Durable and sustainable cement / concrete using calcined clays, methods of making and uses thereof

Abstract

A cementitious composition referred to herein as Recreated Roman Cement / Concrete (RCCe / RCCo) and method of making thereof, are disclosed. The RCCe is made from a binder composition. The binder composition (herein Recreated Roman Cement) is formulated with: (i) calcined clay, (ii) hydraulic lime, and optionally, (iii) ground granulated blast furnace slag (GGBFS). Also provided Recreated Roman Concrete (RCCo) or mortar, which is produced by mixing Recreated Roman Cement with either seawater or sodium sulfate solution or a mixtures of sodium sulfate and solidum chloride to produce paste compositions. The paste can be further mixed with sand or coarse aggregate to produce mortar or concrete, respectively. This developed cementitious system is referred to herein as Recreated Roman Cement / Concrete (RRCe / RCCo). The disclosed composition can be used to make various construction end products, especially construction products applicable to coastal areas.

Description

[0001] DURABLE AND SUSTAINABLE CEMENT / CONCRETE USING CALCINED CLAYS, METHODS OF MAKING AND USES THEREOF

[0002] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0003] This invention was made with government support under W911NF2010308 awarded by US Defense Advanced Research Projects Agency (DARPA). The government has certain rights in the invention.

[0004] FIELD OF THE INVENTION

[0005] The disclosed invention is generally in the field of cement-based construction materials and specifically in the area of cementitious materials for coastal construction.

[0006] BACKGROUND OF THE INVENTION

[0007] Ordinary Portland Cement (OPC)-based materials are often heavily criticized because of their high carbon footprint, energy-intensive manufacturing process, and consumption of freshwater (Monteiro et al., 2017; K. L. Scrivener et al., 2018; Miller et al., 2018). The production of OPC contributes to 7-8% of anthropogenic CO2 emissions and plays a crucial role in global infrastructure [2,3]. The International Energy Agency (IEA) aims to reduce CO2 emissions from the global cement industry by 24% by 2050 [4].

[0008] The sustainability challenges faced by the concrete industry extend beyond greenhouse gas emissions to include the significant use of freshwater, minerals, and energy [11,12]. It extensively relies on a substantial volume of fresh water, with an annual consumption of 16.6xl09m3for global concrete production, constituting approximately 18% of the total yearly industrial water usage worldwide and is roughly equivalent to the annual water usage of 150 million residents in the United States [13,14]. In areas like islands and coastal regions where access to fresh water is limited, the long-distance transportation of water can escalate costs and energy consumption

[0012] . In such situations, the use of seawater as a substitute for fresh water in concrete mixing presents a promising alternative

[0015] . Nevertheless, the existence of chloride ions in seawater can lead to severe corrosion in reinforced concrete, ultimately resulting in deterioration and significantly restricting practical implementation

[0016] .

[0009] Most of these environmental impacts could be minimized using the construction materials used by ancient Roman engineers nearly 2000 years ago (addressed as 'Roman concrete’ hereafter). Roman concrete offers a lower carbon footprint and lower freshwater consumption compared to OPC (Marie D. Jackson et al., 2012a; Palomo et al., 2019; Yi et al., 2020). In addition to the environmental considerations, Roman concrete also represents the epitome of extremely durable cement-based materials, especially against seawater and alkalisilica reaction (ASR). Roman concrete exposed to harsh maritime environments remains in a remarkable condition even 2000 years after construction, while modern ordinary Portland cement (OPC) concrete shows degradation within 32 weeks of exposure to seawater (Santhanam et al., 2006; Yi et al., 2020).

[0010] Various attempts have been made to reproduce Roman concrete. It is important to note that Roman concrete was essentially formed by mixing pozzolanic material (e.g., volcanic ash, aggregates) and portlandite (slaked lime) whereas modem efforts of replicating this ancient material have mostly involved using additional alkali activators, such as NaOH, Na2SO4, and Na2SiO3 (Palomo et al., 2019). Due to the presence of alkali activators, the modern replicates often contain additional sodium-rich gel phases which are unlikely or 70 present in lesser amounts in Roman concrete (S Alonso and Palomo, 2001; Santiago Alonso and Palomo, 2001; Granizo et al., 2002; Garcia-Lodeiro et al., 2013; Palomo et al., 2019). The challenging aspect is that the commonly used alkali activators have high carbon footprints, and depending on the activator sources, some of these alternative cementitious materials may even pose a higher carbon footprint than OPC (Habert and Ouellet-plamondon, 2016). In addition to the activator use, the selection of appropriate pozzolanic material poses a challenge for the reproduction of Roman concrete.

[0011] There remains a need for methods of making Roman concrete and the products made therefrom.

[0012] It is an object of the present invention to provide a cementation process of making cementitious materials with properties provided by Roman concrete.

[0013] It is also an object of the present invention to provide compositions with properties similar to Roman concrete.

[0014] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.

[0015] BRIEF SUMMARY OF THE INVENTION

[0016] A cementitious composition referred to herein as Recreated Roman Cement / Concrete (RCC) and method of making thereof, are disclosed.

[0017] RCC is made from a binder composition. The binder composition (herein Recreated Roman Cement) is formulated with: (i) calcined clay, (ii) hydraulic lime, and optionally, (iii) ground granulated blast furnace slag (GGBFS).

[0018] In some forms, the Recreated Roman Cement contains about 30- 70% by wt. medium grade kaolin clay about 10-40% by wt. hydraulic lime and about 0-40% by weight GGBFS. In some forms, the ratio of clay:lime:GGBFS = 3:1:1. In some forms, the ratio of clay:lime:GGBFS= 3:1:0 i.e., there is no GGBFS in the Recreated Roman Cement.

[0019] Also provided Recreated Roman Concrete or mortar, which is produced by mixing Recreated Roman Cement with either seawater or sodium sulfate solution or a mixtures of sodium sulfate and solidum chloride to produce paste compositions. The paste can be further mixed with sand or coarse aggregate to produce mortar or concrete, respectively. This developed cementitious system is referred to herein as Recreated Roman Cement / Concrete (RRC).

[0020] The disclosed composition can be used to make various construction end products, especially construction products applicable to coastal areas.

[0021] Examples of end-products that can be produced using the disclosed compositions, by mixing the compositions with water / liquids include, but not limited to, bridge girders, beams, blocks, hardscape components such as pavers, edging blocks, stepping stones, etc.

[0022] Additional advantages of the disclosed method and compositions will be set forth in part in the description which follows, and in part will be understood from the description, or can be learned by practice of the disclosed method and compositions. The advantages of the disclosed method and compositions will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings illustrate several embodiments of the disclosed method and compositions and together with the description, serve to explain the principles of the disclosed method and compositions.

[0025] FIG. 1 is a comparison of OPC and RRC length expansion due to ASR.

[0026] FIG. 2 is a carbon footprint comparison of RRC and OPC.

[0027] Fig. 3 shows availability of various cementitious materials.

[0028] FIGs. 4A-4C: Oyster growth on various cementitious composites within 2 months: (FIG. 4A) OPC, (FIG. 4B) alkali-activated slag, and (FIG. 4C) RRC

[0029] FIG. 5 is a strength comparison of RRC and OPC after 5 months of seawater exposure .

[0030] FIG. 6 is a strength comparison of RRC prepared with seawater and sodium sulfate solution.

[0031] FIG. 7 shows compressive strength of different mixes over 56 days.

[0032] FIG. 8A shows heat flow and (FIG. 8B) total heat released from the samples over 168 hr. FIG. 9 shows quantification of the unreacted clay content of different samples over 28 days of curing.

[0033] FIG. 10. Shows derivative weight percentage of different mixes after 6 hours of curing.

[0034] FIG. 11A and FIG. 11B show weight percentage and derivative weight percentage of different mixes after the curing durations of (FIG. 11A) 7 days and (FIG. 11B) 56 days.

[0035] FIG. 12A-12F show FTIR spectra of (FIG. 12A-12B) Cl + SO4, (FIG. 12C-12C) SO4, and (FIG. 12E-12F) seawater sample at different curing durations.

[0036] FIG. 13A-13B show X-ray powder diffraction patterns of (a) Cl + SO4, (b) SO4, and (c) seawater samples at different durations of curing.

[0037] FIG. 14-14B show BSE images with EDS indicating different phases in the binder matrix after curing duration of 56 days. The scale bar represents 100 pm.

[0038] FIG. 15A-15B show Hydration products in seawater sample, FIG. 15C-15D hydration product in Na2SO4 incorporated sample, and FIG. 15E-15F hydration product in NaCl+Na2SO4 incorporated sample after curing duration of 56 days. The scale bar represents 30 pm.

[0039] FIG. 16 shows the effect of NaCl and Na2SO4 salt incorporation on the gel phases of the binder matrix.

[0040] FIG. 17 shows GWP of different mixes.

[0041] DETAILED DESCRIPTION OF THE INVENTION

[0042] The disclosed method and compositions can be understood more readily by reference to the following detailed description of particular embodiments and the Example included therein and to the Figures and their previous and following description.

[0043] The unique aspects of RRC in comparison to OPC and other greener concrete alternatives are briefly discussed below.

[0044] The use of Recreated Roman Cement instead of traditional cement is expected to bring major benefits to the customers such as: (a) reduced maintenance cost: Due to the high durability of RRC, it is expected that the utilization of this material instead of OPC should increase the service life of concrete structures and thus reduce the maintenance cost; (b) environmental benefits: Considering RRC composites have a 60% lower global warming potential compared to OPC at the same performance level, the use of RRC composites should lower the overall carbon footprint of infrastructure.

[0045] It is to be understood that the disclosed method and compositions are not limited to specific synthetic methods, specific analytical techniques, or to particular reagents unless otherwise specified, and, as such, can vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0046] I. DEFINITIONS

[0047] “Medium to high grade clay as used herein is based on the kaolinite content, and it refers to clay with > 40% kaolinite content as measured by thermogravimetric analysis (TGA) and quantitative X-ray diffraction (XRD) using the Rietveld refinement method.

[0048] Recreated Roman Cement is used herein interchangeably with “RCC binder”.

[0049] As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and / or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising”. The transitional terms / phrases (and any grammatical variations thereof) “comprising”, “comprises”, “comprise”, “consisting essentially of”, “consists essentially of”, “consisting” and “consists” can be used interchangeably.

[0050] The phrases “consisting essentially of’ or “consists essentially of’ indicate that the claim encompasses embodiments containing the specified materials or steps and those that do not materially affect the basic and novel characteristic(s) of the claim.

[0051] Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein.

[0052] Use of the term “about” is intended to describe values either above or below the stated value in a range of approximately + / - 10%; in other forms the values may range in value either above or below the stated value in a range of approximately + / - 5%; in other forms the values may range in value either above or below the stated value in a range of approximately + / - 2% ; in other forms the values may range in value either above or below the stated value in a range of approximately + / - 1%. The preceding ranges are intended to be made clear by context, and no further limitation is implied.

[0053] II. RECREATED ROMAN CEMENT / CONCRETE (RCC)

[0054] The unique aspects of RRC in comparison to OPC and other greener concrete alternatives are briefly discussed below.

[0055] Superior compatibility with marine habitat

[0056] The pH of RRC is lower compared to the OPC (around 13) due to differences in hardening mechanisms and the formation of binding agents. Due to the low pH, RRC is more compatible with marine organisms compared to the OPC and other sustainable concrete (i.e., alkali- activated slag). As shown in Fig. 4, under the same laboratory test environment, a higher number of oysters was observed to settle and grow on the RRC composite compared to that of OPC. This indicates, compared to traditional concrete, RRC can be a more appropriate candidate for various marine constructions, including seawalls, artificial reefs, breakwaters, and jetties, as it will serve the purpose of coastal protection and enhance the marine habitat. Important to note that such growth of marine organisms was not found to affect the mechanical performance of either RRC or OPC.

[0057] Superior durability performance

[0058] Ancient Roman concrete shows superior durability in a wide range of scenarios, including seawater and compatibility of reactive aggregates. Traditional OPC concrete is susceptible to alkali-silica reaction (ASR) damage when used with silica-rich reactive aggregates. Such deleterious processes limit the types of aggregates that can be used in concrete or require the use of expensive admixtures to reduce the damage. As shown in Fig.l, the RRC composites showed significantly superior resistance to ASR damage (i.e., 90% enhancement) compared to the OPC indicating an extended service life of those composites.

[0059] Reduced embodied carbon footprint

[0060] The excessive carbon footprint of OPC originates from the need for a high production temperature of 1450°C in addition to burning limestone. Unlike OPC, the key ingredients of RRC, including calcined clay and portlandite, are produced in the temperature range of 700 to 800°C. Because of this low-temperature need, the carbon footprint of RRC mortars is 60% lower than that of OPC (Fig.2). At this time, the use of workability-enhancing admixture is the primary cause of RRC’s carbon footprint. As shown in the examples below, the GWP (global warming potential) associated with using OPC as the binder for mortar production amounts to 11 kg CO2 eq / (m3. MPa). In contrast, the use of calcine clay binders prepared with seawater or Na-bearing salt demonstrated a significant (40-50%) reduction in carbon footprint compared to OPC.

[0061] Availability of raw ingredients

[0062] Due to the high carbon footprint of OPC, a wide range of sustainable concrete has gained popularity in the past few decades, such as geopolymer, various types of pozzolanic materials, etc. The key ingredients of these alternative concrete are various industrial waste products, e.g., fly ash, slag, etc. A recent study revealed that the availability of such ingredients is extremely limited and does not stand a chance of matching the production and consumption volume of Portland cement (OPC). Contradictory to those sustainable concrete materials, the key ingredient of RRC is medium-grade clays, which are abundantly available. Specifically, there are around 6000 clay pits in the U.S. producing 25 million tons of clay per year, and the world reserve of clay is identified as ‘extremely large’. Therefore, RRC has the realistic potential of satisfying the supply-demand of Portland cement compared to other sustainable alternatives (Fig. 3). This further ensures reduced environmental impacts of RRC and the ability to produce within the US without facing material supply issues.

[0063] Continuous strength improvement in marine environment

[0064] RRC, without using any traditional cement, can achieve the same strength as those of OPC mortar / concrete (normal strength concrete, 30 to 40 MPa). The uniqueness of RRC is that it shows continuous improvement of strength after exposure to seawater (measured by measuring the compressive strength of 50 x 50 x 50 mm mortar cubes made from RCC). In some forms, the 50 x 50 x 50 mm mortar cube has a compressive strength of up to about 30 MPa, for example, about 20, 21, 22, 23, 24, 25, 26, 27. 28, 29 or 30 MPa. As shown in Fig 5, after 5 months of exposure to seawater (Baffin Bay, Corpus Christi, TX), the compressive and tensile strengths of RRC composites were observed to increase by 40% and 50%, respectively. While OPC composites showed a similar increase in compressive strength, the increase in tensile strength was much lower (~ 13%).

[0065] A. Recreated Roman Cement

[0066] The disclosed Recreated Roman Cement is made from: (i) calcined clay, (ii) hydraulic lime, and optionally (iii) ground granulated blast furnace slag (GGBFS).

[0067] In some forms, the ratio of clay:lime:GGBFS = 3: 1: 1. In some forms, the ratio of clay:lime:GGBFS= 3:1:0 i.e., there is no GGBFS in the Recreated Roman Cement.

[0068] In some forms, the Recreated Roman Cement contains about 60% by wt. medium grade kaolin clay, about 20% by wt. natural hydraulic lime, and about 20% by weight GGBFS.

[0069] Exemplary elemental compositions (wt.%) of the raw materials used to make Recreated Roman Cement are shown in Tables 1 and 3.

[0070] ( i ) Calcined clay

[0071] Calcined clay is a material obtained from processing clay with sufficient mechanical strength for a particular purpose. Once the clay is calcined (burned at high temperatures >550 °C), it develops new properties allowing it to be used as SCMs (supplementary cementitious materials).

[0072] Based on the kaolinite content, common clay deposits can be categorized as high (>65% kaolinite content), medium (40% ~ 65% kaolinite content), and low grade (< 40% kaolinite content) kaolin clays. The binder composition contains about 30- 70% by wt. medium grade clay, for example, about 30, 35, 40, 45, 50, 55, 60, 65 and about 70% by wt. medium grade clay.

[0073] In some forms, the clay is medium grade kaolin clay. There are around 6000 clay pits in the U.S. producing 25 million tons of clay per year, and the world reserve of clay is identified as ‘extremely large’].

[0074] The medium grade kaolin clay can be calcined at a between about 550 °C to about 850 °C, for example, at a temperature of about 550 °C, 600 °C, 650 °C, 700 °C, or about 750 °C.

[0075] (ii) Hydraulic lime

[0076] The disclosed compositions are made using natural hydraulic lime.

[0077] The binder composition contains about 10-40% by wt. hydraulic lime, for example, about 10, 15, 20, 25, 30, 235 and about 40% by wt. hydraulic lime.

[0078] Hydraulic lime is used to rerefer to calcium oxide a variety of lime also called quicklime, that sets by hydration. This is in contrast to calcium hydroxide (aka slaked line or air lime) that is used to make lime mortar, the other common type of lime mortar, which sets by carbonation (re- absorbing carbon dioxide (CO2) from the air). There are two basic types of hydraulic limes:

[0079] Hydraulic lime (HL), which is produced by heating (calcining) limestone that naturally contains clay and other impurities: no materials may be added to create the hydraulicity. In the United States HL may be called 'hydrated hydraulic lime' (HHL) per ASTM C-141 Standard Specification for Hydrated Hydraulic Lime for Structural Purposes; and

[0080] Artificial hydraulic lime (AHL) or artificial lime (AL) becomes hydraulic when hydraulic and / or pozzolan materials are added either before or after burning in a lime kiln. Artificial limes are more specifically identified as 'hydraulic lime’ (HL), as defined European Norm 459 (EN- 459), "Consists of lime and other materials such as Portland cement, blast furnace slag, fly ash, limestone filler and other suitable materials."; 'formulated lime' (FL) (EN-459) consists of "...mainly of hydrated lime and or NHL with added hydraulic and / or pozzolanic material. It is identical to HL but its composition must be declared on the CE marking." https: / / www.limes.us / wp-content / uploads / 2014 / 03 / TheLastStraw.pdf.

[0081] (Hi) ground granulated blast furnace slag (GGBFS)

[0082] The binder composition in some forms, contains about 0-40% by weight GGBFS, for example, about 0, 5, 10, 15, 20, 25, 30, 35, and about 40 % by weight GGBFS. Ground granulated blast-furnace slag (GGBS or GGBFS) is obtained by quenching molten iron slag (a by-product of iron and steel-making) from a blast furnace in water or steam, to produce a glassy, granular product that is then dried and ground into a fine powder. Ground granulated blast furnace slag is a latent hydraulic binder forming calcium silicate hydrates (C-S-H) after contact with water. It is a strength-enhancing compound improving the durability of concrete.

[0083] Iron blast furnace slag results from the fusion of iron ore, fluxing materials, and coke; the reduction reactions; and the separation of iron from the ore. the term blast furnace slag is used often to refer to iron blast furnace slag to distinguish it from other types of blast furnace slag such as copper, lead, and zinc blast furnace slag. Because the blast furnace operation is a continuous process with carefully controlled raw materials being fed in and furnace conditions, among the various slags, iron blast furnace slag is the easiest to deal with technically to use in construction-related applications. Like other slags, although blast furnace slag varies in chemical and mineral composition, its physical structures depend on the method of cooling of the slag and the processing method used. The nature of the minerals formed when slag cools slowly is of concern in the use of the materials as a dense aggregate. It is of less direct interest for slag in the glassy, or granulated form used as an aggregate, but its hydraulic activity is essential in its use as a cementitious material. Liquid blast furnace slag cooling regimes traditionally include air- cooling, granulating (wet), expanding, and pelletizing, and result in four distinct types of blast furnace slag: air-cooled slag, solidified under ambient conditions; granulated slag, solidified by quick water quenching to a vitrified (glassy) state; expanded or foamed slag, solidified with controlled quantities of water, sometimes with air or steam; and pelletizing slag. In terms of quantity produced, granulated slag is the predominant product.

[0084] Because of its relatively consistent quality, blast furnace slag is generally covered by conventional specifications for aggregate and cementitious applications. Processed air-cooled blast furnace slag and unground blast furnace slag is generally considered to be a construction aggregate and ground granulated blast furnace slag (GGBFS) is considered a supplementary cementitious material (George C. Wang, in The Utilization of Slag in Civil Infrastructure Construction, 2016; https: / / www.sciencedirect.com / topics / engineering / blast-furnace-slag)

[0085] The chemical composition of a slag varies considerably depending on the composition of the raw materials in the iron production process. Silicate and aluminate impurities from the ore and coke are combined in the blast furnace with a flux which lowers the viscosity of the slag. In the case of pig iron production, the flux consists mostly of a mixture of limestone and forsterite or in some cases dolomite. In the blast furnace the slag floats on top of the iron and is decanted for separation. Slow cooling of slag melts results in an unreactive crystalline material consisting of an assemblage of Ca-Al-Mg silicates. To obtain a good slag reactivity or hydraulicity, the slag melt needs to be rapidly cooled or quenched below 800 °C in order to prevent the crystallization of merwinite and melilite. In order to cool and fragment the slag, a granulation process can be applied in which molten slag is subjected to jet streams of water or air under pressure. Alternatively, in the pelletization process, the liquid slag is partially cooled with water and subsequently projected into the air by a rotating drum.

[0086] B. Recreated Roman Concrete

[0087] Also provided Recreated Roman Concrete or mortar, which is produced by mixing Recreated Roman Cement with either seawater or sodium sulfate solution or a mixtures of sodium sulfate and solidum chloride to produce paste compositions. The paste can be further mixed with sand or coarse aggregate to produce mortar or concrete, respectively.

[0088] For a good concrete mix, aggregates need to be clean, hard, strong particles free of absorbed chemicals or coatings of clay and other fine materials that could cause the deterioration of concrete. Aggregates, which account for 60 to 75 percent of the total volume of concrete, are divided into two distinct categories— fine and coarse. Fine aggregates generally consist of natural sand or crushed stone with most particles passing through a 3 / 8-inch sieve. Coarse aggregates are any particles greater than 0.19 inch, but generally range between 3 / 8 and 1.5 inches in diameter.

[0089] Coarse aggregate concrete is a key component of concrete and other construction applications. Coarse aggregates are irregular, granular materials that are larger than 0.19 inches in diameter, but typically range from 3 / 8 to 1.5 inches. They are usually made from natural gravel or crushed stone, which can be obtained by dredging or digging from rivers, lakes, pits, or the seabed, or by crushing quarry rock, boulders, cobbles, or large grave.

[0090] Coarse aggregates are used in concrete to: Increase crushing strength, Reduce costs, Control shrinkage, and Prevent cracking.

[0091] The type of rock used to create the aggregate determines its characteristics, and the selection of good quality coarse aggregate is essential for producing concrete that meets the desired strength and durability.

[0092] Gravels constitute the majority of coarse aggregate used in concrete with crushed stone making up most of the remainder. Natural gravel and sand are usually dug or dredged from a pit, river, lake, or seabed. Crushed aggregate is produced by crushing quarry rock, boulders, cobbles, or large-size gravel.

[0093] Natural gravel and sand are usually dug or dredged from a pit, river, lake, or seabed. Crushed aggregate is produced by crushing quarry rock, boulders, cobbles, or large-size gravel. Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular subbases, soil-cement, and in new concrete. After harvesting, aggregate is processed: crushed, screened, and washed to obtain proper cleanliness and gradation. If necessary, a benefaction process such as jigging or heavy media separation can be used to upgrade the quality. Once processed, the aggregates are handled and stored to minimize segregation and degradation and prevent contamination.

[0094] Particle shape and surface texture influence the properties of freshly mixed concrete more than the properties of hardened concrete. Rough-textured, angular, and elongated particles require more water to produce workable concrete than smooth, rounded compact aggregate. Consequently, the cement content must also be increased to maintain the water-cement ratio. Generally, flat and elongated particles are avoided or are limited to about 15 percent by weight of the total aggregate. Unit-weight measures the volume that graded aggregate and the voids between them will occupy in concrete.

[0095] The void content between particles affects the amount of cement paste required for the mix. Angular aggregates increase the void content. Larger sizes of well-graded aggregate and improved grading decrease the void content. Absorption and surface moisture of aggregate are measured when selecting aggregate because the internal structure of aggregate is made up of solid material and voids that may or may not contain water. The amount of water in the concrete mixture must be adjusted to include the moisture conditions of the aggregate.

[0096] III. METHODS OF MAKING AND USING

[0097] The method of making RRC instead of traditional cement is expected to bring the following benefits to the customers as discussed below:

[0098] Reduced construction cost: The production temperature requirements for RRC are significantly lower than that of OPC (800°C vs 1450°C). Therefore, it is expected that the energy requirements and the cost of production for RRC will be lower than the OPC. Such lower energy requirements can reduce the construction cost of concrete when RRC is used instead of OPC. To verify and estimate such potential cost benefits, the proposed task list includes a comprehensive techno-economic assessment.

[0099] In some preferred embodiments, RRC binder is formulated by combining about 55% medium-grade kaolin clay, about 25% HL 2, and about 20% GGBFS.

[0100] In some forms the calcined clay and lime are combined at a ratio of 3: 1. In some forms the calcined clay, lime and GGBFS are at a ratio of about 2.75: 1: 1.

[0101] In some forms, water reducing admixture up to about to 2% of binder mass is used to increase workability; tap water can be premixed to ensure its uniform distribution.

[0102] A 2: 1 ratio of seawater and tap / fresh water can be used as the mixing water, maintaining a water-to-binder (RRC) ratio (w / b) of about 0.28 to about 0.66; for example, 0.29, 0.30, 0.31, 0.32, to provide mortar composition. Here, water reducing admixtures type A, D, E, F and G as specified by the ASTM C494 can be used. In some form, the compositions include Superplasticizer (Sika Viscocrete 6100)).

[0103] In some forms, the compositions further include Na2SO4 and / or NaCl at a concentration between about 10 g / lOOg binder, for example, about 2, 3, 4, 5, 6, 7, 8, 9 or about 10 g / 100 g RCC binder.

[0104] In some forms, the salts were dissolved in 2 / 3 of the total mixing water. In the remaining 1 / 3 of the mixing water, the superplasticizer is dissolved.

[0105] In some forms, the compositions include sand, at a concentration of sand:binder of about 0.88.

[0106] The present invention can be further understood in view of the following non-limiting examples.

[0107] EXAMPLES

[0108] EXAMPLE 1

[0109] Materials

[0110] Medium-grade clay was thermally activated by calcining at 750°C and was subsequently ball-milled for 3 hours. The elemental composition of the raw materials was analyzed using X- ray fluorescence (XRF) and shown in Table 1. Artificial seawater was created by dissolving 1 pound of Instant Ocean Sea salt in 5 gallons of water, maintaining a concentration of 34 g / L to aid in mixing and curing. The seawater composition closely follows the ASTM DI 141 and is shown in Table 2. Additionally, sodium chloride and sodium sulfate were purchased from VWR (>95% purity). GGBFS and natural hydraulic lime (NHL 2) were procured from CEMEX and Saint Astier respectively. For aiding in workability sika viscocrete was used as the superplasticizer.

[0111] Tabic 1: Elemental composition (wt.%) of the raw materials _

[0112] Mass fraction w / % Raw material

[0113] AI2O3 SiO2CaO Fe2O3Na2O MgO SO3K2O

[0114] Medium-grade

[0115] 32.9 55.7 2.17 4.18 0.479 0.743 0.686 1.34 kaolin

[0116] Slag 15.6 29.6 36.4 0.372 0.762 9.69 5.19 0.305

[0117] N tural Lime 1.16 3.73 90.9 1.05 - 1.24

[0118] (NHL 2) Table 2: Chemical composition of artificial seawater

[0119] Composition Cl Na S Mg K Ca CO3 Br Sr g / L 19.29 10.78 2.66 1.32 0.42 0.4 0.2 0.056 0.0088

[0120] Methods for Seawater mixing

[0121] RRC binder was formulated by combining 55% medium-grade kaolin clay, 25% NHL 2, and 20% GGBFS. Superplasticizer equivalent to 2% of binder mass was used to increase workability; tap water was premixed to ensure its uniform distribution. Therefore, a 2:1 ratio of seawater and tap water was utilized for the mixing water, maintaining a water-to-binder ratio (w / b) of 0.36. The prepared samples included 50mm3mortar cubes to assess mechanical properties.

[0122] The mixing process involved combining all the dry components within a Hobart mixer and blending them at the initial speed of 140 rpm for 1 minute. Subsequently, the introduction of seawater was carried out, followed by the inclusion of the mixture containing tap water and superplasticizer. After 30 seconds of blending the mix, the speed was promptly elevated to 580 rpm, and the mixing process was continued until a uniform consistency was attained. The curing was conducted under seawater and water was replaced every 28 days to ensure abundance supply of ions.

[0123] Methods for salt-containing sample mixing

[0124] For preparing 50 mm mortar cubes, calcined clay, and natural hydraulic lime were taken at a clay: lime = 3:1, sand: binder = 0.88, and water: binder = 0.36. A total of 4 g of Na2SO4 was dissolved for 100 g of the binder for the SO4 batch, and 3.55 g of Na2SO4 and 3.30 g of NaCl were dissolved for 100 g of the binder for the Cl + SO4 batch. For the SO4 batch, only Na2SO4 salt was dissolved in the tap water with a magnetic stirrer at 500 rpm for 5 min. For the Cl + SO4 sample, both NaCl and Na2SO4 salts were dissolved similarly, keeping the Na2O quantity the same as the SO4 samples. The total Na2O content was 3.3% by the weight of the binder. The salts were dissolved in 2 / 3 of the total mixing water. The superplasticizer was dissolved in the remaining 1 / 3 of the mixing water. The same mixing procedure was followed as the seawater. For curing, the salt-containing batches were kept in a box, and tap water was sprayed every day.

[0125] Results and Discussion

[0126] The primary goal of the project was to develop a highly durable cementitious material for coastal applications. Because of this, seawater was used for mixing and curing RRC to ensure superior compatibility with marine environments. However, the present studies revealed that among various salts present in seawater, sodium sulfate was the key component that contributed to the strength of RRC. As a result, the innovation includes the production of RRC of the same target strength using sodium sulfate (Na^SOU solution instead of seawater (Fig.6). This approach also eliminates the use of chlorides (beneficial for steel reinforcement). Noteworthy, sodium sulfate is a by-product of various industrial processes, including lithium battery recycling and metal mining (e.g., copper mining). This ensures that at this time, the application of RRC is not limited to only coastal areas (due to the availability of seawater), rather it can be used as a durable and sustainable concrete for inland applications as well.

[0127] Ancient Roman concrete shows superior durability in a wide range of scenarios, including seawater and compatibility of reactive aggregates. Traditional OPC concrete is susceptible to alkali-silica reaction (ASR) damage when used with silica-rich reactive aggregates. Such deleterious processes limit the types of aggregates that can be used in concrete or require the use of expensive admixtures to reduce the damage. As shown in Fig.l, the RRC composites showed significantly superior resistance to ASR damage (i.e., 90% enhancement) compared to the OPC indicating an extended service life of those composites.

[0128] The excessive carbon footprint of OPC originates from the need for a high production temperature of 1450°C in addition to burning limestone. Unlike OPC, the key ingredients of RRC, including calcined clay and portlandite, are produced in the temperature range of 700 to 800°C. Because of this low-temperature need, the carbon footprint of RRC mortars is 60% lower than that of OPC (Fig.2). At this time, the use of workability-enhancing admixture is the primary cause of RRC’s carbon footprint. It is expected that the GWP of RRC will be further reduced once an appropriate admixture is selected.

[0129] Due to the high carbon footprint of OPC, a wide range of sustainable concrete has gained popularity in the past few decades, such as geopolymer, various types of pozzolanic materials, etc. The key ingredients of these alternative concrete are various industrial waste products, e.g., fly ash, slag, etc. A recent study revealed that the availability of such ingredients is extremely limited and does not stand a chance of matching the production and consumption volume of Portland cement (OPC)

[0011] . Contradictory to those sustainable concrete materials, the key ingredient of RRC is medium-grade clays, which are abundantly available. Specifically, there are around 6000 clay pits in the U.S. producing 25 million tons of clay per year, and the world reserve of clay is identified as ‘extremely large’ [12,13]. Therefore, RRC has the realistic potential of satisfying the supply-demand of Portland cement compared to other sustainable alternatives (Fig. 3). This further ensures reduced environmental impacts of RRC and the ability to produce within the US without facing material supply issues.

[0130] The pH of RRC is lower compared to the OPC (around 13) due to differences in hardening mechanisms and the formation of binding agents. Due to the low pH, RRC is more compatible with marine organisms compared to the OPC and other sustainable concrete (i.e., alkali- activated slag). As shown in Fig.4, under the same laboratory test environment, a higher number of oysters was observed to settle and grow on the RRC composite compared to that of OPC. This indicates, compared to traditional concrete, RRC can be a more appropriate candidate for various marine constructions, including seawalls, artificial reefs, breakwaters, and jetties, as it will serve the purpose of coastal protection and enhance the marine habitat. Important to note that such growth of marine organisms was not found to affect the mechanical performance of either RRC or OPC.

[0131] RRC, without using any traditional cement, can achieve the same strength as those of OPC mortar / concrete (normal strength concrete, 30 to 40 MPa). The uniqueness of RRC is that it shows continuous improvement of strength after exposure to seawater. As shown in Fig 5, after 5 months of exposure to seawater (Baffin Bay, Corpus Christi, TX), the compressive and tensile strengths of RRC composites were observed to increase by 40% and 50%, respectively. While OPC composites showed a similar increase in compressive strength, the increase in tensile strength was much lower (~ 13%).

[0132] EXAMPLE 2

[0133] This study aimed to replicate the cementation mechanism of the recreated Roman concrete [6] without seawater by the inclusion of sodium-based salts into fresh water, keeping the total sequestered Na2O quantity constant. For this, medium-grade calcined clay and commercially available lime were utilized as the binder. The incorporation of sodium-based salts (Na2SO4 and NaCl) into the freshwater ensures the development of similar mineral phases in freshwater cementitious systems, thereby enhancing durability and minimizing global warming potential. For comparison with the recreated Roman concrete binder with seawater, both NaCl and Na2SO4 were mixed in water to replicate the seawater effect. Additionally, solely Na2SC>4 was employed to mitigate the corrosion issues associated with chloride ions. A diverse array of characterization methods was utilized, encompassing thermogravimetric analysis, chemical extraction, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Backscattered Scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). Furthermore, the environmental impact of such binders was quantified.

[0134] Materials and Methods

[0135] Raw materials

[0136] In this investigation, medium-grade kaolin clay with a purity ranging from 55% to 60% was employed (Table 1). The impurities include primarily quartz and calcite. NaCl and Na2SO4 were procured from VWR (> 95% pure) and used without further modification. The clay was calcined at 750°C. The rationale for using this specific calcination temperature is detailed elsewhere [3,6]. Superplasticizer (Sika Viscocrete 6100) was used by 2% of the total binder [8].

[0137] Table 3: Chemical composition of medium-grade clay and lime.

[0138] Sample preparation

[0139] For preparing 50 mm mortar cubes, calcined clay, and lime were taken at a clay: lime = 3:1 [6,8], sand: binder = 0.88 [8], and water: binder = 0.36 [8].

[0140] For the SO4 batch, only Na SO4 salt was dissolved in the tap water with a magnetic stirrer at 500 rpm for 5 min.

[0141] For the Cl + SO4 sample, both NaCl and Na2SO4 salts were dissolved similarly, keeping the Na2<3 quantity the same as the SO4 samples.

[0142] For both systems, the total Na2O content was 3.3% by the weight of the binder. The quantity of salts added to the samples is given in Table 2. The quantities were obtained from a previous study, where the seawater-cured sample sequestrated equivalent chloride and sulfate ions over 56 days of the curing period [8]. All the salts were dissolved in 2 / 3 of the total mixing water. In the remaining 1 / 3 of the mixing water, the superplasticizer was dissolved. The mixing procedure was followed as per our previous studies [8]. For the seawater batch, seawater was taken as 2 / 3 of the mixing water. Superplasticizer (2% by wt.) was incorporated similarly to the rest of the mixing water for better solubility. After 24 hours, the samples were de-moled and kept for curing. Two different curing regimes were followed. In the first regime, the salt-containing batches were kept in a box, and water was sprayed every day. In the second regime, the seawater samples were cured under seawater. After every 28 days, the seawater was changed to ensure an abundant supply of ions.

[0143] The paste samples were prepared without the sand to monitor the microstructural evolution. They were cured in a similar way to the mortar cubes. After every curing duration, the reaction was arrested following the solvent-exchange method, and for this, laboratory-grade isopropanol was utilized

[0026] . Then, they were kept in a vacuum desiccator for drying for 14 days, manually ground in a mortar-pastel, and utilized for microstructural studies like TGA, FT1R, and XRD. Table 4: Mix details

[0144] 3 Experimental methods

[0145] The heat released from the paste samples due to hydration was monitored utilizing an isothermal calorimeter (TAM Air, TA instruments). The water / binder was 0.36 without the superplasticizer. This test aimed to observe the hydration reaction at its initial stages. In the case of saltcontaining samples, the salts were dissolved in water 24 hr. prior to the test to prevent heat generation from salt dissociation in water. Heat release data was continuously recorded for 168 hr. at 25°C.

[0146] The compressive strength of 50 x 50 x 50 mm mortar cubes was collected at 1, 3, 7, 28, and 56 days of their corresponding curing at room temperature.

[0147] Extraction using hydrochloric acid (HC1) involved blending one gram of hydrated paste sample (sieved through #200 mesh) with 250 mL of hydrochloric acid at a 1:20 by volume (1 part 37% HC1 and 20 parts H2O)

[0027] . The resulting mixture was agitated for 3 hours and then filtered through a 0.2 mm Whatman filter paper. The weight of the remaining solid residue was measured after drying at 100°C for 24 hours. This residual weight corresponds to the unreacted precursors.

[0148] Thermogravimetric analysis was conducted using a TGA 550 TA instrument. The paste samples were finely ground, and approximately 30 to 35 mg of ground powder sample was used. The instrument was stabilized at an isothermal condition for 3 minutes at around 25 °C. The temperature range was spanned from 25°C to 980°C with a rate of 15°C / min under N2 environment. Because of the minimal deviation (< 2%), the experiment was conducted once for all samples.

[0149] Nicolet iS5 instrument was utilized for Fourier Transform Infrared Spectroscopy (FTIR). An attenuated total reflectance (ATR) accessory was used for the experiments presented in this study. The frequency analyzed here ranged from 400 to 4000 cm'1where the resolution was 4 cm'1. X-ray Diffraction (XRD) was carried out with a Br ker D8 diffractometer in a two-theta configuration using a CuKa source. The data were acquired over the two-theta ranging 5°-60° with a scanning rate of 0.03 (29) / s. The fine powder obtained from paste samples was used for XRD to determine the hydration product's mineralogy. To identify phases, a commercially available software called "Match! Phase Analysis using Powder Diffraction" was employed with a Crystallographic Open Database (COD).

[0150] The chemical composition of different reaction products was quantified with backscattered electron mode (BSE) using the Hitachi 3000N SEM (accelerating voltage 25 - 30 kV, working distance = 15 mm). For this, the solid portion of the samples underwent impregnation in a low-viscosity epoxy resin and subsequent lapping / polishing to achieve a shiny surface like a mirror and coated with Gold (Au)-Platinum (Pt). Energy Dispersive Spectroscopy (EDS) data points were collected under an identical environment.

[0151] The procedure to determine the global warming potential (GWP) of the mortar mixes was followed by fixing the functional unit, acquiring the GWP values for each of the raw materials, and calculating the ultimate value. Compressive strength was incorporated as a parameter, and therefore, the functional unit was set as the mass of binder required to achieve Compressive strength was incorporated as a parameter, and therefore, the functional unit was set as the mass of binder required to attain a compressive strength of 1 MPa / m3of mortar (kg / m3MPa) [28,29]. The majority of the Global Warming Potential (GWP) data for raw materials was acquired through an analysis of the Ecoinvent 3 dataset using the Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI) in SimaPro 9.0.0.48. The mediumgrade kaolin clay used in this study was considered to be collected directly from the clay pit, transported to the binder plant, and calcined at 750°C without undergoing any purification process and grinding. The energy consumed for calcining clay was accumulated from previous studies, which suggests that 20 kWh of electricity is needed to calcine and grind per ton of clay [30,31]. Another binder component, lime, has varied ranges of GWP depending on its purity, available free Ca(OH)2, and ability to reabsorb CO2; for this study, the GWP used was 0.446 kg CO2 eq per kg of natural hydraulic lime

[0032] . Apart from the above raw materials, the GWP used for the Sika viscocrete superplasticizer was 1.53 kg CO2 eq

[0033] . Moreover, Na2SO4 was considered an industrial byproduct, and no carbon emission was considered for it. To compare the GWP reduction achieved by the mortar mixes in this study with OPC, GWP data for an OPC mortar mix with a w / c= 0.45 and a sand / binder= 2.75 were retrieved from a prior study

[0034] . 3 shows the material categories that were collected from the Ecoinvent 3 dataset for different raw materials. Table 5: Material categories used from Ecoinvent 3

[0152] Results

[0153] Mechanical performance

[0154] The compressive strength of different batches is presented in Error! Reference source not found.. The samples with salts showed higher early strength. After one day, both of them achieved approximately 3 ~ 4 times higher compressive strength than the seawater batch. For both of the salt-containing batches, after 3 days of curing, they achieved almost 80% of the strength. The Cl + SO4 batch achieved the maximum strength (31 MPa) after its corresponding curing for 56 days. The faster rate of gaining strength can be attributed to the formation of gypsum and ettringite in both salt-containing batches. The detailed mechanism will be discussed in the following sections.

[0155] The seawater-cured sample attained strength slowly with time. As the samples were cured under seawater, the chloride and sulfate ions diffused into the sample, and this process took time. As a result, it achieved almost similar strength to the salt-containing batches after 7 days of exposure (20.96 MPa) in seawater. Although the initial strength was lower for the seawater batch, the pozzolanic reaction continued, and as a result, after 28 days of seawater curing it achieved 28 MPa and 29 MPa and 56 days, respectively.

[0156] Reaction rate and extent

[0157] Hydration reaction kinetics

[0158] To monitor the early-stage reaction mechanism of the samples, the heat of hydration over 168 hours was observed, and the results are presented in Error! Reference source not found. A- 8B. The first peak, attributed to the precursors' dissolution, was similar for the seawater and SO4 batch, which were higher than the Cl + SO4 batch (Error! Reference source not found.A). The later sample delayed the hydration reaction by 2 hours compared to the SO4 batch. The hydration reaction of the seawater sample started almost at the same time as the SO4 batch. The seawater sample showed a broader peak than the others in both cases, and the hydration was delayed by 1.5 hours compared to the SO4 specimen. This indicates the prolonged dissolution and subsequent hydration reaction in the cementitious matrix. The delayed hydration of this sample compared to the other solutions was attributed to the presence of Mg in seawater, considering past studies showed MgO can suppress cement hydration reactions

[0035] . Noteworthy, the availability of Ca was similar for all of the samples. The total heat of the SO4 batch was the maximum (118.5 J / g of binder), followed by Cl + SO4 batch (104.02 J / g of binder) and the seawater batch (88.73 J / g of binder). The SO4 and C1+ SO4 batches also showed steeper slopes than those of the seawater batch. This indicates that the rate of reaction is higher in these samples compared to the seawater sample within 168 hours.

[0159] Degree of reaction

[0160] In this study, the precursor used was amorphous aluminosilicate (calcined clay) and a major portion of the reaction product was also amorphous gel. It becomes challenging to characterize the reaction product from the unreacted precursor from the conventional XRD. Under these circumstances, various selective dissolution techniques can be utilized to eliminate specific phases, enhancing the signal from others and enabling more accurate characterization. Insights gained from these selective dissolution studies have played a crucial role in eliminating ambiguity in the phase analysis of precursor, paving the way for characterization using alternative methods like XRD-Rietveld

[0027] . Error! Reference source not found, illustrates the weight percentage of the sample that persisted following its dissolution in hydrochloric acid (HC1), which dissolves all components, excluding the unreacted clay [27,36,37]. From Error! Reference source not found., it is evident that within the first 6 hours of hydration reaction, more than 50% of the raw calcined clay reacted, whereas approximately 65% of the calcined clay remained unreacted in the case of the seawater sample. For the salt-containing batches, the degree of reaction was rather slower over the 28-day curing period. The seawater sample reacted slowly over time, and after 28 days of curing, it achieved a similar degree of hydration as the other salt-containing samples. After 28 days, approximately 40-45% clay remained unreacted. It also indicated that the metakaolin fraction of the calcined impure clay reacted over the first 28 days, as metakaolin is known to be the most reactive clay component

[0038] .

[0161] Microstructural phase characterization Thermogravimetric analysis

[0162] Thermogravimetric analysis was performed for the raw clay binder, and the samples at initial curing durations are presented in Figure 4. In the raw clay mix (Error! Reference source not found.), the peak in the range of 300 - 400°C and 400 - 500°C represents the dehydroxylation of brucite and portlandite, respectively

[0026] . There is a broad peak from 600 to 800°C, which is due to the dehydroxylation of 2:1 layered clay and decomposition of calcite impurity in the raw clay 139 ]. This also indicates that the calcination temperature was not enough to dehydroxylate the 2:1 layered clay constituent of the raw clay.

[0163] For the salt-containing batches, after 6 hours of hydration, a peak was observed below 100°C, which represents the weight loss due to the evaporation of free water associated with the reaction products. For the seawater batch after 6 hours of hydration, this peak was rather broader and smaller than the salt-containing batches. AU the samples exhibited a peak around 100 - 150°C, which is attributed to the weight loss due to the dehydration of gypsum

[0026] . The availability of sulfate ions facilitated the formation of this reaction product in all the samples. In the C1+ SO4 batch, a small peak around 250 - 300°C was observed due to the weight loss of hydrocalumite

[0026] . Although chloride ions were present in seawater, the reaction rate of the seawater-containing sample was slower than that of the other samples, and consequently, the hydrocalumite peak was not observed after 6 hours of hydration. Notably, for the first 24 hours, all of the samples were in the mold and sealed, and the w / b ratio was also very low. The dissolution of the clay constituents was not sufficient at the early stage, and due to the lack of adequate ions (chloride, alkalis, sulfate), the reaction was slower. This finding aligns with the observation from the heat of hydration (Error! Reference source not found.).

[0164] The peak around 300 - 400°C due to dehydroxylation of brucite was observed in all the samples. For the salt-containing batches, no peak was observed in the 400 - 500°C temperature range. This confirms that within 6 hours of hydration, portlandite was consumed. However, the seawater sample showed a reduced peak of portlandite after 6 hours which is due to the slower rate of reaction as discussed above. The peak ranging from 600-700°C resulting from weight loss of calcite was observed for all of the samples

[0040] .

[0165] Figure 11A represents the thermogravimetric analyses of the samples after 7 days of their corresponding curing. The primary differences between 6 hours and 7 days of curing were noticeable for the seawater sample. After 7 days of curing in seawater, the peak due to weight loss of hydrocalumite was evident in the temperature range of 250 - 300°C. There was no peak observed in the temperature range of 400-500°C marking the consumption of portlandite. Nonetheless, the first peak remarking the evaporation of free water from reaction products was still lower than those of the salt-containing samples. This indicated that the quantity of reaction products was still lower than the other samples at this curing stage. That is why the compressive strength (Error! Reference source not found.) of this sample was also lower than the others after 7 days. Another interesting observation from Error! Reference source not found.a is that a shoulder was developed for salt-containing batches at around 100°C due to the weight loss from ettringite, which became very prominent after 56 days of curing (Figure 11B). All the peaks look very similar to the 7-day sample. It also confirms that the mineralogical formation was completed within the first 7 days of curing.

[0166] Fourier Transform Infrared Spectra (FTIR)

[0167] The FTIR spectroscopy was employed to monitor the change in the molecular bonding of the minerals over the curing duration as the hydration reaction proceeds with time, and the results are presented in Error! Reference source not found.. In the range from 800 to 1200 cm' different silica polymerization peaks (Q1, Q2, Q3, Q4) are imbricated [5]. The spectrum at 0 hr. represents the raw binder mixer, where a relatively sharp peak at wavenumber 1050 cm'1represents the asymmetric vibration band (V3) of the Si-0 bond of solid precursor. It also indicates the higher polymerized state (Q3) of the aluminosilicate structure of the calcined clay [7]. The 3640 cm1and 3690 cm1peaks represent the V3 vibration of the O-H of portlandite and brucite, respectively [41,42], These two minerals are the constituents of commercial lime.

[0168] For both of the salt batches (Figure 12A-12D), after 6 hr. of hydration, the peak at 3640 cm'1representing Ca(OH)2 also disappeared, remarking the consumption of portlandite. The peak at 1050 cm'1became broader, with a shoulder at 960 cm1. The latter shoulder confirms the Q2polymerization (V3 of Si-O) of calcium silicate hydrate- the primary binding phase of cementitious materials. This also confirms that the strength achievement was due to the formation of C-A-S-H, apart from gypsum and ettringite. From Figure 12E-12F, it is evident that the seawater batch reacted slower than the salt-containing batches. After 1 day of curing, the primary peak at 1050 cm'1started to become broader. For all of the samples, the peak at 3690 cm'1, corresponding to brucite, remained unchanged over the 7 days of their corresponding curing. The peak at 871 cm'1and 1420 cm'1represents the out-of-plane bending vibration (V2) and asymmetric stretching (V3) of the C-0 bond

[0040] .

[0169] The early stage FTIR spectra of the SO4 (Error! Reference source not found.c) and CI+SO4 (Figure 12A) samples revealed that within 6 hours of reaction, there was a shoulder formation at a higher wavenumber (around 1110 cm'1). This could be attributed to the symmetric stretching of S-0 present in SO42" from either gypsum or ettringite, or both

[0043] . However, this shoulder formation was not prominent in the seawater sample (Figure 12E).

[0170] The XRD was utilized to study the mineralogy of the reaction products presented in Error! Reference source not found.. The XRD spectrum of the raw binder mix (Ohr) exhibited primarily quartz, montmorillonite, portlandite, and brucite. Quartz and montmorillonite were the constituents of the medium-grade clay, and the latter two were from commercial lime. The presence of the 2: 1 layered clay component was also observed in Figure 10. The quartz remained unaltered, irrespective of curing duration [5]. As the reaction proceeded, the reaction product formation was observed. The portlandite peak disappeared after 6 hours of hydration for both CI+SO4 (Figure 13A) and SO4 (Figure 13B) samples. For the CI+SO4 sample, ettringite [Ca6A12(SO4)3(OH)i2-26H2O], hydrocalumite [Ca2Al(OH)6C1-2H2O], gypsum [CaSO4.2H2O], calcium aluminum silicate hydrate (C-A-S-H), and calcite [CaCOs] formed as reaction products. The seawater sample also exhibited similar types of reaction products as the C1+SO4specimen [6]. For the SO4sample, the reaction products were similar except for the formation of hydrocalumite. The formation of ettringite at a very early stage of reaction (6 hr.) of the SO4batch is also in agreement with Error! Reference source not found.. Over the curing duration, unreacted montmorillonite and brucite were observed for all the samples.

[0171] Chemical composition of the reaction products (BSE)

[0172] Backscattered electron (BSE) imaging coupled with Energy Dispersive Spectroscopy (EDS) was utilized to evaluate the composition of the binding gel phases along with other hydration products in the matrix of different samples. Different hydration products detected after 56 days from the BSE analysis were identified with EDS and are shown in Error! Reference source not found.. The darker region in Error! Reference source not found.A displays the gel hydration product, indicating the concurrent presence of geopolymer gel and calcium aluminum silicate hydrate (C- A-S-H). Moreover, there is clear evidence of the incorporation of magnesium ions with both of these gel phases. As observed in Error! Reference source not found., around 40 - 45% of clay remained unreacted after 28 days of hydration, which is observable from the uneven grey region (Figure 14A). The smooth grey region in the same figure signifies the presence of quartz, which came from the medium-grade impure clay. This is also consistent with the results obtained from XRD (Error! Reference source not found.A-13C). Except for these gel phases, the presence of ettringite was consistently identified in all analyzed samples. Error! Reference source not found.A- 15C show the BSE images of the hydration reaction products observed in all the analyzed samples; notably, the binder matrix exhibits a uniform appearance in all samples and is characterized by a dense matrix.

[0173] Around 100 EDS points were collected from the gel phases; the plot Error! Reference source not found, illustrates the Na / (Si+Al) vs. Ca / (Si+Al) ratio based on these points, where Alessi were utilized to represent Si replacement per Al. Addition of NaCl and Na2SO4salts substantially increased the Na / (Si+Al) ratio. As per Mota et al., sodium decreases the solubility of calcium ions and becomes incorporated in the interlayer of C-S-H, substituting calcium [44,45]. Error! Reference source not found, validates this statement, depicting that the distribution range of the Na / (Si+Al) ratio in the salt samples (-0.015-0.08) was higher relative to the seawater sample (-0.01-0.04), while the Ca / (Si+Al) ratio acted the opposite. The wide range of calcium content in the gel phases of seawater samples (Ca / Si+Al~0.1-1.3) indicates the coexistence of calcium aluminum silicate hydrate (C-A-S-H) and geopolymer gel. In contrast, the salt-containing samples primarily consisted of geopolymer gel.

[0174] Global warming potential

[0175] Error! Reference source not found, shows the global warming potential (GWP) for different calcined clay-lime binders prepared with either seawater or Na-bearing salt. The mix with NaCl and Na2SO4 salt portrayed the highest emission (16% higher) among the mixes due to having the lowest compressive strength (25 MPa) after the initial curing of 28 days. Additionally, NaCl salt contributed towards higher GWP. With comparable compressive strength and Na SCC being an industrial byproduct, the mix containing Na2SC>4 exhibited a GWP similar to that of the seawater sample. Thus, they can be interchangeably used depending on the specific purpose. Furthermore, a comparison was conducted between the GWP of these clay-lime mortar samples and that of OPC mortar. OPC undergoes a clinkerization process involving high- temperature burning, reaching up to 1500°C

[0046] , resulting in the emission of 0.915 kg of CO2 per kg, as documented in the ecoinvent 3 database. Consequently, the GWP associated with using OPC as the binder for mortar production amounts to 11 kg CO2 eq I (m3. MPa). In contrast, the use of calcine clay binders prepared with seawater or Na-bearing salt demonstrated a significant (40-50%) reduction in carbon footprint compared to OPC.

[0176] Discussion

[0177] In this study, Na2SO4, an industrial byproduct, was utilized to produce calcined clay and portlandite-based durable cementitious composites. Na2SO4, with or without the addition of NaCl solution, was utilized as the mixing water to replicate the effect of seawater. Water was sprayed on the salt-containing samples for curing, and the seawater-containing sample was cured by submerging in seawater. The reason behind choosing the spray curing regime was to develop a durable cementitious system that is comparable to the developed seawater concrete [6] for nonmarine applications. The results of these two different systems at macro and micro scales were compared.

[0178] It was found that the addition of Na2SC>4 alone to the binder accelerated the hydration reaction (Error! Reference source not found.A-8B) by gypsum and ettringite formation within the first 6 hours of hydration. The mineralogical formation was confirmed by both X-ray powder diffraction data (Figure 13B) and thermogravimetric analyses (Error! Reference source not found.). However, the addition of chloride ions, irrespective of the sources, delayed the hydration. For CI+SO4 and seawater samples, it was delayed by 2 hours and 1.25 hours, respectively (Error! Reference source not found.A-8B). For the seawater sample, the second peak of the heat flow curve was broader, which indicates the slower and prolonged hydration reaction in the seawater system. Interesting to note, Cl-based salts are well-known set accelerator for ordinary Portland cements 147 ]This study revealed that, in the presence of Al-rich precursors, the acceleration effect of Cl is reversed due to the formation of hydrocalumite.

[0179] After 6 hours, all of the portlandite added to the system was consumed in the saltcontaining specimens, whereas a reduced peak of portlandite (compared to the raw sample) was observed in the seawater sample, which is evident from Error! Reference source not found.A- 12F and Error! Reference source not found.. In spite of having a slower rate of reaction at a very early age, the seawater sample achieved compressive strength similar to the other two seawater-cured samples over 7 days (Error! Reference source not found.). Afterward, the strength remained in a comparable range (~30 MPa) for all of the samples. This finding coincides with the findings from the quantity of unreacted clay content present in the sample (Figure 9). The rate of reaction of the salt-containing batch improved by 10% and 8% for SO4 and CI+SO4 samples, respectively, whereas seawater showed a significant rate of reaction (35%) over 28 days of the curing period. This clearly indicates that the dissolution of clay was completed at a very early stage for the salt-containing samples. Noteworthy, the pH of Na2SC>4 and NaCl is close to 7. The addition of lime increased the pH of the cementitious matrix initially, which was similar for all of the specimens. The Al and Si from the precursor reacted with the Ca from commercial lime and formed gypsum, ettringite, and hydrocalumite primarily. More binding phases like geopolymer gel and C-A-S-H formed with time, and consequently, compressive strength increased. The supply of the ions came from gypsum, ettringite, and hydrocalumite due to phase alteration. This mechanism can be compared to the super sulfated cement system where the initial product formation is due to sulfate activation, and later, the phases re-assemble among themselves to form binder gels

[0048] . In super super-sulfated system, either gypsum

[0049] , hemihydrate

[0050] , or anhydrite

[0051] is added as a source of sulfate in most of the cases. In contrast, gypsum was formed as an intermediate product during the hydration process due to the reaction between readily available Ca2+and SO42" in the pore solution and later served as a source of sulfate in the SO4 and CI+SO4 specimens.

[0180] Thermogravimetric analyses after 7 days (Figure 11A-1 IB) of their corresponding curing showed pronounced product formation in the SO4 samples, followed by the CI+SO4 sample due to the formation of gypsum and ettringite which contains a large quantity of water. Compared to these two specimens, the seawater sample had a very small quantity of reaction product formation at that stage. The source of the ions in the seawater samples was seawater. Infringement of the ions in the cementitious system is usually slower and depends on several factors, including the pore solution chemistry, porosity, and degree of hydration [52,53]. This facilitated the dissolution of the Al and Si from the precursor, which reacted and formed more calcium aluminum silicate hydrate (C-A-S-H) in this specimen compared to the others. This observation is in line with the findings from section 3.2.2. On the other hand, geopolymer gel predominated in the salt-containing samples caused by the high Na incorporation into the gel phases (Figure 16). Furthermore, the life cycle assessment of these cementitious composite mortars indicated a 40-50% reduction in GWP compared to conventional Portland cement mortar. The mixes utilizing seawater and N 2SO4 exhibited comparable carbon footprints.

[0181] Conclusion

[0182] The following are the concluding remarks of this study:

[0183] I. The SO4 and Cl+SCU-containing batch achieved nearly 50% of the compressive strength within 24 hours of hydration. Nevertheless, the long-term strength of all the samples was -30 MPa.

[0184] II. The chloride ion incorporated samples delayed the hydration. For CI+SO4 and seawater samples, it was delayed by 2 hours and 1.25 hours, respectively.

[0185] III. The initial strength of the salt-containing samples came from the formation of gypsum, ettringite, and hydrocalumite. Geopolymer gel predominated in the salt-containing samples, whereas calcium aluminum silicate hydrate (C-A-S-H) gel phase was also found in the seawater sample.

[0186] IV. A reduction in the carbon footprint of up to 50% compared to OPC mortars is attainable through the application of lime-clay mortars, as investigated in this study.

[0187] In summary, employing waste Na2SO4 as an activator to produce calcined clay-based cement composites not only reduces the burden on landfills for industrial waste but also improves concrete durability. This approach has the potential to foster sustainability and resilience in the concrete industry while minimizing its carbon footprint.

[0188] REFERENCES

[0189] [1] Miller, et al., Environ Sci Technol 54 (2019) 677-686.

[0190] [2] Damtoft, et al., Cem Concr Res 38 (2008) 115-127.

[0191] [3] Borno, W et al., Adv Civ Eng Mater 11 (2022) 20210156. https : / / doi.org / l 0.1520 / ACEM20210156.

[0192] [4] Technology Roadmap Low-Carbon Transition in the Cement Industry, Paris, France, 2018.

[0193] [5] Borno, et al., Cem Concr Compos 147 (2024) 105417. https: / / doi.Org / 10.1016 / j.cemconcomp.2023.105417.

[0194] [6] Ashraf, et al., Appl Clay Sci 230 (2022) 106696.

[0195] [7] Borno, et al., Appl Clay Sci 231 (2023) 106742. 18 ] Tahsin, et al.,-, J Sustain Cem Based Mater 12 (2023) 1564-1576. https: / / doi.org / 10.1080 / 21650373.2023.2243480.

[0196] [9] Seymour, J et al., Sci Adv 9 (2023) eaddl602.

[0197]

[0010] Borno, et al., Cem Concr Res 173 (2023) 107292. https: / / doi.org / 10. 1016 / j.cemconres.2023. 107292.

[0198]

[0011] Dhondy, et al., Australian Journal of Structural Engineering 20 (2019) 280-289.

[0199]

[0012] Li, et al., Cem Concr Compos 121 (2021) 104100. https : / / doi .org / 10.1016 / j .cemconcomp .2021.104100.

[0200]

[0013] Miller, et al., Nat Sustain 1 (2018) 69-76.

[0201]

[0014] Ebead, et al., Cem Concr Res 152 (2022) 106666.

[0202]

[0015] Li, et al., Cem Concr Compos 138 (2023) 105007. https : / / doi .org / 10.1016 / j .cemconcomp .2023.105007.

[0203]

[0016] Malik, et al., Cem Concr Compos 26 (2004) 235-242. https: / / doi.org / 10.1016 / S0958- 9465(03)00042-8.

[0204]

[0017] Khalifa, et al., Cem Concr Res 132 (2020) 106050.

[0205]

[0018] Work, G.O. Smith, R.C.W. Washington, DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY SODIUM SULPHATE: ITS SOURCES AND USES GOVERNMENT PRINTING OFFICE 1 923, n.d.

[0206]

[0019] Joseph, et al., Cem Concr Compos 104 (2019) 103417. https: / / doi.Org / 10.1016 / j.cemconcomp.2019.103417.

[0207]

[0020] Xia, M et al.,=, J Clean Prod 351 (2022) 131568. https : / / doi .org / 10.1016 / j .j clepro .2022.131568.

[0208]

[0021] Garcia-Lodeiro, et al., Cem Concr Compos 39 (2013) 82-92.

[0209]

[0022] Mota, et al., Cem Concr Res 108 (2018) 172-185. https : / / doi .org / 10.1016 / j .cemconres .2018.03.017.

[0210]

[0023] Velandia, et al., Constr Build Mater 128 (2016) 248-255. https: / / doi.Org / 10.1016 / j.conbuildmat.2016.10.076.

[0211]

[0024] Marangu, et al., J Chem 2018 (2018) 1-8. https: / / doi.org / 10-l 155 / 2018 / 1595230.

[0212]

[0025] Shen, et al., ACS Sustain Chem Eng 11 (2023) 5164-5174. https: / / doi.org / 10.1021 / acssuschemeng.2c07495.

[0213]

[0026] Scrivener, et al., Crc Press Boca Raton, FL, USA:, 2016.

[0214]

[0027] Puligilla, et al., Cem Concr Res 70 (2015) 39-49. https : / / doi .org / 10.1016 / j .cemconres .2015.01.006. |28| Sagastume Gutierrez et al., J Clean Prod 168 (2017) 463-473. https : / / doi .org / 10.1016 / j .j clepro .2017.09.007.

[0215]

[0029] Damineli, et al., Cem Concr Compos 32 (2010) 555-562. https : / / doi .org / 10.1016 / j .cemconcomp .2010.07.009.

[0216]

[0030] Habert, et al., 2013. https: / / doi.Org / 10.1533 / 9780857097729.2.199.

[0217]

[0031] Pradhan, et al., J Clean Prod 342 (2022). https: / / doi.Org / 10.1016 / j.jclepro.2022.130847.

[0218]

[0032] Diaz-Basteris, et al., Constr Build Mater 326 (2022). https : / / doi .org / 10.1016 / j .conbuildmat.2022.126863.

[0219]

[0033] Declaration of conformity for products with Model EPDs, 2022.

[0220]

[0034] Tahsin, et al., J Sustain Cem Based Mater (2023). https: / / doi.org / 10.1080 / 21650373.2023.2243480.

[0221]

[0035] Zheng, C et al., Cem Concr Res 22 (1992) 1-5. https: / / doi.org / 10.1016 / 0008- 8846(92)90129-1.

[0222]

[0036] Chen, et al., J Solgel Sci Technol 96 (2020) 589-603.

[0223]

[0037] Taylor, Cement chemistry, Thomas Telford London, 1997.

[0224]

[0038] Fernandez, et al.,-, Cem Concr Res 41 (2011) 113-122.

[0225]

[0039] Hanein, et al., Mater Struct 55 (2022) 3.

[0226]

[0040] Haque, et al., Cem Concr Compos 136 (2023) 104888.

[0227]

[0041] Zarzuela, et al., Cem Concr Res 130 (2020) 106008. https: / / doi.Org / 10.1016 / j.cemconres.2020.106008.

[0228]

[0042] Qu, et al., J Mater Sci 53 (2018) 396-408. https: / / doi.org / 10.1007 / sl0853-017-1503-x.

[0229]

[0043] Yaseen, et al., ACS Omega 4 (2019) 10160-10170.

[0230]

[0044] Mota, et al., Cem Concr Res 108 (2018) 172-185. https: / / doi.Org / 10.1016 / j.cemconres.2018.03.017.

[0231]

[0045] Lothenbach, et al., Cem Concr Res 78 (2015) 57-70. https: / / doi.Org / 10.1016 / j.cemconres.2015.03.019.

[0232]

[0046] He, et al., Constr Build Mater 211 (2019) 965-973. https: / / doi.Org / 10.1016 / j.conbuildmat.2019.03.289.

[0233]

[0047] Montanari, et al., Journal of Materials in Civil Engineering 31 (2019) 04019154.

[0234]

[0048] Wu, Q et al., J Clean Prod 294 (2021) 126228. https : / / doi. org / 10.1016 / j .j clepro.2021. 126228.

[0235]

[0049] Pinto, et al., Cem Concr Res 136 (2020) 106172. https: / / doi.Org / 10.1016 / j.cemconres.2020.106172. 150] Cabrera-Luna, E et al., Constr Build Mater 176 (2018) 145-155. https : / / doi . org / 10. 1016 / j .conbuildmat.2018.05.024.

[0236]

[0051] Angulski da Luz, et al., Cem Concr Res 77 (2015) 69-75. https: / / doi.Org / 10.1016 / j.cemconres.2015.07.002.

[0237]

[0052] Gao, et al., Constr Build Mater 145 (2017) 361-366. https: / / doi.org / 10. 1016 / j. conbuildmat.2017.03.220.

[0238]

[0053] Lloyd, et al., Cem Concr Res 40 (2010) 1386-1392. https: / / doi.Org / 10.1016 / j.cemconres.2010.04.008.

[0239] Vogel, et al., Journal of Geophysical Research : Atmospheres 9485-9514. https: / / doi.org / 10.1002 / 2016JD026328

[0240] Ababneh, A., Matalkah, F., Matalkeh, B., 2022. Effects of kaolin characteristics on the mechanical properties of alkali-activated binders. Constr Build Mater 318. https : / / doi .org / 10.1016 / j .conbuildmat.2021.126020

[0241] Alonso, et al., 2001. Alkaline activation of metakaolin and calcium hydroxide mixtures : influence of temperature , activator concentration and solids ratio. Mater Lett.

[0242] Alonso, Santiago, Palomo, A., 2001. Calorimetric study of alkaline activation of calcium hydroxide ± metakaolin solid mixtures. Cem Concr Res 31.

[0243] Amilton, J.A.P.H., Rantley, S.U.L.B., Antano, C.A.G.P., Riscenti, L.O.J.C., Ubicki, J.A.D.K., 2001. Dissolution of nepheline Jadeite and albite glasses : Toward better models for aluminosilicate dissolution. Geochim Cosmochim Acta 65, 3683-3702.

[0244] Ashraf, W., 2018. Microstructure of chemically activated of gamma-dicalcium silicate paste. Constr Build Mater 185, 617-627. https: / / doi.Org / 10.1016 / j.conbuildmat.2018.07.030

[0245] Bonjean, S., Chandrasiri, P., Pimraksa, K., 2014. Lime-calcined clay materials with alkaline activation : Phase development and reaction transition zone. Appl Clay Sci 95, 357-364. https : / / doi.org / 10.1016 / j .clay .2014.05.002

[0246] Chen, et al., 2018a. Effects of calcium on setting mechanism of metakaolin-based geopolymer. Journal of the American Ceramic Society 101, 957-968 https: / / doi.org / 10. I l l 1 / jace.15249

[0247] Chen, et al., 2018b. Effects of calcium on setting mechanism of metakaolin-based geopolymer. Journal of the American Ceramic Society 101, 957-968.

[0248] 541 https: / / doi.org / 10.l ll l / jace.15249.

[0249] Ashraf, et al., Applied Clay Sci., 230, 2022,

[0250] 106696, ISSN 0169-1317, https: / / doi.Org / 10.1016 / j.clay.2022.106696.

[0251] Bediako et al. Journal of Engineering. 2016:Article ID 7210891 (2016). Aras, et al, Clay Miner. 42 (2007) 233-244.

[0252] Alutas, et al, Appl Clay Sei. 108 (2015) 94-101. West, D. N. Clays, in U.S. Geological Survey, Mineral Commodity Summaries 48-49 (2019). doi: 10.1017 / CBO9781107415324.004.

[0253] Mineral Resources Data System, https: / / mrdata.usgs.gov / mrds / map- commodity ,html#home.

[0254] Scrivener, K., Martirena, F., Bishnoi, S. & Maity, S. Calcined clay limestone cements (LC3). Cement and Concrete Research 114, 49-56 (2018).

[0255] It is understood that the disclosed method and compositions are not limited to the particular methodology, protocols, and reagents described as these can vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention which will be limited only by the appended claims.

[0256] Those skilled in the art will recognize, or be able to ascertain, using no more than routine experimentation, many equivalents to the specific embodiments of the method and compositions described herein. Such equivalents are intended to be encompassed by the following claims.

Claims

CLAIMSWe claim:

1. A Recreated Roman Cement (Rocca) composition comprising (i) calcined clay, (ii) hydraulic lime, and optionally, (iii) ground granulated blast furnace slag (GGBFS).

2. The composition of claim 1, comprising between about 30- 70% by wt. medium grade clay.

3. The composition of claim 1 or 2, comprising about 10-40% by wt. hydraulic lime.

4. The composition of any one of claims 1-3, comprising about 0-40% by weight GGBFS.

5. The composition of any one of claims 1-4, comprising between about 55 and 65 % by wt. medium grade clay.

6. The composition of aby one of claims 1-5 comprising between about 10 and about 20 % by weight hydraulic lime.

7. The composition of any one of claims 1-6, comprising 0% by weight GGBFS.

8. The composition of any one of claims 1-7, comprising between about 10 and 35 % by weight GGBFS.

9. The composition of any one of claims 1-8, in the form of a solid.

10. The composition of any one of claims 1-8, wherein the calcined clay comprises medium grade clay calcined at least 55O°C.

11. The composition of any one of claims 1-8, further comprising sodium sulphate (Na2SO4) and / or sodium chloride (NaCl).

12. The composition of claim 10, further comprising sea water or fresh water.

13. The composition of claim 12, further comprising fresh water.

14. The composition of any one of claims 11-13, wherein the Na2SO4 and / or NaCl is at a concentration between about 5-15 g / lOOg Rice,15. A Recreated Roman concrete (Ricco) comprising the composition of any one of claims 1-14 and a coarse aggregate.

16. The composition of any one of claims 1-12, wherein, when formed into mortar 50 x 50 x 50 mm mortar cubes have a compressive strength ranging from about maximum strength (31 MPa).

17. A method of making a composition of cany one of claims 1-9, comprising combining (i) calcined clay, (ii) hydraulic lime, and optionally, (iii) ground granulated blast furnace slag (GGBFS).

18. A method of making Recreated Roman concrete comprising combining the composition of any one of claims 1-14 with a coarse aggregate.

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