Methods of analyzing supplementary cementitious materials (SCMS) and predicting the behavior of scms in cementitious mixtures

Abstract

A method of analyzing a supplementary cementitious material (SCM) may include obtaining a sample comprising a SCM; submerging the sample in an alkaline or acidic aqueous solution, whereby the sample undergoes dissolution; determining an ion concentration in the alkaline or acidic aqueous solution at a predetermined time after submerging the sample; and predicting the reactivity of the SCM in a cementitious mixture based on the ion concentration. In another implementation, a method of analyzing a SCM may include obtaining a sample comprising a SCM; positioning the sample on a porous substrate in contact with a water supply; measuring a change in water level of the water supply as the sample absorbs water through the porous substrate; and determining water absorption of the sample. The water absorption may be predictive of yield stress and / or viscosity of a cementitious mixture including the SCM.

Description

METHODS OF ANALYZING SUPPLEMENTARY CEMENTITIOUS MATERIALS (SCMs) AND PREDICTING THE BEHAVIOR OF SCMs IN CEMENTITIOUS MIXTURESRELATED APPLICATION

[0001] The present patent document claims the benefit of priority to U.S. Provisional Patent Application 63 / 538,623, which was filed on September 15, 2023, and is hereby incorporated by reference in its entirety.FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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

[0003] The present disclosure is related generally to the analysis of supplementary cementitious materials (SCMs) and, more particularly, to methods to rapidly analyze SCMs such as clays, either in pristine condition or subjected to activation, and predict their performance in cementitious mixtures.BACKGROUND

[0004] More than 4 billion tons of cement are produced globally every year, which accounts for 6-8% of CO2 emissions. The use of supplementary cementitious materials (SCMs) to replace part of the clinker in cement is the most successful strategy to reduce CO2 emissions in the global cement industry. However, limited supplies of conventional SCMs make it difficult to take this strategy further unless new types of SCMs become available. One type of material available in the quantities needed to meet that demand is clay, which can be calcined to produce an effective SCM. To be usable in construction materials, certain reactivity is required to facilitate the development of material strength. Clays calcined at 700 - 850 °C show optimal reactivity in cementitious mixtures but transform into less-reactive crystalline phases when calcined at higher temperatures. In industrial-scale production, clays can originate from various sources, contain diverse mineral compositions, experience different calcination temperatures, have different particle sizes due to grinding, and / or can be subjected to mechanochemical activation, all of these resulting in variations in reactivity. Theevaluation of the reactivity would be advantageous for quality control of clay activation. However, current reactivity tests are time and labor-intensive. For example, the ASTM Cl 897 R3method requires up to 7 days of testing time and a trained technician.

[0005] The presence of clays in the cementitious mixture modifies its rheology.Moreover, the calcination temperature impacts the physical-hygroscopic properties of clays and directly influences the rheology (or workability) of cementitious mixtures. The use of clay as SCMs increases the water demand for desired workability, with the extent depending on its composition, particle size, and calcination temperatures. Therefore, it is beneficial to quantify the rheological properties of clays to ensure their suitability for practical application. The current ASTM standard C1749 for rheology is applicable to pure cementitious systems and is extremely sensitive to sample preparation. Execution of ASTM C1749 also requires meticulous training to minimize the variability in the results, particularly for SCMs such as reactive clays.SUMMARY

[0006] Methods of analyzing supplementary cementitious materials (SCMs) and predicting the behavior of SCMs in cementitious mixtures are described in this disclosure.

[0007] A method of analyzing SCM includes, according to one implementation: obtaining a sample comprising a SCM; submerging the sample in an alkaline or acidic aqueous solution, whereby the sample undergoes dissolution; determining an ion concentration in the alkaline or acidic aqueous solution at a predetermined time after submerging the sample; and predicting reactivity of the SCM in a cementitious mixture based on the ion concentration.

[0008] A method of analyzing a SCM includes, according to another implementation: obtaining a sample comprising a SCM; positioning the sample on a porous substrate in contact with a water supply; measuring a change in water level of the water supply as the sample absorbs water through the porous substrate; and determining water absorption of the sample, the water absorption being predictive of yield stress and viscosity of a cementitious mixture including the SCM.

[0009] A method for predicting the behavior of clays in cementitious mixtures includes: after activation has occurred, obtaining one or more samples from a clay mass, each sample comprising an activated clay, the one or more samples including or being divided into first and second samples; determining, at a predetermined time, a concentration of silicon ions and a concentration of aluminum ions in respective first and second batches of an alkaline oracidic aqueous solution containing the first sample; determining water absorption of the second sample; predicting reactivity of the activated clay in a cementitious mixture based on the concentrations of silicon and aluminum ions; predicting yield stress and / or viscosity of a cementitious mixture including the activated clay based on the water absorption; and adjusting activation conditions of the clay mass if the predicted reactivity, yield stress, and / or viscosity is non-optimal.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a schematic showing an example of a continuous calcination process followed by the collection of a calcined clay sample.

[0011] FIG. 2 illustrates two approaches to colorimetric analysis for determining the ion concentration of the calcined clay or other SCM sample after being submerged in an alkaline aqueous solution.

[0012] FIGS. 3A-3C illustrate dissolution of an exemplary calcined clay sample, followed by optional filtration and dilution steps.

[0013] FIGS. 4A-4C illustrate exemplary steps in the analysis of SCMs, including obtaining multiple batches of the alkaline aqueous solution, adding one or more chemicals (or color agents) to each batch, and conducting colorimetric analysis using UV-vis spectroscopy or photographic image analysis.

[0014] FIGS. 4D and 4E illustrate calibration approaches for the UV-vis spectroscopy and photographic image analysis.

[0015] FIG. 5 plots data for a number of clay samples showing a strong correlation between ion concentration results obtained using the rapid analysis method of this disclosure and R3 cumulative heat results obtained according to ASTM Cl 897.

[0016] FIG. 6A illustrates an approach to measuring water absorption of the calcined clay or other SCM sample.

[0017] FIG. 6B shows an exemplary plot of water absorption as a function of time.

[0018] FIGS. 6C and 6D show perspective views of an alternative set-up for measuring water absorption.

[0019] FIG. 7A plots data for a number of samples showing a strong correlation between absorption results obtained using the rapid analysis method of this disclosure and the yield stress of the cement, cement / fly ash blends, and cement / clay blends measured via rheometer.

[0020] FIG. 7B plots data for a number of samples showing a strong correlation between absorption results obtained using the rapid analysis method of this disclosure and theviscosity of the cement, cement / fly ash blends, and cement / clay blends measured via rheometer.

[0021] FIGS. 8A-8C show evolution of cumulative heat release measured by isothermal calorimeter with the duration of R3test for high grade kaolinite, Na-montmorillonite, and a 70 / 30 illite / smectite mixed layer, respectively.

[0022] FIG. 8D shows seven-day cumulative heat release for the samples calcined at 400- 1000 °C; uncalcined samples are plotted at 25 °C.

[0023] FIGS. 9A-9C show aluminum (Al) concentrations, silicon (Si) concentrations, and Si / Al ratios, respectively, during the dissolution of uncalcined high-grade kaolinite as well as high-grade kaolinite calcined at different temperatures in 4M NaOH solution at 90 °C. The x- axis in all figures is time (minutes).

[0024] FIGS. 10A-10C show Al concentrations, Si concentrations, and Si / Al ratios, respectively, during the dissolution of uncalcined Na-montmorillonite as well as Na- montmorillonite calcined at different temperatures in 4M NaOH solution at 90 °C. The x-axis in all figures is time (minutes).

[0025] FIGS. 11A-11C show Al concentrations, Si concentrations, and Si / Al ratios, respectively, during the dissolution of 70 / 30 uncalcined illite / smectite mixed layer as well as 70 / 30 illite / smectite calcined at different temperatures in 4M NaOH solution at 90 °C. The x- axis in all figures is time (minutes).

[0026] FIGS. 12A and 12B show the correlations between the Al concentrations and Si concentrations determined using camera image analysis and a UV-vis spectrophotometer.

[0027] FIGS. 13A-13C show correlations between the 7d cumulative R3heat and the dissolved Al concentrations at 1-15 min from high grade kaolinite, Na-montmorillonite, and 70 / 30 illite / smectite mixed layer calcined at different temperatures.

[0028] FIG. 13D shows the R-squared value (R2) of the correlations in FIGS. 13A-13C.

[0029] FIGS. 14A-14C show correlations between the 7d cumulative R3heat and the dissolved Si concentrations at 1-15 min from high grade kaolinite, Na-montmorillonite, and 70 / 30 illite / smectite mixed layer calcined at different temperatures; uncalcined samples are plotted at 25 °C.

[0030] FIG. 14D shows the R2of the correlations in FIGS. 12A-12C.

[0031] FIGS. 15A-15C show correlations between the 7d cumulative R3heat and the Al concentrations, the Si concentrations, and the dissolved mass of AI2O3 and SiO2 dissolved within 5 min from high-grade kaolinite, Na-montmorillonite, and 70 / 30 illite / smectite mixed layer calcined at different temperatures and commercial metakaolin samples C1-C5;uncalcined samples are plotted at 25 °C. Error bars show the standard error between replicate tests.

[0032] FIG. 16A shows correlations between the 7d cumulative R3heat and the dissolution index, 1.54 times of Al concentration plus Si concentration, dissolved within 5 min from high grade kaolinite, Na-montmorillonite, and 70 / 30 illite / smectite mixed layer calcined at different temperatures; uncalcined samples are plotted at 25 °C. Error bars show the standard error between replicate tests.

[0033] FIG. 16B shows the correlations after adding natural clays N1-N17.

[0034] FIG. 16C shows the correlations between the 7d cumulative R3heat and the index, 1.54 Al + Si, using the Al and Si concentrations from calcined samples subtracting dissolved Al and Si from uncalcined samples. For commercial metakaolin, the dissolved Al and Si from uncalcined high grade kaolinite were subtracted.

[0035] FIG. 17 shows the applicability of the UR2method described in this disclosure on another type of SCM, coal fly ash. For various fly ash samples, the dissolved concentration of Al at 15 min of dissolution is multiplied by a factor of 0.4 and added to the dissolved concentration of Si at 15 min of dissolution to form a 15 min UR2dissolution index, and its correlation with the 7d R3 results is shown.DETAILED DESCRIPTION

[0036] As indicated above, activated clay is an important supplementary cementitious material (SCM) for meeting the growing demand of the cement industry and reducing its carbon footprint. A real-time method for predicting the behavior of clays and other SCMs in cementitious mixtures during industrial production is explained in reference to FIG. 1. In addition to unactivated and activated (e.g., calcined) clays, the method may be applicable to SCMs such as fly ash, silica fume, reclaimed ash, ground granulated blast furnace slags, nonferrous slags, steel slags, copper slags, natural pozzolan, ash from agriculture waste, waste to energy ash, waste glass, bauxite residue, limestone, zeolites, and / or filler materials. The concentrations of the major elements present in the respective SCMs, measured through rapid dissolution of the SCM, and their water uptake capacity can be key factors in determining their performance. The term “cementitious mixture” or “cementitious mixture including the SCM” may be understood to refer to a mixture that may include some or all of the following constituents: one or more SCMs, cement, cement clinker, water, and / or other additive(s). In some examples, the cementitious mixture may comprise concrete.

[0037] It is understood that activated clays may be produced by thermal activation (e.g., heating or calcination), mechanical activation, and / or mechanochemical activation of clay minerals such as hydrous aluminum phyllosilicates, including alumina, silica and possibly other phases. Calcination in particular is illustrated in FIG. 1 and discussed below. Mechanical or mechanochemical activation may be understood to entail using mechanical energy (e.g., grinding) to induce activation of the clay minerals. During activation (e.g., thermal, mechanical, mechanochemical), the hydroxyl (OH) group is released from the clay minerals and water is formed. Following the structural changes due to dehydroxylation, AI2O3 and SiO2 in the activated clay may become reactive; the extent of reactivity may depend, for example, on the calcination temperature or mechanochemical activation conditions (e.g., grinding time). (Reactive AI2O3 and SiO2can contribute to the formation of calcium aluminosilicate hydrates during the pozzolanic reaction of activated clay in cementitious mixtures, which can refine the micro structure and improve the mechanical strength of activated clay-blended cementitious materials. Thus, reactivity is a key aspect in determining the suitability of an activated clay for use in a cementitious mixture.) Clays may include any of a number of mineral phases, such as kaolinite, montmorillonite, illite, and / or smectite, at varying mass percentages. Low-grade clays containing, for example, less than 20% kaolinite, can be obtained from natural mineral and waste deposits in various locations and may contain several mineral phases and other components. Such low homogeneity of clay sources makes real-time reactivity monitoring advantageous if not necessary for separating unreactive, moderately reactive, and highly reactive activated clays.

[0038] Referring to FIG. 1, the method includes obtaining a sample 102 comprising a SCM for the analysis. In some examples, the sample 102 may be obtained from a clay mass 104 after calcination has occurred, e.g., after being conveyed through a heating zone 106a of a kiln 106 in a continuous process, as illustrated in FIG. 1. Typically, industrial scale calcination takes place in a kiln calciner or a flash calciner. In this disclosure, references to a kiln may be understood to refer to either of these calciners. It is understood that the clay mass 104 comprises clay minerals. In the kiln 106, the clay mass 104 may be exposed to an elevated temperature (e.g., the calcination temperature) for a residence time determined by the rate at which the clay mass 104 is transported through the heating zone 106a. As illustrated in FIG. 1, a conveyer belt 108 may be employed to transport the clay mass 104 through the kiln 106. In other examples, the class mass 104 may be exposed to the elevated temperature in a batch process, e.g., the clay mass 104 may be placed in a furnace for calcination. Alternatively, the sample 102 may be obtained from a clay mass 104 aftergrinding or other mechanochemical activation has taken place. In some examples, the sample 102 may be obtained from a pristine (unactivated) clay mass prior to processing, e.g., directly from a quarry or clay pit. It is also contemplated that the sample 102 may be obtained after co-grinding or mixing with one or more other materials, such as cement, limestone, or gypsum, for example. If the sample 102 comprises a non-clay SCM as described above, the sample may be obtained from a quarry, an agricultural source, or an industrial source. Typically, the sample 102 may take the form of powder, particles, agglomerates, and / or granules.

[0039] As indicated above, the sample 102 may in some examples be obtained postcalcination (or, more generally speaking, post-activation) either in real-time during a continuous process, or after completion of a batch process. In the example shown in FIG. 1, after the clay mass 104 leaves the heating zone 106a of a kiln 106, the sample 102 falls by gravity through an opening 110 in the conveyer belt 108 into a collection receptacle 112. Alternatively, other collection strategies may be used to obtain the sample 102. Multiple samples 102 may be obtained from the clay mass 104 and / or a single sample 102 may be separated into multiple samples 102 for analysis. An amount of the sample 102 required for the rapid dissolution and water absorption analyses described below is typically less than 500 grams, less than 200 grams, less than 100 grams, less than 50 grams, less than 20 grams, less than 10 grams, less than 5 grams, less than 2 grams, or less than 1 gram, and / or as low as 0.1 gram, as low as 0.01 gram, or as low as 0.001 gram, e.g., from 0.1 gram to 0.5 gram, or from 0.1 gram to 0.3 gram. The analyses may be carried out in a short time so that modifications can be made in-line to the calcination or activation conditions (e.g., the elevated temperature, residence time, grinding time, etc.), as needed. For example, the ion concentration and absorption analyses may each be carried out in 15 minutes or less, in 5 minutes or less, or even in 2 minutes or less.

[0040] The rapid dissolution analysis method is described first. Once the sample 102 is obtained, e.g., from the clay mass 104, as illustrated in FIG. 1, it may be submerged in an alkaline aqueous solution 114, typically at a temperature in a range from 25 °C to 100°C, or from 60°C to 95°C. The alkaline aqueous solution 114 may include a base such as sodium hydroxide (NaOH), potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, and / or lithium carbonate and water. In one example, the alkaline aqueous solution comprises a 4M NaOH solution. In other examples, an acidic aqueous solution including hydrochloric, nitric and / or sulfuric acid in water may be used in place of the alkaline aqueoussolution. Upon being submerged, the sample 102 begins to dissolve, as illustrated in the leftmost schematic of FIG 2.

[0041] Of interest is determining ion concentration in the alkaline or acidic aqueous solution 114 at a predetermined time or at predetermined times after submerging the sample 102, as dissolution rate is correlated with reactivity. The determination may be made rapidly, e.g., within 60 minutes, within 30 minutes, within 15 minutes, within 5 minutes, within 2 minutes, or within 1 minute of submerging the sample 102. The ions of interest may include aluminum, silicon, calcium, sodium, potassium, magnesium, iron, and / or sulfur. Ion concentrations can be determined using a suitable analytical technique, such as colorimetric analysis, atomic adsorption spectroscopy, optical emission spectroscopy, mass spectroscopy, titration, selective ion electrode, precipitation, chromatography, fluorescence spectroscopy, and / or electrophoresis. In some examples, multiple batches of the alkaline or acidic aqueous solution may be obtained, where each batch contains a dissolving sample and is used for determining the concentration of a different ion. As discussed below, the dissolution results obtained for clays according to the method described in this disclosure are consistent with the pozzolanic reactivity determined using the ASTM Cl 897 R3isothermal calorimetry method. Accordingly, the ion concentration(s) determined by the rapid analysis method may be used to predict the reactivity of the SCM in a cementitious mixture.

[0042] After dissolution, which is illustrated for an exemplary calcined clay sample in FIG. 3A, and prior to carrying out the colorimetric analysis or another analytical technique, the method may further comprise filtering (FIG. 3B), diluting (FIG. 3C), and / or acidifying the alkaline or acidic aqueous solution or the multiple batches of the alkaline or acidic aqueous solution.

[0043] Colorimetric analysis, which is illustrated in FIG. 2 and in FIG. 4C, is of particular interest for determining ion concentrations. In preparation for colorimetric analysis, one or more chemicals 116 configured to induce a color change in the presence of the particular ion of interest may be added to the alkaline or acidic aqueous solution 114 (or to each batch of the alkaline or acidic aqueous solution 114), as illustrated in FIG. 2 and FIG. 4B. The one or more chemicals 116, or “color agents,” may be selected from, for example, molybdate, eriochrome cyanine R, chrome azural S, lumogallion, oxine, salicylaldehyde picolinoylhydrazone, morin, pyrocatechol violet, quercetin, ferron, aluminon, and / or o- cresolphthalein Complexone. In addition to the chemical(s) 116 added to induce the color change, a pH buffer, reducer, and / or masking agents may be added to the alkaline or acidic aqueous solution 114. These may help to control pH of the alkaline or acidic aqueoussolution, remove interference from other ions, and / or enhance color detection, and may be selected from hydrochloric acid, acetate, oxalic acid, amino-naphthol- sulfonic acid, and / or ascorbic acid. The intensity of the color change may be correlated with the concentration of the particular ion of interest using a method such as UV-vis spectroscopy or photographic image analysis, as indicated by the schematics in FIG. 4C and described below.

[0044] In one example, where two batches of the alkaline or acidic aqueous solution 114 are obtained and concentrations of aluminum and silicon ions are to be determined, the one or more chemicals 116 may include a first set of chemicals configured to induce a color change according to the presence of silicon ions and a second set of chemicals configured to induce a color change according to the presence of aluminum ions. The first set of chemicals (which may include a single chemical or multiple chemicals) may be added to one of the two batches of the alkaline or acidic aqueous solution, and the second set of chemicals (which may include a single chemical or multiple chemicals) may be added to the other of the two batches. To determine silicon ion concentration, the first set of chemicals may be selected according to ASTM D859: Standard Test Method for Silica in Water. To determine aluminum ion concentration, the second set of chemicals may be selected according to 3500- Al B: Eriochrome Cyanine R Method.

[0045] As indicated above, colorimetric analysis may be carried out using UV-vis spectroscopy. With UV-vis spectroscopy, the dissolving sample 102 may be illuminated with ultraviolet and / or visible light, and an absorbance spectrum 118 may be obtained as a function of wavelength using a spectrophotometer 120, as illustrated in the lower pathway of FIG. 2. More typically, the method may be carried out by measuring absorbance at a predetermined wavelength. Absorption of light occurs at different wavelengths for different ions. In some examples, the wavelength corresponding to the maximum absorbance of the particular ion of interest is chosen for analysis to ensure maximum sensitivity, although other wavelengths may also be suitable.

[0046] Prior to conducting UV-vis spectroscopy to determine the ion concentration in the alkaline or acidic aqueous solution 114, absorbance spectra for a series of reference solutions having known ion concentrations may be obtained, as illustrated in FIG. 4D, and these may be used to construct a plot of absorbance versus concentration. A calibration curve may be created using a least squares linear regression equation, and this equation may be employed to determine the concentration of the particular ion of interest in an unknown sample based on the measured absorbance. Accordingly, the concentrations of the particular ions of interest(e.g., silicon and aluminum ions) may be determined based on the absorbance spectra 118 for the sample 102.

[0047] Alternatively, colorimetric analysis may be carried out using photographic image analysis. In this case, determining the ion concentrations may entail obtaining a photographic image of the sample 102 using a camera 122, as illustrated schematically in the upper pathway of FIG. 2, and converting the photographic image to red-green-blue (RGB) format. Mean luminance intensity values may be obtained for the red, green and blue channels, and the mean luminance intensity values can be normalized to a range of 0 to 1. Using calibration data obtained from reference solutions having known ion concentrations, concentrations of the ions (e.g., silicon and aluminum ions) in the alkaline or acidic aqueous solutions 114 may be determined based on the normalized luminance intensity values. It is also contemplated that the colorimetric analysis may be carried out via visual comparison of the alkaline or acidic aqueous solution 114 with the reference solutions (e.g., using the naked eye).

[0048] As discussed in the examples below, the reactivities of a series of pure clays (kaolinite, montmorillonite, illite / smectite mixed layer), uncalcined as well as calcined, and several commercial calcined clays (25 different clays in total) were evaluated using an isothermal calorimeter according to the ASTM Cl 897 standard method and the ion concentration data obtained using the rapid dissolution. The results, which are presented in FIG. 5, reveal a strong correlation between the 7-day ASTM standard test and the 5-min (in these examples) dissolution analysis method. Based on the dissolution enthalpy of alumina and silica, a predetermined factor is applied to (multiplied by) the Al concentration in pM and added to the Si concentration in p M. The predetermined factor may be in a range from 1.1 to 1.7, or more preferably from 1.2 to 1.6, e.g., about 1.5 or more specifically 1.54 for some clay samples. For other SCMs, such as fly ash, the predetermined factor may be different, such as in a range from 0.2 to 0.6, or more preferably 0.4. The predetermined factor may in some examples be as low as zero. Accordingly, the ion concentration(s) determined as described in this disclosure may be used to predict the reactivity of the clay, or more generally speaking the SCM, in a cementitious mixture.

[0049] The method may also or alternatively include predicting the workability (rheology) of a cementitious mixture including the SCM. For example, the yield stress and / or viscosity of the cementitious mixture (e.g., at room temperature (e.g., 18-22°C)) may be predicted based on water absorption of the SCM, as described below. The sample 102 comprising the SCM may be obtained as described above, e.g., in reference to FIG. 1. Once obtained, the sample 102 may be positioned on a porous substrate 124 in contact with a watersupply 126, as shown in FIG. 6A. The porous substrate 124 may comprise filter paper or another porous material. A burette 128 including a u-curve and positioned in a horizontal configuration at a level equal to the filter paper 124 may be employed to hold the water supply. In one example, the burette 128 may have a capacity of 10 ml of water or greater with a division of 0.1 ml. The inner diameter of the burette 128 defines the resolution of water uptake capacity measurement. A porous substrate 124 having a small pore size (e.g., 0.2 micron or less) may help to avoid filtering of clay particles. A camera 122 may be placed adjacent to the burette 128 to observe the change in the water level upon placement of the sample 102 on the filter paper 124. The amount of the SCM employed can vary from 0.1 gram to 2 grams or more. Smaller amounts can cause inconsistency due to mass measurement and sample placement, and larger amounts can increase the amount of time for water absorption.

[0050] As the sample 102 absorbs water through the filter paper or other porous substrate 124, a change in the water level of the water supply 146 may be measured (e.g., using the camera 122, as illustrated). More specifically, as the sample 102 absorbs water, the water level of the water supply 146 decreases, and thus the amount of water absorbed by the sample 102 may be determined based on the measured decrease. An exemplary plot of water absorption as a function of time is shown in FIG. 6B. The water absorption of a SCM may be an indicator of its rheological properties in use, where a highly absorbent SCM has less water available for the cementitious mixture to flow. Water absorption may thus be an indicator of the need for superplasticizers to improve workability. Alternatively, the adsorption setup can be modified as shown in FIGS. 6C and 6D, where a pump 129 can be added to the system to refill the water automatically from a water reservoir on one end. Moreover, the burette 128 can be modified to have a serpentine pattern, maintaining the same height, such that multiple samples can be analyzed by refilling the burette 128 with water one time, either manually or through the pump 129.

[0051] A greater amount of water absorption is correlated with a higher yield stress (or yield strength) and viscosity of a cementitious mixture that includes the SCM (e.g., the calcined clay), as illustrated in FIGS. 7A-7B. Rheological properties, such as yield stress and viscosity, may be indicative of concrete’s fresh properties, such as mini-slump spread, stickiness, filling capacity, passing ability, pumping, placing, handling, and finishing. The results shown in FIGS. 7 A and 7B were obtained for sixteen calcined clays (14 commercial clays and 2 kaolinitic clays calcined at 600 °C and 800 °C, respectively) and four Type IL Ordinary Portland cements (OPC) and three fly ashes. A rheometer was used to measure therheology of a cement / SCM (80:20) blend in case of the calcined clays and fly ashes, and 100% cement in the case of the Type IL cements for a water / binder ratio of 0.5. The set-up of FIG. 6A was used to measure water absorption. In these examples, a 0.7 pm filter paper was placed on a filter holder which was connected to a burette in a horizontal layout at a level equal to the filter paper, as illustrated in FIG. 6 A. The burette may be a Kimex 51, which has a capacity (10 ml) sufficient for a sample of 0.3 gram in size. A higher amount of clay can be analyzed using a longer burette or modified geometry, as shown in FIG. 6D. The total time for the measurement was less than 3 min in this example. As can be seen, the water demand of the clay shows a strong correlation with the yield stress and viscosity of the cement / SCM (fly ash and calcined clay) blend and 100% cement. Accordingly, the rapid water absorption results described in this disclosure may be used to predict yield stress and viscosity of a cementitious mixture including the unactivated or activated clay of different cement / SCM ratios, e.g., at least 50:50 or as high as 50:50, at least 55:45 or as high as 55:45, at least 60:40 or as high as 60:40, at least 65:35 or as high as 65:35, at least 70:30 or as high as 70:30, at least 75:25 or as high as 75:25, at least 80:20 or as high as 80:20, at least 85:15 or as high as 85:15, at least 90:10 or as high as 90:10, and / or at least 95:5 or as high as 95:5, once the calibration curve is generated. Furthermore, the rapid water adsorption method can be employed to measure the demand for water reducers and / or superplasticizers in the cement system once the calibration curve has been established. Water absorption by SCMs, which is greater for particles with a large surface area and internal porosity, can decrease the effective water content in the system. This decrease in water can increase particle-particle contact and forces, ultimately reducing flow properties of the cementitious mixture such as yield stress and / or viscosity. Therefore, water reducers or superplasticizers may be added to counteract the higher interparticle forces caused by SCMs. Superplasticizer demand is typically determined by adjusting the water reducer's or superplasticizer's dosage to achieve a specific flow, a process that can be labor-intensive and requires multiple flow-related tests involving systematic dosage variation. It is possible to utilize the relation between water adsorption and the water reducer or superplasticizer demand to predict the water reducer or superplasticizer demand of SCMs rapidly. To do so, a calibration curve relating the demand for an individual water reducer or superplasticizer for different SCMs, and their water adsorption can be established. Such a calibration curve can be used to rapidly test the water reducer or superplasticizer demand for new SCMs. The water reducers and superplasticizers are defined by ASTM C49. Chemically, they can be based on, but are not limited to, lignosulfonic acid, modified lignosulfonates, hydroxycarboxylic acid, hydroxylated polymers, sulfonatedmelamine, sulfonated naphthalene— formaldehyde condensates, and / or polycarboxylate ethers.

[0052] The determination of ion concentrations and water absorption for predicting the reactivity and rheological properties (e.g., yield stress and viscosity) of SCM-containing cementitious mixtures may be done in parallel in an inline process. An exemplary inline process is shown in FIG. 1. In this example, after calcination has occurred, a plurality of samples (z.e., at least two samples) each comprising a calcined clay may be obtained from a clay mass being conveyed through a kiln. For example, the conveyor belt 108 shown in FIG. 1 may include one or more additional openings (not visible) for collection of multiple samples. The samples may be obtained from adjacent regions of the clay mass. One of the samples may be submerged in an alkaline or acidic aqueous solution, as described above. As the sample undergoes dissolution, the concentration of ion(s) in the alkaline or acidic aqueous solution is determined, also as described above, in order to predict reactivity. While this analysis takes place, another of the samples may be positioned on a porous substrate in contact with a water supply, and the water absorption analysis described above may be carried out to predict yield stress and / or viscosity. Adjustments may be made in-line to the calcination conditions (e.g., calcination temperature, residence time) or activation conditions (e.g., grinding, blending, homogenizing) as needed based on the analysis.

[0053] More generally, a method for predicting the behavior of activated clays in cementitious mixtures may include, after activation or calcination has occurred, obtaining one or more samples from a clay mass, where each sample comprises an activated clay. The one or more samples may be obtained from adjacent regions of the clay mass. Multiple batches of an alkaline or acidic aqueous solution containing a portion of the one or more samples (e.g., a first sample) may be analyzed as described above to determine a concentration of aluminum ions and a concentration of silicon ions as a function of time or at a predetermined time. The water absorption of a second sample may also be determined as described above. The method may include predicting the reactivity of the activated clay in a cementitious mixture based on the determined concentrations of aluminum and silicon ions (e.g., utilizing the predetermined factor described above applied to the aluminum ion concentration in pM and adding that to the Si concentration in p M; see FIG. 5). The method may also or alternatively include predicting yield stress and / or viscosity of a cementitious mixture including the activated clay based on the water absorption determination (e.g., see FIG. 7). Finally, calcination conditions in the kiln or mechanochemical activation conditions may be adjusted if the predicted reactivity and / or rheological property (yield stress and / or viscosity) is non-optimal.EXAMPLES

[0054] The dissolution of various uncalcined and calcined clays was monitored in NaOH solutions at 90 °C and the dissolution behaviors were correlated with the reactivity measured by the 7-day R3isothermal calorimeter method.Materials and Methods

[0055] Materials

[0056] Three pure clays were obtained from the Clay Minerals Society, including a low- defect kaolinite from Warren County, Georgia, USA, a Na-rich montmorillonite from Victoria, Australia, and an illite- smectite mixed layer (70 / 30 ordered) from Slovakia. In addition, five calcined clays and seventeen uncalcined clays were obtained from different commercial companies and various countries.

[0057] Calcination of clays

[0058] The clays were calcined in alumina crucibles using an MTI furnace. The temperature was ramped up at a rate of 10 °C / min to the desired temperature and maintained for two hours before cooling down to 150 °C. The crucibles were transferred to a desiccator and further cooled down to room temperature. The high-grade kaolinite was calcined at 400- 1000 °C. The Na-montmorillonite and 70 / 30 illite / smectite mixed layer were calcined at 600- 1000 °C. Seventeen natural clays were calcined at 800 °C, which has been reported to be optimal for certain types of low grade kaolinitic clays.

[0059] ASTM C1897 R3tests

[0060] Pozzolanic reactivity of the uncalcined and calcined clays was tested using the ASTM Cl 897 R3isothermal calorimetry method. Calcium hydroxide (Acros Organics, >98%), calcium carbonate (Acros Organics, >99%), potassium hydroxide (Fisher Scientific, ACS grade), and potassium sulfate (Fisher Scientific, ACS grade) were mixed withthe clays using a hand mixer at 1600 rpm for two minutes. The heat of hydration was monitored using an isothermal calorimeter (TAM Air, TA Instruments) at 40 °C for seven days.

[0061] Dissolution tests and spectrophotometric analysis

[0062] The dissolution of the clays in 4M NaOH solution were tracked with a solid to liquid ratio of 0.5 g / L. A water bath was used to maintain a temperature at 90+0.5 °C. Solution samples were collected at 1-15 min, filtered using 0.22 pm PTFE filters, and acidified using HC1 acid.

[0063] The Si concentration was determined using ASTM D859. Ammonium molybdate was added to diluted sample solutions acidified with HC1, followed by oxalic acid and amino-naphthol-sulfonic acid solutions. The absorbance at 815 nm was measured using a Cary 5G spectrophotometer. A calibration curve was prepared using a silicon standard solution (Millipore), and was used to determine the Si concentration in the sample solutions.

[0064] Al concentrations were determined using the 3500-Al B standard method. Sodium acetate buffer was used to achieve a pH of 6.0. Eriochrome Cyanine R solution was added to form pink colored complexation with Al and the absorbance at 535 nm was used to determine the Al concentrations.

[0065] Camera measurement

[0066] A camera image analysis method was developed as a low-cost option for the determination of Al and Si. Instead of measuring absorbance using a spectrophotometer, a camera was used to obtain images of the colored solutions. A code was developed to extract the red (r), green (g), and blue (b) values from the images. The b values were used in alternative to the absorbance at 815 nm to obtain linear calibration curves and determine Si concentrations in solutions. The 3r + b values were used in alternative to the absorbance at 535 nm to determine Al concentrations. Referring to FIG. 4E, reference color strips with precisely known RGB values was included in each image capture session alongside the sample vials to serve as a standard to calibrate the camera's color response for each set of measurements. There is a camera on the right side (not shown in the figure), pointing to the left, so that the liquid specimen and color strips are in the same image and the color strips can be used for calibration. Upon capturing the image, the RGB values of the reference strips are extracted and compared against their known values to compute the correction matrix for each color channel. These factors are then applied to normalize the RGB values obtained from the sample vials, ensuring that the color measurements are consistent and reproducible across different lighting conditions and camera setups. By incorporating these calibration steps, it is possible to enhance the reliability and inter-laboratory reproducibility of the camera-based colorimetric analysis, making it a viable alternative to more traditional spectrophotometric methods.Results and Discussion

[0067] R3cumulative heat release of clays

[0068] The evolution of cumulative heat release during the R3test of the high-grade kaolinite, the Na-montmorillonite, and the 70 / 30 illite / smectite mixed layer for 0-7d is shown in FIGS. 8A-8C. The high-grade kaolinite reacted quickly with -80% reaction finished within the first day of R3test. The Na-montmorillonite reacted more slowly, and most of the reactiongradually slowed after three days (3d). The 800 °C sample did not show higher heat release than other samples in the first day, and ramped up after that, indicating delayed reaction in the dehydroxyled phases. The 70 / 30 illite / smectite mixed layer calcined at 600-800 °C showed slow and continuously increasing cumulative heat, and the curves did not tend to flatten even at seven days (7d). This observation is consistent with the finding in a previous study that calcined illite is a slow-reacting material. The delayed reaction was more evident for the 70 / 30 illite / smectite mixed layer: the sample calcined at 800 °C did not release more heat than the 700 °C sample until two days. The heat release from the 70 / 30 illite / smectite mixed layer calcined at 900 °C was lower than uncalcined samples in the first two days and became higher than other samples only after five days. The delayed reaction of montmorillonite and illite can be related to their incomplete amorphization during calcination and the sintering of fine particles, which can explain their low reactivity.

[0069] The 7d R3heat is plotted in FIG. 8D. The high-grade kaolinite was activated at a wide range of 500-900 °C. The R3heat at these temperatures were similar at -1000 J / g SCM, with the maximum reached at 700 °C. The optimal temperature range, maximum temperature and R3heat value were all consistent with the results reported in previous studies on high grade kaolinite. The sample over-calcined at 1000 °C, the uncalcined high grade kaolinite and the sample calcined at 400 °C were unreactive (<100 J / g SCM). In contrast, the uncalcined Na-montmorillonite demonstrated a certain level of pozzolanic reactivity with a 7d R3heat of 156 J / g SCM. Reactivity gradually increased after calcination at 600-800 °C, with a 7d R3heat of 457 J / g SCM reached at 800 °C, and became unreactive at 900 and 1000 °C. Montmorillonite’s much lower reactivity than kaolinite and its optimal calcination temperature at 800 °C were consistent with findings in previous studies. The uncalcined 70 / 30 illite / smectite mixed layer had a 7d R3heat of 84 J / g SCM, and gradually increased to 260 J / g SCM with temperature of calcination increased to 900 °C. At 1000 °C, the 70 / 30 illite / smectite mixed layer was over-calcined and became unreactive. The low reactivity and optimal calcination conditions at 900 °C were consistent with recent observations on illite.

[0070] Dissolution of clays

[0071] In addition to the R3test, the dissolution behavior of the high-grade kaolinite, Na- montmorillonite, and 70 / 30 illite / smectite mixed layer in 4M NaOH solution at 90 °C was monitored for 15 min, according to the methods described in this disclosure. The release of Al and Si from the high-grade kaolinite showed a similar trend with the heat generation during the R3test: the samples calcined at 500-900 °C dissolved rapidly, and the concentrations of Al and Si reached plateau after 5 min (FIGS. 9A and 9B). The dissolutionof uncalcined samples and samples calcined at 400 and 1000 °C were much slower than other samples, and the Al and Si concentrations kept increasing for 1-15 min, with 1000 °C > 400 °C > uncalcined. Regarding the Si / Al ratios, the 500-900 °C samples mostly showed congruent dissolution with Si / Al close to 1 (FIG. 9B). Uncalcined samples kept Si / Al ratios below 0.5, indicating preferential dissolution of Al. The 400 °C sample showed preferential dissolution of Al at 1 min, and gradually became Si preferentially dissolved at 15 min. Such a difference indicates that although the calcination temperature of 400 °C did not lead to pozzolanic reactive material, certain changes in the structure of the mineral occurred. The 1000 °C sample dissolved congruently during the first 2 mins. The Si / Al ratio increased to 1.8 at 5 min and gradually decreased at 10-15 min. The increase of Si / Al ratio could be due to the dissolution of amorphous silica formed after recrystallization of metakaolin. The later decrease of Si / Al seemed to suggest that the Al was still slowly soluble at the used conditions even after recrystallization at 1000 °C. All these differences in dissolution behaviors could help distinguish properly and improperly calcined materials.

[0072] The dissolution of the Na-montmorillonite was slower than the high grade kaolinite, which was consistent with their reactivities (FIGS. 10A and 10B). The Al and Si concentrations from all samples kept increasing from 1-15 min, with ranking of 800 °C > 700 °C > 600 °C > uncalcined > 900 °C ~ 1000 °C, aligning with R3results. The Si / Al ratios for 25-800 °C samples were close to 3, suggesting congruent dissolution (FIG. 10C). The 900 and 1000 °C samples showed preferential dissolution of Al in the first 2 mins, and preferential dissolution of Si after 5 min, which shed light on the dissolution of inert phases formed during over-calcination of montmorillonite.

[0073] The dissolution of the 70 / 30 illite / smectite mixed layer was slower (FIGS. 11A and 1 IB) than the Na-montmorillonite, also consistent with its lower reactivity. The Al and Si concentrations released from the 800 °C sample were lower than those from the 700 °C at 1 and 2 min, and became higher after 5 min. The Si concentrations of the 900 °C sample were lower than the uncalcined sample at 1 and 2 min, and became highest after 10 min. Their trends aligned with the delayed reaction of dehydroxylated phases observed on the R3heat release, indicating that evolution of Al and Si concentrations was highly consistent with the reactivity measured by the R3test. The Si / Al ratios of the 70 / 30 illite / smectite mixed layer showed congruent dissolution of uncalcined and properly calcined samples (FIG. 11C), and the over-calcined sample showed increasing Si / Al ratios over time, similar to the overcalcined montmorillonite (FIG. 10C).

[0074] Determination of ion concentrations using camera

[0075] The standard methods used above employed colorimetry analysis using a spectrophotometer to determine Al and Si concentrations instead of higher-cost methods such as inductively coupled plasma optical emission spectroscopy (ICP-OES) or mass spectroscopy (ICP-MS). To further reduce the cost of instruments, a colorimetry analysis method based on camera images was developed. FIGS. 12A and 12B show that the Al and Si concentrations determined using this camera image analysis method were comparable with the results obtained using a spectrophotometer. It suggests that color analysis based on camera imaging of the colored solutions can be used as an alternative to the absorbance at certain wavelengths for quantitative analysis.

[0076] Correlation between dissolution and R3heat

[0077] To provide a more quantitative comparison between reactivity and dissolution, FIGS. 13A-13D and 14A-14D show the correlation between the 7d R3heat and the Al and Si concentrations at 1-15 min dissolution. For the high-grade kaolinite, because the reactivity was either -1000 J / g SCM or below 50 J / g SCM, the R2was high before 5 min, and decreased after 10 min due to the dissolution of over-calcined sample (FIGS. 13A and 14A). For the Na-montmorillonite, the Al and Si concentrations after 5 min aligned best with the 7d R3heat, mainly because the most reactive sample, which was calcined at 800 °C, had lower dissolved Al and Si concentrations than the sample calcined at 700 °C at 1-2 min, which was consistent with the lower cumulative heat at Id (FIGS. 13B and 14B). For illite-based clays, due to the slow reaction of illite calcined at 900 °C, the best correlation was achieved using the dissolved Al and Si concentrations at 15 min (FIGS. 13C and 14C). If the composition of the targeted clay is known, it may be better to choose a specific duration of dissolution best suited to the targeted clay phase. For a general analysis of diverse types of clays, a duration of 5 min was used in the following analysis in the current study, because the reactivity of illite was low and negligible compared to that of kaolinite and montmorillonite.

[0078] FIGS. 15A-15C show the correlation between the 7d cumulative R3result and the dissolution of all three pure clays, and five commercial metakaolins C1-C5. Both the Al and Si concentrations matched with the 7d cumulative heat with R2values of 0.97 and 0.95, respectively. However, the high R2was mainly because the pure metakaolin samples showed much higher reactivity than other samples. A closer examination on other samples showed that the Al concentrations underestimated the reactivities of montmorillonite, while the Si concentrations overestimated them. The reason is that the Al:Si ratio in montmorillonite is -1:3, in contrast to the -1:1 in kaolinite. Thus, methods using either reactive alumina or silica content may have limitations. For an index applicable to diverse types of clays, the Al and Siconcentrations are preferably combined. This investigation has demonstrated that better correlation (R2=0.98) can be achieved using the total dissolved mass of alumina and silica (FIG. 15C). A problem with this approach is that the different contributions of Al and Si to heat generation are not considered. Based on the dissolution enthalpy of alumina and silica, a factor of 1.54 may be applied to the Al concentration in pM and added to the Si concentration in pM. FIG. 16A shows that this new dissolution index gives the best correlation to the 7d R3cumulative heat of the clays with R2=0.98. These results show that the indexes based on dissolved Al and Si can accurately predict the R3cumulative heat (reactivity) for these clays.

[0079] To further examine the applicability of the developed method to impure clays, 5 commercial samples and 17 natural impure samples were tested, with their dissolution indexes and R3results shown in FIG. 16B. Although the R2of linear correlation is still as good as 0.900, several natural samples have higher dissolved Al and Si concentrations than their R3heat, indicating the dissolution of other phases in these samples.

[0080] In order to address this issue, an approach to mitigate the impact of these dissolving impurities was developed by subtracting the dissolved Al and Si of pristine samples before calcination from the calcined samples. For industrial production, the samples before calcination are readily available. Taking advantage of this, it is assumed that the reactivity of clays is provided by calcination and the dissolution of at least some of the impurities are not affected by calcination. Thus, the subtraction of the dissolved Al and Si concentrations from uncalcined samples is likely to remove the impact of such impurity phases. The results of the subtraction, resulting in what may be referred to as an Adjusted UR2Dissolution Index, are shown in FIG. 16C. The deviation of the natural samples is mitigated, and the R2of linear fitting increases to about 0.92.

[0081] In addition to the clays described above, the applicability of the developed UR2method on another type of SCM, coal fly ash, is verified. It is noted that UR2method refers to “ultra-rapid reactivity” method. The R3or “rapid” method takes 7 days, so the UR2method was employed here. Thirty-seven class C and class F fly ashes are dissolved in 50 mM KOH solutions at 90 °C. The dissolved concentration of Al at 15 min of dissolution is multiplied by a factor of 0.4 and added to the dissolved concentration of Si at 15 min of dissolution to form a 15 min UR2dissolution index. Its correlation with the 7d R3 results is shown in FIG. 17, and the R2is as high as 0.91. These results show that the UR2method can also accurately predict the R3 cumulative heat (reactivity) for fly ashes.

[0082] This disclosure includes the follow aspects:

[0083] A first aspect relates to a method of analyzing a supplementary cementitious material (SCM), the method comprising: obtaining a sample comprising a SCM; submerging the sample in an alkaline or acidic aqueous solution, whereby the sample undergoes dissolution; determining an ion concentration in the alkaline or acidic aqueous solution at a predetermined time after submerging the sample; and predicting reactivity of the SCM in a cementitious mixture based on the ion concentration.

[0084] A second aspect relates to the method of the first aspect, wherein the SCM is selected from the group consisting of an unactivated clay, an activated clay, a calcined clay, fly ash, silica fume, reclaimed ash, ground granulated blast furnace slag, non-ferrous slag, steel slag, copper slag, natural pozzolan, ash from agriculture waste, waste to energy ash, waste glass, bauxite residue, limestone, zeolite, and / or filler material.

[0085] A third aspect relates to the method of any preceding aspect, wherein the ion concentration is determined for one or more ions selected from the group consisting of aluminum, silicon, calcium, sodium, potassium, magnesium, iron, and sulfur.

[0086] A fourth aspect relates to the method of the preceding aspect, wherein the ions are selected from the group consisting of aluminum and silicon.

[0087] A fifth aspect relates to the method of any preceding aspect, further comprising: prior to obtaining the sample, activating a clay mass, the sample being obtained from the clay mass after activation.

[0088] A sixth aspect relates to the method of the preceding aspect, wherein the activating comprises calcination, thermal activation, mechanical activation, and / or mechanochemical activation.

[0089] A seventh aspect relates to the method of any preceding aspect, wherein the clay mass is conveyed through a kiln for activation.

[0090] An eighth aspect relates to the method of the preceding aspect, wherein, after the clay mass leaves a heating zone of the kiln, the sample falls by gravity through an opening in a conveyer belt into a collection receptacle.

[0091] A ninth aspect relates to the method of any preceding aspect, wherein the sample is obtained after co-grinding or mixing with one or more other materials.

[0092] A tenth aspect relates to the method of any preceding aspect, further comprising obtaining a plurality of the samples for analysis; or further comprising separating the sample into multiple samples for analysis.

[0093] An eleventh aspect relates to the method of any preceding aspect, wherein an amount of the sample obtained is less than 500 grams, less than 200 grams, less than 100grams, less than 50 grams, less than 20 grams, less than 10 grams, less than 5 grams, less than 2 grams, less than 1 gram, and / or as low as 0.1 gram, as low as 0.01 gram, or as low as 0.001 gram.

[0094] A twelfth aspect relates to the method of any preceding aspect, wherein the sample is submerged in the alkaline or acidic aqueous solution at a temperature in a range from 25°C to 100°C, and / or in a range from 60°C to 95°C.

[0095] A thirteenth aspect relates to the method of any preceding aspect, where a concentration of the sample in the alkaline or acidic aqueous solution is at least 1 ng / L and as high as 1 kg / L.

[0096] A fourteenth aspect relates to the method of any preceding aspect, wherein the predetermined time is 60 minutes or less, 30 minutes or less, 15 minutes or less, 5 minutes or less, and / or at least 2 minutes, or at least 1 minute.

[0097] A fifteenth aspect relates to the method of any preceding aspect, wherein the acidic aqueous solution comprises an acid selected from the group consisting of hydrochloric acid, nitric acid, and sulfuric acid, and / or wherein the alkaline aqueous solution comprises a base selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0098] A sixteenth aspect relates to the method of any preceding aspect, further comprising: obtaining a plurality of the samples; and preparing multiple batches of the alkaline or acidic aqueous solution, each batch containing one of the samples.

[0099] A seventeenth aspect relates to the method of the preceding aspect, wherein each batch of the alkaline or acidic aqueous solution is used for determining the ion concentration of a different ion.

[0100] An eighteenth aspect relates to the method of any preceding aspect, further comprising: separating and / or diluting the alkaline or acidic aqueous solution containing the sample to form multiple batches of the alkaline or acidic aqueous solution.

[0101] A nineteenth aspect relates to the method of any preceding aspect, wherein each batch of the alkaline or acidic aqueous solution is used for determining the ion concentration of a different ion.

[0102] A twentieth aspect relates to the method of any preceding aspect, wherein determining the ion concentration comprises conducting colorimetric analysis, atomic adsorption spectroscopy, optical emission spectroscopy, mass spectroscopy, titration, selective ion electrode, precipitation, chromatography, fluorescence spectroscopy, and / or electrophoresis.

[0103] A twenty-first aspect relates to the method of any preceding aspect, wherein determining the ion concentration comprises conducting colorimetric analysis, and further comprising: adding one or more chemicals configured to induce a color change in the presence of a particular ion to the alkaline or acidic aqueous solution.

[0104] A twenty- second aspect relates to the method of the preceding aspect, wherein the one or more chemicals are selected from the group consisting of molybdate, eriochrome cyanine R, chrome azural S, lumogallion, oxine, salicylaldehyde picolinoylhydrazone, morin, pyrocatechol violet, quercetin, ferron, aluminon, and o-cresolphthalein Complexone.

[0105] A twenty-third aspect relates to the method of any preceding aspect, further comprising adding a pH buffer, reducer, and / or masking agent to the alkaline or acidic aqueous solution.

[0106] A twenty-fourth aspect relates to the method of any preceding aspect, wherein the one or more chemicals includes a first set of chemicals and a second set of chemicals, wherein the first set of chemicals is configured to induce a color change according to the presence of silicon ions and is added to a first batch of the alkaline or acidic aqueous solution, and wherein the second set of chemicals is configured to induce a color change according to the presence of aluminum ions and is added to a second batch of the alkaline or acidic aqueous solution.

[0107] A twenty-fifth aspect relates to the method of the preceding aspect, wherein the first set of chemicals is selected according to ASTM D859.

[0108] A twenty- sixth aspect relates to the method of any preceding aspect, wherein the second set of chemicals is selected according to 3500- Al B.

[0109] A twenty- seventh aspect relates to the method of any preceding aspect, wherein conducting the colorimetric analysis comprises utilizing UV-vis spectroscopy, camera image analysis, or visual comparison.

[0110] A twenty-eighth aspect relates to the method of the preceding aspect, wherein utilizing UV-vis spectroscopy comprises: illuminating the sample with ultraviolet and / or visible light; measuring absorbance at a predetermined wavelength; determining the ion concentration based on the absorbance.

[0111] A twenty-ninth aspect relates to the method of any preceding aspect, wherein utilizing camera image analysis comprises: obtaining a photographic image of the sample; converting the photographic image to RGB format including red, green and blue channels; determining mean luminance intensity values for the red, green and blue channels;normalizing the mean luminance intensity values to a range of 0 to 1; and determining the ion concentrations based on the normalized luminance intensity values.

[0112] A thirtieth aspect relates to the method of any preceding aspect, wherein predicting the reactivity of the SCM comprises: multiplying the ion concentration of aluminum in pM by a predetermined factor to obtain a product; adding the product to the ion concentration of silicon in M; and determining R3cumulative heat with a R2value of at least 0.98.

[0113] A thirty-first aspect relates to the method of any preceding aspect, wherein the predetermined factor is in a range from about 1.1 to 1.7.

[0114] A thirty- second aspect relates to the method of any preceding aspect, further comprising adjusting activation conditions of a clay mass if the predicted reactivity of the SCM is non-optimal.

[0115] A thirty-third aspect relates to the previous aspect wherein adjusting the activation conditions comprises adjusting grinding time of the clay mass.

[0116] A thirty-fourth aspect relates to the method of any preceding aspect, wherein adjusting the activation conditions comprises adjusting calcination temperature and / or residence time of the clay mass.

[0117] A thirty-fifth aspect relates to the method of any preceding aspect, further comprising: obtaining a plurality of samples of the SCM, the plurality including a first sample and a second sample, the first sample being submerged in the alkaline or acidic aqueous solution for the determination of ion concentration; and determining water absorption of the second sample, the water absorption being indicative of the workability of the SCM.

[0118] A thirty- sixth aspect relates to the method of any preceding aspect, wherein determining the water absorption of the second sample comprises: positioning the second sample on a material in contact with a water supply; and measuring a change in water level of the water supply as the second sample absorbs water through the porous material.

[0119] A thirty- seventh aspect relates to a method of analyzing a SCM, the method comprising: obtaining a sample comprising a SCM; positioning the sample on a porous substrate in contact with a water supply; measuring a change in water level of the water supply as the sample absorbs water through the porous substrate; and determining water absorption of the sample, the water absorption being predictive of rheological properties (yield stress and / or viscosity) of a cementitious mixture including the SCM.

[0120] A thirty-eighth aspect relates to the method of any preceding aspect, further comprising: predicting the yield stress and / or viscosity of a cementitious mixture including the SCM based on the water absorption.

[0121] A thirty-ninth aspect relates to the method of any preceding aspect, further comprising quantifying an amount of water reducer(s) and / or superplasticizer(s) to be added to the cementitious mixture based on the water absorption.

[0122] A fortieth aspect relates to the method of any preceding aspect, further comprising adjusting activation conditions of a clay mass if the predicted yield stress and / or viscosity are non-optimal.

[0123] A forty-first aspect relates to the method of any preceding aspect, further comprising utilizing a burette to hold the water supply, the burette including a u-curve and being positioned in a horizontal configuration at a level equal to that of the porous substrate.

[0124] A forty- second aspect relates to the method of any preceding aspect, wherein the water absorption is determined within 10 minutes, or within 2 minutes, of positioning the sample on the porous substrate.

[0125] A forty-third aspect relates to the method of any preceding aspect, wherein an amount of the sample obtained is less than 5 grams, 2 grams, less than 1 gram, and / or as low as 0.1 gram, or as low as 0.01 gram.

[0126] A forty-fourth aspect relates to the method of any preceding aspect, wherein the SCM is selected from the group consisting of an unactivated clay, an activated clay, a calcined clay, fly ash, silica fume, reclaimed ash, ground granulated blast furnace slag, natural pozzolan, ash from agriculture waste, a zeolite, and / or a filler material.

[0127] A forty-fifth aspect relates to the method of any preceding aspect, method for predicting the behavior of clays in cementitious mixtures, the method comprising: after activation has occurred, obtaining one or more samples from a clay mass, each sample comprising an activated clay, the one or more samples including or being divided into first and second samples; determining, at a predetermined time, a concentration of silicon ions and a concentration of aluminum ions in respective first and second batches of an alkaline or acidic aqueous solution containing the first sample; determining water absorption of the second sample; predicting reactivity of the activated clay in a cementitious mixture based on the concentrations of silicon and aluminum ions; predicting rheological properties (yield stress and viscosity) of a cementitious mixture including the activated clay based on the water absorption; and adjusting activation conditions of the clay mass if the predicted reactivity and / or yield stress is non-optimal.

[0128] Although the present invention has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible without departing from the present invention. The spirit and scope of the appended claims should not be limited, therefore, to the description of the preferred embodiments contained herein. All embodiments that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein.

[0129] Furthermore, the advantages described above are not necessarily the only advantages of the invention, and it is not necessarily expected that all of the described advantages will be achieved with every embodiment of the invention.

Claims

CLAIMS1. A method of analyzing a supplementary cementitious material (SCM), the method comprising: obtaining a sample comprising a SCM; submerging the sample in an alkaline or acidic aqueous solution, whereby the sample undergoes dissolution; determining an ion concentration in the aqueous solution at a predetermined time after submerging the sample; and predicting reactivity of the SCM in a cementitious mixture based on the ion concentration.

2. The method of claim 1, wherein the SCM is selected from the group consisting of an unactivated clay, an activated clay, a calcined clay, fly ash, silica fume, reclaimed ash, ground granulated blast furnace slag, non-ferrous slag, steel slag, copper slag, natural pozzolan, ash from agriculture waste, waste to energy ash, waste glass, bauxite residue, limestone, zeolite, and / or filler material.

3. The method of claim 1, wherein the ion concentration is determined for one or more ions selected from the group consisting of aluminum, silicon, calcium, sodium, potassium, magnesium, iron, and sulfur.

4. The method of claim 3, wherein the ions are selected from the group consisting of aluminum and silicon.

5. The method of claim 1, further comprising: prior to obtaining the sample, activating a clay mass, the sample being obtained from the clay mass after activation.

6. The method of claim 5, wherein the activating comprises calcination, thermal activation, mechanical activation, and / or mechanochemical activation.

7. The method of claim 5, wherein the clay mass is conveyed through a kiln for activation.

8. The method of claim 7, wherein, after the clay mass leaves a heating zone of the kiln, the sample falls by gravity through an opening in a conveyer belt into a collection receptacle.

9. The method of claim 1, wherein the sample is obtained after co-grinding or mixing with one or more other materials.

10. The method of claim 1, further comprising obtaining a plurality of the samples for analysis; or further comprising separating the sample into multiple samples for analysis.

11. The method of claim 1, wherein an amount of the sample obtained is less than 500 grams, and / or as low as 0.001 gram.

12. The method of claim 1, wherein the sample is submerged in the alkaline or acidic aqueous solution at a temperature in a range from 25°C to 100°C.

13. The method of claim 1, where a concentration of the sample in the alkaline or acidic aqueous solution is at least 1 ng / L and as high as 1 kg / L.

14. The method of claim 1, wherein the predetermined time is 60 minutes or less.

15. The method of claim 1, wherein the acidic aqueous solution comprises an acid selected from the group consisting of hydrochloric acid, nitric acid, and sulfuric acid, and / or wherein the alkaline aqueous solution comprises a base selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

16. The method of claim 1, further comprising: obtaining a plurality of the samples; and preparing multiple batches of the alkaline or acidic aqueous solution, each batch containing one of the samples.

17. The method of claim 16, wherein each batch of the alkaline or acidic aqueous solution is used for determining the ion concentration of a different ion.

18. The method of claim 1, further comprising: separating and / or diluting the alkaline or acidic aqueous solution containing the sample to form multiple batches of the alkaline or acidic aqueous solution.

19. The method of claim 18, wherein each batch of the alkaline or acidic aqueous solution is used for determining the ion concentration of a different ion.

20. The method of claim 1, wherein determining the ion concentration comprises conducting colorimetric analysis, atomic adsorption spectroscopy, optical emission spectroscopy, mass spectroscopy, titration, selective ion electrode, precipitation, chromatography, fluorescence spectroscopy, and / or electrophoresis.

21. The method of claim 1, wherein determining the ion concentration comprises conducting colorimetric analysis, and further comprising: adding one or more chemicals configured to induce a color change in the presence of a particular ion to the alkaline or acidic aqueous solution.

22. The method of claim 21, wherein the one or more chemicals are selected from the group consisting of molybdate, eriochrome cyanine R, chrome azural S, lumogallion, oxine, salicylaldehyde picolinoylhydrazone, morin, pyrocatechol violet, quercetin, ferron, aluminon, and o-cresolphthalein Complexone.

23. The method of claim 21, further comprising adding a pH buffer, reducer, and / or masking agent to the alkaline or acidic aqueous solution.

24. The method of claim 21, wherein the one or more chemicals includes a first set of chemicals and a second set of chemicals, wherein the first set of chemicals is configured to induce a color change according to the presence of silicon ions and is added to a first batch of the alkaline or acidic aqueous solution, and wherein the second set of chemicals is configured to induce a color change according to the presence of aluminum ions and is added to a second batch of the alkaline or acidic aqueous solution.

25. The method of claim 24, wherein the first set of chemicals is selected according to ASTM D859.

26. The method of claim 24, wherein the second set of chemicals is selected according to 3500- Al B.

27. The method of claim 21, wherein conducting the colorimetric analysis comprises utilizing UV-vis spectroscopy, camera image analysis, or visual comparison.

28. The method of claim 27, wherein utilizing UV-vis spectroscopy comprises: illuminating the sample with ultraviolet and / or visible light; measuring absorbance at a predetermined wavelength; determining the ion concentration based on the absorbance.

29. The method of claim 27, wherein utilizing camera image analysis comprises: obtaining a photographic image of the sample; converting the photographic image to RGB format including red, green and blue channels; determining mean luminance intensity values for the red, green and blue channels; normalizing the mean luminance intensity values to a range of 0 to 1; and determining the ion concentrations based on the normalized luminance intensity values.

30. The method of claim 1, wherein predicting the reactivity of the SCM comprises: multiplying the ion concentration of aluminum in pM by a predetermined factor to obtain a product; adding the product to the ion concentration of silicon in M; and determining R3cumulative heat with a R2value of at least 0.98.

31. The method of claim 30, wherein the predetermined factor is in a range from about 1.1 to 1.7.

32. The method of claim 30, further comprising adjusting activation conditions of a clay mass if the predicted reactivity of the SCM is non-optimal.

33. The method of claim 32, wherein adjusting the activation conditions comprises adjusting grinding time of the clay mass.

34. The method of claim 32, wherein adjusting the activation conditions comprises adjusting calcination temperature and / or residence time of the clay mass.

35. The method of claim 1, further comprising: obtaining a plurality of samples of the SCM, the plurality including a first sample and a second sample, the first sample being submerged in the alkaline or acidic aqueous solution for the determination of ion concentration; and determining water absorption of the second sample, the water absorption being indicative of the workability of the SCM.

36. The method of claim 35, wherein determining the water absorption of the second sample comprises: positioning the second sample on a material in contact with a water supply; and measuring a change in water level of the water supply as the second sample absorbs water through the porous material.

37. A method of analyzing a SCM, the method comprising: obtaining a sample comprising a SCM; positioning the sample on a porous substrate in contact with a water supply; measuring a change in water level of the water supply as the sample absorbs water through the porous substrate; and determining water absorption of the sample.

38. The method of claim 37, further comprising: predicting the yield stress and / or viscosity of a cementitious mixture that includes the SCM based on the water absorption.

39. The method of claim 37, further comprising: quantifying an amount of water reducer(s) and / or superplasticizer(s) to be added to a cementitious mixture that includes the SCM based on the water absorption.

40. The method of claim 38, further comprising adjusting activation conditions of a clay mass if the predicted yield stress and / or viscosity are non-optimal.

41. The method of claim 37, further comprising utilizing a burette to hold the water supply, the burette including a u-curve and being positioned in a horizontal configuration at a level equal to that of the porous substrate.

42. The method of claim 37, wherein the water absorption is determined within 10 minutes of positioning the sample on the porous substrate.

43. The method of claim 37, wherein an amount of the sample obtained is less than 5 grams, and / or as low as 0.01 gram.

44. The method of claim 37, wherein the SCM is selected from the group consisting of an unactivated clay, an activated clay, a calcined clay, fly ash, silica fume, reclaimed ash, ground granulated blast furnace slag, natural pozzolan, ash from agriculture waste, a zeolite, and a filler material.

45. A method for predicting the behavior of clays in cementitious mixtures, the method comprising: after activation has occurred, obtaining one or more samples from a clay mass, each sample comprising an activated clay, the one or more samples including or being divided into first and second samples; determining, at a predetermined time, a concentration of silicon ions and a concentration of aluminum ions in respective first and second batches of an alkaline or acidic aqueous solution containing the first sample; determining water absorption of the second sample; predicting reactivity of the activated clay in a cementitious mixture based on the concentrations of silicon and aluminum ions; predicting yield stress and / or viscosity of the cementitious mixture based on the water absorption; and adjusting activation conditions of the clay mass if the predicted reactivity, yield stress, and / or viscosity is non-optimal.

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