A high-strength carbonated aerated concrete and its preparation method

Abstract

The present invention discloses a high-strength carbonated aerated concrete. The raw materials and their respective weight parts include: 85-90 parts of modified carbonated slurry, 10-15 parts of cement, 3-5 parts of mixing water, 0.1-0.2 parts of physical foaming agent, and 0.2-0.3 parts of water reducing agent. The modified carbonated slurry is mainly made of air-hardening materials and crystal form regulators, which are stirred evenly with water, and then CO2 gas is introduced into the obtained mixed slurry for stirring treatment. The present invention uses air-hardening materials as the main raw materials and combines an optimized secondary carbonation process, which can greatly shorten the preparation cycle of carbonated aerated concrete, effectively balance strength, heat preservation performance and shrinkage performance, has significant environmental and economic benefits, high operability, and is suitable for popularization and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to a high-strength carbonated aerated concrete and a preparation method thereof. Background Art

[0002] Aerated concrete has excellent properties such as light weight, heat insulation, earthquake resistance, and fire resistance, and is widely used as a new type of building energy-saving wall material. Autoclaved aerated concrete generally has problems such as high requirements for the quality of siliceous materials, high energy consumption costs, and high carbon emissions during the preparation process; carbonated aerated concrete mainly provides strength by accelerating the carbonation reaction of cementitious materials to generate calcium carbonate and silica gel, and has the advantages of energy conservation and emission reduction.

[0003] However, there are still several problems to be solved urgently in the current carbonated maintenance of aerated concrete: (1) High requirements for carbonated maintenance conditions: Currently, the carbonated maintenance system for aerated blocks requires a relatively high CO2 concentration (above 80%) and a relatively long carbonated maintenance time (more than 1 day); (2) Low carbonation efficiency of aerated blocks, low carbonation degree of the green body, and low amount of carbonation products resulting in low carbonation strength; (3) Uneven distribution of carbonation products in aerated blocks, poor adhesion between each other resulting in low structural strength; (4) High dosage of air-hardening materials will cause slow hardening of the green body, resulting in a long static stopping time. Summary of the Invention

[0004] The main purpose of the present invention is to provide a high-strength carbonated aerated concrete based on a secondary carbonation process in view of the problems and deficiencies existing in the prior art. Using air-hardening materials as the main raw materials and combining with an optimized secondary carbonation process, it can significantly shorten the preparation cycle of carbonated aerated concrete, effectively balance strength, heat insulation performance and shrinkage performance, has significant environmental and economic benefits, is highly operable, and is suitable for popularization and application.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A high-strength carbonated aerated concrete, the raw materials and their weight portions include: 85 - 90 parts of modified carbonated slurry, 10 - 15 parts of cement, 3 - 5 parts of mixing water, 0.1 - 0.2 parts of physical foaming agent, 0.2 - 0.3 parts of water reducing agent; wherein the modified carbonated slurry uses air-hardening materials and crystal form regulators as the main raw materials, adds water and stirs evenly, and then stirs and processes by introducing CO2 gas into the obtained mixed slurry.

[0007] In the above solution, the total content of carbonation active mineral components CS, C3S2, C3S, and C2S in the air-hardening materials is greater than 80wt%; its specific surface area is 300 - 400m 2 / kg.

[0008] In the above solution, the air-hardening material can be selected from one or a combination of magnesium slag, steel slag, etc.

[0009] Preferably, the air-hardening material includes a combination of magnesium slag and steel slag; further, the content of magnesium slag in the air-hardening material is 40-60%.

[0010] In the above solution, the crystal form regulator can be any one of MgCl2, soluble phosphate, AlCl3, etc.

[0011] In the above solution, the mass ratio of the air-hardening material to the crystal form regulator in the modified carbonized slurry is 80-90:10-20; the water content is 27-30 wt%.

[0012] In the above solution, the cement can be selected from portland cement, etc., and its specific surface area is 300-400 m 2 / kg.

[0013] In the above solution, the physical foaming agent can be selected from protein-based foaming agents, and the foaming multiple is 25-50 times; the water reducing agent can be selected from high-performance polycarboxylate water reducing agents, and the water reducing efficiency is 30-50%.

[0014] The preparation method of the above high-strength carbonized aerated concrete specifically includes the following steps:

[0015] 1) Preparation of modified carbonized slurry: Mix the air-hardening material and the crystal form regulator with water according to the ratio and stir evenly, then introduce CO2 gas to obtain the modified carbonized slurry;

[0016] 2) Preparation of slurry solution: Mix the modified carbonized slurry, cement and water reducing agent according to the ratio and stir evenly to prepare the slurry solution;

[0017] 3) Preparation of finished slurry: Weigh the physical foaming agent and mixing water according to the ratio, dilute them to make foam; add the foam to the slurry solution and stir evenly to obtain the finished slurry;

[0018] 4) Casting, static curing: Pour the finished slurry into the mold for forming, and place the mold in the static curing chamber for curing;

[0019] 5) Wet carbonization curing: After the green body is demolded and cut, put it into the carbonization kettle and introduce carbon dioxide gas for carbonization curing to obtain the final high-strength carbonized aerated concrete product.

[0020] In the above solution, in step 1), the reaction temperature of the slurry is controlled at 60 - 80°C; the stirring time of the air-hardening material and the crystal form modifier with water is 3 - 5 min, and the stirring rate is 600 - 1350 r / min; the concentration of the CO2 gas introduced is preferably 80 - 100 vol%; the stirring treatment step is to introduce CO2 at a certain flow rate under stirring conditions (stirring while introducing CO2), where the flow rate of the introduced CO2 is preferably 0.2 - 0.4 L / (min·kg), the stirring time of the slurry is 40 - 60 min, and the stirring rate is 300 - 600 r / min.

[0021] In the above solution, in step 2), the stirring time is 40 - 60 s, and the stirring rate is 300 - 600 r / min.

[0022] In the above solution, in step 3), the stirring time of the finished product slurry is 3 - 4 min, and the stirring rate is 450 - 750 r / min.

[0023] In the above solution, in step 4), the temperature for static curing is 50 - 70°C, and the time is 2 - 3 h; the specific method is not strictly limited. For example, the temperature of the static curing chamber can be maintained by using waste heat containing carbon dioxide gas.

[0024] In the above solution, for the wet carbonization curing in step 5), the CO2 concentration in the carbon dioxide-containing gas is not less than 15%, preferably 25 - 35%; the carbonization curing temperature is 50 - 70°C, the relative humidity is 50 - 70%, the pressure is 0.1 - 0.3 MPa, and the time is 8 - 12 h; there is no strict limitation on the introduced CO2-containing gas. For example, the flue gas from the industrial furnace or boiler in the factory can be introduced into the carbonization kettle for curing.

[0025] The high-strength carbonized aerated concrete prepared according to the above solution has its performance reaching above the excellent product grade of B06 - B07 level.

[0026] In the preparation process of the modified carbonized slurry of the present invention, CO2 gas is introduced while stirring, and under the influence of the crystal form regulator, by controlling the slurry reaction temperature, stirring rate and CO2 flow rate, aragonite whiskers with a specific morphology can be rapidly generated on the surface of the air-hardening material. At the same time, the content of aragonite whiskers in the slurry is controlled by the CO2 introduction time; during the static curing process, the formed aragonite whiskers can effectively accelerate the cement hydration and shorten the static curing time of the green body; during the secondary carbonization curing process, the aragonite whiskers serve as the initial skeleton, and the carbonization hydration reaction products grow around the needle-like aragonite whiskers. The "nested" structure can make the carbonization product structure uniform and dense. At the same time, under the action of the nano-calcium carbonate crystal nucleus effect formed by the primary carbonization, the carbonization degree and efficiency of the secondary carbonization are further improved.

[0027] The principle of the present invention is:

[0028] 1) The present invention uses air-hardening materials and crystal form regulators as the main raw materials. During the stirring process of the modified carbonized slurry, CO2 is introduced to perform a primary carbonization treatment on the air-hardening materials. By controlling the flow rate of the introduced CO2, the supersaturation of the slurry can be controlled, and initial nucleation sites can be quickly formed on the surface of the air-hardening materials. At the same time, by controlling the reaction temperature of the slurry (whisker formation requires additional energy to overcome the nucleation energy. When the temperature is between 60 and 80 °C, the length and aspect ratio of the whiskers are significantly increased, and the uniformity is good), and the stirring rate of the slurry (appropriate stirring can ensure the uniformity of the temperature and concentration of the reaction system, and promote the large-scale formation of aragonite whiskers), aragonite whiskers with excellent aspect ratio can be in-situ grown on the surface of the air-hardening materials. Compared with externally added aragonite whiskers, the interfacial adhesion between them and the uncarbonized components on the surface of the air-hardening materials is stronger. At the same time, the content of aragonite whiskers in the slurry is controlled by the time of introducing CO2 (too many aragonite whiskers will instead lead to an increase in the penetration rate of micropores, a decrease in the internal strength of the cement stone, and the formation of microcracks under external loads, resulting in a decrease in performance).

[0029] 2) During the secondary carbonization curing process, the nucleation effect of the aragonite whiskers makes the carbonization products more dispersed, reduces the thickness of the carbonization product layer on the surface of the air-hardening materials, promotes the dissolution of Ca 2+ , and thus improves the carbonization efficiency and degree. The two ends of the aragonite whiskers can be bonded to the carbonization products, playing a "bridge" role. The needle-like aragonite whiskers connect the chain-like calcium carbonate formed by the carbonization reaction and the cross-linked network structure of the silica gel, forming a "nesting" structure, improving the adhesion between the carbonization products, and thus improving the structural strength of the aerated concrete. At the same time, the growth of the carbonization products on the aragonite whiskers obtained in the present invention is conducive to filling the pore structure on the pore walls of the green body, refining the pore diameter, reducing the proportion of connected pores, and improving the thermal insulation performance of the aerated concrete. And due to the increase in carbonization products under the carbonization effect, the air-hardening materials will produce a phenomenon of slight volume expansion (different from the hydraulic system), which can neutralize the natural "shrinkage" phenomenon of the aerated concrete and endow it with good shrinkage performance.

[0030] 3) During the cement hydration process, the heterogeneous nucleation effect of the aragonite whiskers provides a larger reaction area for the deposition of hydration products, accelerates the growth and precipitation rate of the hydration product C-S-H gel, and promotes the hydration of cement.

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

[0032] 1) Adopt the primary carbonization treatment and the secondary carbonization maintenance process of wet carbonization to improve the carbonization efficiency and degree of aerated concrete; during the primary carbonization treatment process, aragonite whiskers with a specific morphology can be generated and the air-hardening material can be pre-carbonized to increase the nucleation sites. The secondary wet carbonization can improve the adhesion of carbonization products in aerated concrete and optimize its pore structure, refine the pore diameter, and reduce the proportion of connected pores, so as to prepare high-strength carbonized aerated concrete, and its mechanical properties, heat insulation properties, shrinkage properties, etc. all meet the standard requirements of the first-class products of aerated concrete blocks of models B06 - B07;

[0033] 2) The regulated aragonite whisker fibers can effectively improve the cement hydration rate, accelerate the hardening rate of the green body, shorten the static maintenance time, and significantly improve the factory turnover efficiency; the aragonite whisker fibers can also improve the hydration strength of aerated concrete and reduce the cement dosage, saving raw material costs;

[0034] 3) It has significant environmental and economic benefits; during the mixing process of the slurry described in the present invention, the air-hardening material has been initially carbonized, and the introduced aragonite whisker fibers can effectively improve the carbonization and hydration reaction rates, and can greatly shorten the carbonization maintenance time; at the same time, low-concentration carbon dioxide-containing gas can be used for wet carbonization maintenance, reducing the maintenance energy consumption and the carbon emissions of the factory, with wide applicability. Description of the Drawings

[0035] Figure 1 It is a schematic diagram of the production process flow of carbonization-enhanced aerated concrete. Detailed Embodiments

[0036] The present invention will be further explained below in conjunction with embodiments. Among them, the embodiments are only used for illustrative purposes and do not limit the scope of implementation of the present invention.

[0037] In the following examples and comparative examples, the P.O42.5 Portland cement, magnesium slag and water reducer are provided by Huaxin Cement Co., Ltd., among which the specific surface area of P.O42.5 Portland cement is 350m 2 / kg, and the main mineral components and their mass percentages in magnesium slag are: C3S 10%, β-C2S 34%, C3S2 11%, CS 38%, SiO2 4.9%, MgO 2%, and the specific surface area after ball milling is 330m 2 / kg, and the water reducing efficiency of the water reducer is 30%; the MgCl2 and AlCl3 used are provided by Tianjin Kemiou Chemical Reagent Co., Ltd. with a purity of 98%; the steel slag used is a by-product generated during the iron-making process of the steel mill, and its main mineral components and their mass percentages include: C2S 26.2%, C3S2 8.6%, CS 32.6%, C3S 10.8%, quartz 9%, limonite dolomite 12.7%, and the specific surface area after ball milling is 320m 2 / kg; The physical foaming agent used is an animal protein-based concrete foaming agent, with a 1-hour sedimentation distance of 6.5 mm, a 1-hour bleeding water volume of 78.5 ml, and a foaming multiple of 25 times.

[0038] Example 1

[0039] A high-strength carbonated aerated concrete, and its preparation method includes the following steps:

[0040] 1) Weigh each raw material according to the ratio. The raw materials and their respective weight parts are: 90 parts of modified carbonated slurry, 10 parts of cement, 3 parts of mixing water, 0.2 parts of physical foaming agent, and 0.3 parts of water reducing agent; among which, the mass ratio of the air-hardening material to the crystal form regulator MgCl2 in the modified carbonated slurry is 90:10. The raw materials and their proportions in the air-hardening material are: 40wt% of magnesium slag, 60wt% of steel slag, and the carbonation active mineral component in the air-hardening material is 84%;

[0041] 2) Stir the weighed magnesium slag, steel slag, MgCl2 and water (the slurry reaction temperature is 70 °C, and the water accounts for 27wt% of the mass of the modified carbonated slurry) at a rate of 850 r / min for 4 min, and then introduce 100% concentration CO2 under the stirring condition of 450 r / min. The CO2 flow rate is 0.3 L / (min·kg), and continue to stir for 50 min to obtain the modified carbonated slurry;

[0042] 3) Stir the weighed modified carbonated slurry, cement and water reducing agent at 500 r / min for 50 s, then dilute and stir the physical foaming agent and mixing water into foam and add it to the slurry, and continue to stir at 600 r / min for 4 min to obtain the finished slurry;

[0043] 4) Pour the finished slurry into the mold frame, and after static curing at 60 °C for 2 h, it can be demolded and cut. After cutting, the blank is put into the autoclave for wet carbonation curing (wherein, control the CO2 concentration of the carbon dioxide gas to be 35%, the autoclave pressure to be 0.2 MPa, the temperature to be 60 °C, and the relative humidity to be 65%). The carbonation time is 8 h (#1), 10 h (#2), and 12 h (#3) respectively.

[0044] Refer to the standard GB / T11969-2008 to detect the performance of the carbonated aerated concrete in this example. The specific detection results are shown in Table 1.

[0045] Table 1 Performance detection results of the aerated concrete obtained in Example 1 Example 2

[0046] A high-strength carbonated aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that: the crystal form regulator is AlCl3, the air-hardening material in the modified carbonated slurry: AlCl3 = 80:20, the CO2 concentration in the wet carbonation maintenance is controlled at 15%, and the carbonation time is 10 h; the specific performance test results are shown in Table 2.

[0047] Table 2 Performance test results of the aerated concrete obtained in Example 2 Example 3

[0048] A high-strength carbonated aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that: the raw materials and their proportions in the air-hardening material are: 60 wt% of magnesium slag, 40 wt% of steel slag, the carbonation active mineral component in the air-hardening material is 87%, and the carbonation time is 10 h; the specific performance test results are shown in Table 3.

[0049] Table 3 Performance test results of the aerated concrete obtained in Example 3 Comparative Example 1

[0050] A high-strength carbonated aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that: no crystal form regulator is used, the air-hardening material in the modified carbonated slurry: MgCl2 = 100:0, the static setting and maintenance time of the prepared green body is 8 h, and the carbonation times in the carbonation maintenance process are 8 h, 10 h, and 12 h respectively; the specific performance test results are shown in Table 4.

[0051] Table 4 Performance test results of the aerated concrete obtained in Comparative Example 1

[0052]

[0053]

[0054] Comparative Example 2

[0055] A high-strength carbonated aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that:

[0056] No crystal form regulator is used, the air-hardening material in the modified carbonated slurry: aragonite whiskers = 92:8, aragonite whiskers are directly externally added (the aragonite whiskers are provided by Hubei Langbowan Biopharmaceutical Co., Ltd., with an average diameter of 1 μm and an average aspect ratio of 35), the stirring system and the maintenance system are both kept consistent, and the carbonation time is 10 h; the specific performance test results are shown in Table 5.

[0057] Table 5 Performance test results of the aerated concrete obtained in Comparative Example 2

[0058]

[0059] Comparative Example 3

[0060] A high-strength carbonated aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that:

[0061] During the preparation of the modified carbonated slurry, the slurry reaction temperature is 50 °C (#10), 90 °C (#11); the carbonation duration is 10 h; the specific performance test results are shown in Table 6.

[0062] Table 6 Performance test results of the aerated concrete obtained in Comparative Example 3

[0063] Comparative Example 4

[0064] A high-strength carbonated aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that: during the preparation of the modified carbonated slurry, the stirring rate after introducing CO2 gas is 750 r / min, and the stirring time is 90 min; the carbonation duration is 10 h; the specific performance test results are shown in Table 7.

[0065] Table 7 Performance test results of the aerated concrete obtained in Comparative Example 4

[0066] Comparative Example 5

[0067] A high-strength carbonated aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that: during the preparation of the modified carbonated slurry, the flow rate of the introduced CO2 gas is 0.8 L / (min·kg); the carbonation duration is 10 h; the specific performance test results are shown in Table 8.

[0068] Table 8 Performance test results of the aerated concrete obtained in Comparative Example 5 Comparative Example 6

[0069] A high-strength carbonated aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that:

[0070] During the wet carbonation process, (#13) the temperature in the autoclave is 30 °C and the relative humidity is 30%, (#14) the temperature in the autoclave is 90 °C and the relative humidity is 90%, and the carbonation duration is 10 h; the specific performance test results are shown in Table 8.

[0071] Table 9 Performance test results of the aerated concrete obtained in Comparative Example 6 The present invention is not limited to the above embodiments. For those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications are also considered within the scope of protection of the present invention. The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

Claims

1. A method for preparing high-strength carbonized aerated concrete, characterized in that: The steps include: 1) Preparation of modified carbonized slurry: Add water to the air-hardening material and the crystal form modifier according to the ratio and stir evenly, then introduce CO2 gas for stirring to obtain the modified carbonized slurry; the mass ratio of the air-hardening material and the crystal form modifier in the modified carbonized slurry is 80~90:10~20; the water content is 27~30wt%; the total content of the carbonization active mineral components CS, C3S2, C3S, and C2S in the air-hardening material is greater than 80wt%; its specific surface area is 300~400m 2 / kg; the crystal form regulator is any one of MgCl2, soluble phosphate, and AlCl3; 2) Preparation of slurry solution: Mix the modified carbonized slurry, cement and water reducer according to the proportion to prepare the slurry solution; 3) Preparation of finished slurry: weigh the physical foaming agent and mixing water according to the ratio, dilute to form foam; add the foam to the slurry solution and stir evenly to obtain the finished slurry; 4) Casting and curing: pour the finished slurry into the mold for molding, and place the mold in a curing room for curing; 5) Wet carbonization curing: After the green body is demoulded and cut, it is placed in a carbonization kettle and carbonized and cured by passing carbon dioxide gas to obtain the final high-strength carbonized aerated concrete product; The high-strength carbonized aerated concrete comprises the following raw materials and their weight proportions: 85-90 parts of modified carbonized slurry, 10-15 parts of cement, 3-5 parts of mixing water, 0.1-0.2 parts of physical foaming agent, and 0.2-0.3 parts of water reducer; In step 1), the slurry reaction temperature is controlled at 60-80°C; After the CO2 is introduced in step 1), the slurry is stirred for 40 to 60 minutes at a stirring rate of 300 to 600 r / min. CO2 is introduced at a flow rate of 0.2 to 0.4 L / (min·kg) under stirring conditions, and stirring is carried out while the CO2 is introduced.

2. The preparation method according to claim 1, characterized in that The cement is silicate cement with a specific surface area of 300-400m 2 / kg.

3. The preparation method according to claim 1, characterized in that The physical foaming agent is a protein foaming agent with a foaming multiple of 25 to 50 times; the water reducer is a high-efficiency polycarboxylic acid water reducer with a water reduction efficiency of 30 to 50%.

4. The preparation method according to claim 3, characterized in that In step 5), the wet carbonization curing comprises a CO2 concentration in the carbon dioxide-containing gas of not less than 15%; the carbonization curing temperature is 50-70°C, the relative humidity is 50-70%, the pressure is 0.1-0.3 MPa, and the time is 8-12 hours.

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