Autoclaved aerated concrete product and preparation method thereof

Abstract

The invention discloses autoclaved aerated concrete added with a specific binding material and a preparation method of the autoclaved aerated concrete, and by optimizing the proportion of the binding material and the preparation process of the autoclaved aerated concrete, the mechanical property, heat insulation performance and durability of a concrete product are improved. According to the present invention, the cementing material comprises the combination of fly ash, sand and silicon-containing tailings, and is supplemented with gypsum and a gas forming agent, and a series of accurately controlled preparation steps are performed to finally obtain the high-performance autoclaved aerated concrete product;

Description

Technical Field

[0001] The invention relates to the technical field of building materials, in particular to an autoclaved aerated concrete product and a preparation method thereof. Background Art

[0002] At present, in the domestic aerated concrete industry, the utilization rate of various waste materials is increasing year by year. Since the main components of aerated concrete production are silicon and calcium, some companies use lime and fly ash as the main production raw materials to achieve the purpose of rapid production and increase output. However, with the domestic environmental protection requirements and restrictions on lime ore mining, the output of lime has been significantly reduced. The aerated concrete industry has begun to try to use other calcium materials for aerated concrete production. Since the aerated concrete production process is simple and the equipment is highly operable, it can be used as a raw material for aerated concrete production when the calcium content meets the requirements. At present, a large amount of ore tailings or waste materials from the smelting industry are increasingly replacing fly ash in the aerated concrete production industry. Moreover, these tailings have a high silicon and calcium content, and the casting is stable during the production process, and the product strength meets the standards.

[0003] With the development of industrial production, the amount of industrial waste is increasing day by day. Its passive stacking occupies land, pollutes soil, water sources and atmosphere, affects crop growth, and endangers human health. After industrial waste is generated, it must be stacked on land. The larger the stacking amount, the more land it occupies. When waste is piled up, the harmful components in it are easy to pollute the land. When pathogenic microorganisms and other harmful substances in the contaminated soil enter the water body with natural precipitation, runoff or seepage, they may further endanger human health. Industrial solid waste will also destroy the ecological balance in the soil. Therefore, how to use industrial solid waste to manufacture autoclaved aerated concrete blocks and make autoclaved aerated concrete blocks have better performance, achieve waste utilization, be beneficial to environmental protection, and truly turn waste into treasure, is a technical problem to be solved. Summary of the invention

[0004] The object of the present invention is to provide an autoclaved aerated concrete product and a preparation method thereof to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: The autoclaved aerated concrete product and the preparation method thereof are characterized by comprising the following steps: S1: Stone powder preparation: pre-treat the stone powder in the raw materials to ensure its fineness and activity; S2: Mixed ash preparation: fly ash, sand and silicon-containing tailings are mixed evenly according to the proportion; S3: Batching, pouring and static stopping: put the mixed ash, slurry, gypsum and gas generating agent into a mixer according to the proportion, mix them evenly, pour them into the mold, and perform static stopping treatment; S4: Flip cutting: After the concrete has initially set, flip the mold for cutting; S5: Autoclave curing: The cut concrete blocks are placed in an autoclave for pressurized steam curing, which usually takes 8-12 hours; S6: Finished product processing: demoulding after curing, necessary finishing and maintenance, and finally the finished product is obtained.

[0006] As a further solution of the present invention: in the step S3, the fly ash containing silicon dioxide is classified into coarse and fine particles by a high-fineness classification cyclone or an electromagnetic vibrating fine screen to separate the coarse particles with high silicon content from the fine particles with low silicon content.

[0007] As a further solution of the present invention: the fine-grained fly ash with low silicon content is pulped and water-added, and then fed into a stirring and pouring equipment in a metered manner. The fine-grained fly ash with low silicon content has a lower content of silicon dioxide, and thus can reduce the catalysis of the gas generating agent aluminum powder under reaction conditions, making the gas generation easier to control and improving the success rate of pouring.

[0008] As a further solution of the present invention: the coarse particles with high silicon content are separated and pre-treated by grinding to become ultrafine fly ash, and silicon dioxide is extracted. The extracted silicon dioxide is slurried and measured in a slurry tank and sprayed into the mold and on the concrete products in the curing stage to undergo hydration reaction.

[0009] As a further solution of the present invention: the silicon dioxide is purified by an alkali fusion-acid leaching method, a thermal phase separation-acid leaching method or a template-free method, so as to accurately control the amount of silicon dioxide and ensure the quality of concrete products.

[0010] As a further solution of the present invention: one or more of the fly ash, sand and silicon-containing tailings are combined into a cementitious material, with a total proportion of 25%-40%; the slurry is prepared by mixing lime and cement with water, accounting for 5%-95%; the gypsum accounts for 1.5%-3.5%; the gas generating agent is aluminum powder, accounting for the remaining proportion.

[0011] As a further solution of the present invention: the gelling material further contains sodium silicate.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. The autoclaved aerated concrete product and the preparation method thereof improve the mechanical properties, thermal insulation properties and durability of the concrete product by optimizing the proportion of the cementitious material and the preparation process of the autoclaved aerated concrete. The cementitious material of the present invention comprises a combination of fly ash, sand and silicon-containing tailings, supplemented with gypsum and a gas generating agent. After a series of precisely controlled preparation steps, a high-performance autoclaved aerated concrete product is finally obtained.

[0013] 2. The autoclaved aerated concrete product and its preparation method separate fly ash into two qualities, high and low, according to the silicon content. The coarse-grained powder with high silicon content is extracted to produce silicon dioxide, and the fine-grained powder with low silicon content is directly used for mixed preparation. This can not only improve the pouring success rate by controlling the gas emission, but also the extracted silicon dioxide can be sprayed in appropriate amounts during the subsequent static curing and steaming process, thereby improving the performance of cement products. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A process flow chart of an autoclaved aerated concrete product and a preparation method thereof; Figure 2 This is a list of inspection items for autoclaved aerated concrete products; Figure 3 It is a strength test table for autoclaved aerated concrete products. DETAILED DESCRIPTION

[0015] See also Figure 1 In an embodiment of the present invention, an autoclaved aerated concrete product and a preparation method thereof are characterized by comprising the following steps; S1: Stone powder preparation: pre-treat the stone powder in the raw materials to ensure its fineness and activity; S2: Mixed ash preparation: fly ash, sand and silicon-containing tailings are mixed evenly according to the proportion; S3: Batching, pouring and static stopping: put the mixed ash, slurry, gypsum and gas generating agent into a mixer according to the proportion, mix them evenly, pour them into the mold, and perform static stopping treatment; S4: Flip cutting: After the concrete has initially set, flip the mold for cutting; S5: Autoclave curing: The cut concrete blocks are placed in an autoclave for pressurized steam curing, which usually takes 8-12 hours; S6: Finished product processing: demoulding after curing, necessary finishing and maintenance, and finally the finished product is obtained. In the preparation process of traditional autoclaved aerated concrete, the performance of the product is often unstable due to improper selection of cementitious materials or unreasonable proportions. In order to improve the comprehensive performance of concrete products, it is necessary to optimize the types and proportions of cementitious materials and improve the preparation process. Various attempts have been made in this industry. For example, Chinese Patent No. 201510156288 discloses an A2.0B04 autoclaved aerated concrete block prepared from quartz weathered sand. It is an A2.0B04 high-performance autoclaved aerated concrete block made of quartz weathered sand, cement, quicklime, industrial waste phosphogypsum, aluminum powder paste and water as raw materials. The block has a dry density of 415kg / m3, an average cubic compressive strength of 2.1MPa, a single group minimum of 1.9Mpa, a splitting compression ratio of 0.19, a mass loss after freezing of 3.7%, a strength after freezing of 1.7Mpa, and a thermal conductivity (dry state) of 0. .116W / (m·K), drying shrinkage value (standard method) 0.22mm / m, qualified rate>98%, Chinese Patent No.201510087601 discloses an aerated concrete block, comprising the following components: 55-75 parts of iron ore tailings, 50-60 parts of fly ash, 15-25 parts of cement, 20-30 parts of quicklime, 5-10 parts of desulfurized gypsum, 8-15 parts of silica sand, 0.1-0.2 parts of aluminum powder, 1-2 parts of water glass, 0.05-0.1 parts of foam stabilizer, and 0.02-0.03 parts of polypropylene fiber. Chinese Patent No.201510085511 discloses a nickel slag autoclaved aerated concrete block and a preparation method thereof, wherein the raw materials comprise basic materials, admixtures and water, the basic materials comprise nickel slag, fly ash, cement, quicklime, aluminum powder and gypsum; the admixtures comprise a thickening stabilizer and an ion crystallizer. The quality of the nickel slag autoclaved aerated concrete blocks of this patent meets the requirements of the national standard GB11968-2006, which finds a way to utilize the nickel slag in large quantities. However, the prior art has not yet disclosed or studied the method of preparing aerated concrete using polysilicon production waste (such as waste liquid or waste slag). The field still needs a new method for preparing concrete, at least to provide a new alternative.

[0016] In a preferred embodiment, in step S3, the fly ash containing silicon dioxide is pre-selected into coarse and fine particles by a high-fineness classification cyclone or an electromagnetic vibrating fine screen, and the coarse particles with high silicon content are separated from the fine particles with low silicon content. The fly ash is classified according to the silicon content, and the fine particles with low silicon content are used for mixing, stirring and pouring, and the coarse particles with high silicon content are used for the extraction of silicon dioxide, thereby avoiding the accumulation of fly ash. The fly ash can be better recovered by extracting silicon dioxide.

[0017] In a preferred embodiment, the fine-grained fly ash with low silicon content is pulped and watered, and then fed into the stirring and pouring equipment by metering. The fine-grained powder with low silicon content has a lower content of silicon dioxide, so it can reduce the catalysis of the gas generating agent aluminum powder under the reaction conditions, and the gas generation amount is easier to control, thereby improving the casting success rate and reducing the silicon dioxide occupancy rate in the mixed stirring and pouring process. Through subsequent steps such as spraying and steaming, the silicon dioxide extracted from the coarse-grained powder with high silicon content is used in the spraying and steaming step, and is evenly distributed by spraying. When applied to concrete products, silica has excellent volcanic ash activity, which can improve the pore structure and micro-defects in concrete and make the internal structure of concrete denser. In addition, silica can form closed and uniform bubbles, reduce the permeability of concrete, and improve frost resistance and durability. By controlling the time and amount of addition, the success rate of pouring can be improved. After the pouring is successful, silica is added to it. Silica penetrates into the concrete products and reacts with some by-products in the concrete products for a secondary reaction, thereby improving the density of the concrete products.

[0018] In a preferred embodiment, the coarse particles with high silicon content are separated and pre-treated by grinding to become ultrafine fly ash, and silicon dioxide is extracted. The extracted silicon dioxide is measured through slurry making in a slurry tank and sprayed into the mold and onto the concrete products in the curing stage to undergo hydration reaction.

[0019] In a preferred embodiment, the silicon dioxide is purified by an alkali fusion-acid leaching method, a thermal phase separation-acid leaching method or a template-free method, so as to accurately control the amount of silicon dioxide and ensure the quality of concrete products.

[0020] In a preferred embodiment, one or more of the fly ash, sand and silicon-containing tailings are combined into a cementitious material, with a total proportion of 25%-40%; the slurry is prepared by mixing lime and cement with water, accounting for 5%-95%; the gypsum accounts for 1.5%-3.5%; the gas generating agent is aluminum powder, accounting for the remaining proportion.

[0021] In a preferred embodiment, the gelling material further contains sodium silicate.

[0022] The object of the present invention is to provide a method for preparing autoclaved aerated concrete by adding a specific cementitious material, which is achieved by the following technical solutions: 1. Raw material ratio: - Cementitious materials: including one or more combinations of fly ash, sand and silicon-containing tailings, accounting for 25%-40% in total.

[0023] - Slurry: It is made by mixing lime and cement with water, accounting for 5%-95%.

[0024] - Gypsum: 1.5%-3.5%.

[0025] - Gas generating agent: Aluminum powder is used to account for the remaining proportion.

[0026] According to a first aspect of the present invention, there is provided a method for preparing aerated concrete, comprising the following steps: The slurry preparation step, the pouring step, the foaming and hardening step and the steam pressure curing step are used in the steps. The raw materials used in the steps include basic materials and water. The basic materials are included in the cementitious material production process. The basic materials also include cement, quicklime, aluminum powder, gypsum and optional fly ash. The gypsum can be industrial waste phosphogypsum, desulfurized gypsum, etc. Relative to 100 parts by weight of the basic materials, the content of the cementitious material is 10 parts by weight to 40 parts by weight, more preferably 15 parts by weight to 30 parts by weight. The raw materials used in the steps also include an added aluminum powder reaction inhibitor, which is selected from water glass (Na2SiO3). The raw materials used in the steps do not contain an added foam stabilizer, an added aluminum powder reaction inhibitor and / or an added lime scavenger. The basic material further comprises fly ash. Relative to 100 parts by weight of the basic material, the content of cement is 10 to 18 parts by weight, preferably 10 to 15 parts by weight, the content of quicklime is 20 to 28 parts by weight, preferably 20 to 25 parts by weight, the content of aluminum powder is 0.08 to 0.15 parts by weight, preferably 0.08 to 0.15 parts by weight, the content of gypsum is 1 to 3 parts by weight, and the balance is the fly ash. Preferably, the cement is cement with a grade of P.O42.5, and the content of calcium oxide in the cement is above 70% by weight, preferably, the content of calcium oxide in the quicklime is above 80% by weight. In the step, the cementitious material and gypsum are crushed to a sieve residue of less than 15% passing through a square hole sieve with a fineness of 0.080 mm. Optionally, the fly ash is crushed to a sieve residue of less than 5% passing through a square hole sieve with a fineness of 0.2 mm.

[0027] The steps are carried out at a temperature of 40-60°C, in which the foaming and hardening temperature is 40-65°C, preferably 45-60°C, and the hardening time is 0.5-2 hours, preferably 1-1.5 hours. In one embodiment, the temperature is 180-250°C, preferably 190-200°C, and the pressure is 1-1.8MP, preferably 1.15-1.35MP, and high-temperature autoclaving is performed for 5-15 hours, preferably 5-8 hours. In another aspect, the present invention also provides an aerated concrete, which is prepared by the above method. In one embodiment, the aerated concrete prepared by the method of the present invention is generally an aerated concrete block.

[0028] The aerated concrete prepared by the cementitious material of the present invention has the characteristics of high compressive strength and low bulk density, and the test indexes meet or even exceed the national standards. In addition, since the cementitious material contains some sodium silicate, the lime dissolution can be inhibited, thereby controlling the gas emission of aluminum powder, greatly improving the stability of the casting slurry and adjusting the speed of aluminum powder participating in the reaction. The method of the present invention can also replace the traditional production of improving the casting stability by adding admixtures, thereby reducing the casting failure caused by the fast initiation speed and reducing economic losses. In addition, the method of the present invention can also expand the scope of use of fly ash. For example, due to the high silica content of the fly ash itself, the fly ash fineness is small, the activity is high and the temperature of the fly ash itself is high, so that the gas generating agent aluminum powder is catalyzed under the reaction conditions, the reaction is fast, and the gas emission speed is not easy to control, resulting in casting failure and certain economic losses. The addition of cementitious materials can effectively slow down the occurrence of such problems.

[0029] Preparation method: Stone powder preparation: Pre-treat the stone powder in the raw materials to ensure its fineness and activity.

[0030] Preparation of mixed ash: Mix fly ash, sand and silicon-containing tailings in a uniform ratio.

[0031] Batching, pouring and static stopping: put the mixed ash, slurry, gypsum and gas generating agent into the mixer according to the proportion, mix them evenly, pour them into the mold and perform static stopping treatment.

[0032] Flip cutting: After the concrete has initially set, flip the mold over for cutting.

[0033] Autoclave curing: The cut concrete blocks are placed in an autoclave for pressurized steam curing, which usually takes 8-12 hours.

[0034] Finished product processing: demoulding after curing, necessary finishing and maintenance, and finally the finished product is obtained.

[0035] The autoclaved aerated concrete of the present invention adopts a cementitious material with a specific ratio and has the following technical effects through an optimized preparation process: 1. Improve mechanical properties: The compressive strength, flexural strength and other mechanical properties of concrete products are significantly improved; 2. Enhance thermal insulation performance: Good pore structure and selection of cementitious materials make concrete products have excellent thermal insulation performance; 3. Improved durability: Through reasonable mix ratio and autoclave curing, the durability indicators of concrete products such as water resistance and freeze-thaw resistance are significantly improved.

[0036] The invention adopts cementitious material to add to autoclaved aerated concrete and the preparation method thereof, optimizes the raw material ratio and the preparation process, significantly improves the comprehensive performance of concrete products, has broad application prospects and market value, and provides a method for preparing aerated concrete. The method uses a new material-cementitious material in the slurry preparation step. The invention also provides aerated concrete prepared by the above method. According to the method of the invention, the cementitious material can effectively control the gas generation speed of the aerated concrete, ensure the pouring stability, reduce or eliminate the use of external foam stabilizing additives, reduce production costs, and improve product quality.

[0037] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0038] The above-mentioned embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. Autoclaved aerated concrete product and preparation method thereof, characterized in that: The steps include: S1: Stone powder preparation: pre-treat the stone powder in the raw materials to ensure its fineness and activity; S2: Mixed ash preparation: fly ash, sand and silicon-containing tailings are mixed evenly according to the proportion; S3: Batching, pouring and static stopping: put the mixed ash, slurry, gypsum and gas generating agent into a mixer according to the proportion, mix them evenly, pour them into the mold, and perform static stopping treatment; S4: Flip cutting: After the concrete has initially set, flip the mold for cutting; S5: Autoclave curing: The cut concrete blocks are placed in an autoclave for pressurized steam curing, which usually takes 8-12 hours; S6: Finished product processing: demoulding after curing, necessary finishing and maintenance, and finally the finished product is obtained.

2. The autoclaved aerated concrete product and the preparation method thereof according to claim 1, characterized in that: In step S3, the fly ash containing silicon dioxide is classified into coarse and fine particles by a high-fineness classification cyclone or an electromagnetic vibrating fine screen to separate the coarse particles with high silicon content from the fine particles with low silicon content.

3. The autoclaved aerated concrete product and the preparation method thereof according to claim 2, characterized in that: The fine-grained fly ash with low silicon content is pulped and water-added and then fed into a mixing and pouring device in a metered manner. The fine-grained fly ash with low silicon content has a lower content of silicon dioxide and can therefore reduce the catalysis of the gas generating agent aluminum powder under reaction conditions, making the gas generation easier to control and improving the success rate of pouring.

4. The autoclaved aerated concrete product and the preparation method thereof according to claim 2, characterized in that: The coarse particles with high silicon content are separated and pre-treated by grinding to become ultrafine fly ash, and silicon dioxide is extracted. The extracted silicon dioxide is measured by slurry tank slurry making and sprayed into the mold and on the concrete products in the curing stage to react with water.

5. The autoclaved aerated concrete product and the preparation method thereof according to claim 4, characterized in that: The silicon dioxide is purified by an alkali fusion-acid leaching method, a thermal phase separation-acid leaching method or a template-free method, so as to accurately control the amount of silicon dioxide and ensure the quality of concrete products.

6. The autoclaved aerated concrete product and the preparation method thereof according to claim 1, characterized in that: The fly ash, sand and silicon-containing tailings are combined into one or more cementitious materials, accounting for 25%-40% in total; the slurry is prepared by mixing lime and cement with water, accounting for 5%-95%; the gypsum accounts for 1.5%-3.5%; the gas generating agent is aluminum powder, accounting for the remaining proportion.

7. The autoclaved aerated concrete product and the preparation method thereof according to claim 6, characterized in that: The gelling material further contains sodium silicate.

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