concentration of phases that disappear during ash treatment of ash 2.

[0024] FIG. 7D shows the concentration of phases that form during ash treatment of ash 2.

[0025] FIG. 8A shows the crystalline constituents of ash 3 matrix identified via X-rayDiffraction.

[0026] FIG. 8B shows the proportions of crystalline constituents in the ash 3 matrix obtained from Rietveld refinement of powder diffraction patterns shown in FIG. 8A.

[0027] FIG. 8C shows the concentration of phases that disappear during ash treatment of ash 3.

[0028] FIG. 8D shows the concentration of phases that form during ash treatment of ash 3.

[0029] FIG. 9A shows the crystalline constituents of ash 4 matrix identified via X-rayDiffraction.

[0030] FIG. 9B shows the proportions of crystalline constituents in the ash 4 matrix obtained from Rietveld refinement of powder diffraction patterns shown in FIG. 9A.

[0031] FIG. 9C shows the concentration of phases that disappear during ash treatment of ash 4.

[0032] FIG. 9D shows the concentration of phases that form during ash treatment of ash 4.

[0033] FIG. 10A shows changes in median equivalent spherical diameter Dv50 in ash 1, ash2, ash 3, and ash 4 with treatment.

[0034] FIG. 10B shows concomitant changes to density in ash 1, ash 2, ash 3, and ash 4 with treatment.

[0035] FIG. 11A shows changes in median equivalent spherical diameter Dv10 in untreated and treated ash 1, ash 2, ash 3, and ash 4 with treatment.

[0036] FIG. 11B shows changes in median equivalent spherical diameter Dv90 in ash 1, ash2, ash 3, and ash 4 with treatment.

[0037] FIG. 12 shows the release of K from treated and untreated ash 2 and ash 3 in a stimulated pore solution at different times. IP denotes the time at the end of the induction period, and PHF indicates the time at which the peak heat flow occurs.

[0038] FIG. 13 shows the release of S from treated and untreated ash 2 and ash 3 in a stimulated pore solution at different times.

[0039] FIG. 14 shows the release of Na from treated and untreated ash 2 and ash 3 in a stimulated pore solution at different times.

[0040] FIG. 15 shows the release of Ca from treated and untreated ash 2 and ash 3 in a stimulated pore solution at different times.

[0041] FIG. 16 shows the release of Br from treated and untreated ash 2 and ash 3 in a stimulated pore solution at different times.

[0042] FIG. 17 shows As mobility in treated and untreated ash 1, ash 2, ash 3, ash 4 determined via TCLP method 1311. As per TCLP method 1311, As mobility in treated and untreated ashes was evaluated with extraction fluid 2 prepared from glacial acetic acid (pH =2.88).

[0043] FIG. 18 shows Ba mobility in treated and untreated ash 1, ash 2, ash 3, ash 4 determined via TCLP method 1311.

[0044] FIG. 19 shows Cr mobility in treated and untreated ash 1, ash 2, ash 3, ash 4 determined via TCLP method 1311.

[0045] FIG. 20 is a schematic illustration showing chlorellestadite in the treated ash being used in cementitious systems via two pathways.

[0046] FIG. 21A shows a comparison of reference chlorellestadite (CE) and synthetic chlorellestadite (CE) powder X-ray diffraction patterns. FIG. 21B shows a comparison of reference chlorellestadite (CE) and synthetic chlorellestadite (CE) Raman spectra.

[0047] FIG. 22A shows a sample thermogravimetric response of a chlorellestadite pellet after 28 days of carbonation. FIG. 22B shows the concentration of H2O and CO2(weight percentage) in the chlorellestadite pellets after 2 hours, 12 hours, 1 day, 7 days, 14 days, and28 days of exposure to CO2(determined through thermogravimetric analysis).

[0048] FIG. 23A is a comparison of powder X-ray diffraction pattern of chlorellestadite after28 days of CO2exposure with reference powder X-ray diffraction files of chlorellestadite, vaterite, calcite, calcium chlorosilicate, and gypsum. FIG. 23B is a comparison of the Raman spectrum of chlorellestadite after 28 days of CO2exposure with reference Raman spectra of chlorellestadite, gypsum, vaterite, calcium chlorosilicate, and calcite.

[0049] FIG. 24 shows the mineralogical composition of chlorellestadite after 28 days of CO2exposure.

[0050] FIG. 25A shows the Raman spectra of synthesized calcium chlorosilicate (syntheticCCS) and reference calcium chlorosilicate (reference CCS). FIG. 25B shows the comparison of the experimental powder diffraction pattern of carbonated calcium chlorosilicate with reference powder diffraction patterns of calcite (CaCO3) and sinjarite (CaCI2·2H2O).

[0051] FIG. 26 is a mass-balance representation of mineralogical transformations occurring during chlorellestadite carbonation via reactions Rl, R2, and R3.

[0052] FIG. 27A shows the hydration heat flow curves of the initial 72 hours of cement replaced with 10% by weight of carbonated chlorellestadite (C_CE 10), chlorellestadite (CE10), and quartz (QZ 10). FIG. 27B shows the cumulative heat of the initial 72 hours of cement replaced with 10% by weight carbonated chlorellestadite (C_CE 10), chlorellestadite (CE 10), and quartz (QZ 10).

[0053] FIG. 28A shows the hydration heat flow of pure calcium chlorosilicate (100% CCS) and type l / ll cement (Ordinary Portland Cement or OPC). FIG. 28B shows the cumulative heat of pure calcium chlorosilicate (100% CCS) and type l / ll cement (ORC).

[0054] FIG. 29 shows the chloride concentration of 50 ml synthetic pore solutions in contact with 0.5 grams of chlorellestadite (CE) and carbonated chlorellestadite (Carb CE) at different times. Induction Period in FIG. 29 corresponds to the time at the end of the induction period, while Peak Heat Flow denotes the time at which the peak heat flow is observed.

[0055] FIG. 30 shows the compressive strength of cement pastes containing 20% chlorellestadite and carbonated chlorellestadite (by weight) under two different curing conditions.

[0056] FIG. 31 is a schematic illustration of microstructural changes and strength development in CO2cured paste specimen prepared from 80% by weight of type l / ll cement(OPC) and 20% by weight of chlorellestadite.DETAILED DESCRIPTION

[0057] A process for the treatment of a waste-to-energy (WTE) ash from municipal waste incineration is described herein for transforming non-readily removable chlorides in WTE ashes into chlorellestadite, potentially enabling their use within cementitious systems. The transformation to chlorellestadite may have various benefits, such as negligible chloride release from the treated ash in an alkaline cementitious environment and a reduced heavymetal mobility (primarily Pb and Cd) in the treated ash below the toxicity limits. The method described in this disclosure may pave the way for utilizing WTE ash with cement-based materials with and without CO2curing while diverting WTE ash from landfills.

[0058] The process for the treatment of a waste-to-energy ash, which includes soluble and insoluble chlorides and one or more heavy metals, is described in reference to FIGS. 1 and 2.Referring to FIG. 1, the ash treatment process includes removing 102 (also illustrated as step1 in FIG. 2) the soluble chlorides from the untreated waste-to-energy (WTE) ash (illustrated as step 0 in FIG. 2) by dissolution, such that a WTE ash residue including the insoluble chlorides and the one or more heavy metals is formed. After removing the soluble chlorides, chlorellestadite is formed 104 (also illustrated as step 2 in FIG. 2), e.g., by a heat treatment as discussed below, from the insoluble chlorides in the waste-to-energy ash residue. In other words, the insoluble chlorides in the waste-to-energy ash residue are transformed to chlorellestadite. In forming 104 the chlorellestadite, the mobility of the one or more heavy metals is reduced and / or maintained below a toxicity limit; in one example, this may be achieved by crystallo-chemically incorporating one or more of the heavy metals into the chlorellestadite as it is formed. The result of the process is a treated waste-to-energy (WTE) ash 106. Details of various implementations of the process are described below, including additional optional steps shown in FIG. 2.

[0059] The untreated waste-to-energy (WTE) ash may include incinerator bottom ash, fly ash, and combinations thereof. Typically, the untreated WTE ash includes a number of phases, including soluble and insoluble chlorides, and minerals such as anhydrite (CaSO4), calcite(CaCO3), enstatite (MgSiO3), quartz (SiO2), lime (CaO), leucite (K8Mg4Si20O48), and / orportlandite (Ca(OH)2). The untreated WTE ash also includes heavy metals such as copper (Cu), zinc (Zn), cadmium (Cd), tin (Sn), lead (Pb), and / or antimony (Sb), and other inorganic analytes such as arsenic (As), chromium (Cr), barium (Ba) and / or selenium (Se).

[0060] The removal 102 of the soluble chlorides from the WTE ash described above may be achieved by immersing the untreated WTE ash in water (illustrated as step 1 in FIG. 2). The soluble chlorides are water soluble and thus dissolve in the water. The immersing is any exposure to water. For example, the immersing may include the act of washing, rinsing, soaking, or submerging the ash in water or an aqueous solution including water. The soluble chlorides in the ash may include, for example, calcium chloride hydroxide (CaClOH), halite(NaCI), and sylvite (KCI). In some examples, halite and sylvite are present in the initial untreated ash at about 7 to 18 weight percent. The immersion may be carried out for a time sufficient for dissolution to occur, e.g., about 0.25 to about 24 hours. In some embodiments, the immersion may be carried out for about 24 hours. The immersion may be carried out at a liquid to solid ratio (l / s) ranging between 1 : 1 and 20 : 1, where l / s is expressed as volume units of liquid per dry mass of solid material (ml / g-dry). In some examples, the immersion may be carried out at a liquid to solid ratio (l / s) of 20 : 1. Many of the minerals mentioned above may also be removed by dissolution in water during the removing step 102.

[0061] After the immersion in water and dissolution of the soluble chlorides, the WTE ash may be filtered from the water to obtain the WTE ash residue. As shown in FIG. 3A, the chloride concentration may decrease from about 25 to 30 weight percent in the initial untreated ash to about 2 to 5 weight percent in the WTE ash residue. The reduction in chloride concentration is a result of the dissolution of soluble chlorides such as halite, sylvite, andcalcium chloride hydroxide in water. In addition to reduction in chloride concentration, another potential benefit to immersing the WTE ash in water prior to forming the chlorellestadite 104 is to limit heavy metal volatilization in the ash. Without implementing the removing 102 step, alkali chlorides that persist in the ash may promote the volatilization of metals, such as Zn and Pb, during thermal treatment. Such volatilization is not desired because the evaporated metal species require condensate collection systems. Condensate collection system requirements for metal volatilization are stringent because the size of metal condensates is finer than typical WTE ash.

[0062] As indicated above, the WTE ash residue includes the insoluble chlorides and the one or more heavy metals that remain after dissolution of the soluble chlorides. The one or more heavy metals remaining in the WTE ash residue may include copper (Cu), zinc (Zn), cadmium (Cd), tin (Sn), lead (Pb), and / or antimony (Sb). The WTE ash residue may also contain other inorganic analytes such as arsenic (As), chromium (Cr), barium (Ba) and / or selenium(Se). Chlorides not readily removed may include calcium chloride hydroxide (CaClOH) and hydrocalumite (3CaO.Al2O3.CaCI2.10H2O). Hydrocalumite has low solubility in water and whereas calcium chloride hydroxide may sometimes have low solubility in water. In some examples, calcium chloride hydroxide may dissolve in water and precipitate as portlandite(Ca(OH)2) shown in the following reaction:2CaOHCI → Ca(OH)2+ Ca+2+ 2Cl- (Reaction 1).

[0063] After filtering from the water, the WTE ash residue may be heat treated (illustrated as step 2 in FIG. 2) to transform 104 the insoluble chlorides to chlorellestadite and form 106 the treated WTE ash. The heat treatment may be carried out in a furnace, such as in an open-air furnace. The heating may take place at a temperature from about 500 °C to about 800 °C, and / or for a time duration of about 0.25 to about 5 hours. In some examples, the heating may be carried out for about 4 hours at a temperature of about 700 °C.

[0064] The heat treatment may affect the WTE ash chemistry in a number of ways. For example, the heat treatment vaporizes the unburnt organic carbon in the WTE ash that could act as ligands and increase heavy metal mobility in the ash. Additionally, vaporizing the organic carbon ensures that the treated WTE ash does not interfere with the air-entrainment of concrete when partially substituting for cement in concrete. Further, as mentioned above, the heat treatment transforms the chloride species remaining after the immersion in water to chlorellestadite. This transformation is beneficial because chlorellestadite is considered hydraulically inactive and thus may be an excellent insoluble repository of chlorine species left after the immersion in water.

[0065] In one example, the insoluble chlorides are transformed into chlorellestadite during the forming step 104 by the following reaction:6CaO + CaCI2+ 3CaSO4+ 3SiO2Ca10(SiO4)3(SO4)3Cl2(Reaction 2).

[0066] Chlorellestadite formation, in the above reaction 2, depends on CaO, CaCI2, CaSO4, and SiO2. CaO (lime) may come from the dehydroxylation of portlandite Ca(OH)2during heat treatment, whereas CaSO4(anhydrite) and SiO2may be present in all the WTE ash after the immersion in water. The source of CaCI2may come from residual chlorides remaining after the immersion in water, which decompose during the heat treatment. An example of this behavior is shown by hydrocalumite, a double-layered hydroxide, which is unstable at high temperatures and first breaks down to form CaO, Ca12Al14O33, and CaCIOH. This is followed bythe further breakdown of CaClOH during the heat treatment to form CaCI2and CaO. These compounds all react according to reaction 2 to form chlorellestadite, having the chemical formula Ca10(SiO4)3(SO4)3CI2. Chlorellestadite may also be referred to as chloroellestadite and having the chemical formula (Ca5(SiO4)1.5(SO4)1.5CI.

[0067] The chlorellestadite concentration present in the treated WTE ash after heat treatment may range between about 10 and 60 weight percent. The variability in chlorellestadite concentration may be attributed to the differences in the chemical composition of the initial untreated WTE ash (See Examples 1-4 below).

[0068] In reaction 2, the limiting reagents that govern chlorellestadite formation can be Si or Cl (See Example 5). In an example where Si is the limiting reagent, not all CaCI2formed during the heat treatment may react to form chlorellestadite. Consequently, the excess CaCI2remaining after the forming step 104 may be removed from the treated ash. In such case, the treated WTE ash containing chlorellestadite may be subjected to a second immersion in water(illustrated as step 3 in FIG. 2). After which, the treated WTE ash may be filtered from the water. This additional immersion step in water may remove by dissolution any residual chlorides, such as CaCI2, from the treated WTE ash after the heat treatment. The immersion may be carried out for about 0.25 to about 24 hours or another time duration sufficient for dissolution to occur. In some embodiments, the immersion may be carried out for about 24 hours. The immersion may be carried out at a liquid to solid ratio (l / s) from 1 : 1 to 20 : 1.

[0069] After the heat treatment and / or after the optional second immersion in water, the treated WTE ash may further be subjected to an immersion in an alkali metal hydroxide solution (illustrated as step 4 in FIG. 2) and then may be filtered from the alkali metalhydroxide solution. This optional immersion step may be added to the process so as to replace chloride ions in the chlorellestadite with hydroxide ions, considering that the treated WTE ash is to substitute cement and be present in an alkaline environment. The alkali metal hydroxide solution may include an alkali metal hydroxide such as potassium hydroxide or sodium hydroxide. In some examples, the alkali metal hydroxide solution may have an alkali metal hydroxide concentration of 0.1 M. The immersion may include the act of washing, rinsing, soaking, or submerging the ash in the alkali metal hydroxide solution. The immersion may be carried out for a time sufficient for dissolution to occur, e.g., about 0.25 to about 24 hours. In some embodiments, the immersion may be carried out for about 24 hours. The immersion may be carried out at a liquid to solid ratio (l / s) from 1 : 1 to 20 : 1.

[0070] The chloride concentration of the treated WTE ash is measured from the WTE ash residue or filtrates collected after different treatment steps, as shown in FIG. 3B. The ash residue collected after the removal of the soluble chlorides 102 (step 1 of FIG. 2) had about7000 mg / l and about 9000 mg / l of chlorides. After step 3 shown in FIG. 2, the chloride concentration in the filtrates were reduced to about 65 and 130 mg / l. The extent to which hydroxide replaces chloride in chlorellestadite may be accessed by measuring chloride concentration in the filtrate or ash residue obtained after step 4; referring to FIG. 3B, the chloride concentration in the filtrates were further reduced to about 15 and 25 mg / l. Based on the data in these examples, the chloride release after step 4 treatment may be reduced fivefold relative to step 3 treatment (FIG. 3B).

[0071] As indicated above, the transformation to chlorellestadite may inhibit chloride release from the WTE ash in an alkaline cementitious environment, enabling the use of WTEash with cementitious systems. The stability of the treated WTE ash in an alkaline cementitious environment was thus tested as discussed below (See Example 6). It was found that the chloride release from an untreated WTE ash is typically from ~1500 to 2000 mg / l, whereas after the ash treatment, a significant reduction in chloride release was observed (FIG.4A). In some examples, the chloride release from a treated WTE ash in an alkaline cementitious system may be reduced over two orders of magnitude, from 1500 mg / l to less than about 10 mg / l. In other embodiments, the chloride release from the treated WTE ash in an alkaline cementitious environment may be less than about 5 mg / l, and may even be reduced below the instrument detection limit of 1.6 mg / l (FIG. 4A).

[0072] As indicated above, an advantage of the method is that the mobility of the one or more heavy metals in the WTE ash may be reduced and / or maintained below a toxicity limit.The mobility of the heavy metals (and other inorganic analytes) in the treated ash were evaluated using Toxicity Characteristic Leaching Procedure (TCLP) method 1311 as discussed below (See Example 7). Generally, the TCLP test determines the mobility of organic and inorganic contaminants in waste materials. The results are usually compared to the TCLP regulatory limits (or toxicity limits) to ensure that all waste is TCLP compliant and able to be processed to a landfill without special consideration for public health and safety.

[0073] In the case of WTE ash, the problematic heavy metals whose mobility typically surpasses regulatory thresholds are Pb and Cd. When untreated WTE ash is used with cementbased materials, the short-term mobility of heavy metals is usually not of concern as these metals are immobilized within cementitious matrices. However, cementitious materials deteriorate with time, and therefore the long-term leaching of heavy metals, mainly Pb, canexceed regulatory thresholds. The deterioration of cement-based materials over the long term is inevitable, implying that the mobility of heavy metals in WTE ash, particularly Pb, must be reduced through treatment to avoid long-term leaching risks. The transformation to chlorellestadite described herein may reduce the heavy metal mobility in the treated ash below the toxicity limits, which are element specific. The mobility of the one or more heavy metals (measured by TCLP method 1311) is maintained below a range from 1.00 to 100.00 mg / l for meeting the regulatory standards. Specifically, the TCLP method 1311 derived mobility of As, Ba, Cd, Cr, Pb, and Se is kept below 5 mg / l, 100 mg / l, 1 mg / l, 5 mg / l, 5 mg / l, and 1 mg / l, respectively.

[0074] As expected, Pb mobility exceeded the regulatory threshold limit for the untreated ash. However, after treatment, a significant reduction in Pb mobility was observed (FIG. 5B).It is believed the reduced Pb (and other heavy metals) mobility may be attributed to the structural adaptability of chlorellestadite, which is a member of the ellestadite family represented by the formula [A(1)]4[A(2)]6(BO4)6X2(A=Ca, B=Si / P / S, and X=F / CI / OH). In chlorellestadite (Ca10(SiO4)3(SO4)3CI2), position A is occupied by Ca, B is equally divided amongst Si and 5, and Cl occupies position X. Position A, i.e., Ca, in chlorellestadite can be replaced by Pb, thereby reducing Pb mobility in treated WTE ash. In one example, the ash treatment reduces the Pb mobility in the treated WTE ash from about 8 mg / l to less than about 0.5 mg / l. In other embodiments, the mobility of Pb in the treated WTE ash may be reduced to less than 0.4 mg / l.

[0075] Described in detail below is a treated WTE ash that can be used for cementitious systems. The treated WTE ash, which may be prepared as described above, includeschlorellestadite; and one or more heavy metals each having a mobility below a toxicity limit.At least one of the one or more heavy metals may be crystallo-chemically incorporated into the chlorellestadite. In one example, the treated WTE ash may also include calcite and / or portlandite in addition to the chlorellestadite. The one or more heavy metals in the treated ash may include copper (Cu), zinc (Zn), cadmium (Cd), tin (Sn), lead (Pb), and / or antimony(Sb). Typically, the treated WTE ash includes Pb and / or Cd. The mobility of Pb in the treated ash may be less than 0.5 mg / l. In other examples, the mobility of Pb may be less than 0.4 mg / l. The mobility of the one or more heavy metals in the treated ash is maintained below a range from 1.00 to 100.0 mg / l, and advantageously each of the heavy metals may be present in the treated ash at a concentration below the respective limit. Specifically, the TCLP method1311 derived mobility of As, Ba, Cd, Cr, Pb, and Se is kept below 5 mg / l, 100 mg / l, 1 mg / l, 5 mg / l, 5 mg / l, and 1 mg / l, respectively. In some embodiments, the chloride release from the treated WTE ash in an alkaline cementitious environment may be less than 10 mg / l. In other embodiments, the chloride release from the treated WTE ash in an alkaline cementitious environment may be less than 5 mg / l, and may be below the detection limit of 1.6 mg / l.

[0076] The cementitious system described herein may include a cementitious material and a supplementary cementitious material. The cementitious material may include any principal ingredients that make up the concrete mixture, such as any of various building materials that may be mixed with water (or other liquids) to form a plastic paste. The supplementary cementitious material may include commonly used secondary cementitious materials such as, fly ash (Type C, Type F), slag cement, silica fume, natural pozzolana and natural calcined pozzolana. In one example, the supplementary cementitious material may include a treatedWTE ash. The treated WTE ash may include chlorellestadite; and one or more heavy metals each having a mobility below a toxicity limit. At least one of the one or more heavy metals may be crystallo-chemically incorporated into the chlorellestadite. The one or more heavy metals in the treated ash may include copper (Cu), zinc (Zn), cadmium (Cd), tin (Sn), lead (Pb), and / or antimony (Sb). Typically, the treated WTE ash contains Pb and / or Cd. The mobility ofPb in the treated ash may be less than 0.5 mg / l. In other examples, the mobility of Pb may be less than 0.4 mg / l. The mobility of the one or more heavy metals in the treated ash may be maintained below a range from 1.00 to 100.0 mg / l, and advantageously each of the heavy metals may be present in the treated ash at a concentration below the respective limit.Specifically, the TCLP method 1311 derived mobility of As, Ba, Cd, Cr, Pb, and Se is kept below5 mg / l, 100 mg / l, 1 mg / l, 5 mg / l, 5 mg / l, and 1 mg / l, respectively. In some embodiments, the chloride release from the treated WTE ash in an alkaline cementitious environment may be less than 10 mg / l. In other embodiments, the chloride release from the treated WTE ash in an alkaline cementitious environment may be less than 5 mg / l, and may be below the detection limit of 1.6 mg / l.

[0077] Chlorellestadite described herein, which is the primary mineral phase formed after thermal treatment of waste-to-energy ashes, may also be present in eco-cements.Chlorellestadite has been found to develop strength in cementitious composites by reacting with CO2. In one example, after the treatment of a waste-to-energy ash from municipal waste incineration, the process described herein may include subjecting the treated waste-to- energy ash to CO2curing to form a carbonated ash. The chlorellestadite in the treated wasteto-energy ash reacts with CO2to form a carbonated chlorellestadite. The carbonatedchlorellestadite may contain the following mineral phases: gypsum, various calcium carbonate polymorphs (such as vaterite, calcite, calcium chlorosilicate, amorphous CaCO3) and / or amorphous SiO2.

[0078] The CO2curing described herein may include exposing the treated waste-to-energy ash to an atmospheric air containing about 3 to 100% of CO2gas. In one example, the treated waste-to-energy ash may be exposed to an atmospheric air containing about 10 to 90% ofCO2gas. In other examples, the treated waste-to-energy ash may be exposed to an atmospheric air containing about 20 to 80% of CO2gas. In other examples, the treated waste- to-energy ash may be exposed to an atmospheric air containing about 30 to 70% of CO2gas.In other examples, the treated waste-to-energy ash may be exposed to an atmospheric air containing about 40 to 60% of CO2gas. In some examples, the treated waste-to-energy ash may be exposed to an atmospheric air containing about 3 to 25% of CO2gas. In some examples, the treated waste-to-energy ash may be exposed to CO2from the flue gas of an industrial facility such as coal-fired power plants or natural gas-fired power plants. The CO2concentration sourced from the flue gas of a coal-fired power plant may be from about 13 to15 volume% and the CO2concentration sourced from the flue gas of a natural gas-fired power plant may be from about 3 to 4 volume%.

[0079] The relative humidity of the CO2curing may be in the range from about 50 to 90%.In one example, the relative humidity of the CO2curing may be in the range from about 60 to80%. In other examples, the relative humidity of the CO2curing may be in the range from about 65 to 75%.

[0080] The temperature of the CO2curing may be from about 25 to 85 °C. In one example, the temperature of the CO2curing may be from about 35 to 75 °C. In other examples, the temperature of the CO2curing may be from about 45 to 65 °C.

[0081] The ability of chlorellestadite to develop strength by reacting with CO2is likely why eco-cements (clinkering at > 1100 °C) prepared from Waste-to-Energy (WTE) ashes may develop strengths over 50 MPa after 28 days of CO2curing. In eco-cements, the primary phases that can react with CO2and develop strength are C2S and chlorellestadite. The inventors studied the extent to which chlorellestadite alone contributes to strength development in these systems. The inventors discovered that chlorellestadite being a promising carbonatable binder, in which chlorellestadite-enriched binders may be used in cementitious systems via two pathways. In the first pathway, chlorellestadite in the treated ash can undergo CO2exposure and be subsequently used to replace cement in a ready-mix concrete. (Figure 20). Through CO2exposure, chlorellestadite will break down to form different polymorphs of calcium carbonate and silica gel shown in Reaction R0:Ca10(SiO4)3(SO4)3CI2(s) + 6CO2(g) + 6H2O6CaCO3(s) + 3(CaSO4·2H2O)(s) + CaCI2(s) + 3SiO2(s) (R0).The polymorphs of calcium carbonate can react with aluminates in cement and form hemicarbonate and monocarbonate, while the silica gel can react with portlandite to form calcium silicate hydrate gel (pozzolanic reaction), contributing to the strength of the cementitious system containing carbonated chlorellestadite. In the second pathway, chlorellestadite can partially replace cement first, and the cement-chlorellestadite system can then be CO2cured directly to develop strength (Figure 20).

[0082] The inventors also found that using carbonated chlorellestadite in cement via pathway 1 may result in a slight reduction of compressive strength likely caused by sulfate imbalance. In pathway 2, CO2curing of cement containing 20% by weight of chlorellestadite develops better strength than the control cement paste specimen. This improvement in strength is likely caused by microstructural refinement from the formation of new mineral phases post-carbonation. These findings demonstrate that chlorellestadite-containing mineral systems derived from the thermal treatment of waste-to-energy ashes may be used in cementitious systems without any performance loss. These findings further elucidate pathways for utilizing a relatively inexpensive source of calcium. As indicated above, the inventors have also discovered chlorellestadite reacts with CO2to form new mineral phases, which may include gypsum, calcium carbonate polymorphs (calcite, vaterite, and amorphousCaCO3), calcium chlorosilicate, and / or amorphous SiO2. These new mineral phases form via three parallel reactions. These parallel reactions include the carbonation of chlorellestadite(reaction Rl), the carbonation of calcium chlorosilicate (Ca3SiO4CI2) (reaction R2), and the carbonation of sinjarite (CaCI2·2H2O) (reaction R3). Based on these three reactions, stoichiometric mass-balance calculations suggest that each gram of chlorellestadite can theoretically sequester 0.297 grams of CO2(29.7% by weight).

[0083] In one example, when the carbonation parameters are set to a relative humidity of65-75%, a temperature at 45 °C, and 20% CO2concentration, it resulted in a H2O uptake of12.3 percent (by weight) and a CO2uptake of 8.1 percent (by weight) in chlorellestadite after28 days of CO2exposure. ~85% of the total CO2is sequestered (6.9 percent by weight) within the first 24 hours. This is significantly higher than the CO2uptake of 4.8 percent (by weight)in chlorellestadite reported by a previous group. In other examples, the CO2uptake in chlorellestadite may be in the range of at least 5 to 30 percent (by weight). In other examples, the CO2uptake in chlorellestadite may be in the range of at least 5 to 20 percent (by weight).In other examples, the CO2uptake in chlorellestadite may be in the range of at least 5 to 10 percent (by weight).

[0084] The cementitious system described herein may include a supplementary cementitious material that includes a carbonated chlorellestadite having mineral phases: gypsum, various calcium carbonate polymorphs (such as vaterite, calcite, calcium chlorosilicate, and amorphous CaCO3) and / or amorphous SiO2.

[0085] In one example, the carbonated ash described herein may be directly mixed with a cementitious material prior to the CO2curing. In another example, the carbonated ash after the CO2curing may partially replace a cementitious material and be mixed with the cementitious material to make a cement paste.

[0086] In one example, a cement paste (or binder) including cement, chlorellestadite, and carbonated chlorellestadite has a compressive strength of at least 50 MPa after 7 days of CO2curing. In another example, a cement paste including cement, chlorellestadite, and carbonated chlorellestadite has a compressive strength of at least 50 MPa after 7 days of CO2curing followed by 21 days of conventional curing under ambient conditions (20 °C and 95%RH). The cement paste may be prepared from about 0 to 90% by weight of cement and about10 to 100% by weight of chlorellestadite. In some examples, the cement paste may be prepared with 100% by weight of chlorellestadite, essentially containing only chlorellestadite with 0% cement. In other examples, the cement paste may be prepared from at least 90% byweight of cement and at most 10% by weight of chlorellestadite. In other examples, the cement paste may be prepared from at least 80% by weight of cement and at most 20% by weight of chlorellestadite. In other examples, the cement paste may be prepared from at least 70% by weight of cement and at most 30% by weight of chlorellestadite. In other examples, the cement paste may be prepared from at least 60% by weight of cement and at most 40% by weight of chlorellestadite. In other examples, the cement paste may be prepared from at least 50% by weight of cement and at most 50% by weight of chlorellestadite. In other examples, the cement paste may be prepared from at least 40% by weight of cement and at most 60% by weight of chlorellestadite. In other examples, the cement paste may be prepared from at least 30% by weight of cement and at most 70% by weight of chlorellestadite. In other examples, the cement paste may be prepared from at least 20% by weight of cement and at most 80% by weight of chlorellestadite. In other examples, the cement paste may be prepared from at least 10% by weight of cement and at most 90% by weight of chlorellestadite.

[0087] The observed increase in strength for chlorellestadite containing cement paste (80% by weight Ordinary Portland Cement (OPC) + 20% by weight chlorellestadite (CE)) sample exposed to CO2is likely caused by microstructural densification during the carbonation curing process (See also, Example 14). The inventors concluded that the exposure to CO2can facilitate strength development in cementitious systems containing chlorellestadite, resulting in the development of chlorellestadite-enriched composites derived from waste by-products such as waste-to-energy ashes. As a result, the cements blended with 20% by weight of chlorellestadite may be subject to simultaneous hydration and carbonation and result in the formation of binders with enhanced strength and a lower CO2footprint.EXAMPLES

[0088] Materials and Methods

[0089] A. Treatment of Waste-to-Energy Ashes

[0090] Samples

[0091] Four unique Waste-to-Energy ashes (A1, A2, A3, and A4) were collected from twoWTE facilities in the United States. The first WTE facility is a mass burn facility (A1, A3, andA4), and the second WTE facility is a modular facility (A2). For all the experiments, the WTE ashes were dried at 105 °C in a gravity convection oven, crushed with a mortar & pestle, and sieved through a 45 μm sieve.

[0092] Analytical Methods

[0093] X-ray Fluorescence

[0094] Elemental concentrations (weight percentage) were measured on a Shimadzu EDX-7000 spectrometer with Rhodium anode as an X-ray source. The X-ray fluorescence spectra were acquired between 0-40 keV in an inert atmosphere (He) on powdered specimens (< 45 μm) in a sample cell covered with an ultralene film with a collimator size of 10 mm. For all these measurements, the live time for all the elements were set at 100 seconds and dead time at 30 percent. The collected spectra were post-processed with PCEDX-Navi - a proprietary software developed by Shimadzu. Quantitative estimates from the processed X- ray fluorescence spectra were calculated from the Fundamental-Parameter algorithm implemented in PCEDX-Navi.

[0095] Powder X-ray Diffraction and Rietveld Refinement

[0096] Powder diffraction patterns of untreated and treated WTE ashes were collected on a Bruker D8 Advance (40 kV and 40 mA) diffractometer in the Bragg-Brentano focusing configuration (θ - 2θ configuration). For this configuration, the goniometer radius is 280 mm, and the diffraction optics included a Goebel mirror (monochromator), incidence divergence slit (0.2 mm slit width), receiving soller slits (2.5°), and a complementary metal-oxide semiconductor (CMOS) detector. The ashes (< 45 μm) were mounted on a polymethyl methacrylate sample holder and irradiated with Cu Kα radiation (λ=1.5418 Å). Diffraction patterns were collected between 10° and 70° 2θ at a step size and step time of 0.01° and 0.15 seconds, respectively.

[0097] The phases in treated and untreated WTE ashes were identified by comparing the collected powder diffraction patterns with the diffraction patterns archived in theInternational Center for Diffraction Data Powder Diffraction File database. After phase identification, the relative proportions of different crystalline constituents in treated and untreated WTE ashes were determined through Rietveld refinement of the collected powder diffraction patterns. The Rietveld refinements were performed on GSAS-II. Parameters refined during Rietveld refinement included the seven Chebyshev background coefficients, sample displacement, and the unit cell parameters. Before the Rietveld refinement, the instrument parameters (U, V, W) for the Bruker D8 Advance were determined on AI2O3. The instrument parameters determined were directly imported and held constant during theRietveld refinement of the powder diffraction patterns of WTE ashes.

[0098] Isothermal Conduction Calorimetry

[0099] The hydration kinetics of cement blended with treated and untreated WTE ashes (10 percent replacement) were monitored on a TAM Air Isothermal Calorimeter (eight-channel).All calorimetry experiments were performed at 22 °C at a water to binder ratio of 0.5.

[0100] Wet Laser Diffraction

[0101] The particle size distributions of untreated and treated WTE ashes were determined by wet laser diffraction on a Malvern Mastersizer 3000 in isopropanol. For particle size measurements with wet laser diffraction (using Mie scattering theory), the knowledge of real and imaginary components of the refractive index is necessary. These indexes for the untreated and treated WTE ashes are detailed below in Table A. The indexes were chosen so that the volume concentration of WTE ash in isopropanol determined by density (through Helium Pycnometry) agreed with the volume concentration determined byBeer-Lambert's law.Table A- Real and imaginary components of refractive indexes used for computing the particle size distribution of untreated and treated WTE ashes

[0102] Dissolution in Synthetic Pore Solution

[0103] Cement hydration is altered in the presence of WTE ash. This is because the dissolution of WTE ash in an alkaline cement-like environment furnishes ions that interferewith cement hydration. The dissolution behavior of untreated and treated WTE ashes was studied in a synthetic pore solution consisting of 0.15 M KOH and 0.05 M NaOH (prepared with ultrapure water, resistivity ~18.2 MQ.cm). Specifically, 0.5 g of WTE ash was put in contact with 50 ml of synthetic pore solution (22 °C, without stirring) and sample aliquots (30 ml) were collected after certain time intervals, e.g., end of the induction period, silicate reaction peak, and 28 days. The collected sample aliquots were filtered through a fresh 0.2 μm polypropylene syringe filter, and later acidified with trace metal grade HNO3(FisherScientific). Finally, ICP-OES and Ion Chromatography were used to monitor the concentration of ions in the acidified solution.

[0104] Toxicity Characteristic Leaching Procedure (TCLP)

[0105] The mobility of inorganic analytes in untreated and treated WTE ashes was tested through the toxicity characteristic leaching procedure method 1311. For these tests, 1 gram of WTE ash was transferred to a centrifuge tube containing 20 grams of extraction fluid, which was a solution of pH 2.88 prepared with glacial acetic acid. The centrifuge tube containing theWTE ash and extraction fluid was allowed to rotate in an end-over-end fashion at 30 rpm for18 hours. At the end of 18 hours, the WTE ash and the extraction fluid were initially separated by filtration. The extraction fluid was further filtered through a fresh 0.2 μm polypropylene syringe filter, acidified with trace metal grade HNO3(Fisher Scientific) and stored at 4 °C before measuring the concentration of inorganic analytes in the acidified extraction fluid byICP-OES.

[0106] Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)

[0107] The concentration of inorganic analytes was measured on an inductively coupled plasma emission spectrometer (Agilent Varian Vista Pro 720 with a radially configured torch).For quality control, one sample after every ten samples was spiked with a known amount of each analyte, and duplicate sample analyses were performed. The measured concentrations satisfied quality control checks if the percentage recovery of each analyte in the spiked samples ranged between 70 to 130%, and the relative percentage difference between duplicate sample analyses was less than 20%. Table B below details the operating conditions of the ICP-OES spectrometer used in the examples.Table B - Instrument operating conditions for the ICP-OES spectrometer (Agilent Varian Vista Pro 720)

[0108] Ion Chromatography

[0109] The chloride and bromide ion concentrations were measured on a Dionex ModelDX500 ion chromatograph equipped with an anion guard column (Dionex AG14), an anion separator column (Dionex AS14), an anion suppressor device (Dionex AERS-500), and a Dionex conductivity detector with cell temperature stabilizer. For quality control during ion chromatography experiments, one sample in every ten samples was spiked with a known amount of each analyte, and duplicate measurements were made. The measured concentrations satisfied quality control checks if the recovery of each analyte in spikedspecimens ranged between 90 and 110%, and the relative percentage difference between duplicate sample analyses was less than 20%. Table C below details the operating parameters for the ion chromatograph used in the examples.Table C - Instrument setup for the ion chromatograph (Dionex Model DX500)

[0110] B. Chlorellestadite Carbonation

[0111] Chlorellestadite and Calcium Chlorosilicate Synthesis

[0112] Chlorellestadite, Ca10(SiO4)3(SO4)3CI2, was synthesized by a solid-state reaction using CaO, CaSO4, CaCI2, and amorphous SiO2(Alfa Aesar). CaO was prepared by heating reagent-grade calcite CaCO3(≤50 μm, 98%, Sigma Aldrich) at 1000 °C for 12 hours. CaSO4was obtained by dehydrating CaSO4.2H2O (≥99%, Sigma Aldrich) at 600 °C for 4 hours. Similarly,CaCI2·2H2O (Aldrich Chemical Company) was heated at 400 °C for 4 hours to form CaCI2. CaO,CaSO4, CaCI2, and SiO2were mixed, ground, and heated in stoichiometric amounts at 900 °C to form chlorellestadite. An excess amount of CaCI2was added to the stoichiometric mix before heating to compensate for the partial evaporation of CaCI2at high temperatures. The product obtained after heating may contain excess CaCI2. Therefore, the remaining CaCI2in the product was removed by washing with distilled water. The concentration of chlorellestadite in the product obtained after water washing was determined through powderX-ray Diffraction.

[0113] The carbonation of chlorellestadite results in the formation of calcium chlorosilicate (CCS), Ca3SiO4Cl2. Therefore, pure CCS was also synthesized to investigate its effect on cement hydration. Stoichiometric amounts of CaO, amorphous SiO2, and CaCI2were mixed homogeneously at a molar ratio 2:1:1 and heated at 800 °C to form CCS. Excess CaCI2was added to the mix before heating to compensate for the partial evaporation of CaCI2. AsCCS reacts with water, the product obtained after heating was washed with isopropanol to remove any remaining CaCI2. The purity of the synthesized CCS was verified by comparing theRaman spectrum of the product with the reported reference Raman spectrum (See, FIG. 25A).

[0114] Chlorellestadite Carbonation and Thermogravimetric Analysis

[0115] To study the carbonation of chlorellestadite, chlorellestadite pellets (8 mm diameter) were made using a pellet press. Each pellet weighed 0.250 g ± 0.025 g and was placed in a CO2incubator (Fisher Scientific) operating at 45 °C, 65-75% relative humidity, and an atmospheric concentration of 20% CO2gas for different durations (2 hours, 12 hours, 1 day, 7 days, 14 days, and 28 days). After carbonation, the pellets were crushed and stored in a vacuum desiccator. The amount of CO2sequestered by chlorellestadite pellets was measured through thermogravimetric analysis on a Q50 thermogravimetric analyzer from TA instruments. For thermogravimetric analysis, ~15-20 mg of carbonated powdered pellets were heated to 900 °C (15 °C / min) in the presence of nitrogen (flow rate of 60 ml / min). The amount of CO2sequestered by chlorellestadite pellets at each duration was measured on duplicate samples, and the thermogravimetric curves for each pellet were obtained.

[0116] Powder X-ray Diffraction (XRD) and Rietveld Refinement

[0117] Powder X-ray diffraction patterns of chlorellestadite specimens were used to identify changes in the mineralogy of chlorellestadite specimens before and after carbonation. After carbonation, amorphous CaCO3and SiO2may form. The concentration of these amorphous minerals in carbonated chlorellestadite was measured using the internal standard method. To measure the concentration of these amorphous minerals, the powdered carbonated chlorellestadite specimens (≤ 45 μm) were homogeneously mixed with 25% corundum (AI2O3as an internal standard) and powder X-ray diffraction patterns of these homogeneously mixed specimens were collected on a Bruker D8 Advance diffractometer operating in the Bragg-Brentano focusing configuration (40 kV and 40 mA) with Cu Kα radiation (λ = 1.5418 Å). The goniometer radius for the employed diffraction setup is 280 mm, and the diffraction optics included a Goebel mirror (monochromator), incidence divergence slit (0.2 mm slit width), receiving soller slits (2.5°), and a complementary metal-oxide semiconductor (CMOS) detector. To collect the powder diffraction patterns, the powdered samples were mounted on a poly (methyl methacrylate) sample holder, and the diffraction patterns between 10 and 70° 26 were collected at a step size and step time of 0.01° and 0.15 s, respectively.

[0118] The crystalline phases in the collected powder diffraction patterns were identified by comparing the collected patterns with the reference patterns cataloged in theInternational Center for Diffraction Data Powder Diffraction File (PDF) database. After phase identification, the concentration of different phases in the uncarbonated and carbonated chlorellestadite specimens was obtained through Rietveld refinement. Rietveld refinement was performed on GSAS-II, and seven Chebyshev background coefficients, sampledisplacement, and the unit cell parameters were refined to obtain quantitative phase concentrations.

[0119] Raman Spectroscopy

[0120] Raman spectra of chlorellestadite, carbonated chlorellestadite, and calcium chlorosilicate were measured using Nanophoton Raman 11 with 532 nm laser excitation wavelength using 10 and 20X objective lenses (numerical aperture - 0.3 for 10X and 0.45 for20X lens, respectively). The measurements were performed on pellets (point scans). For all the samples tested, the laser power applied varied between 0.16 and 5.01 mW, the exposure time varied between 1 and 10 seconds, and the collected spectra were averaged five times to reduce noise. The instrumental configuration used collected the Raman scattered light through the same objective lens and focused onto the input slit with 600 grooves / mm grating.

[0121] Isothermal Calorimetry

[0122] Hydration kinetics of cement (Type l / ll) blended with chlorellestadite, carbonated chlorellestadite, and quartz were monitored on a TAM Air Isothermal Calorimeter (eightchannel) at 22 °C. Additionally, the hydration kinetics of calcium chlorosilicate sample was monitored. All the calorimetry experiments were performed at a water-to-binder ratio of 0.5.The total weight of the binder (cement, chlorellestadite, carbonated chlorellestadite, and calcium chlorosilicate) used for the calorimetry experiments was 5 grams. The weight percentages of binders used in the calorimetry experiments and their abbreviated names are summarized in Table Al.Table Al. Weight percentages of binders in samples used for calorimetry measurements. The chemical formulae for Chlorellestadite (CE) and Calcium Chlorosilicate (CCS) areCa10(SiO4)3(SO4)3CI2and Ca3SiO4CI2, respectively.

[0123] Compressive Strength

[0124] The compressive strength of cubic paste specimens (1 cm3) prepared from 80 percent by weight of cement and 20 percent by weight of chlorellestadite were measured after 7 and 28 days (CE20 and CE20-C). These cubic paste specimens are smaller than the standard 2-inch cubes. The compressive strength measurements were performed on small specimens (1 cm3). Since the tested specimens are small, 8 specimens were tested for each mix to ensure that the reported compressive strength is representative. The cubic paste specimens were exposed to two different curing conditions. The first condition involved curing paste specimens at 45 °C and 70 percent RH under atmospheric CO2concentrations for the first 7 days. For the second curing condition, the paste specimens were kept at 45 °C and70 percent RH in the CO2incubator for the first 7 days. After 7 days, the paste specimens were kept at 20 °C and 95% RH under atmospheric CO2concentrations (for both curing conditions).The compressive strength of two reference paste specimens prepared from 100% cement wasalso measured after curing under two conditions (OPC and OPC-C). Additionally, the compressive strength of the paste specimen prepared from 80% by weight of cement and20% by weight carbonated chlorellestadite was also determined after the first curing condition (C CE20). The mix design and curing conditions for all the samples tested for compressive strength are summarized in Table A2. The compressive strength measurements were performed at a constant displacement rate of 5 mm / minute using a 10 kN load cell.Table A2. Weight percentages of binders in samples used for compressive strength measurements.

[0125] Dissolution in Synthetic Pore Solution and Ion Chromatography

[0126] It was previously observed that the chloride in chlorellestadite is highly stable in an alkaline environment and does not dissolve. However, the stability of chloride in an alkaline solution can increase or decrease after chlorellestadite carbonation. The stability of chloride in uncarbonated chlorellestadite and carbonated chlorellestadite was accessed through a dissolution test. In the dissolution test, 0.5 g of chlorellestadite and carbonated chlorellestadite were put in contact with 50 ml of synthetic pore solution (0.15 M KOH and0.05 M NaOH, pH = 13.23, 22°C). The employed synthetic solution simulated the pore solution of a cementitious system. After specified intervals, sample aliquots (30 ml) were collectedfrom the synthetic pore solution in contact with uncarbonated and carbonated chlorellestadite and filtered through a fresh 0.2 μm polypropylene syringe filter. Then, the filtered solution was acidified with 0.2 ml of trace metal grade HNO3(Fischer Scientific, 67-70% HNO3). The chloride ion concentration in the acidified solution was measured on a Dionex model DX500 ion chromatograph equipped with an anion guard column (Dionex AG14), an anion separator column (Dionex AS14), an anion suppressor device (Dionex AERS-500), and aDionex conductivity detector with a cell temperature stabilizer.

[0127] Laser Diffraction for Particle Size Distribution and Helium Pycnometry for Density

[0128] Three different batches of chlorellestadite were synthesized for all the experiments in this study. These three batches were used for isothermal calorimetry, compressive strength, and dissolution experiments. The particle size distribution of these three different batches of chlorellestadite, carbonated chlorellestadite, calcium chlorosilicate, and quartz was measured by wet laser diffraction on a Malvern Mastersizer 3000 in isopropanol. The real and imaginary components of the refractive index used for determining the particle size distributions were tabulated. These refractive indexes were chosen so that the sample volume concentration in isopropanol determined by density matched the volume concentration determined by Beer-Lambert's law. The density of powdered specimens was measured on an AccuPyc 1330, Micrometries, helium pycnometer.

[0129] Example 1

[0130] The elemental composition (weight %) of WTE Ash 1 before and after treatment steps 1, 2, 3, and 4 (as illustrated in FIG. 2) is shown in Table 1 below.Table 1

[0131] The effects of ash treatment on the mineralogy of ash 1 are shown in FIG. 6A-D.The crystalline constituents of ash 1 matrix were identified via X-ray Diffraction (FIG. 6A). FIG.6B shows the proportions of crystalline constituents in the ash 1 matrix obtained fromRietveld refinement of powder diffraction patterns shown in FIG. 6A. FIG. 6C shows the concentration of phases that disappear during ash treatment. FIG. 6D shows the concentration of phases that form during ash treatment. Chemical formulae for phases that are present in treated and untreated ashes are: hydrocalumite (Ca2Al(OH)6CI2·2H2O, abbreviated as He), anhydrite (CaSO4, abbreviated as An), calcium chloride hydroxide(CaClOH, abbreviated as Cch), halite (NaCI, abbreviated as Ha), calcite (CaCO3, abbreviated asCc), enstatite (MgSiO3, abbreviated as En), sylvite (KCI, abbreviated as Sy), quartz (SiO2,abbreviated as Qz), chlorellestadite (Ca5(SiO4)1.5(SO4)1.5CI, abbreviated as Ce), lime (CaO, abbreviated as Lm).

[0132] Example 2

[0133] The elemental composition (weight %) of WTE Ash 2 before and after treatment steps 1, 2, 3, and 4 (as illustrated in FIG. 2) is shown in Table 2 below.Table 2

[0134] The effects of ash treatment on the mineralogy of ash 2 are shown in FIG. 7A-D.The crystalline constituents of ash 2 matrix were identified via X-ray Diffraction (FIG. 7 A). FIG.7B shows the proportions of crystalline constituents in the ash 2 matrix obtained fromRietveld refinement of powder diffraction patterns shown in FIG. 7A. FIG. 7C shows the concentration of phases that disappear during ash treatment. FIG. 7D shows the concentration of phases that form during ash treatment. Chemical formulae for phases that are present in treated and untreated ashes are: portlandite (Ca(OH)2, abbreviated as Pt), calcium chloride hydroxide (CaClOH or CaOHCI, abbreviated as Cch), anhydrite (CaSO4, abbreviated as An), halite (NaCI, abbreviated as Ha), sylvite (KCI, abbreviated as Sy), lime (CaO,abbreviated as Lm), calcite (CaCO3, abbreviated as Cc), chlorellestadite (Ca5(SiO4)1.5(SO4)1.5CI, abbreviated as Ce).

[0135] Example 3

[0136] The elemental composition (weight %) of WTE Ash 3 before and after treatment steps 1, 2, 3, and 4 (as illustrated in FIG. 2) is shown in Table 3 below.Table 3

[0137] The effects of ash treatment steps on the mineralogy of ash 3 are shown in FIG. 8A-D. The crystalline constituents of ash 3 matrix were identified via X-ray Diffraction (FIG. 8A).FIG. 8B shows the proportions of crystalline constituents in the ash 3 matrix obtained fromRietveld refinement of powder diffraction patterns shown in FIG. 8A. FIG. 8C shows the concentration of phases that disappear during ash treatment. FIG. 8D shows the concentration of phases that form during ash treatment. Chemical formulae for phases thatare present in treated and untreated ashes are: calcium chloride hydroxide (CaClOH, abbreviated as Cch), portlandite (Ca(OH)2, abbreviated as Pt), halite (NaCI, abbreviated as Ha), anhydrite (CaSO4, abbreviated as An), calcite (CaCO3, abbreviated as Cc), leucite(K8Mg4Si20O48, abbreviated as Lc), chlorellestadite (Ca5(SiO4)1.5(SO4)1.5CI, abbreviated as Ce), and lime (CaO, abbreviated as Lm).

[0138] Example 4

[0139] The elemental composition (weight %) of WTE Ash 4 before and after treatment steps 1, 2, 3, and 4 (as illustrated in FIG. 2) is shown in Table 4 below.Table 4

[0140] The effects of ash treatment on the mineralogy of ash 4 are shown in FIG. 9A-D.The crystalline constituents of ash 4 matrix were identified via X-ray Diffraction (FIG. 9A). FIG.9B shows the proportions of crystalline constituents in the ash 4 matrix obtained fromRietveld refinement of powder diffraction patterns shown in FIG. 9A. FIG. 9C shows the concentration of phases that disappear during ash treatment. FIG. 9D shows the concentration of phases that form during ash treatment. Chemical formulae for phases that are present in treated and untreated ashes are: calcium chloride hydroxide (CaClOH, abbreviated as Cch), portlandite (Ca(OH)2, abbreviated as Pt), halite (NaCI, abbreviated as Ha), anhydrite (CaSO4, abbreviated as An), sylvite (KCI, abbreviated as Sy), calcite (CaCO3, abbreviated as Cc), chlorellestadite (Ca5(SiO4)1.5(SO4)1.5CI, abbreviated as Ce), lime (CaO, abbreviated as Lm).

[0141] Amongst the four ashes studied, only ash 1 contained hydrocalumite (a non-readily removable chloride species), and it persisted in ash 1 after step 1. The remaining ashes (ash2, ash 3, and ash 4) contained soluble chloride species, i.e., halite, sylvite, and calcium chloride hydroxide, which disappeared from the ash matrix after step 1. Despite the disappearance of all soluble chloride species, the chloride concentration in ash 2, ash 3, and ash 4 does not reduce to zero after step 1 (See FIG. 3A). It is believed that this may happen for various reasons. First, ash 2, ash 3, and ash 4 may contain additional insoluble chloride species in trace amounts not detected through laboratory X-ray diffraction. Second, some chloride ions may get incorporated into the crystal structure of portlandite that precipitated following the dissolution of calcium chloride hydroxide. Finally, the precipitated portlandite can also absorb some chloride ions. All these interactions possibly limit the extent to which chloride can be removed during the dissolution in water in step 1. As shown in FIG. 3B, the filtrates collected from ash 2 and ash 3 after step 1 had about 7000 mg / l and about 9000 mg / l of chlorides, respectively. Subsequently, for ash 2 and ash 3, chloride concentrations in the filtrate werereduced to 65 and 130 mg / l, respectively after the heat treatment (Step 3). After the step 4 treatment, the chloride concentration in the filtrates of ash 2 and ash 3 were 15 and 25 mg / l, respectively (FIG. 3B). The chloride release during step 4 treatment is reduced fivefold relative to step 3 treatment (FIG. 3B).

[0142] The phase assemblage of treated WTE ash after step 3 heat treatment consisted of chlorellestadite, calcite, portlandite, and anhydrite. Chlorellestadite, calcite, portlandite, and anhydrite concentration in the four WTE ashes after step 3 treatment ranges between 10 to80 percent, 20 to 40 percent, 10 to 70 percent, and 0 to 5 percent, respectively. These variations in phase composition merely reflect the differences in initial ash composition.

[0143] Example 5

[0144] Limiting Reagent Calculations

[0145] Chlorellestadite forms during step 2 treatment according to reaction 2.6CaO + CaCI2+ 3CaSO4+ 3SiO2→ Ca10(SiO4)3(SO4)3CI2(Reaction 2).

[0146] A mole of chlorellestadite contains 10 moles of Ca (400.78 g), 3 moles of Si (84.25 g), 3 moles of S (96.19 g), and 2 moles of Cl (70.90 g). Therefore, the ideal proportion (by weight) of Ca : Cl : S : Si for Ca, Cl, S, and Si to react completely and form chlorellestadite is4.75 : 0.84 : 1.14 : 1. The weight proportion of Ca : Cl : S : Si in ash after step 1 treatment is tabulated in Table D below. These proportions are calculated based on the elemental composition data listed in Tables 1-4. These calculations suggest that Si concentration constrains chlorellestadite formation for ash 1 and ash 2, whereas Cl concentration limits chlorellestadite formation for ash 3 and ash 4.Table D - Ca : Cl : S : Si weight proportion in WTE ash after step 1 treatment. Note that for Ca, Cl, S, and Si to react completely, the ideal ratio of Ca : Cl : S : Si should be 4.75 : 0.84 :1.14 : 1. The calculated weight proportions are based on data listed in Tables 1-4.

[0147] Example 6

[0148] Stability in an alkaline cementitious environment

[0149] Cement hydration is a dissolution and precipitation process. These processes occur in an interstitial solution saturated with respect to calcium hydroxide and is therefore alkaline.This alkaline interstitial solution is usually replicated with a synthetic pore solution prepared from 0.15 M KOH and 0.05 M NaOH. Here, a synthetic pore solution was employed to test the stability of chlorides present as chlorellestadite on two treated WTE ashes (after step 4 treatment) by measuring the chloride concentration of a 50 ml synthetic pore solution in contact with 0.5 g of treated WTE ash. The efficacy of the ash treatment protocol described herein is further accessed by measuring the chloride concentration of a 50 ml synthetic pore solution in contact with 0.5 g of untreated WTE ash (reference sample).

[0150] At the end of step 4 treatment, WTE ashes with two different compositions were obtained. The first composition included ash 1, ash 3, and ash 4 and contained chlorellestadite as the predominant phase (FIG. 6D, 8D, and 9D), whereas the second composition contained ash 2 and had portlandite as the major phase (FIG. 7D). From these two compositions, ash 2 and ash 3 were selected for evaluating the stability of chlorellestadite in treated WTE ash in an alkaline cementitious environment.

[0151] The measured chloride concentration in the synthetic pore solution in contact with ash 2 and ash 3 at different times is depicted in FIG. 4A. Time stamps IP and PHF in FIG. 4A denote the time corresponding to the end of the induction period (IP) and the time at which peak heat flow (PHF) is observed for 90 percent cement and 10 percent ash (treated and untreated) blend. These time stamps were determined from isothermal conduction calorimetry. IP and PHF for the control specimen, i.e., cement specimen, are indicated in FIG.4C-D (blue dashed lines). For the remaining specimens (ash 2 -step 0, ash 2 - step 4, ash 3 - step 0, ash 3 - step 4), these time stamps are tabulated in Table E (see below). Time stampsIP and PHF for ash 2 and ash 3 (before and after treatment) range between 1 - 4.5 hours and6 - 14.5 hours (Table E).Table E - Times corresponding to the end of the induction period (IP), and the silicate reaction peak (PHF) for untreated (Step 0) and treated ashes (Step 4) of ash 2 and ash 3.

[0152] In Table E, the times were determined via isothermal calorimetry at a replacement level of 10 percent.

[0153] The measured chloride concentration in the synthetic pore solution in contact with the untreated WTE ash 2 (step 0) showed no time dependence and was ~1400 mg / l. After treatment, the chloride concentration in the synthetic pore solution in contact with treated ash 2 (step 4) was reduced below the detection limit of 1.6 mg / l (FIG. 4A). A similar reductionin chloride release was observed for ash 3. The untreated ash 3 (step 0) released ~1900 mg / l of chloride in the synthetic pore solution. After treatment, the chloride concentrations in the synthetic pore solution in contact with the treated ash 3 (step 4) remained below the detection limit at IP and 28 days and was ~6 mg / l at PHF (FIG. 4B). The set of treatment steps1-4 also reduced the bromide release from treated WTE ash. For example, before treatment, ash 2 and ash 3 released 50 and 100 mg / l of bromide in the synthetic pore solution. After treatment, the same ash released less than 1 mg / l of bromide ions (FIG. 16). These results confirm that chlorellestadite containing treated WTE ash is stable in an alkaline cementitious environment. Hence, treated WTE ash can be used with cement-based materials without any concerns for halide (chloride and bromide) induced corrosion.

[0154] Beyond halides, the untreated and treated WTE ashes also furnish other ions in the interstitial pore solution, which may interfere with cement hydration. Additional species were detected in the synthetic pore solution in contact with untreated and treated WTE ashes, namely, K, Na, Ca, S, and Zn (FIG. 4B, 12-16). A typical cementitious system is composed of calcium silicates (Ca3SiO5, Ca2SiO4), aluminate (Ca3Al2O6), ferrite (Ca2AIFeO5), and gypsum(CaSO4.2H2O). As a result, the interstitial solution of a typical cementitious system containsCa, Si, Al, Fe, and S. This interstitial solution is modified in the presence of treated and untreated WTE ashes as Na, K, and Zn are introduced to the pore solution, which may affect the hydration characteristics of a cementitious system. It was observed that after treatment, ash 2 and ash 3 release minimal Na and K in the synthetic pore solution (FIG. 12 and 14).However, after treatment, ash 2 and ash 3 release more Zn into the synthetic pore solution(FIG. 4B). The observed increase in Zn release after treatment is likely caused by changes inZn speciation during step 2 thermal treatment. Increased Zn concentration in the interstitial solution is likely to delay cement hydration by promoting the preferential formation of calcium zincate over the calcium silicate hydrate gel. A similar delay in cement hydration was observed with treated WTE ash 2 and ash 3 (FIG. 4C-D). In contrast, both acceleration and retardation in cement hydration of untreated ash were noted. The untreated ash 2 is finer than cement (Dv50 = 3.72 μm) and is concentrated with soluble chlorides (FIG. 10). As a result, it accelerates cement hydration because of the high concentration of chlorides in the interstitial solution and finer particle size (FIG. 4C, 10, 11). Finer particles provide nucleation sites for the precipitation of calcium silicate hydrate, leading to accelerated cement hydration. On the other hand, the chlorides in the interstitial solution promote the formation of flocculated hydrophilic calcium silicate hydrate, facilitating faster diffusion of ions, which also accelerates cement hydration. The ash 2 remains finer than cement after treatment(Dv50 = 6.36 μm) and releases no chloride in the synthetic pore solution (FIG. 4A) but delays cement hydration due to increased Zn release in the synthetic pore solution (FIG. 4B). The untreated ash 3 also releases chloride in the synthetic pore solution; however, it delays cement hydration slightly (FIG. 4D, 10, and 11). It is believed this slight retardation is attributed to the complex intertwined physical and chemical effects when WTE ash is added to a cementitious system. After the treatment, ash 3 is finer than cement (Dv50 = 6.77 μm,FIG. 10-11), releases an insignificant amount of chlorides in the pore solution (FIG. 4B), but delays cement hydration because of increased Zn concentration in the pore solution (FIG. 4B).The slight retardation caused by increased Zn release following ash treatment can be compensated for by commonly used accelerators, such as Ca(NO3)2.

[0155] Example 7

[0156] Mobility of heavy metals / inorganic analytes

[0157] The effect of the ash treatment protocol described herein was evaluated on the mobility of inorganic analytes, namely, As, Ba, Cd, Cr, Pb, and Se, through the ToxicityCharacteristic Leaching Procedure (TCLP). The TCLP test results on untreated WTE ash indicate that the mobility of all the inorganic analytes except Pb is below the toxicity characteristic limit (Table F, FIG. 5, 17, 18, and 19). Pb mobility exceeded the regulatory threshold limit for untreated ash 3 and ash 4. However, after treatment, a significant reduction in Pb mobility was observed for ash 2, ash 3, and ash 4 (FIG. 5B). Note that Pb gets concentrated in WTE ash during different treatment steps (See FIG. 5A with respect to Pb); hence the observed reduction in Pb mobility is not merely caused by the dissolution of Pb bearing phases during different treatment steps. One more inorganic analyte whose mobility shows significant changes after the treatment is Cr. After treatment, Cr mobility increases relative to the untreated ash but remains below the toxicity limit (FIG. 19). This increase is likely caused by the formation of CaCrO4during step 2 thermal treatment. The speciation of other inorganic analytes (As, Ba, Cd, and Se) may also change during the treatment. However, their mobility remains below the toxicity limit after treatment, suggesting that the treated WTE ash is suitable for use with cement-based materials.Table F - Mobility of inorganic analytes in treated and untreated ashes (As, Ba, Cd, Cr, Pb, Se) as perTCLP method 1311

[0158] Example 8

[0159] Synthesis and Characterization of Chlorellestadite

[0160] Carbonation kinetics and the identity of mineral phases formed upon the CO2activation of chlorellestadite will influence the extent to which chlorellestadite can be incorporated within cementitious systems. The carbonation kinetics and the identity of mineral phases were determined by studying the CO2reactivity of pure synthetic chlorellestadite. Synthetic chlorellestadite was synthesized and its purity was tested using powder X-ray diffraction and Raman Spectroscopy. The powder diffraction pattern of the synthesized chlorellestadite is compared with that of the reference chlorellestaditediffraction pattern in Figure 21A. Bragg reflections in the diffraction pattern of synthesized chlorellestadite agree with the reference diffraction pattern and diffraction patterns from past studies. Similarly, the Raman spectrum of synthesized chlorellestadite corresponds well with the reference Raman spectrum reported in other studies (Figure 21B). The Raman spectrum of chlorellestadite has features between 150 - 700 cm-1and 700 - 1200 cm-1. The features below 700 cm-1have low intensity, whereas those above 700 cm-1have high intensity. Specifically, most intense vibrational features occur at 1004 and 854 cm-1(vl symmetric vibrations of SO42-and SiO44-). Overall, all the vibrational features in the Raman spectrum of synthetic chlorellestadite correspond well with the reference Raman spectrum, suggesting that the synthesized chlorellestadite is of high purity.

[0161] Example 9

[0162] Carbonation Kinetics of Chlorellestadite

[0163] The carbonation kinetics of chlorellestadite was monitored by measuring the amount of CO2sequestered in chlorellestadite pellets after 2 hours, 12 hours, 1 day, 7 days,14 days, and 28 days of exposure to CO2inside the incubator (45 °C, 65-75% relative humidity, and an atmospheric concentration 20% of CO2gas). An example thermogravimetric response of the chlorellestadite pellet exposed to CO2for 28 days is shown in Figure 22A. There are two distinct regions in the derivative weight (DW) curve around which the weight loss occurs in the carbonated chlorellestadite specimens. The first region, between 20 and 290 °C, represents the loss of H2O (g), whereas the second region, between 400 and 750 °C, denotes the loss of CO2(g) (Figure 22A).

[0164] A recent study suggested that the minerals formed upon chlorellestadite carbonation include different polymorphs of calcium carbonate, gypsum, calcium chloride, and silica gel. Therefore, the weight loss in the first region likely represents the loss of H2O (g) from hydrated amorphous calcium carbonate and gypsum. The weight loss in the second region can further be divided into three subregions. In the first subregion (400 - 550 °C), theCO2(g) loss occurs from the decomposition of amorphous calcium carbonate. The second subregion (550 - 650 °C) denotes the loss of CO2(g) from poorly crystalline forms of CaCO3(aragonite and vaterite). Finally, the third subregion (650 - 750 °C) represents the loss of CO2(g) from highly crystalline CaCO3. Note that the loss of CO2(g) in the second and third subregions is evident as peaks in the DW curve (Figure 22A). However, the CO2(g) loss in the first subregion does not show a clear peak in the DW curve and occurs over a broad temperature range.

[0165] The total amount of CO2sequestered (weight loss between 400 and 750 °C) and H2O (weight loss between 20 and 290 °C) in chlorellestadite pellets after different durations of CO2exposure is plotted in Figure 22B. After 28 days of CO2exposure, the amount of CO2and H2O in the chlorellestadite pellet is 8.1 and 12.3 percent by weight, respectively. The CO2uptake progresses rapidly during the initial 24 hours, and further uptake in chlorellestadite pellets occurs slowly. In the first 24 hours, ~85 percent of the total CO2is sequestered (6.9 percent by weight). The decline in CO2uptake rate after 24 hours is likely caused by the newly formed mineral phases (chlorellestadite carbonation) that fill the pores and reduce CO2diffusion. A similar reduction in CO2diffusion was observed in the case of CO2-cured cement pastes and mineral carbonation of fly ash. The decline in CO2uptake with time can also bemonitored by measuring the weights of chlorellestadite pellet exposed to CO2. It was found that the change in weight of chlorellestadite pellets is not significant after 24 hours, indicating the reduction in CO2diffusion. The carbonation parameters (relative humidity, temperature, and CO2concentration) adopted in the examples resulted in a CO2uptake of 8.1 percent (by weight) in chlorellestadite. This is significantly higher than the CO2uptake of 4.8 percent (by weight) in chlorellestadite reported by a previous group. By analyzing the thermogravimetric response of carbonated chlorellestadite, the formation of different polymorphs of calcium carbonate was confirmed. However, the reaction between CO2and chlorellestadite can also result in the formation of other mineral phases. The other mineral phases that form after chlorellestadite carbonation are identified in Example 10.

[0166] Example 10

[0167] Newly Formed Mineral Phases after Chlorellestadite Carbonation

[0168] The minerals present in chlorellestadite after 28 days of CO2exposure were identified by powder X-ray diffraction and Raman spectroscopy (Figures 23A and 23B).Characteristic Bragg reflections in the powder diffraction pattern of carbonated chlorellestadite indicated the possible presence of residual chlorellestadite, newly formed gypsum (11.60°, 20.74° 2θ), vaterite (24.87°, 27.01°, 32.71° 2θ), calcium chlorosilicate (30.93°,32.60° 2θ), and calcite (29.42° 2θ) (Figure 23A). The inventors did not observe any Bragg reflections corresponding to calcium chloride in the powder diffraction pattern of carbonated chlorellestadite. The Bragg reflections for chlorellestadite and calcium chlorosilicate overlap, so the presence of calcium chlorosilicate in carbonated chlorellestadite cannot be confirmed by powder X-ray diffraction alone. Therefore, additional Raman spectrum of chlorellestaditewere collected after 28 days of CO2exposure (Figure 23B). Characteristic Raman peaks corresponding to newly formed gypsum (1009 cm-1S-O symmetric stretching vibration), calcite (1086 cm-1v1(CO3)2-stretching), vaterite (triplet v1(CO3)2-stretching between 1074 and 1091 cm-1) are present in the Raman spectrum of carbonated chlorellestadite. The prominent characteristic Raman peaks for calcium chlorosilicate overlap with the v1symmetric vibration of SiO44-in chlorellestadite (Figure 23B). Therefore, the presence of calcium chlorosilicate in carbonated chlorellestadite also cannot be confirmed throughRaman spectroscopy.

[0169] Some studies have reported the coexistence of chlorellestadite and calcium chlorosilicate in the natural environment. Hence, it is likely that calcium chlorosilicate is present in the carbonated chlorellestadite specimen. The concentration of residual chlorellestadite and newly formed mineral phases (including calcium chlorosilicate) in carbonated chlorellestadite was determined through the Rietveld refinement of the powder diffraction pattern of carbonated chlorellestadite containing AI2O3as an internal standard(Figure 24). From Rietveld refinement, it was found that the concentrations (weight percentages) of different minerals in carbonated chlorellestadite (28-day CO2exposure) are: uncarbonated chlorellestadite (40.4%), amorphous phases (24%), gypsum (19.9%), vaterite(11.8%), calcium chlorosilicate (2.1%), and calcite (1.7%). Amorphous phases are present in significant amounts in the carbonated chlorellestadite specimen. These amorphous phases include amorphous CaCO3, silica gel, and calcium silicate hydrate gel (arising from the hydration of calcium chlorosilicate).

[0170] The presence of amorphous phases (CaCO3and silica gel), gypsum, vaterite, calcium chlorosilicate, and calcite in the carbonated chlorellestadite specimen suggests that chlorellestadite carbonates via reaction R1 (shown below). Assuming reaction R1 is the only reaction involved in chlorellestadite carbonation, the concentration of calcium chlorosilicate in the carbonated chlorellestadite specimen should be ~12.79% by weight. However, the observed concentration of calcium chlorosilicate is only 2.1% by weight (Figure 24), suggesting that the calcium chlorosilicate formed after chlorellestadite carbonation participates in other chemical reactions. In terms of crystal structure, calcium chlorosilicate resembles alite, where free oxide ions have been replaced by Cl-. The replacement of free oxide by Cl- is incomplete in alinite - a chloride-containing calcium silicate mineral found in clinkers prepared from chlorine-bearing waste materials. As alinite is present in clinkers synthesized from chlorine-rich raw materials, its hydration behavior has been investigated in previous studies. However, there is limited knowledge about the performance of calcium chlorosilicate as a cementitious material. A potential chemical reaction is the further carbonation of calcium chlorosilicate via reaction R2 (shown below). The carbonation reactivity of calcium chlorosilicate has not been tested before. Therefore, pure calcium chlorosilicate (CCS) was synthesized and its carbonation reactivity investigated after 7 days ofCO2exposure (45 °C, 65-75% relative humidity, and 20% CO2concentration) (FIG. 25A). After7 days of CO2exposure, calcium chlorosilicate reacted completely and formed calcite and sinjarite (CaCI2·2H2O, Figure 25B). This observation confirms that calcium chlorosilicate formed via reaction R1 reacts with CO2further and forms sinjarite, matching with known study where CaCI2was found to form upon chlorellestadite carbonation. However, theexistence of sinjarite was not observed here in carbonated chlorellestadite (Figures 23A and23B), likely because the CaCI2.2H2O formed via R2 reacted with CO2and formed CaCO3as per reaction R3 (shown below).Ca10(SiO4)3(SO4)3CI2(s) + 4CO2(g) + 6H2O4CaCO3(s) + 3(CaSO4·2H2O)(s) + Ca3(SiO4)CI2(s) + 2SiO2(s) (R1)Ca3(SiO4)CI2(s) + 2H2O + 2CO2(g) → 2CaCO3(s) + CaCI2·2H2O(s) + SiO2(s) (R2)CaCI2·2H2O(s) + CO2(g) → CaCO3(s) + 2 HCI (aq) + H2O (R3)

[0171] After 28 days of CO2exposure, 40.4 percent of unreacted (by weight) chlorellestadite remained in the carbonated chlorellestadite specimen. Simple mass-balance calculations based on reaction Rl stoichiometry suggest that 53.07 percent by weight of chlorellestadite reacted after 28 days of CO2exposure. Calcium chlorosilicate formed after chlorellestadite carbonation also reacts with CO2via reaction R2 and forms sinjarite. Finally, sinjarite reacts with CO2and forms CaCO3via reaction R3. Assuming that 85 percent of calcium chlorosilicate formed in reaction Rl and the entire sinjarite formed in reaction R2 reacted with CO2, simple mass-balance calculations suggest that the concentration of different minerals in carbonated chlorellestadite are: chlorellestadite (39.2%), gypsum(22.6%), and calcium chlorosilicate (1.8%). These concentrations strongly agree with the weight fractions determined through Rietveld refinement, suggesting that reactions Rl, R2, and R3 explain chlorellestadite carbonation adequately. Stochiometric calculations based on reactions R1, R2, and R3 indicate that each gram of chlorellestadite can react with at most0.297 grams of CO2(theoretical CO2uptake) to form gypsum (36.97 wt. %), CaCO3(50.13 wt.%), and amorphous SiO2(12.90 wt. %) (Figure 26). Due to the formation of new mineral phasespost-carbonation, the hydration kinetics of cementitious systems containing carbonated chlorellestadite will likely differ from that of cement. The hydration kinetics of cementitious systems containing chlorellestadite and carbonated chlorellestadite are discussed in Example11.

[0172] Example 11

[0173] Hydration Kinetics of Chlorellestadite, Carbonated Chlorellestadite and CalciumChlorosilicate

[0174] The hydration kinetics of cement replaced with 10 percent by weight of chlorellestadite and carbonated chlorellestadite were measured through isothermal calorimetry and are shown in Figure 27. For reference, the hydration kinetics of cement replaced with 10 percent quartz were also measured. The hydration heat flow and cumulative heat response of cement containing chlorellestadite is similar to cement blended with quartz(Figures 27A and 27B), suggesting that chlorellestadite essentially acts as an inert filler in cementitious matrices. In contrast with chlorellestadite, the presence of carbonated chlorellestadite in cement accelerated cement hydration. The particle size distribution of carbonated chlorellestadite (C_CE-lso) and quartz (QZ-lso) used for calorimetry measurements were similar. Hence, the observed acceleration in hydration kinetics by carbonated chlorellestadite is caused by the new minerals formed after the carbonation of chlorellestadite. The minerals formed after chlorellestadite carbonation include gypsum. vaterite, calcite, amorphous phases (CaCO3and SiO2) and calcium chlorosilicate (Figures 23 and 24). These minerals can accelerate cement hydration through different mechanisms. For example, gypsum is reported to enhance C3S hydration by changing the morphology of theprecipitated calcium silicate hydrate gel to a divergent needle structure. The presence of gypsum in carbonated chlorellestadite also increases the amount of available sulfate, affecting the sulfate balance of the system. As a result, the aluminate peak is not distinct from the main silicate peak in the heat flow response of cement-containing carbonated chlorellestadite (C_CE 10, Figure 27A). The availability of additional sulfates from carbonated chlorellestadite ensures that gypsum is not depleted through adsorption on calcium silicate hydrate gel and ettringite precipitation, preventing the onset of aluminate peak. In addition to gypsum, the polymorphs of CaCO3and amorphous SiO2in carbonated chlorellestadite can also accelerate cement hydration by providing additional active nucleation sites for the precipitation of calcium silicate hydrate gels. Finally, the calcium chlorosilicate in carbonated chlorellestadite is hydraulic and reacts with water to form calcium silicate hydrate gel and portlandite. The hydration heat flow and cumulative heat of calcium chlorosilicate (CCS) is shown and compared to an ASTM Type l / ll cement (ORC) in Figures 28A and 28B. From the heat flow and cumulative heat curves, it was observed that calcium chlorosilicate reacts rapidly with water. The peak heat flows for calcium chlorosilicate and cement are 54.9 and3.9 mW / g, respectively. Despite having a limited concentration of 2.1 percent in carbonated chlorellestadite, calcium chlorosilicate can accelerate cement hydration significantly due to its fast hydration kinetics. The chlorides present in calcium chlorosilicate can become available in the pore solution after hydration, limiting the application of cement-containing carbonated chlorellestadite to systems without any reinforcements. Therefore, we measure the increase in chloride availability through a dissolution test in Example 12.

[0175] Example 12

[0176] Influence of Chlorellestadite Carbonation on Chloride Availability

[0177] It has been shown that chlorellestadite is stable under alkaline conditions and releases minimal chloride ions in the alkaline pore solution. The speciation of chloride ions changes after carbonation (from chlorellestadite to calcium chlorosilicate). This change in speciation will also increase the availability of chloride ions under alkaline conditions, as calcium chlorosilicate possesses hydraulic characteristics (Figures 28A and 28B). The availability of chloride ions in the synthetic pore solution before and after carbonation was tested through a dissolution test. In the dissolution test, the chloride concentrations of a synthetic pore solution (50 ml) in contact with 0.5 grams of chlorellestadite and carbonated chlorellestadite were measured at three specific times. These times corresponded to the end of the Induction Period (IP), the time at which Peak Heat Flow is observed (PHF), and at 28 days. IP and PHF were derived from the hydration heat flow curves of cement containing 10 percent by weight of chlorellestadite and carbonated chlorellestadite (Figure 27A). The chloride concentrations of synthetic pore solution in contact with chlorellestadite (CE) at IP and PHF were 38.2 mg / l and 46.3 mg / l (Figure 29). By the end of 28 days, the chloride concentration of the synthetic pore solution in contact with chlorellestadite increased to122.5 mg / l. For carbonated chlorellestadite (Carb CE), the chloride concentrations of the synthetic pore solution at IP and PHF were 218.6 and 219.6 mg / l, respectively. This observed5-fold increase in chloride concentrations for carbonated chlorellestadite is likely caused by the release of chloride ions during the hydration of calcium chlorosilicate and the free chlorides available after the carbonation of CaCI2·2H2O (reaction R3). These results suggest that the use of carbonated chlorellestadite will be limited to systems without reinforcements.Additionally, using chlorellestadite as a carbonatable binder alone (without any cement) can have increased Cl- leaching risks. The Cl- leaching risks can be mitigated by blending cement and chlorellestadite as Al+3released by cement can react with chloride ions in the alkaline pore solution to form hydrocalumite (Ca2AI(OH)6.5Cl0.5.3H2O). The compressive strength of cementitious systems containing chlorellestadite and carbonated chlorellestadite is discussed in Example 13.

[0178] Example 13

[0179] Compressive Strength of Cement Pastes Containing Chlorellestadite andCarbonated Chlorellestadite

[0180] Chlorellestadite (with or without carbonation) can be used in cementitious systems through two unique pathways (Figure 20). In the first pathway, chlorellestadite can act as a filler and replace a part of cement. Similarly, carbonated chlorellestadite can also replace a part of cement. Carbonated chlorellestadite consists of different CaCO3polymorphs, amorphous SiO2, gypsum, and calcium chlorosilicate. So, the effect of carbonated chlorellestadite on the properties of the cementitious system is not limited to that of a filler since amorphous SiO2and calcium chlorosilicate possess pozzolanic and hydraulic properties, respectively. The compressive strength of cement pastes prepared from 80% type l / lI cement(by weight) and 20% chlorellestadite (CE20) and carbonated chlorellestadite (C_CE20) (by weight) after curing at 45°C, 70% RH, and atmospheric CO2conditions are shown in Figure 30.At 7 days, the compressive strength of cement paste containing 20% chlorellestadite was similar (24.9 MPa for CE20) to the control cement paste sample (24.8 MPa for OPC). In contrast, the 7-day compressive strength of cement paste containing carbonatedchlorellestadite (20.7 MPa for C_CE20) was slightly lower than that of the control sample (24.8MPa for OPC). Carbonated chlorellestadite released chloride ions in the pore solution and accelerated cement hydration. The accelerated cement hydration caused by the chlorides should result in higher 7-day strength for the C_CE20 sample. In addition to chlorides, carbonated chlorellestadite also contained gypsum (Figures 23A and 23B). Excess gypsum from carbonated chlorellestadite can lower the intrinsic strength of calcium silicate hydrate gel. Overall, the effect of gypsum is greater than that of chlorides in cement pastes containing carbonated chlorellestadite, reducing the 7-day compressive strength for C_CE20 samples.This observation suggests that it is necessary to optimize the sulfate content of the cementitious system when replacing cement with carbonated chlorellestadite. At 28 days, the compressive strength of cement pastes containing chlorellestadite (29.8 MPa for CE20) and carbonated chlorellestadite (29.6 MPa for C_CE20) was slightly lower than that of the control sample (31.8 MPa for OPC). This slight reduction in strength can be attributed to the reduced cement content in CE20 and C_CE20 samples.

[0181] The second pathway to use chlorellestadite in cementitious systems is through CO2curing. Specifically, cement paste specimens prepared from cement and chlorellestadite can be exposed to CO2to develop strength. For these specimens, the development in strength can be attributed to traditional cement hydration and strengthening facilitated by carbonation of chlorellestadite and cement hydration products. The 7-day compressive strength of the cement paste specimen prepared from 80% cement (by weight) and 20% chlorellestadite (CE20-C) (by weight) after 7 days of CO2curing (45 °C, 70% RH, and 20% CO2) is shown in Figure 30. After CO2curing, the CE20-C sample developed a 7-day strength of 52MPa. The 7-day strength for CE20-C is slightly higher than that of the control OPC-C sample(46 MPa). This observation suggests that the minerals formed after chlorellestadite carbonation (gypsum, CaCO3polymorphs, amorphous SiO2, and calcium chlorosilicate) enhance the microstructure, enabling superior strength development. Furthermore, the 28- day strength of the CE20-C sample (CO2exposure limited to an initial 7 days) is also slightly higher (58.1 MPa) than that of the control OPC-C sample (55.5 MPa). A detailed explanation for the observed increase in strength for CO2cured chlorellestadite containing cement paste sample (CE20-C) is provided in Example 14.

[0182] Example 14

[0183] Role of Chlorellestadite during Simultaneous Hydration & Carbonation

[0184] The observed increase in strength for chlorellestadite containing cement paste(80% OPC + 20% CE) sample exposed to CO2is likely caused by microstructural densification during the carbonation curing process. Microstructural densification for chlorellestadite containing cement paste sample is shown schematically in Figure 31 and compared with that of cement paste specimen (with and without CO2curing). For the OPC paste sample not subjected to CO2curing, the observed strength development is attributed solely to the formation of hydration products. In contrast, the strength development in OPC paste samples exposed to CO2occurs through hydration and carbonation. The microstructural densification through the formation of hydration and carbonation products (CaCO3polymorphs) is superior to the densification achieved by hydration alone. As a result, the strength of the OPC paste sample subjected to CO2curing is higher than the OPC paste sample not subjected to CO2. Like the CO2-cured OPC paste sample, microstructural densification for the chlorellestadite-containing cement paste sample (80% OPC + 20% CE) occurs via hydration and carbonation.The minerals formed upon carbonation of chlorellestadite-containing cement paste sample include CaCO3polymorphs, SiO2, sinjarite, gypsum, and calcium chlorosilicate (Figure 31). Due to the formation of these new minerals, the microstructural densification is better than theOPC paste sample subjected to CO2curing, resulting in higher strength development. These findings suggest that exposure to CO2can facilitate strength development in cementitious systems containing chlorellestadite, resulting in the development of chlorellestadite-enriched composites derived from waste by-products such as waste-to-energy ashes.

[0185] While various embodiments have been described, it will be apparent to those with ordinary skill in the art that many more embodiments and implementations are possible.Accordingly, the embodiments described herein are examples, not the only possible embodiments and implementations.

[0186] The subject-matter of the disclosure may also relate to the following aspects:

[0187] A first aspect relates to a process for the treatment of a waste-to-energy ash from municipal waste incineration, the waste-to-energy ash includes soluble and insoluble chlorides, and one or more heavy metals. The process comprises removing the soluble chlorides from the waste-to-energy ash by dissolution, thereby obtaining a waste-to-energy ash residue including the insoluble chlorides and the one or more heavy metals; and forming chlorellestadite from the insoluble chlorides in the waste-to-energy ash residue, whereby a mobility of the one or more heavy metals is reduced and / or maintained below a toxicity limit, thereby forming a treated waste-to-energy ash.

[0188] A second aspect relates to the process of the first aspect, wherein chloride release from the treated waste-to-energy ash in an alkaline cementitious environment is reduced compared to the untreated waste-to-energy ash.

[0189] A third aspect relates to the process of the first or second aspect, wherein at least one of the one or more heavy metals is crystallo-chemically incorporated into the chlorellestadite.

[0190] A fourth aspect relates to the process of any preceding aspect, wherein removing the soluble chlorides from the waste-to-energy ash by dissolution comprises immersing the waste-to-energy ash in water, whereby the soluble chlorides are dissolved in the water; and filtering the waste-to-energy ash from the water to obtain the waste-to-energy ash residue.

[0191] A fifth aspect relates to the process of any preceding aspect, wherein the immersing is carried out for about 0.25 to about 24 hours.

[0192] A sixth aspect relates to the process of any preceding aspect, wherein the immersing is carried out at a liquid to solid ratio (l / s) from 1 : 1 to 20 : 1.

[0193] A seventh aspect relates to the process of any preceding aspect, wherein the immersing comprises the act of washing, rinsing, soaking or submerging in water.

[0194] An eighth aspect relates to the process of any preceding aspect, wherein forming chlorellestadite from the insoluble chlorides comprises heating the waste-to-energy ash residue at a temperature from about 500 °C to about 800 °C, whereby the insoluble chlorides are transformed into the chlorellestadite.

[0195] A ninth aspect relates to the process of any preceding aspect, wherein the heating takes place in an open-air furnace.

[0196] A tenth aspect relates to the process of any preceding aspect, wherein the heating is carried out from about 0.25 to about 5 hours.

[0197] An eleventh aspect relates to the process of any preceding aspect, further comprising removing soluble chlorides from the treated waste-to-energy ash.

[0198] A twelfth aspect relates to the process of any preceding aspect, wherein removing the soluble chlorides comprises immersing the treated waste-to-energy ash containing the chlorellestadite in water; and filtering the treated waste-to-energy ash from the water.

[0199] A thirteenth aspect relates to the process of any preceding aspect, wherein the immersing is carried out for about 0.25 to about 24 hours.

[0200] A fourteenth aspect relates to the process of any preceding aspect, wherein the immersing is carried out at a liquid to solid ratio (l / s) from 1 : 1 to 20 : 1.

[0201] A fifteenth aspect relates to the process of any preceding aspect, wherein the immersing comprises the act of washing, rinsing, soaking or submerging in water.

[0202] A sixteenth aspect relates to the process of any preceding aspect, further comprising replacing chloride ions in the chlorellestadite with hydroxide ions in the treated waste-to-energy ash.

[0203] A seventeenth aspect relates to the process of any preceding aspect, wherein replacing chloride ions with hydroxide ions comprises immersing the treated waste-to-energy ash containing the chlorellestadite in an alkali metal hydroxide solution, whereby chloride ions are exchanged with hydroxide ions; and after the immersing, filtering the treated waste- to-energy ash from the alkali metal hydroxide solution.

[0204] An eighteenth aspect relates to the process of any preceding aspect, wherein the alkali metal hydroxide solution includes an alkali metal hydroxide selected from the group consisting of potassium hydroxide and sodium hydroxide.

[0205] A nineteenth aspect relates to the process of any preceding aspect, wherein the immersing is carried out for about 0.25 to about 24 hours.

[0206] A twentieth aspect relates to the process of any preceding aspect, wherein the immersing is carried out at a liquid to solid ratio (l / s) from 1 : 1 to 20 : 1.

[0207] A twenty-first aspect relates to the process of any preceding aspect, wherein the immersing comprises the act of washing, rinsing, soaking or submerging in the alkali metal hydroxide solution.

[0208] A twenty-second aspect relates to the process of any preceding aspect, wherein the waste-to-energy ash comprises incinerator bottom ash and / or fly ash.

[0209] A twenty-third aspect relates to the process of any preceding aspect, wherein the treated waste-to-energy ash comprises calcite and / or portlandite.

[0210] A twenty-fourth aspect relates to the process of any preceding aspect, wherein the one or more heavy metals comprise copper (Cu), zinc (Zn), cadmium (Cd), tin (Sn), lead (Pb), and / or antimony (Sb).

[0211] A twenty-fifth aspect relates to the process of any preceding aspect, wherein the one or more heavy metals comprise Pb and / or Cd.

[0212] A twenty-sixth aspect relates to the process of any preceding aspect, wherein the mobility of Pb in the treated waste-to-energy ash is less than 0.5 mg / l.

[0213] A twenty-seventh aspect relates to the process of any preceding aspect, wherein the mobility of Pb in the treated waste-to-energy ash is less than 0.4 mg / l.

[0214] A twenty-eighth aspect relates to the process of any preceding aspect, wherein the mobility of the one or more heavy metals is maintained below a range from 1.00 to 100.00 mg / l.

[0215] A twenty-ninth aspect relates to the process of any preceding aspect, wherein chloride release from the treated waste-to-energy ash in an alkaline cementitious environment is less than 10 mg / l.

[0216] A thirtieth aspect relates to the process of any preceding aspect, wherein chloride release from the treated waste-to-energy ash in an alkaline cementitious environment is less than 5 mg / l.

[0217] A thirty-first aspect relates to the process of any preceding aspect, wherein chloride release from the treated waste-to-energy ash in an alkaline cementitious environment is below a detection limit of 1.6 mg / l.

[0218] A thirty-second aspect relates to the process of any preceding aspect, the process further comprises subjecting the treated waste-to-energy ash to CO2curing to form a carbonated ash, wherein the chlorellestadite in the treated waste-to-energy ash reacts withCO2to form a carbonated chlorellestadite.

[0219] A thirty-third aspect relates to the process of any preceding aspect, wherein the carbonated chlorellestadite comprises mineral phases including gypsum, vaterite, calcite, calcium chlorosilicate, amorphous CaCO3and / or amorphous SiO2.

[0220] A thirty-fourth aspect relates to the process of any preceding aspect, wherein theCO2curing comprises exposing the treated waste-to-energy ash to an atmospheric air containing about 3% to 100% of CO2gas.

[0221] A thirty-fifth aspect relates to the process of any preceding aspect, wherein the relative humidity of the CO2curing is from about 50% to 90%.

[0222] A thirty-sixth aspect relates to the process of any preceding aspect, wherein the temperature of the CO2curing is from about 25 °C to 85 °C.

[0223] A thirty-seventh aspect relates to the process of any preceding aspect, wherein the mineral phases are formed via three parallel reactions.

[0224] A thirty-eighth aspect relates to the process of any preceding aspect, wherein at least 5% to 30% by weight of CO2is sequestered by the chlorellestadite within 24 hours.

[0225] A thirty-ninth aspect relates to the process of any preceding aspect, wherein the treated waste-to-energy ash is mixed with a cementitious material prior to the CO2curing.

[0226] A fortieth aspect relates to the process of any preceding aspect, wherein the carbonated ash after the CO2curing is mixed with a cementitious material to make a cement paste.

[0227] A forty-first aspect relates to a treated waste-to-energy ash for use in cementitious systems. The treated waste-to-energy ash comprises chlorellestadite; and one or more heavy metals each having a mobility below a toxicity limit. At least one of the one or more heavy metals is crystallo-chemically incorporated into the chlorellestadite.

[0228] A forty-second aspect relates to the treated waste-to-energy ash of the forty-first aspect, wherein the treated waste-to-energy ash comprises calcite and / or portlandite.

[0229] A forty-third aspect relates to the treated waste-to-energy ash of the forty-first or forty-second aspect, wherein the one or more heavy metals comprise copper (Cu), zinc (Zn), cadmium (Cd), tin (Sn), lead (Pb), and / or antimony (Sb).

[0230] A forty-fourth aspect relates to the treated waste-to-energy ash of any preceding aspect, wherein the one or more heavy metals comprise Pb and / or Cd.

[0231] A forty-fifth aspect relates to the treated waste-to-energy ash of any preceding aspect, wherein the mobility of Pb in the treated waste-to-energy ash is less than 0.5 mg / l.

[0232] A forty-sixth aspect relates to the treated waste-to-energy ash of any preceding aspect, wherein the mobility of Pb in the treated waste-to-energy ash is less than 0.4 mg / l.

[0233] A forty-seventh aspect relates to the treated waste-to-energy ash of any preceding aspect, wherein the mobility of the one or more heavy metals is maintained below a range from 1.00 to 100.00 mg / l.

[0234] A forty-eighth aspect relates to the treated waste-to-energy ash of any preceding aspect, wherein chloride release from the treated waste-to-energy ash in an alkaline cementitious environment is less than 10 mg / l.

[0235] A forty-ninth aspect relates to the treated waste-to-energy ash of any preceding aspect, wherein chloride release from the treated waste-to-energy ash in an alkaline cementitious environment is less than 5 mg / l.

[0236] A fiftieth aspect relates to the treated waste-to-energy ash of any preceding aspect, wherein chloride release from the treated waste-to-energy ash in an alkaline cementitious environment is below a detection limit of 1.6 mg / l.

[0237] A fifty-first aspect relates to a cementitious system including a cementitious material and a supplementary cementitious material. The supplementary cementitious material comprises a treated waste-to energy ash that includes chlorellestadite; and one or more heavy metals each having a mobility below a toxicity limit. At least one of the one or more heavy metals is crystallo-chemically incorporated into the chlorellestadite.

[0238] A fifty-second aspect relates to the cementitious system of the fifty-first aspect, wherein the one or more heavy metals comprise copper (Cu), zinc (Zn), cadmium (Cd), tin(Sn), lead (Pb), and / or antimony (Sb).

[0239] A fifty-third aspect relates to the cementitious system of the fifty-first or fifty- second aspect, wherein the one or more heavy metals comprise Pb and / or Cd.

[0240] A fifty-fourth aspect relates to the cementitious system of any preceding aspect, wherein the mobility of Pb in the treated waste-to-energy ash is less than 0.5 mg / l.

[0241] A fifty-fifth aspect relates to the cementitious system of any preceding aspect, wherein the mobility of Pb in the treated waste-to-energy ash is less than 0.4 mg / l.

[0242] A fifty-sixth aspect relates to the cementitious system of any preceding aspect, wherein the mobility of the one or more heavy metals is maintained below a range from 1.00 to 100.00 mg / l.

[0243] A fifty-seventh aspect relates to the cementitious system of any preceding aspect, wherein chloride release from the treated waste-to-energy ash is less than 10 mg / l.

[0244] A fifty-eighth aspect relates to the cementitious system of any preceding aspect, wherein chloride release from the treated waste-to-energy ash is less than 5 mg / l.

[0245] A fifty-ninth aspect relates to the cementitious system of any preceding aspect, wherein chloride release from the treated waste-to-energy ash in an alkaline cementitious environment is below a detection limit of 1.6 mg / l.

[0246] A sixtieth aspect relates to the cementitious system of any preceding aspect, wherein the supplementary cementitious material further comprises a carbonated ash comprising a carbonated chlorellestadite comprising at least 5% to 30% by weight of CO2.

[0247] A sixty-first aspect relates to the cementitious system of the sixtieth aspect, wherein the carbonated chlorellestadite comprises mineral phases including gypsum, vaterite, calcite, calcium chlorosilicate, amorphous CaCO3and / or amorphous SiO2.

[0248] A sixty-second aspect relates to a carbonated chlorellestadite including at least 5% to 30% by weight of CO2, wherein the carbonated chlorellestadite comprises mineral phases including gypsum, vaterite, calcite, calcium chlorosilicate, amorphous CaCO3and / or amorphous SiO2,

[0249] A sixty-third aspect relates to a cement paste including cement, chlorellestadite, and the carbonated chlorellestadite of the sixty-second aspect, wherein the cement paste has a compressive strength of at least 50 MPa after 7 days of CO2curing.

[0250] A sixty-fourth aspect relates to the cement paste of the sixty-third aspect, wherein the cement paste is prepared from about 0 to 90% by weight of the cement and about 10 to100% by weight of the chlorellestadite.

[0251] A sixty-fifth aspect relates to a cement paste including cement, chlorellestadite, and the carbonated chlorellestadite of the sixty-second aspect, wherein the cement paste hasa compressive strength of at least 50 MPa after 7 days of CO2curing, followed by 21 days of conventional curing under ambient conditions.

[0252] A sixty-sixth aspect relates to the cement paste of the sixty-fifth aspect, wherein the cement paste is prepared from about 0 to 90% by weight of the cement and about 10 to100% by weight of the chlorellestadite.

[0253] In addition to the features mentioned in each of the independent aspects enumerated above, some examples may show, alone or in combination, the optional features mentioned in the dependent aspects and / or as disclosed in the description above and shown in the figures.

Claims

CLAIMS1. A process for the treatment of a waste-to-energy ash from municipal waste incineration, the waste-to-energy ash comprising soluble and insoluble chlorides, and one or more heavy metals, the process comprising: removing the soluble chlorides from the waste-to-energy ash by dissolution, thereby obtaining a waste-to-energy ash residue including the insoluble chlorides and the one or more heavy metals; and forming chlorellestadite from the insoluble chlorides in the waste-to-energy ash residue, whereby a mobility of the one or more heavy metals is reduced and / or maintained below a toxicity limit, thereby forming a treated waste-to-energy ash.

2. The process of claim 1, wherein chloride release from the treated waste-to- energy ash in an alkaline cementitious environment is reduced compared to the untreated waste-to-energy ash.

3. The process of claim 1, wherein at least one of the one or more heavy metals is crystallo-chemically incorporated into the chlorellestadite.

4. The process of claim 1, wherein removing the soluble chlorides from the waste-to-energy ash by dissolution comprises:immersing the waste-to-energy ash in water, whereby the soluble chlorides are dissolved in the water; and filtering the waste-to-energy ash from the water to obtain the waste-to-energy ash residue.

5. The process of claim 4, wherein the immersing is carried out for about 0.25 to about 24 hours.

6. The process of claim 4, wherein the immersing is carried out at a liquid to solid ratio (l / s) from 1 : 1 to 20 : 1.The process of claim 4, wherein the immersing comprises the act of washing, rinsing, soaking or submerging in water.

8. The process of claim 1, wherein forming chlorellestadite from the insoluble chlorides comprises: heating the waste-to-energy ash residue at a temperature from about 500 °C to about 800 °C, whereby the insoluble chlorides are transformed into the chlorellestadite.

9. The process of claim 8, wherein the heating takes place in an open-air furnace.

10. The process of claim 8, wherein the heating is carried out from about 0.25 to about 5 hours.

11. The process of claim 1, further comprising removing soluble chlorides from the treated waste-to-energy ash.

12. The process of claim 11, wherein removing the soluble chlorides comprises: immersing the treated waste-to-energy ash containing the chlorellestadite in water; and filtering the treated waste-to-energy ash from the water.

13. The process of claim 12, wherein the immersing is carried out for about 0.25 to about 24 hours.

14. The process of claim 12, wherein the immersing is carried out at a liquid to solid ratio (l / s) from 1 : 1 to 20 : 1.

15. The process of claim 12, wherein the immersing comprises the act of washing, rinsing, soaking or submerging in water.

16. The process of claim 1, further comprising replacing chloride ions in the chlorellestadite with hydroxide ions in the treated waste-to-energy ash.

17. The process of claim 16, wherein replacing chloride ions with hydroxide ions comprises: immersing the treated waste-to-energy ash containing the chlorellestadite in an alkali metal hydroxide solution, whereby chloride ions are exchanged with hydroxide ions; and after the immersing, filtering the treated waste-to-energy ash from the alkali metal hydroxide solution.

18. The process of claim 17, wherein the alkali metal hydroxide solution includes an alkali metal hydroxide selected from the group consisting of potassium hydroxide and sodium hydroxide.

19. The process of claim 17, wherein the immersing is carried out for about 0.25 to about 24 hours.

20. The process of claim 17, wherein the immersing is carried out at a liquid to solid ratio (l / s) from 1 : 1 to 20 : 1.

21. The process of claim 17, wherein the immersing comprises the act of washing, rinsing, soaking or submerging in the alkali metal hydroxide solution.

22. The process of claim 1, wherein the waste-to-energy ash comprises incinerator bottom ash and / or fly ash.

23. The process of claim 1, wherein the treated waste-to-energy ash comprises calcite and / or portlandite.

24. The process of claim 1, wherein the one or more heavy metals comprise copper (Cu), zinc (Zn), cadmium (Cd), tin (Sn), lead (Pb), and / or antimony (Sb).

25. The process of claim 24, wherein the one or more heavy metals comprise Pb and / or Cd.

26. The process of claim 25, wherein the mobility of Pb in the treated waste-to- energy ash is less than 0.5 mg / l.

27. The process of claim 25, wherein the mobility of Pb in the treated waste-to- energy ash is less than 0.4 mg / l.

28. The process of claim 1, wherein the mobility of the one or more heavy metals is maintained below a range from 1.00 to 100.00 mg / l.

29. The process of claim 2, wherein chloride release from the treated waste-to- energy ash in an alkaline cementitious environment is less than 10 mg / l.

30. The process of claim 2, wherein chloride release from the treated waste-to- energy ash in an alkaline cementitious environment is less than 5 mg / l.

31. The process of claim 2, wherein chloride release from the treated waste-to- energy ash in an alkaline cementitious environment is below a detection limit of 1.6 mg / l.

32. The process of claim 1, further comprising subjecting the treated waste-to- energy ash to CO2curing to form a carbonated ash, wherein the chlorellestadite in the treated waste-to-energy ash reacts with CO2to form a carbonated chlorellestadite.

33. The process of claim 32, wherein the carbonated chlorellestadite comprises mineral phases including gypsum, vaterite, calcite, calcium chlorosilicate, amorphous CaCO3and / or amorphous SiO2.

34. The process of claim 32, wherein the CO2curing comprises exposing the treated waste-to-energy ash to an atmospheric air containing about 3% to 100% of CO2gas.

35. The process of claim 32, wherein the relative humidity of the CO2curing is from about 50% to 90%.

36. The process of claim 32, wherein the temperature of the CO2curing is from about 25 °C to 85 °C.

37. The process of claim 33, wherein the mineral phases are formed via three parallel reactions.

38. The process of claim 33, wherein at least 5% to 30% by weight of CO2is sequestered by the chlorellestadite within 24 hours.

39. The process of claim 32, wherein the treated waste-to-energy ash is mixed with a cementitious material prior to the CO2curing.

40. The process of claim 32, wherein the carbonated ash after the CO2curing is mixed with a cementitious material to make a cement paste.

41. A treated waste-to-energy ash for use in cementitious systems, the treated waste-to-energy ash comprising: chlorellestadite; and one or more heavy metals each having a mobility below a toxicity limit, wherein at least one of the one or more heavy metals is crystallo-chemically incorporated into the chlorellestadite.

42. The treated waste-to-energy ash of claim 41, wherein the treated waste-to- energy ash comprises calcite and / or portlandite.

43. The treated waste-to-energy ash of claim 41, wherein the one or more heavy metals comprise copper (Cu), zinc (Zn), cadmium (Cd), tin (Sn), lead (Pb), and / or antimony(Sb).

44. The treated waste-to-energy ash of claim 43, wherein the one or more heavy metals comprise Pb and / or Cd.

45. The treated waste-to-energy ash of claim 44, wherein the mobility of Pb in the treated waste-to-energy ash is less than 0.5 mg / l.

46. The treated waste-to-energy ash of claim 44, wherein the mobility of Pb in the treated waste-to-energy ash is less than 0.4 mg / l.

47. The treated waste-to-energy ash of claim 41, wherein the mobility of the one or more heavy metals is maintained below a range from 1.00 to 100.00 mg / l.

48. The treated waste-to-energy ash of claim 41, wherein chloride release from the treated waste-to-energy ash in an alkaline cementitious environment is less than 10 mg / l.

49. The treated waste-to-energy ash of claim 41, wherein chloride release from the treated waste-to-energy ash in an alkaline cementitious environment is less than 5 mg / l.

50. The treated waste-to-energy ash of claim 41, wherein chloride release from the treated waste-to-energy ash in an alkaline cementitious environment is below a detection limit of 1.6 mg / l.

51. A cementitious system comprising a cementitious material and a supplementary cementitious material, wherein the supplementary cementitious material comprises a treated waste-to energy ash, wherein the treated waste-to-energy ash comprises chlorellestadite; and one or more heavy metals each having a mobility below a toxicity limit, wherein at least one of the one or more heavy metals is crystallo-chemically incorporated into the chlorellestadite.

52. The cementitious system of claim 51, wherein the one or more heavy metals comprise copper (Cu), zinc (Zn), cadmium (Cd), tin (Sn), lead (Pb), and / or antimony (Sb).

53. The cementitious system of claim 51, wherein the one or more heavy metals comprise Pb and / or Cd.

54. The cementitious system of claim 53, wherein the mobility of Pb in the treated waste-to-energy ash is less than 0.5 mg / l.

55. The cementitious system of claim 53, wherein the mobility of Pb in the treated waste-to-energy ash is less than 0.4 mg / l.

56. The cementitious system of claim 51, wherein the mobility of the one or more heavy metals is maintained below a range from 1.00 to 100.00 mg / l.

57. The cementitious system of claim 51, wherein chloride release from the treated waste-to-energy ash is less than 10 mg / l.

58. The cementitious system of claim 51, wherein chloride release from the treated waste-to-energy ash is less than 5 mg / l.

59. The cementitious system of claim 51, wherein chloride release from the treated waste-to-energy ash in an alkaline cementitious environment is below a detection limit of 1.6 mg / l.

60. The cementitious system of claim 51, wherein the supplementary cementitious material further comprises a carbonated ash comprising a carbonated chlorellestadite comprising at least 5% to 30% by weight of CO2.

61. The cementitious system of claim 60, wherein the carbonated chlorellestadite comprises mineral phases including gypsum, vaterite, calcite, calcium chlorosilicate, amorphous CaCO3and / or amorphous SiO2.

62. A carbonated chlorellestadite comprising at least 5% to 30% by weight of CO2, wherein the carbonated chlorellestadite comprises mineral phases including gypsum, vaterite, calcite, calcium chlorosilicate, amorphous CaCO3and / or amorphous SiO2.

63. A cement paste comprising cement, chlorellestadite, and the carbonated chlorellestadite of claim 62, wherein the cement paste has a compressive strength of at least 50 MPa after 7 days of CO2curing.

64. The cement paste of claim 63, wherein the cement paste is prepared from about 0 to 90% by weight of the cement and about 10 to 100% by weight of the chlorellestadite.

65. A cement paste comprising cement, chlorellestadite, and the carbonated chlorellestadite of claim 62, wherein the cement paste has a compressive strength of atleast 50 MPa after 7 days of CO2curing, followed by 21 days of conventional curing under ambient conditions.

66. The cement paste of claim 65, wherein the cement paste is prepared from about 0 to 90% by weight of the cement and about 10 to 100% by weight of the chlorellestadite.

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