Auxiliary determination method for carbonization performance of cement-based material

Abstract

The invention belongs to the technical field of cement-based materials, and particularly relates to an auxiliary determination method for carbonization performance of a cement-based material. Comprising the following steps: (1) mixing thymol blue and a sodium hydroxide solution, adding water for dilution, and uniformly stirring to obtain a carbonization determination reagent; the use amount of the sodium hydroxide solution is 3-5 mL by taking the use amount of thymol blue as 1 g, and the step of diluting by adding water is that water is added to dilute to 500-1000 mL; (2) drying the cement-based material, and grinding the cement-based material into powder to obtain a to-be-tested sample; (3) adding a to-be-tested sample into the carbonization determination reagent, and soaking for a period of time to obtain a mixed solution; and (5) judging whether the cement-based material is carbonized or not according to the color of the mixed solution. The determination method can be used for auxiliary determination of carbonized and uncarbonized samples of a low-alkalinity cementing material system sample, solves the problem of unobvious color development of a low-alkalinity cement-based material through traditional phenolphthalein titration, can be used for determination through colors, and is simple and practical.

Description

Technical Field

[0001] The invention belongs to the technical field of cement-based materials, and in particular relates to a method for auxiliary determination of carbonization performance of cement-based materials. Background Art

[0002] The pH value of ordinary Portland cement hardened paste or concrete is about 13.0, which is a strong alkaline cementitious system. The phenolphthalein method is generally used to determine the carbonation depth. Cut the concrete sample into appropriate sizes and apply a layer of phenolphthalein indicator solution on the surface of the sample. The phenolphthalein indicator solution will form a red (such as Figure 1 (left) to determine the carbonation depth of cement paste / concrete. With the advancement of dual carbonization, various solid waste-based or even all-solid waste cementitious materials have gradually emerged. Solid waste-based cementitious materials have a common characteristic, which is the reduction of alkalinity. The traditional phenolphthalein method is used to measure the carbonation depth. Sometimes the color changes are obvious and sometimes there is almost no color change (such as Figure 1 (right)), it is difficult to determine the carbonation depth of cement paste / concrete. Summary of the invention

[0003] The purpose of the present invention is to provide a method for assisting in determining the carbonization performance of cement-based materials, which can assist in determining the carbonization and non-carbonization of low-alkalinity cementitious material system samples, solve the problem that low-alkalinity cement-based materials do not show obvious color through traditional phenolphthalein titration, and can determine by color, which is simple and practical.

[0004] Specifically, the present invention provides the following technical solutions:

[0005] A method for assisting determination of carbonization performance of cement-based materials, comprising the following steps:

[0006] (1) mixing thymol blue and sodium hydroxide solution, diluting with water, and stirring evenly to obtain a carbonization determination reagent;

[0007] The concentration of the sodium hydroxide solution is 0.03-0.1 mol / L; based on the dosage of thymol blue being 1 g, the dosage of the sodium hydroxide solution is 3-5 mL, and the dilution with water is dilution with water to 500-1000 mL;

[0008] (2) drying the cement-based material and grinding it into powder to obtain a sample to be tested;

[0009] (3) adding the sample to be tested into the carbonization determination reagent and soaking for a period of time to obtain a mixed solution;

[0010] (4) Determining whether the cement-based material is carbonized based on the color of the mixed liquid: when the color of the mixed liquid is purple-pink, it is determined to be carbonized; when the color of the mixed liquid is steel blue, it is determined to be not carbonized.

[0011] Preferably, in step (2), the cement-based material is a low-alkalinity cement-based material with a pH value of 10.0 to 12.0. When the low-alkalinity cement-based material is subjected to the conventional phenolphthalein method for measuring the carbonation depth, the color sometimes changes significantly, and sometimes there is almost no color change, making it difficult to determine the carbonation depth of cement paste / concrete. The present invention can solve this technical problem and is particularly suitable for determining the carbonation depth of low-alkalinity cement-based materials.

[0012] The pH value of the cement-based material of the present invention is determined by the following method: taking the cement-based material, crushing and grinding it into a powder of ≥100 mesh, mixing the powder with distilled water at a mass ratio of 1:2, taking the upper aqueous solution, and testing its pH value using pH test paper.

[0013] The cement-based material of the present invention may be a cement-based pure paste hardened body, a mortar hardened body containing fine aggregates, or a concrete hardened body containing coarse and fine aggregates.

[0014] Preferably, in step (2), the content of cement clinker in the cement-based material is less than 10 wt %. The lower the content of cement clinker in the cement-based material, the lower its alkalinity and the more environmentally friendly it is.

[0015] Preferably, in step (2), the drying temperature is above 45°C;

[0016] And / or, the fineness of the powder is above 100 mesh.

[0017] Preferably, in step (3), the mass ratio of the sample to be tested to the carbonization determination reagent is 1:(3-8).

[0018] Preferably, in step (3), the soaking time is more than 2 hours. The present invention has certain requirements on the soaking time, which must be more than 2 hours, otherwise it is difficult to determine whether it is carbonized based on the color.

[0019] Beneficial effects achieved by the present invention:

[0020] (1) The method for assisting in determining the carbonization performance of cement-based materials provided by the present invention can assist in determining the carbonization and non-carbonization of low-alkalinity cementitious material system samples by preparing a specific carbonization determination reagent, thereby solving the problem of unclear color development of the traditional phenolphthalein method. The method can be determined by color, which is simple and practical.

[0021] (2) In the auxiliary determination method for carbonization performance of cement-based materials provided by the present invention, the ratio of thymol blue and sodium hydroxide solution in the carbonization determination reagent, as well as the amount of water added for dilution are very critical to the color development effect of the final mixed solution. If they are not within the scope of the present invention, the color development is not obvious or cannot be developed, resulting in the inability to determine whether carbonization has occurred based on the color results.

[0022] (3) The auxiliary determination method for carbonization performance of cement-based materials provided by the present invention has certain requirements on the immersion time of the test sample in the carbonization determination reagent, which must be more than 2 hours. Otherwise, it is difficult to determine whether it is carbonized based on the color. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a color comparison of conventional cement-based materials and low-alkali cement-based materials after being measured by the traditional phenolphthalein method; the left picture is the color of conventional cement-based materials measured by the traditional phenolphthalein method, and the right picture is the color of low-alkali cement-based materials measured by the traditional phenolphthalein method.

[0024] Figure 2 It is a color comparison of the mixed solution of carbonized cement-based materials and non-carbonized cement-based materials after being soaked in a carbonization determination reagent; among them, the left picture is the color of the mixed solution of carbonized cement-based materials after being soaked in a carbonization determination reagent, and the right picture is the color of the mixed solution of non-carbonized cement-based materials after being soaked in a carbonization determination reagent. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in the field or the product manual shall be followed.

[0026] Example 1

[0027] A method for assisting determination of carbonization performance of cement-based materials, comprising the following steps:

[0028] (1) Take 1 g of thymol blue, add 5 ml of 0.03 mol / L sodium hydroxide solution to dissolve it, then add water to dilute it to 500 ml, and stir it thoroughly to obtain a carbonization determination reagent;

[0029] (2) The cement-based material was dried at 45°C and ground into a powder with a fineness of 100 mesh to obtain a sample to be tested;

[0030] (3) Add the sample to be tested into the carbonization determination reagent at a mass ratio of 1:8, stir evenly, and soak for 2.5 hours to obtain a mixed solution;

[0031] (4) Determine whether the cement-based material is carbonized based on the color of the mixed solution: When the color of the mixed solution is purple-pink (such as Figure 2 (left)), it is determined to be carbonized; when the color of the mixed solution is steel blue (as shown in Figure 2 (right)), it was judged that there was no carbonization.

[0032] In this embodiment, the cement-based material is a low-alkalinity gypsum slag cement-based material, wherein the mass ratio of cement clinker: mineral powder: gypsum is 5:80:15.

[0033] Example 2

[0034] A method for assisting determination of carbonization performance of cement-based materials, comprising the following steps:

[0035] (1) Take 1 g of thymol blue, add 3 ml of 0.1 mol / L sodium hydroxide solution to dissolve it, then add water to dilute it to 1000 ml, stir it thoroughly to obtain a carbonization determination reagent;

[0036] (2) After drying the cement-based material, grind it into a powder with a fineness of 200 mesh to obtain a sample to be tested;

[0037] (3) Dry the sample to be tested at 45°C;

[0038] (4) The dried test sample and the carbonization determination reagent are fully stirred at a mass ratio of 1:8 and immersed for 2.5 hours to obtain a mixed solution;

[0039] (5) Determine whether the cement-based material is carbonized based on the color of the mixed solution: when the color of the mixed solution is purple-pink, it is determined to be carbonized; when the color of the mixed solution is steel blue, it is determined to be not carbonized.

[0040] In this embodiment, the cement-based material is composed of PO42.5 cement, mineral powder, gypsum, and fly ash, and the mass ratio of each component is 10:65:10:15.

[0041] Although the present invention has been described in detail above by general description, specific implementation methods and experiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for auxiliary determination of carbonization performance of cement-based materials, characterized in that: The following steps are involved: (1) mixing thymol blue and sodium hydroxide solution, diluting with water, and stirring evenly to obtain a carbonization determination reagent; The concentration of the sodium hydroxide solution is 0.03-0.1 mol / L; based on the dosage of thymol blue being 1 g, the dosage of the sodium hydroxide solution is 3-5 mL, and the dilution with water is dilution with water to 500-1000 mL; (2) drying the cement-based material and grinding it into powder to obtain a sample to be tested; (3) adding the sample to be tested into the carbonization determination reagent and soaking for a period of time to obtain a mixed solution; (4) Determining whether the cement-based material is carbonized based on the color of the mixed liquid: when the color of the mixed liquid is purple-pink, it is determined to be carbonized; when the color of the mixed liquid is steel blue, it is determined to be not carbonized.

2. The method for auxiliary determination of carbonization performance of cement-based materials according to claim 1, characterized in that: In step (2), the cement-based material is a low-alkalinity cement-based material with a pH value of 10.0 to 12.

0.

3. The method for auxiliary determination of carbonization performance of cement-based materials according to claim 1 or 2, characterized in that: In step (2), the content of cement clinker in the cement-based material is less than 10%.

4. The method for auxiliary determination of carbonization performance of cement-based materials according to claim 1 or 2, characterized in that: In step (2), the drying temperature is above 45°C; And / or, the fineness of the powder is above 100 mesh.

5. The method for auxiliary determination of carbonization performance of cement-based materials according to claim 1 or 2, characterized in that: In step (3), the mass ratio of the sample to be tested to the carbonization determination reagent is 1:(3-8).

6. The method for auxiliary determination of carbonization performance of cement-based materials according to claim 1 or 2, characterized in that: In step (3), the soaking time is more than 2 hours.

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