Interface reinforced high-strength carbonized aerated concrete and preparation method thereof

Abstract

The application discloses an interface-reinforced high-strength carbonized aerated concrete, which comprises a carbonizable slurry and modified foam; wherein the carbonizable slurry takes steel slag, water and a water reducing agent as main raw materials; and the modified foam adopts a foaming mother liquor component which comprises a foaming agent, water, a soluble magnesium salt, urea, urease and polyacrylic acid. The application effectively improves the strength of the aerated concrete by optimizing the pore interface of the carbonized aerated concrete, and ensures good mechanical properties and durability under the premise of ensuring a low bulk density; and the preparation method is simple, convenient to operate, low in cost and suitable for popularization and application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to an interface-reinforced high-strength carbonized aerated concrete and a preparation method thereof. BACKGROUND

[0002] At present, the overall utilization rate of industrial solid wastes such as steel slag and magnesium slag is low. The utilization rate can be effectively improved by using steel slag, magnesium slag and the like with carbonation activity as raw materials to prepare aerated concrete. In addition, the carbonation curing using factory carbon-containing waste gas as a carbon source can also effectively reduce carbon emissions. Although the carbonized aerated concrete has many advantages such as heat preservation, heat insulation, fire resistance and low carbon green, it still has the problems of high bulk density and low strength compared with autoclaved aerated concrete, which seriously restricts its production and application. Therefore, it has become a technical difficulty in the industrialization process of carbonized aerated concrete to improve the strength of carbonized aerated concrete while keeping the bulk density basically unchanged.

[0003] The carbonized aerated concrete is a porous material, and stress concentration phenomenon exists at small pores in the stress process, and cracks are easy to expand along the defects of the pore wall until the whole is destroyed. Defects such as pore wall collapse, wrinkles and uneven distribution of carbonation products inevitably exist in the pore wall of the carbonized aerated concrete during forming and curing, which further affects the comprehensive performance of the obtained carbonized product. SUMMARY

[0004] The main purpose of the present application is to provide a high-strength carbonized aerated concrete based on interface reinforcement to solve the problems and deficiencies of the prior art. By optimizing the pore interface of the carbonized aerated concrete, the strength of the carbonized aerated concrete can be significantly improved, and good mechanical properties and durability can be achieved while keeping the bulk density low. The preparation method is simple and easy to operate, and is suitable for popularization and application.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0006] An interface-reinforced high-strength carbonized aerated concrete, wherein the raw materials include carbonizable slurry and modified foam; the carbonizable slurry is mainly made of steel slag, water and water reducing agent; the modified foam uses a foaming mother liquor composition including a foaming agent, water, a soluble magnesium salt, urea, urease and polyacrylic acid.

[0007] In the above scheme, the mass ratio of the carbonizable slurry and the modified foam is 100:4-6.

[0008] In the above scheme, the mass ratio of the steel slag, water and water reducing agent in the carbonizable slurry is 100:20-30:0.1-0.5.

[0009] In the above scheme, the mass ratio of the foaming agent, water, soluble magnesium salt, urea, urease, and polyacrylic acid in the modified foam is 1:40-80:5-10:20-40:0.05-0.1:0.03-0.06.

[0010] Preferably, the mass ratio of the soluble magnesium salt and polyacrylic acid is 120-180:1.

[0011] In the above scheme, the main chemical compositions and mass percentages in the steel slag include C2S 40-60%, C3S 5-15%, Ca(OH)2 0-1%, Ca2Fe2O5 0-20%, CaCO3 0-10%, SiO2 0-10%, and the specific surface area is 300-400 m 2 / kg.

[0012] In the above scheme, the water-reducing rate of the water-reducing agent is 35-45%, and preferably, the water-reducing agent is a polycarboxylic acid superplasticizer.

[0013] In the above scheme, the foaming agent is preferably a physical foaming agent, the pH value is 6-8, the prepared foam has a bleeding amount of 40 ml or less, a sedimentation distance of 10 mm or less, and a density of 30-50 kg / m 3 ; and specifically, a protein foaming agent can be selected.

[0014] In the above scheme, the water temperature is 20-35°C.

[0015] In the above scheme, the soluble magnesium salt includes at least one of magnesium chloride and magnesium sulfate, and the effective component content is required to be not less than 95%.

[0016] In the above scheme, the total nitrogen content of the urea is 46 wt% or more, and the biuret content is 1.5 wt% or less.

[0017] In the above scheme, the urease activity (pH increment method) is 1.0-2.0, and the effective component content is not less than 99%.

[0018] In the above scheme, the polyacrylic acid has a molecular weight of 3000-8000, and the effective component content is not less than 99%.

[0019] The preparation method of the above interface-strengthened high-strength carbonized aerated concrete includes the following steps: weighing the foaming agent, water, soluble magnesium salt, urea, urease, and polyacrylic acid in a proportion, stirring them uniformly until they are fully dissolved to obtain a foaming mother liquor, and then foaming to obtain a modified foam; weighing the steel slag, water, and water-reducing agent in a proportion, and stirring them uniformly to obtain a carbonizable slurry; weighing the modified foam and the carbonizable slurry in a proportion, and stirring them uniformly to obtain a foam slurry; pouring the foam slurry into a mold for static standing, and after hardening, demolding to obtain a blank; and after carbonization and curing, obtaining a high-strength carbonized aerated concrete product.

[0020] In the above scheme, the stirring time of the foaming mother liquor is 2-3 min, and the stirring rate is 30-60 r / min.

[0021] In the above scheme, the prepared modified foam has a bleeding amount of 50 ml or less, a sedimentation distance of 12 mm or less, and a density of 40-60 kg / m 3 .

[0022] In the above scheme, the stirring time of the carbonizable slurry is 3-6 min, and the stirring rate is 45-90 r / min.

[0023] In the above scheme, the stirring time of the carbonizable slurry and the modified foam is 2-3 min, and the stirring rate is 45-60 r / min.

[0024] In the above scheme, the static standing time is 3-4 h, the temperature is 25-35℃, and the relative humidity is 50-80%.

[0025] In the above scheme, the carbonization curing time is 4-10 h, the temperature is 40-60℃, the pressure is 0.3-0.5 MPa, and the carbon dioxide concentration is 20-100 vol%.

[0026] The high-strength carbonized aerated concrete prepared according to the above scheme has a compressive strength of 4.5-5.5 MPa, a bulk density of 600-650 kg / m 3 , a dry shrinkage of 0.2 mm / m or less, a splitting tensile strength of 1.0-1.2 MPa, and a thermal conductivity of not more than 0.12 W / (m·K).

[0027] The performance optimization mechanism of the carbonized aerated concrete according to the present application includes:

[0028] 1) After the modified foam is uniformly stirred with the alkaline carbonizable slurry, the flocculated magnesium hydroxide formed by the magnesium salt is mainly concentrated near the bubble wall. During the carbonization process, the magnesium ions can inhibit calcite and promote the generation of whisker-shaped aragonite, which promotes the growth of aragonite near the pore wall. Aragonite has high tensile strength, and can effectively delay the crack propagation during the stress process and improve the strength by filling and lapping with other carbonization products such as calcite and silica gel.

[0029] 2) Urea gradually decomposes under the catalysis of urease and releases carbon dioxide inside the slurry, which can promote the rapid setting of the pore wall, effectively reduce defects such as pore wall collapse and wrinkle cracks, and shorten the static standing time. In addition, the flocculated magnesium hydroxide near the bubble wall is beneficial to inhibit the diffusion of urea and urease into the slurry, so that the carbon dioxide generated by the decomposition of urea is mainly concentrated near the pore wall, and the carbonization degree of the pore wall is increased, which also effectively improves the strength.

[0030] 3) The soluble magnesium salt and the polyacrylic acid jointly adjust the pH value of the pore wall of the slurry, so that the urease has high activity and gradually catalyzes the decomposition of urea. In addition, the polyacrylic acid is preferentially adsorbed on the surface of the aragonite whisker, inhibits the transformation of the aragonite crystal phase to calcite, so that the aragonite crystal phase stably exists, and the performance degradation of the carbonated aerated concrete in the later period is prevented.

[0031] Compared with the prior art, the beneficial effects of the present application are:

[0032] 1) After using the modified foam, the amount of carbonation products at the pore wall of the carbonated aerated concrete is increased; after the pore wall is strengthened, the strength of the carbonated aerated concrete can be effectively improved without changing the bulk density.

[0033] 2) The steel slag used in the present application is a by-product in the steel smelting process, and the hardening process comes from the carbonation reaction of the steel slag, without introducing cement and other raw materials, which has significant economic and environmental benefits.

[0034] 3) The magnesium salt as the carbonation product crystal form control agent mainly acts on the pore wall, and adjusts the pH value to ensure that the urea catalytic decomposition process proceeds normally; in addition, the generated flocculent magnesium hydroxide can inhibit the diffusion of urea and urease to a certain extent, promote the generation of carbon dioxide mainly at the pore wall, improve the interfacial strength, and thus effectively improve the strength of the carbonated aerated concrete, etc.

[0035] 4) The decomposition of urea produces carbon dioxide, which plays a good internal curing role in the carbonated aerated concrete, which is beneficial to shorten the carbonation curing time. DETAILED DESCRIPTION

[0036] The present application will be further described in detail below in combination with examples, so as to more clearly understand the present application, but they do not constitute a limitation on the present application.

[0037] In the following examples and comparative examples, the main chemical composition and mass percentage of the steel slag used include: C2S 58%, C3S 8%, Ca(OH)2 0.5%, Ca2Fe2O5 12%, CaCO3 9%, SiO2 8%, and the specific surface area is 372 m 2 / kg; the polycarboxylic acid superplasticizer used has a solid content of 46%, and a water-reducing rate of 42%; the physical foaming agent used is HTW-1 plant protein composite foaming agent provided by Henan Huatai New Material Technology Co., Ltd., with a pH value of 6.5, a prepared foam bleeding amount of 30 ml, a sedimentation distance of 8 mm, and a density of 41 kg / m 3; the water temperature used for foaming is 28 DEG C; the magnesium chloride used has an active ingredient of 98%, and the magnesium sulfate has an active ingredient of 96%; the urea used has a total nitrogen mass fraction of 46.2%, and the biuret is 0.8%; the urease activity used (pH increment method) is 1.9, and the active ingredient is 99.3%; the polyacrylic acid has an average molecular weight of 5000, and the active ingredient is 99.1%.

[0038] Example 1

[0039] A high-strength carbonated aerated concrete, and a preparation method thereof, the preparation method comprising the following steps:

[0040] 1) taking 1 part (by weight, the same below) of a foaming agent, 60 parts of water, 6 parts of magnesium chloride, 25 parts of urea, 0.06 parts of urease, and 0.04 parts of polyacrylic acid, and stirring uniformly to obtain a foaming mother liquor, wherein the stirring time is 3 min, and the stirring rate is 45 r / min; foaming the foaming mother liquor to obtain modified foam, the modified foam having a bleeding amount of 32 ml, a sedimentation distance of 6 mm, and a density of 45 kg / m 3 ;

[0041] 2) taking 100 parts of steel slag, 25 parts of water, and 0.8 parts of a water reducing agent, and stirring uniformly to obtain carbonizable slurry, wherein the stirring time is 4 min, and the stirring rate is 60 r / min;

[0042] 3) taking 100 parts of the carbonizable slurry and 5 parts of the modified foam, and stirring uniformly to obtain foam slurry, wherein the stirring time is 3 min, and the stirring rate is 60 r / min;

[0043] 4) pouring the foam slurry into a mold for static standing, and demolding after hardening to obtain a green body, wherein the static standing time is 4 h, the temperature is 30 DEG C, and the relative humidity is 70%;

[0044] 5) obtaining carbonated aerated concrete products after carbonization curing of the green body, wherein the carbonization curing time is 10 h, the temperature is 40 DEG C, the pressure is 0.3 MPa, and the carbon dioxide concentration is 23 vol%.

[0045] Example 2

[0046] A high-strength carbonated aerated concrete, and a preparation method thereof, the preparation method being substantially the same as that of Example 1, except that the soluble magnesium salt in the foaming solution is magnesium sulfate.

[0047] Example 3

[0048] A high-strength carbonated aerated concrete, and a preparation method thereof, the preparation method being substantially the same as that of Example 1, except that the urea in the foaming solution is 30 parts, and the urease is 0.07 parts.

[0049] Example 4

[0050] A high-strength carbonized aerated concrete is prepared in a manner largely the same as in Example 1, except that the carbonization curing time is 5 hours, the temperature is 40°C, the pressure is 0.5 MPa, and the carbon dioxide concentration is 92 vol%.

[0051] Comparative Example 1

[0052] A high-strength carbonized aerated concrete is prepared in a manner similar to that of Example 1, except that soluble magnesium salts are not used in the foaming solution.

[0053] Comparative Example 2

[0054] A high-strength carbonized aerated concrete is prepared in a manner largely the same as in Example 1, except that urease is not used in the foaming solution.

[0055] Comparative Example 3

[0056] A high-strength carbonized aerated concrete is prepared in a manner largely the same as in Example 1, except that polyacrylic acid is not used in the foaming solution.

[0057] Comparative Example 4

[0058] A high-strength carbonized aerated concrete is prepared in a manner similar to that of Example 1, except that the amount of soluble magnesium salt in the foaming solution is adjusted to 5 parts and the amount of polyacrylic acid is adjusted to 0.06 parts.

[0059] The carbonized aerated concrete obtained in Examples 1-4 and Comparative Examples 1-4 was subjected to performance tests, and the results are shown in Table 1.

[0060] Table 1. Performance test results of carbonized aerated concrete

[0061]

[0062] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A high-strength carbonized aerated concrete with interface strengthening, characterized in that, Its raw materials include carbonizable slurry and modified foam; the carbonizable slurry mainly uses steel slag, water and water-reducing agent as raw materials; the foaming mother liquor used in the modified foam includes foaming agent, water, soluble magnesium salt, urea, urease and polyacrylic acid. The mass ratio of the soluble magnesium salt to polyacrylic acid is 120~180:1; The mass ratio of the carbonizable slurry to the modified foam is 100:4~6; The mass ratio of steel slag, water, and water-reducing agent in the carbonizable slurry is 100:20~30:0.1~0.

5.

2. The high-strength carbonized aerated concrete according to claim 1, characterized in that, The mass ratio of foaming agent, water, soluble magnesium salt, urea, urease, and polyacrylic acid in the modified foam is 1:40~80:5~10:20~40:0.05~0.1:0.03~0.

06.

3. The high-strength carbonized aerated concrete according to claim 1, characterized in that, The main chemical composition and mass percentage of the steel slag include: C2S 40~60%, C3S 5~15%, Ca(OH)2 0~1%, Ca2Fe2O5 0~20%, CaCO3 0~10%, SiO2 0~10%; specific surface area 300~400m² 2 / kg.

4. The high-strength carbonized aerated concrete according to claim 1, characterized in that, The water-reducing agent has a water reduction rate of 35-45%.

5. The high-strength carbonized aerated concrete according to claim 1, characterized in that, The foaming agent is a physical foaming agent with a pH of 6-8. The prepared foam has a water exudation volume of less than 40 ml, a settling distance of less than 10 mm, and a density of 30-50 kg / m³. 3 .

6. The high-strength carbonized aerated concrete according to claim 1, characterized in that, The total nitrogen content of the urea is above 46 wt%, and the biuret content is below 1.5 wt%.

7. The high-strength carbonized aerated concrete according to claim 1, characterized in that, The urease activity is 1.0~2.

0.

8. The method for preparing high-strength carbonized aerated concrete according to any one of claims 1 to 7, characterized in that, The process includes the following steps: Weigh foaming agent, water, soluble magnesium salt, urea, urease, and polyacrylic acid according to the proportion, stir and dissolve to obtain foaming mother liquor, and then foam to obtain modified foam; Weigh steel slag, water, and water-reducing agent according to the proportion, stir evenly to obtain carbonizable slurry; Weigh modified foam and carbonizable slurry according to the proportion, stir evenly to obtain foam slurry; Pour the foam slurry, let it stand still, and after it hardens, demold to obtain a green body; Carbonize and cure the green body to obtain high-strength carbonized aerated concrete products.

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