Caco3 amount estimation method and carbonation degree determination method

Abstract

To provide a CaCO3 amount estimation method and a carbonation degree determination method which can be easily executed in carbonation treatment of a material containing a cement solidified object.SOLUTION: A CaCO3 amount estimation method and a carbonation degree determination method include measuring a color specification value of an L*a*b* color space of the target material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for estimating the amount of CaCO3 and a method for determining the degree of carbonation. [Background technology]

[0002] Methods for estimating the amount of CO2 fixed in concrete have been under study for a long time. For example, Non-Patent Document 1 reports a case in which the amount of CO2 fixed was estimated from the results of thermogravimetric analysis and another case in which the amount of CO2 fixed was estimated from the results of inorganic carbon analysis. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Tsuyoshi Torimachi, Kosuke Yokozeki, Ichiro Yoshioka, and Minoru Morioka, "Study on evaluation methods for CO2 fixation amount and changes in physical properties in carbonated cement-based materials," Journal of the Japan Society of Civil Engineers, Vol. 77, No. 2, pp. 37-54, 2021 Summary of the Invention [Problem to be solved by the invention]

[0004] Thermogravimetric analysis and inorganic carbon analysis are well-known and proven methods for estimating the amount of CO2 fixed in concrete. However, the analytical equipment required for thermogravimetric analysis and inorganic carbon analysis is expensive and takes a long time to complete. In addition, the analytical equipment is not portable, so it is not possible to analyze samples on-site and estimate the amount of CO2 fixed immediately.

[0005] Carbonation of cementitious materials is a reaction in which calcium hydroxide, calcium silicate hydrate, and other substances contained in the cementitious material react with carbon dioxide to produce calcium carbonate (CaCO3). Therefore, the degree of carbonation can be determined by the amount of CaCO3 in the cementitious material.

[0006] It is against this background that the present disclosure has been made. An object of the present disclosure is to provide a method for estimating the amount of CaCO3 and a method for determining the degree of carbonation that can be easily performed in the carbonation treatment of materials containing cement solidified substances. [Means for solving the problem]

[0007] Specific means for solving the above problems include the following aspects. <1> A method for estimating the amount of CaCO3 in a material during or after carbonation treatment in a carbonation treatment of a material containing cement solidified material, The method includes the following steps (1) to (3): The color values ​​in the following steps (1) to (3) are L * a * b * Color space L * value, a * value and b * The component values ​​are of the same type selected from the values, Method for estimating CaCO3 content. Step (1): From the color value of high-purity calcium carbonate that can be considered to be 100% CaCO3 by mass and the CaCO3 amount (% by mass) and color value of the material before carbonation treatment, p and q in the relationship between the CaCO3 amount (% by mass) and the color value are determined: CaCO3 amount = p × color value + q. Step (2): The color value of the material is measured during or after the carbonation treatment. Step (3): The color value obtained in step (2) is substituted into the relational equation, CaCO3 amount = p × color value + q, where p and q are determined in step (1), to determine the CaCO3 amount (mass %). <2> The color specification value is L * is the value, <1> The method for estimating the amount of CaCO3 described in <3> A method for determining the degree of carbonation of a material during or after carbonation treatment in a carbonation treatment of a material containing cement solidified material, comprising: The method includes the following steps (A) and (B): The color values ​​in the following steps (A) and (B) are L * a * b *Color space L * value, a * value and b * The component values ​​are of the same type selected from the values, Method for determining carbonation. Step (A): The color value of the material is measured during or after carbonation treatment. Step (B): When the color value obtained in step (A) is within the range between the color value of high-purity calcium carbonate that can be considered to be 100% by mass of CaCO3 and the color value of a material whose carbonation degree has reached the expected value, the carbonation degree of the material during or after the carbonation treatment is determined to be acceptable. <4> A method for determining the degree of carbonation of a material during or after carbonation treatment in a carbonation treatment of a material containing cement solidified material, comprising: The method includes the following steps (AL) and (BL): Method for determining carbonation. Step (AL): L of the material during or after carbonation treatment * a * b * Color space L * Measure the value. Step (BL): L obtained in step (AL) * The L value indicates the carbonation level of the material has reached the expected value. * If the value is equal to or greater than this value, the carbonation level of the material during or after the carbonation process is judged to be acceptable. <5> A method for determining the degree of carbonation of a material during or after carbonation treatment in a carbonation treatment of a material containing cement solidified material, comprising: The method includes the following steps (Ab) and (Bb): Method for determining carbonation. Step (Ab): L of the material during or after carbonation treatment * a * b * Color space b * Measure the value. Step (Bb): b obtained in step (Ab) * The value is the b value of the material whose carbonation has reached the expected value. *If the carbonation level is equal to or less than the value, the carbonation level of the material during or after the carbonation process is judged to be acceptable. [Effects of the Invention]

[0008] According to the present disclosure, a method for estimating the amount of CaCO3 and a method for determining the degree of carbonation are provided that can be easily performed in the carbonation treatment of materials containing cement solidified substances. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a wet carbonation apparatus used for carbonating cement-based materials. [Figure 2] This is a scatter diagram showing the relationship between the CaCO3 concentration and each component value of the L*a*b* color space. The covering member is a glass plate. [Figure 3] This is a scatter diagram showing the relationship between CaCO3 concentration and each component value of the L*a*b* color space. The covering member is a polyethylene sheet. [Figure 4] 1 is a coordinate system for explaining an embodiment of a method for estimating the amount of CaCO3 and a method for determining the degree of carbonation. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes embodiments of the present invention. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the present invention.

[0011] In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In the numerical ranges described in this disclosure, the upper or lower limit value of the numerical range may be replaced with the value shown in the examples.

[0012] In the present disclosure, "A and / or B" is synonymous with "at least one of A and B." In other words, "A and / or B" means that it may be only A, only B, or a combination of A and B.

[0013] In the present disclosure, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

[0014] In the present disclosure, when referring to the amount of each component in a composition, if multiple substances corresponding to each component are present in the composition, the total amount of the multiple substances present in the composition is meant unless otherwise specified.

[0015] In this disclosure, * a * b * The color space is CIE1976L, standardized by the International Commission on Illumination (CIE) in 1976. * a * b * It means color space.

[0016] <Color change of cement-based materials with the progress of carbonation> The method for estimating the amount of CaCO3 and the method for determining the degree of carbonation of the present disclosure were created based on the results of experiments conducted by the present inventor. First, the experiments conducted by the present inventor and the results thereof will be described.

[0017] Carbonation of cementitious materials is a reaction in which calcium hydroxide, calcium silicate hydrate, and other substances contained in cementitious materials react with carbon dioxide to produce calcium carbonate (CaCO3). Therefore, the color of the cementitious material may approach that of high purity calcium carbonate as carbonation progresses. The color change of cementitious materials that accompanies carbonation is difficult to distinguish visually, but it may be possible to distinguish the color change using a colorimeter. Based on this hypothesis, the following experiment was conducted.

[0018] (1) Preparation of recycled fine powder Concrete was produced and demolished, and recycled aggregate was produced, and recycled fines generated during the production of recycled aggregate were collected.

[0019] The concrete materials listed below were prepared and mixed according to the composition shown in Table 1. Water: Tap water Cement: Ordinary Portland cement River sand: River sand from the Uga River basin Crushed sand: Crushed hard sandstone from Ehime Crushed stone (1): Hard crushed sandstone from Mie Crushed stone (2): Crushed hard sandstone from Ehime Water reducing agent (1): Product name: "Chupol NV-G" (Takemoto Oil & Fat Co., Ltd.) Water reducing agent (2): Product name: Master Polyhede 15S (Sika Japan Co., Ltd.) Water reducing agent (1) was used to make concrete for recycled fine powder A, and water reducing agent (2) was used to make concrete for recycled fine powder B.

[0020] The concrete for recycled fine powder A was made by mixing the materials and then pouring them into a flat formwork measuring 2500mm x 1000mm x 200mm. After demolding, the concrete was steam cured at 70°C for two weeks, then dried for one week before being demolished. The concrete for recycled fine powder B was prepared by mixing the materials and then pouring them into a flat formwork measuring 2200mm x 1100mm x 410mm. The concrete was then left to cure for four weeks as per the standard procedure and then demolished. Demolition debris was subjected to autogenous blasting to produce recycled aggregate, and the recycled fines generated during the autogenous blasting process were collected.

[0021] [Table 1]

[0022] The volume-based median diameter of the recycled fine powder A-1 was 54.5 μm. The volume-based median diameter of the recycled fine powder A-2 was 71.6 μm. The volume-based median diameter of recycled fine powder B was 135.1 μm.

[0023] (2) Manufacturing of hardened cement powder Ordinary Portland cement and tap water were mixed at a water-cement ratio of 50%. After mixing, the mixture was spread into a plate and left to stand at room temperature for 182 days to harden. After hardening, the mixture was crushed using a crusher until it passed through a 100 μm sieve. The volume-based median diameter of the hardened cement powder was 29.6 μm.

[0024] (3) Carbonation treatment of cement-based materials Carbonation treatment of recycled fine powder and hardened cement powder was carried out using a bench-scale wet carbonation equipment (reaction tank capacity 2m 3 ) was used. Figure 1 shows an outline of the wet carbonation device. The wet carbonation process using this device is as follows.

[0025] The powder was added from the top of a reactor containing tap water and stirred with a stirring blade for 1 hour. After that, CO2 gas was supplied from the bottom while continuing to stir. Stirring and CO2 gas supply were continued for the specified time. After that, the contents were withdrawn from the bottom of the reactor in a solid-liquid mixture state, and the carbonated powder was recovered using a filter press. After recovery, the carbonated powder was dried. Samples 1 to 4 in Table 2 were prepared by changing the length of time for which CO2 gas was supplied.

[0026] (4) Estimation of CaCO3 concentration in cement-based materials The ignition loss of the sample was quantified by thermogravimetric analysis. The ignition loss was considered to be the amount of CO2 released by the thermal decomposition of CaCO3, and the CaCO3 concentration was calculated using the following formula.

[0027]

number

[0028] In the formula, CaCO3 is the CaCO3 concentration (mass%), W is the mass of the sample (g), ΔW is the weight loss (g) at 600°C to 800°C, and M CaCO3 is the molecular weight of CaCO3, and M CO2 is the molecular weight of CO2.

[0029] (5) Color measurement of cement-based materials When measuring the color of powder, there was a concern that the measured values ​​would change depending on the density and surface condition of the powder.To address this issue, a colorless, transparent, and flat covering member was placed over the measurement port of the colorimeter, and the measurement port was pressed against the powder through the covering member, thereby smoothing and densifying the powder surface before measuring the color.

[0030] The covering member was attached to the measurement port of a spectrophotometer (product name: CM-26dG, Konica Minolta Japan, Inc.) without any gaps or floating. The covering member was a glass plate (thickness: 1.3 mm), a polyethylene sheet (thickness: 0.04 mm), or an acrylic plate (thickness: 1.5 mm). An appropriate amount of sample was placed on a medicine wrapping paper, and while looking through the observation window of the spectrophotometer, the sample and the measurement port were aligned, and the covering member of the measurement port was pressed against the sample to make the sample even and dense, and then color measurement was performed. CaCO3 reagent (purity ≥ 99.9%, product name: calcium carbonate, 99.9%, Fujifilm Wako Pure Chemical Industries, Ltd.) was prepared, and color measurement was carried out in the same manner as above.

[0031] (6) Relationship between CaCO3 concentration and color value The CaCO3 concentration and L of each sample * a * b * The three component values ​​of the color space are shown in Table 2 and Figures 2 and 3. In the scatter diagrams of Figures 2 and 3, the horizontal axis is L * value, a * value or b * The vertical axis represents the CaCO3 concentration (mass%), and the vertical axis represents the CaCO3 concentration (mass%). Figure 2 shows the measured values ​​when a glass plate was used as the covering member, and Figure 3 shows the measured values ​​when a polyethylene sheet was used as the covering member.

[0032] [Table 2]

[0033] As can be seen from Table 2 and Figures 2 and 3, the L of cement-based materials * value, a * value and b * Both values ​​are correlated with the CaCO3 concentration, and the L of high-purity calcium carbonate increases as carbonation progresses. * value, a * value and b * It was confirmed that the values ​​converged linearly. This was a universal phenomenon regardless of the type of cement-based material or the type of covering material.

[0034] L * a * b * Color space L * The value ranges from 0 to 100, and the L * It was confirmed that the value approached 100 (i.e., became brighter) as carbonation progressed. This was a universal phenomenon regardless of the type of cementitious material or covering material.

[0035] L * a * b * Color space b * The value ranges from -60 to +60, and the b * It was confirmed that the value of the carbonation decreased from a positive value to zero (i.e., the yellowness decreased) as carbonation progressed. This was a universal phenomenon regardless of the type of cementitious material or the type of covering material.

[0036] L * a * b * Color space a * The value ranges from -60 to +60, and the a * The a value of high purity calcium carbonate increases with the progress of carbonation. * The values ​​converged to the same value, but the direction of convergence differed depending on the type of cementitious material. * The a value tends to go from positive to negative as carbonation progresses, and the a value of the hardened cement powder* The values ​​tended to go from negative to positive as carbonation progressed. The difference in the trend was presumed to be due to the presence or absence of aggregate. In addition, the a of cement-based materials * The a value of high purity calcium carbonate increases with the progress of carbonation. * The convergence point differed depending on the type of coating material. * The range of change in the value is small (b * the value of the coating material itself) * It was assumed that the value was affected.

[0037] Based on the above experimental results, the present disclosure provides a method for estimating the amount of CaCO3 and a method for determining the degree of carbonation of a material containing cement solidified matter. The method for estimating the amount of CaCO3 and the method for determining the degree of carbonation of the present disclosure are described below.

[0038] <Target materials> The target materials for the CaCO amount estimation method and carbonation degree determination method of the present disclosure are materials containing cement solidified materials, such as recycled materials derived from waste concrete and recycled materials derived from waste mortar.

[0039] The target material is preferably in the form of particles or powder. When the target material is in the form of particles or powder, its volume-based median diameter may be on the order of centimeters, millimeters, micrometers, or nanometers. The volume-based particle size distribution is measured, for example, using a laser diffraction particle size distribution analyzer.

[0040] When the target material is in the form of particles or powder, the particle size is preferably equivalent to that of coarse aggregate, fine aggregate, admixture, or cement. The particle size equivalent to fine aggregate is a size that passes entirely through a 10 mm sieve and 85% by mass or more passes through a 5 mm sieve. It is preferable that the particle size of the target material is equal to or smaller than this size.

[0041] When the particle size of the target material is large (for example, when the volume-based median diameter is on the order of centimeters, or when the particle size is equivalent to that of coarse aggregate), it is preferable to crush the target material to an appropriate size and subject the crushed material to color measurement.

[0042] The target material may be a mixture of multiple materials with different particle sizes or multiple materials of different origins.

[0043] <Carbonation treatment> The method for estimating the amount of CaCO3 and the method for determining the degree of carbonation of the present disclosure are carried out in the carbonation treatment of a material containing a cement-solidified substance. The carbonation treatment of a material is not limited to an embodiment as long as it is a treatment in which the material is brought into contact with a CO2-containing gas. Examples of the CO2-containing gas include air, a gas with a CO2 concentration of 1% to 20% by volume, and CO2 gas. The carbonation treatment of a material also includes leaving the material in air.

[0044] The CO2-containing gas may be exhaust gas generated from a coal-fired power plant, an LNG-fired power plant, a cement factory, a steel mill, an oil refinery, a waste incineration plant, etc. When using such exhaust gas, it is preferable to remove soot, NOx, and SOx before use. The carbonation process of materials can reduce the amount of CO2 in the environment, or reduce the amount of CO2 emitted into the atmosphere from power plants, factories, treatment plants, etc.

[0045] Carbonation of the material may involve, for example, placing a CO2-containing gas in the environment during the carbonation process and / or transporting the CO2-containing gas through the environment during the carbonation process. Preferably, the material is stirred, vibrated, or fluidized during the carbonation process.

[0046] In order to increase the efficiency of carbonation, the carbonation treatment of the material is preferably carried out in a humid environment, such as in water or in a high-humidity chamber. It is presumed that on the surface of a material in a humid environment, calcium hydroxide or the like in the material dissolves in water, the reaction between the dissolved calcium hydroxide or the like and carbon dioxide proceeds, and the efficiency of carbonation increases. Further, in this case, it is presumed that CaCO3 is generated on the surface of the material, and a color change approaching the color of high-purity calcium carbonate is likely to appear.

[0047] As the scale of the carbonation treatment of the material, the CaCO3 amount estimation method and the carbonation degree determination method of the present disclosure are applicable in any of the laboratory scale, bench scale, pilot scale, and commercial scale.

[0048] <CaCO3 amount estimation method> The CaCO3 amount estimation method of the present disclosure is a method for estimating the amount of CaCO3 in a material during or after carbonation treatment in the carbonation treatment of a material containing a cement solidified product.

[0049] The CaCO3 amount estimation method of the present disclosure includes steps (1) to (3), and the colorimetric values in steps (1) to (3) are L * a * b * value in the color space of L * value, a <00000�4>value and b * values, which are the same type of component values selected from.

[0050] 0Step (1): From the colorimetric value of high-purity calcium carbonate that can be regarded as 100% by mass of CaCO3, the amount of CaCO3 (mass%) and the colorimetric value of the material before carbonation treatment, determine p and q in the relational expression CaCO3 amount = p × colorimetric value + q between the amount of CaCO3 (mass%) and the colorimetric value. Step (2): Measure the colorimetric value of the material during or after carbonation treatment. Step (3): Substitute the colorimetric value obtained in step (2) into the relational expression CaCO3 amount = p × colorimetric value + q in which p and q are determined in step (1) to obtain the amount of CaCO3 (mass%).

[0051] [[ID=?]] Step (2) is a step of analyzing the material during or after the carbonation process, and this step is to measure the color value of the target material. Compared to thermogravimetric analysis and inorganic carbon analysis, colorimetry is simple in terms of sample preparation and analysis methods, and also requires a short analysis time. Therefore, the method for estimating the amount of CaCO3 disclosed herein can be easily performed. In addition, because compact, lightweight colorimeters are widely available, color measurements of target materials can be performed one after another at the carbonation treatment site. Furthermore, by performing step (1) in advance and preparing the relationship equation (CaCO3 content = p × color specification value + q) in which p and q are determined, step (3) can be performed immediately after step (2) at the carbonation treatment site. Therefore, the CaCO3 content estimation method of the present disclosure is highly responsive to on-site measurements.

[0052] The color values ​​in steps (1) to (3) are L * a * b * Color space L * value, a * value and b * In other words, the colorimetric values ​​obtained by measuring the color of the target material are the same as the component values ​​of L * When the value is , the color value of the relational equation CaCO3 amount = p × color value + q is L * The color value obtained by measuring the color of the target material is a * When the value is a, the color value of the relational equation CaCO3 amount = p × color value + q is a * The color value obtained by measuring the color of the target material is b * When the value is , the color value of the relational equation CaCO3 amount = p × color value + q is b * value. In the following explanation, the values ​​of the three components are represented by L * In some cases, values ​​are given to explain the * value or b * When using values, refer to "L * Value" to "a * value" or "b * Repeat the same process, substituting "value".

[0053] [Process (1)] Step (1) is a step of determining p and q in the relationship between the amount of CaCO3 (mass%) and the color value, CaCO3 amount = p × color value + q, from the color value of high-purity calcium carbonate that can be considered to be 100% CaCO3 by mass and the CaCO3 amount (mass%) and color value of the material before carbonation treatment.

[0054] Step (1) is a step for obtaining a formula for calculating the amount of CaCO3 in the material during or after the carbonation treatment in step (3). Cement-based materials L * value, a * value and b * The L values ​​of high-purity calcium carbonate increase with the progress of carbonation. * value, a * value and b * Therefore, the CaCO3 content and L * value, a * value or b * The coefficients p and q are determined by solving simultaneous linear equations with two unknowns relating to the relational equation CaCO3 amount = p × color specification value + q, which shows a linear correlation, from the values. The relational equation CaCO3 amount = p × color specification value + q, after the coefficients p and q have been determined, is the calculation formula used in step (3).

[0055] The two samples used to solve the simultaneous linear equations with two unknowns are: one is high-purity calcium carbonate that can be considered to be 100% CaCO3 by mass, and the other is a material before carbonation treatment. The CaCO3 content (mass%) and L * value, a * value or b * From this value, the coefficients p and q of the relational expression CaCO3 amount = p × color value + q are determined.

[0056] High-purity calcium carbonate that can be considered to be 100% CaCO3 by mass (referred to as "high-purity calcium carbonate" in this disclosure) is calcium carbonate with a purity of 99.5% by mass or more. The higher the purity of calcium carbonate, the more preferable it is, with a purity of 100% by mass being ideal. The high-purity calcium carbonate is preferably a calcium carbonate reagent that meets the quality requirements of JIS K8617 "Calcium carbonate (reagent)." The high-purity calcium carbonate is in the form of a powder. The amount of CaCO3 in high-purity calcium carbonate is considered to be 100% by mass.

[0057] High purity calcium carbonate L * value, a * value and b * The values ​​may be literature values, previously measured and recorded values, or newly measured values. When measuring, it is preferable to use the same model of colorimeter as that used in step (2), use the same type of covering member, and measure under the same measurement conditions.

[0058] The amount of CaCO3 (mass%) of the material before carbonation may be a value recorded in a previous analysis, or may be a value determined by a new analysis. If an analysis is performed, the method is not limited. Methods for determining the amount of CaCO3 (mass%) by analyzing the target material include, for example, thermogravimetric analysis, inorganic carbon analysis, X-ray diffraction, and X-ray fluorescence analysis.

[0059] L of material before carbonation * value, a * value and b * The values ​​may be previously measured and recorded values, or may be newly measured values. When measuring, it is preferable to use the same model of colorimeter as the colorimeter used in step (2), use the same type of covering material, and measure under the same measurement conditions. When the particle size of the target material is large, it is preferable to crush the target material to an appropriate size and subject the crushed material to color measurement. It is preferable to make the particle size of the crushed material the same as the particle size of the crushed material in step (2).

[0060] In step (1), the horizontal axis is L * value, a * value or b * This is equivalent to plotting two points on a Cartesian coordinate system with the CaCO amount (mass%) on the vertical axis and drawing a straight line passing through the two points. In the present disclosure, this straight line is referred to as a calibration curve.

[0061] The calibration curve was created by *The values ​​are listed and explained using FIG. For example, high-purity calcium carbonate L * When the value is 96, (L * The value, CaCO3 amount) is plotted at (96,100) ("●" in Figure 4). For example, if the CaCO3 content of the material before carbonation is 7% by mass, * When the value is 70, (L * The value, CaCO3 amount) is plotted at (70,7) ("■" in Figure 4). Then, draw a straight line that passes through the above two coordinates. This line is the calibration curve.

[0062] In the above example (L * When solving the simultaneous linear equations with two unknowns relating to the relationship CaCO3 amount = p × color value + q for (p, CaCO3 amount) = (96,100) · (70,7), p = 3.58 and q = -243.38. In this example, the calculation formula used in step (3) is CaCO3 amount = 3.58 × L * The value is -243.38. In the above example, the coefficients p and q are expressed as significant figures up to the second decimal place, but the number of significant figures is arbitrary.

[0063] Step (1) is L * value, a * value and b * It is sufficient to carry out the analysis for at least one component value selected from the above values, but it may also be carried out for two or three component values. Step (1) is at least L * It is preferable to perform the calculation for the L value. * The value of L shows the largest change with the progress of carbonation. * The relationship between the values ​​allows for a more accurate estimation of the amount of CaCO3.

[0064] [Process (2)] Step (2) is a step of measuring the color value of the material during or after the carbonation treatment.

[0065] The colorimeter is L* a * b * There are no restrictions on the principle or specifications as long as the component values ​​of the color space can be measured. A small, lightweight colorimeter that can be carried to the carbonation treatment site is preferred. The color measurement conditions should follow the specifications of the colorimeter to be used.

[0066] If the carbonation process is carried out in a humid environment, the material is dried before being subjected to color measurement.

[0067] When the sample to be subjected to colorimetry is granular or powdery, the colorimetric measurement value may vary depending on the density and surface condition of the sample. To prevent this, it is preferable to interpose a colorless, transparent, and flat covering member between the measurement port of the colorimeter and the sample, and press the measurement port against the sample through the covering member, thereby smoothing and densely distributing the sample surface during colorimetry. The covering member may be placed on the measurement port of the colorimeter or on the sample. The material of the covering member is preferably colorless, transparent glass or resin.

[0068] When the particle size of the target material is large, it is preferable to crush the target material to an appropriate size and subject the crushed material to color measurement.

[0069] [Process (3)] Step (3) is a step of substituting the color specification value obtained in step (2) into the relational equation CaCO3 content = p × color specification value + q, where p and q are determined in step (1), to determine the CaCO3 content (mass %).

[0070] In the present disclosure, the relational equation CaCO3 amount=p×color value+q in which the coefficients p and q are determined is referred to as the calculation formula. In step (3), the calculation formula obtained in step (1) is used to calculate the L obtained in step (2). * value, a * value or b * This is the step of calculating the amount of CaCO3 by substituting the values. The calculation can be done by hand, using a calculator, or using a calculation application.

[0071] If a calibration curve is created in step (1), the L obtained in step (2) is added to the calibration curve. *value, a * value or b * The amount of CaCO3 may be estimated by fitting the values ​​and visually reading the calibration curve.

[0072] Step (3) is L * value, a * value and b * It is sufficient to perform this for at least one component value selected from the values, or it may be performed for two or three component values. The CaCO3 amount may be determined from each of the three component values, and a representative value (e.g., average or median) of the three CaCO3 amounts may be determined as the CaCO3 amount.

[0073] Step (3) is at least L * It is preferable to perform the calculation for the L value. * The value of L shows the largest change with the progress of carbonation. * By carrying out steps (1) to (3) on the value, the amount of CaCO3 can be estimated more accurately.

[0074] <Method for determining carbonation level> The carbonation degree determination method of the present disclosure is a method for determining whether the carbonation degree of a material containing a cement-solidified substance is acceptable or not during or after the carbonation treatment. The present disclosure provides three methods for determining carbonation, which will be explained in order below.

[0075] [First carbonation determination method] The first carbonation degree determination method includes steps (A) and (B), and the color values ​​in steps (A) and (B) are L * a * b * Color space L * value, a * value and b * The component values ​​are of the same type selected from the values.

[0076] Step (A): The color value of the material is measured during or after carbonation treatment. Step (B): When the color value obtained in step (A) is within the range between the color value of high-purity calcium carbonate that can be considered to be 100% by mass of CaCO3 and the color value of a material whose carbonation degree has reached the expected value, the carbonation degree of the material during or after the carbonation treatment is determined to be acceptable.

[0077] Step (A) is the same as step (2) in the method for estimating the amount of CaCO of the present disclosure. The specific and preferred forms of step (A) are the same as the specific and preferred forms of step (2).

[0078] The high-purity calcium carbonate and its color specification value in step (B) are synonymous with the high-purity calcium carbonate and its color specification value in step (1) of the method for estimating the amount of CaCO of the present disclosure, and specific and preferred forms are also the same.

[0079] The material whose carbonation degree in step (B) reaches the expected value (referred to as the "reference sample" in this disclosure) means a material that can be considered to be originally the same as the material to be evaluated, but in which carbonation has progressed sufficiently to result in a CaCO3 content equal to or greater than the desired value.

[0080] Examples of reference samples include the following: A portion of the material was taken before or during the carbonation process and carbonated in the laboratory. -Materials that have undergone small-scale carbonation testing and have been carbonated for a relatively long period of time. A material in which the CaCO3 content is equal to or greater than a desired value when subjected to the CaCO3 content estimation method of the present disclosure in a large-scale carbonation process.

[0081] L of the reference sample * value, a * value and b * The value (referred to as "reference value" in the present disclosure) may be a previously measured and recorded value, or may be a newly measured value. When actually measuring, it is preferable to use the same model of colorimeter as that used in step (A), use the same type of covering member, and measure under the same measurement conditions.

[0082] When the particle size of the material to be evaluated is large, it is preferable to crush the material to be evaluated to an appropriate size and subject the crushed material to color measurement. It is preferable to make the particle size of the crushed material uniform between the material in step (A) and the reference sample.

[0083] In step (B), the L of the material to be evaluated is * value, a * value or b * value and L of high-purity calcium carbonate * value, a * value or b * value and the L of the reference sample * value, a * value or b * This is a process of comparing the value with the value to determine whether the carbonation level of the material being evaluated is acceptable or not. When the component values ​​of the material to be evaluated are within the range between the component values ​​of high-purity calcium carbonate and the component values ​​of the reference sample, the carbonation degree of the material to be evaluated is judged to be pass, and when the component values ​​are outside the range, the carbonation degree of the material to be evaluated is judged to be fail.

[0084] Cement-based materials L * value, a * value and b * The L values ​​of high-purity calcium carbonate increase with the progress of carbonation. * value, a * value and b * Therefore, pass / fail determination is possible by performing the above comparison.

[0085] Step (A) and Step (B) are * value, a * value and b * It is sufficient to perform the test for at least one component value selected from the above values, or it may be performed for two or three component values. The pass / fail judgment may be made for each of the three component values, and if all three pass, the test is confirmed as pass.

[0086] Step (A) and step (B) are carried out by at least L * It is preferable to perform the calculation for the L value. *The value of L shows the largest change with the progress of carbonation. * By comparing the values, a pass / fail determination of the carbonation level can be made more accurately.

[0087] [Second carbonation determination method, third carbonation determination method] The second method for determining the degree of carbonation includes steps (AL) and (BL). Step (AL): L of the material during or after carbonation treatment * a * b * Color space L * Measure the value. Step (BL): L obtained in step (AL) * The L value indicates the carbonation level of the material has reached the expected value. * If the value is equal to or greater than this value, the carbonation level of the material during or after the carbonation process is judged to be acceptable.

[0088] The third method for determining the degree of carbonation includes steps (Ab) and (Bb). Step (Ab): L of the material during or after carbonation treatment * a * b * Color space b * Measure the value. Step (Bb): b obtained in step (Ab) * The value is the b value of the material whose carbonation has reached the expected value. * If the carbonation level is equal to or less than the value, the carbonation level of the material during or after the carbonation process is judged to be acceptable.

[0089] Step (AL) and step (Ab) are substantially the same as step (A), that is, substantially the same as step (2). However, the second carbonation determination method is * The third carbonation determination method is b * Therefore, it is sufficient to know the L value from the three component values ​​obtained by color measurement. * value or b * Just extract the value. The specific and preferred embodiments of step (AL) and step (Ab) are the same as the specific and preferred embodiments of step (A) and step (2).

[0090] The material having a carbonation degree that reaches the expected value in steps (BL) and (Bb) is synonymous with the material having a carbonation degree that reaches the expected value in step (B), and the specific and preferred forms are also the same.

[0091] The process (BL) is the L of the material to be judged. * value and the L of the reference sample * This is a process for determining whether the carbonation level of the material to be evaluated is acceptable or not by comparing the L value of the cementitious material. * The judgment is made by taking advantage of the phenomenon that the value approaches 100 as carbonation progresses. L of the material to be judged * The value is the L of the reference sample. * If the value is equal to or greater than the reference sample L, the carbonation level of the material being evaluated is judged to be acceptable. * If it is less than this value, it is judged as a failure.

[0092] Step (Bb) is the step of determining the material b * value and the b of the reference sample * This is a process for determining whether the carbonation level of the material to be evaluated is acceptable or not by comparing the value of b * The determination is made by taking advantage of the phenomenon in which the value changes from a positive number to zero as carbonation progresses. b of the material to be judged * The value is the b * If the value is less than or equal to the value of the reference sample, the carbonation level of the material to be evaluated is judged as passing. * If the value is exceeded, it is judged as a failure.

[0093] The second and third carbonation degree determination methods are simpler than the first carbonation degree determination method in that they do not require information on the color value of high-purity calcium carbonate. The second carbonation determination method and L *Since the first carbonation determination method for the value is a determination method utilizing the same phenomenon, the accuracy of the determination is the same. A third carbonation determination method; and b. * Since the first carbonation determination method for the value is a determination method utilizing the same phenomenon, the accuracy of the determination is the same.

[0094] In the carbonation degree determination method of the present disclosure, steps (A), (AL), and (Ab) are steps of analyzing a material during or after carbonation treatment, and these steps involve measuring the color values ​​of the target material. Compared to thermogravimetric analysis and inorganic carbon analysis, colorimetry is simpler in terms of sample preparation and analysis methods, and requires less time for analysis. Therefore, the carbonation degree determination method of the present disclosure can be easily performed. In addition, since small and lightweight colorimeters are widely available, the colorimetry of the target materials can be performed one after another at the carbonation treatment site. Furthermore, if information on the color values ​​of high-purity calcium carbonate and / or information on the color values ​​of a reference sample is prepared, step (B), step (BL), or step (Bb) can be performed immediately after step (A), step (AL), or step (Ab) at the carbonation treatment site. Therefore, the carbonation degree determination method of the present disclosure is highly responsive to on-site operations. [Example]

[0095] Examples of the CaCO amount estimation method and carbonation degree determination method of the present disclosure are given below. The CaCO amount estimation method and carbonation degree determination method of the present disclosure are not limited to the following examples.

[0096] (1) Manufacturing of recycled fine aggregate Concrete waste generated by the demolition of buildings, bridges, tunnels, etc. is crushed and iron scrap removed. After that, the waste is coarsely crushed, blasted, and classified to obtain recycled fine aggregate.

[0097] (2) Analysis of recycled fine aggregate Before carbonation treatment, the amount of CaCO3 (mass%) in the recycled fine aggregate is estimated. For example, the ignition loss of the recycled fine aggregate is quantified by thermogravimetric analysis, and the amount of CaCO3 is estimated from the ignition loss. In addition, before the carbonation treatment, the L of recycled fine aggregate * a * b * The color space color values ​​are measured using a colorimeter. * a * b * The color space color values ​​are also measured using a colorimeter. High-purity calcium carbonate is, for example, a calcium carbonate reagent that meets the quality requirements of JIS K8617 "Calcium carbonate (reagent)."

[0098] (3) Preparation of calculation formula and calibration curve: Step (1) High purity calcium carbonate L * value (or a * value, or b * value), the CaCO3 content (mass%) and L of the recycled fine aggregate before carbonation treatment * value (or a * value, or b * The p and q in the relational equation CaCO3 content = p × color value + q are determined by the above equation and a formula for calculating the CaCO3 content of recycled fine aggregate during carbonation treatment is obtained. For example, high-purity calcium carbonate L * The value is 96, and the amount of CaCO3 in the recycled fine aggregate before carbonation is 7% by mass. * When the value is 70, p = 3.58, q = -243.38, and the calculation formula is CaCO3 amount = 3.58 x L * The value is -243.38. Enter this formula into the calculator application on your portable electronic device.

[0099] Create a calibration curve. * When the value (CaCO3 amount) = (96,100)·(70,7), the calibration curve shown in Figure 4 is obtained.

[0100] (4) Carbonation treatment of recycled fine aggregate Recycled fine aggregate is placed in a water tank equipped with a stirring device, and CO2-containing gas is supplied from the bottom of the tank while stirring the contents of the tank. The carbonation process of recycled fine aggregate using a water tank can be performed using either a batch method or a flow method. Multiple water tanks can be connected, and the recycled fine aggregate can be transferred from the upstream tank to the downstream tank while the carbonation process is performed.

[0101] (5) Sampling inspection of recycled fine aggregate: Process (2) The recycled fine aggregate was collected from the water tank during the carbonation process, dried, and then * a * b * The color values ​​in the color space are measured using a colorimeter. The model of the colorimeter used is preferably the same as that used for measuring the color of the recycled fine aggregate before carbonation treatment and the color of the high-purity calcium carbonate.

[0102] (6) Estimation of CaCO3 content: Step (3) L obtained by sampling inspection * value (or a * value, or b * The amount of CaCO3 is calculated by substituting the calculated value into the calculation formula on the calculation application of the portable electronic device. For example, the calculation formula is: Amount of CaCO3 = 3.58 x L * The value was -243.38, and the recycled fine aggregate sampled was L * When the value is 75, the amount of CaCO3 is estimated to be 3.58 × 75 - 243.38 = 25.12 mass%. Or, L obtained by sampling inspection * value (or a * value, or b * The value) is applied to the calibration curve, and the calibration curve is visually read to estimate the amount of CaCO3.

[0103] As described above, the color of the recycled fine aggregate is measured at the carbonation treatment site, and the amount of CaCO3 is immediately calculated using a calculation formula or estimated using a calibration curve. When the amount of CaCO3 in the recycled fine aggregate reaches the expected value, the carbonation treatment is terminated and the recycled fine aggregate is recovered from the water tank.

[0104] The recycled fine aggregate with the expected amount of CaCO3 was selected as the standard sample, and its L * value, a * value and b * Record the value as a reference value.

[0105] For example, the color values ​​of high-purity calcium carbonate and the CaCO3 amount and color values ​​of the reference sample are shown in Table 3.

[0106] [Table 3]

[0107] (7) Sampling inspection of recycled fine aggregate: Process (A) In a new carbonation process line, recycled fine aggregate is collected from the water tank during carbonation process, dried, and then * a * b * The color space color values ​​are measured using a colorimeter. The model of the colorimeter used is preferably the same as that used to estimate the amount of CaCO3.

[0108] (8) Carbonation Degree Determination: Step (B) The color values ​​of the high-purity calcium carbonate and the standard sample shown in Table 3 are compared with the color values ​​of the recycled fine aggregate sampled and inspected. The recycled fine aggregate sampled was L * Value 73, a * Value -0.2, b * If the value is 6, the carbonation level is unsuccessful and the carbonation process continues in the aquarium. The recycled fine aggregate sampled was L * Value 76, a * Value -0.5, b * When the value is 4, the carbonation degree is acceptable, the carbonation process is terminated, and the recycled fine aggregate is collected from the water tank.

[0109] As described above, the color of the recycled fine aggregate is measured at the carbonation treatment site, the carbonation degree is immediately determined, and based on the result of the determination, it is determined whether or not the carbonation treatment needs to be continued.

[0110] By automating the random inspection of recycled fine aggregate (steps (2) and (A)), estimation of the amount of CaCO3 (step (3)), and determination of the degree of carbonation (step (B)), it is possible to carry out the carbonation process while constantly monitoring the recycled fine aggregate in the tank.

[0111] For example, a carbonation treatment facility is installed at a thermal power plant or a cement factory, and CO2-containing gas emitted from the thermal power plant or cement factory is used to carbonate recycled fine aggregate.

Claims

1. In the carbonation treatment of materials containing cement solidified material, CaCO of the material during or after the carbonation treatment ３ 1. A method for estimating the amount of The method includes the following steps (1) to (3): The color values ​​in the following steps (1) to (3) are L ＊ a ＊ b ＊ Color space L ＊ Value, a ＊ value and b ＊ The component values ​​are of the same type selected from the values, CaCO ３ Quantity estimation method. Step (1): CaCO ３ The color value of high-purity calcium carbonate that can be considered to be 100% by mass and the CaCO of the material before carbonation treatment ３ From the amount (mass%) and color value, CaCO ３ Relationship between the amount (mass%) and color value CaCO ３ Determine p and q in the formula: quantity = p x color specification value + q. Step (2): The color value of the material is measured during or after the carbonation treatment. Step (3): The color value obtained in step (2) is calculated using the relational formula CaCO in which p and q are determined in step (1). ３ Amount = p × color value + q, and CaCO ３ Calculate the amount (mass%).

2. The color specification value is L ＊ 2. The CaCO of claim 1, ３ Quantity estimation method.

3. A method for determining the degree of carbonation of a material during or after carbonation treatment in a carbonation treatment of a material containing cement solidified material, comprising: The method includes the following steps (A) and (B): The color values ​​in the following steps (A) and (B) are L ＊ a ＊ b ＊ Color space L ＊ Value, a ＊ value and b ＊ The component values ​​are of the same type selected from the values, Method for determining carbonation. Step (A): The color value of the material is measured during or after the carbonation treatment. Step (B): The color value obtained in step (A) is ３ The carbonation degree of the material during or after the carbonation treatment is judged to be acceptable when it is within the range between the color value of high-purity calcium carbonate that can be considered to be 100% by mass and the color value of the material whose carbonation degree has reached the expected value.

4. A method for determining the degree of carbonation of a material during or after carbonation treatment in a carbonation treatment of a material containing cement solidified material, comprising: The method includes the following steps (A-L) and (B-L): Method for determining carbonation. Step (A-L): L of the material during or after carbonation treatment ＊ a ＊ b ＊ Color space L ＊ Measure the value. Step (B-L): L obtained in step (A-L) ＊ The value is the L of the material whose carbonation level has reached the expected value. ＊ If the value is equal to or greater than this value, the carbonation level of the material during or after the carbonation process is judged to be acceptable.

5. A method for determining the degree of carbonation of a material during or after carbonation treatment in a carbonation treatment of a material containing cement solidified material, comprising: The method includes the following steps (A-b) and (B-b): Method for determining carbonation. Step (A-b): L of the material during or after carbonation treatment ＊ a ＊ b ＊ Color space b ＊ Measure the value. Step (B-b): b obtained in step (A-b) ＊ The value is the b value of the material whose carbonation has reached the expected value. ＊ If the carbonation level is equal to or less than the value, the carbonation level of the material during or after the carbonation process is judged to be acceptable.

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