A molding sand-based highly active slurry and low-density autoclaved sand aerated concrete prepared by using the same

Abstract

The present invention discloses a molding sand-based highly active slurry, the raw materials of which include water-cooled calcined material and water; wherein the water-cooled calcined material is obtained by using molding sand, limestone material and high-calorific value solid waste as the main raw materials, mixing, low-temperature calcination, and rapid water-cooling for temperature reduction. The present invention uses molding sand and limestone material as the main raw materials. After mixed calcination, the crystal form transformation of the quartz phase in the molding sand is promoted, impurities in the molding sand are effectively removed, and part of calcium silicate minerals are generated; then rapid cooling is carried out, while effectively improving the activity of the molding sand and retaining part of the expansion effect, the microstructure of lime is optimized, making the calcium silicate reaction during autoclave curing easier to carry out; when it is applied to the preparation of aerated concrete, it can effectively balance the properties such as strength, heat preservation and drying shrinkage, and has remarkable environmental and economic benefits, being suitable for popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a molding sand-based high-activity slurry and a low-density autoclaved sand aerated concrete prepared by using the slurry. Background Art

[0002] At present, the main process for producing autoclaved sand aerated soil is to prepare slurry by ball milling silica sand and gypsum: after mixing the slurry, cement, lime and aluminum powder evenly according to the mix ratio, the finished product is obtained after pouring, gasification and stabilization, cutting, autoclaving and curing. In order to ensure product performance, the standard JC / T622-2009 "Sand for Silicate Building Products" strictly limits the mud content, organic matter content and inclusion content in silica sand. The density grade of sand aeration produced by conventional industrialization is generally B05~B07. The lower the density, the higher the quality requirements for siliceous materials. Otherwise, bubbles are very likely to merge and overflow during the stabilization process, causing the body to sink and collapse, and the strength after autoclaving is unqualified. At present, some scholars have prepared B03~B05 autoclaved aerated concrete, but in order to ensure the stability of pouring, methods such as adding fast-hardening cement / activator or using a higher amount of adhesive are generally used to accelerate the hardening of the slurry. Although the above method can effectively solve the problems of body sinking and mold collapse, it will lead to a substantial increase in production costs, and there is also the risk of strength shrinkage of aerated concrete when the calcium-silicon ratio is too high.

[0003] Molding sand is an industrial solid waste generated after casting of metal castings. Its main mineral component is quartz, which contains more clay and carbon impurities. When using molding sand to prepare low-density autoclaved aerated concrete, the clay and carbon impurities absorb a lot of water, which will increase the setting time of the green body, and the pores are easy to merge and float up, resulting in obvious sinking. The increase in water consumption will also lead to problems such as prolonged constant pressure time during autoclaving. In addition, clay and carbon impurities usually do not participate in chemical reactions, and their own strength is low, which is not conducive to strength development. The silicon in molding sand mainly exists in the form of α quartz, which has good stability and low reactivity. When using molding sand to prepare low-density sand aeration, in order to ensure that the silicon-calcium reaction is fully carried out, the constant temperature and constant pressure time (temperature 180-200℃, pressure 1.2-1.5MPa) usually needs to be controlled at more than 8h. According to actual production experience, the lower the aerated density of the prepared sand, the higher the quality requirements for the siliceous material. When preparing B03 grade sand aeration, the quality of the sand should at least reach the superior grade (mud content less than 3%, no inclusions). Directly using molding sand to prepare aerated concrete cannot effectively guarantee properties such as compressive strength, bulk density, shrinkage, thermal conductivity and tensile strength, and the production efficiency involved is relatively low; further exploring the high-value utilization of molding sand in aerated concrete has important research and application significance. Summary of the invention

[0004] The main object of the present invention is to provide a high-activity slurry based on molding sand in view of the problems and deficiencies existing in the prior art. Using molding sand and limestone materials as the main raw materials, after mixing and calcining, the crystal form transformation of quartz phase in the molding sand is promoted, impurities in the molding sand are effectively removed, and partial calcium silicate minerals are generated; then rapid cooling (water cooling) is carried out, while effectively improving the activity of the molding sand and retaining part of the expansion effect, optimizing the microstructure of lime, making the calcium silicate reaction during autoclave curing easier to carry out; applying it to the preparation of aerated concrete can effectively take into account properties such as strength, heat preservation and drying shrinkage, and has significant environmental and economic benefits, and is suitable for popularization and application.

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

[0006] A high-activity slurry based on molding sand, the raw materials of which include water-cooled calcined material and water; wherein the water-cooled calcined material is obtained by using molding sand, limestone materials and high-calorific solid waste as the main raw materials, mixing, low-temperature calcining and rapid cooling.

[0007] In the above solution, the rapid cooling step adopts the means of high-pressure injection of condensed water; the amount of condensed water used is controlled at 40-50% of the mass of the low-temperature calcined material, and the high-pressure injection time is controlled at 30-60 s.

[0008] In the above solution, the water content in the high-activity slurry based on molding sand is 30-35 wt%.

[0009] In the above solution, the raw materials in the water-cooled calcined material and their mass percentages include: molding sand 65-80%, limestone materials 20-35%, high-calorific solid waste 0-10%.

[0010] In the above solution, the molding sand is a high-carbon and high-silicon industrial waste, its quartz content is more than 65 wt%, its clay content is less than 20 wt%, its calorific value is not less than 1 MJ / kg, and its water content is less than 5%; the particle size is 0-2 mm.

[0011] Further, the main chemical components in the molding sand and their mass percentages include: SiO2 65-80%, Al2O3 5-15%, Fe2O3 0-5%, C 3-8%.

[0012] In the above solution, the limestone materials include but are not limited to limestone or marble, etc., its calcium carbonate content is more than 80 wt%, its magnesium-containing mineral content is less than 10 wt%, its water content is less than 3%; the particle size is 0-10 mm.

[0013] In the above solution, the high-calorific solid waste includes but is not limited to coal gangue, coal slime, sawdust or waste wood boards, etc., its calorific value is not less than 5.5 MJ / kg, its water content does not exceed 5%, and its potassium and sodium content does not exceed 3%; the particle size is 0-2 mm.

[0014] Further, in the gangue or slime, the chemical components and their mass percentages include: SiO2 45 - 75%, Al2O3 10 - 30%, CaO 0 - 10%, Fe2O3 0 - 10%.

[0015] In the above solution, the target temperature for the low-temperature calcination is 850 - 950 °C, and the heat preservation time is 10 - 30 min.

[0016] In the above solution, the cooling rate for the rapid cooling is 500 - 800 °C / min, and the target temperature for the cooling step is 200 - 300 °C.

[0017] Further, the rapid cooling step adopts the method of high-pressure injection of condensed water to exchange heat with the obtained low-temperature calcined material. The condensed water quickly evaporates to form steam, and the pressure regulating valve controls the steam output pressure. When the steam pressure reaches 1.1 - 1.3 MPa, it is introduced into the autoclave for curing autoclaved aerated concrete blocks, which can significantly save the autoclaving energy consumption.

[0018] Further, the condensed water used can be selected from the condensed water discharged during the autoclave curing process of aerated concrete, with a temperature of 90 - 100 °C. Control the injection amount of the condensed water to control the cooling rate of the calcined material at 500 - 800 °C / min.

[0019] The above method for preparing a molding sand-based highly active slurry includes the following steps:

[0020] 1) Mix the weighed molding sand, limestone material, and high-calorific value solid waste evenly, and subject the obtained mixture to low-temperature calcination to obtain a low-temperature calcined material;

[0021] Use the means of high-pressure injection of condensed water to quickly cool the obtained low-temperature calcined material to 200 - 300 °C to obtain a water-cooled calcined material;

[0022] 2) Add water to the obtained water-cooled calcined material and ball mill to obtain the molding sand-based highly active slurry.

[0023] In the above solution, the loss on ignition of the obtained low-temperature calcined material at 950 °C does not exceed 3%.

[0024] In the above solution, the ball milling rate for the ball milling step is 20 - 60 r / min, and the ball milling time is 10 - 25 min.

[0025] In the above solution, the 80 μm sieve residue of the solid content in the obtained molding sand-based highly active slurry is 10 - 30%, and the slurry temperature is 40 - 50 °C.

[0026] In the above solution, the water content in the molding sand-based highly active slurry is 30 - 40 wt%.

[0027] A low-density autoclaved sand aerated concrete based on the above-mentioned molding sand-based highly active slurry, with its components and their respective weight parts including: 80 - 85 parts of the molding sand-based highly active slurry, 13 - 17 parts of cement, 2.5 - 4 parts of hemihydrate gypsum, 0.1 - 0.3 parts of water reducer, and 0.1 - 0.2 parts of foaming agent.

[0028] In the above solution, the cement can be selected as ordinary portland cement, etc., and its grade is above 42.5.

[0029] In the above solution, the water reducer is preferably a polycarboxylate water reducer, and its water reduction rate is 20 - 40%.

[0030] In the above solution, the foaming agent is preferably a protein-based foaming agent, and the foaming multiple is 40 - 60.

[0031] The preparation method of the above-mentioned low-density autoclaved sand aerated concrete includes the following steps: uniformly stirring the weighed molding sand-based highly active slurry, cement, hemihydrate gypsum, and water reducer to prepare a mixed slurry; diluting the foaming agent 40 - 80 times to prepare foam, and uniformly stirring the foam and the mixed slurry to obtain a finished slurry; pouring the finished slurry into a mold frame, demolding and cutting after the blank hardens, and putting the cut blank into an autoclave for autoclave curing.

[0032] In the above solution, the steam temperature used in the autoclave curing step is 160 - 190 °C, the pressure is 0.6 - 1.3 MPa, and the constant temperature and constant pressure time is 4 - 8 h.

[0033] The optimization mechanism adopted in the present invention includes:

[0034] 1) The present invention uses molding sand and limestone materials as the main raw materials. During the low-temperature calcination process, α-quartz in the molding sand first transforms into β-quartz, and then further transforms into tridymite. This crystal form process has a volume expansion of about 17%. During the rapid cooling (water cooling) process, part of the expansion is retained; after the volume expansion, the bond length increases and the bond energy decreases, which is beneficial to promoting the subsequent autoclave curing calcium-silicon reaction; the calcium oxide generated during the calcination process is digested when encountering water under high-temperature conditions. The microstructure of the digestion product calcium hydroxide changes, and a large amount of steam is generated during high-temperature digestion, significantly increasing the specific surface area and pore structure of calcium hydroxide. During the autoclave curing process, calcium ions are more likely to dissolve and diffuse from the surface, thus promoting the calcium-silicon reaction process; in addition, the calcium oxide generated during the calcination process can react with substances such as SiO2, Al2O3, and Fe2O3 in the molding sand to form some hydraulic minerals such as wollastonite, dicalcium silicate, and calcium ferrite. A large amount of hydration products are generated during the autoclave curing process of this part of the minerals, which is beneficial to improving the strength of aerated concrete, etc.;

[0035] 2) During the calcination process of molding sand, carbon impurities and other organic substances are effectively removed, and clay substances such as montmorillonite and kaolin are transformed into active silica-aluminum minerals that can react with lime. In addition, during the high-temperature digestion process, lime further undergoes cation exchange with minerals such as clay and feldspar, which can effectively improve its volume stability, etc.;

[0036] 3) The aluminum element in the calcined clay increases the crystallinity of the reaction product tobermorite and changes the morphology of calcium silicate hydrate, which can effectively improve the shrinkage and splitting tensile properties of aerated concrete, etc.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1) The heat source during the calcination process is mainly the carbon in the molding sand, supplemented by high-calorific value solid waste, which can effectively save energy such as coal and natural gas; the calcareous material (lime) required for the silicon-calcium reaction comes from the decomposition of limestone materials during the combined calcination process, without the need to consume lime additionally, saving raw material costs;

[0039] 2) During the calcination process, clay substances such as montmorillonite and kaolin are transformed into minerals that promote strength development. Even if the clay content in silica sand exceeds the standard limit (the mud content is as high as 13%), aerated concrete with qualified performance can still be prepared;

[0040] 3) The activity of quartz increases during the calcination process, which is beneficial to shortening the curing time and / or reducing the autoclave curing temperature, and is beneficial to improving production efficiency and saving energy;

[0041] 4) Quicklime has a large volume expansion when it reacts with water and has self-pulverization properties; quartz undergoes a crystal form transformation during the calcination process, with volume expansion, and a large amount of temperature stress is generated during the rapid cooling process, increasing its grindability; the self-pulverization phenomenon of quicklime and the increase in the grindability of quartz can significantly reduce the grinding requirements for the calcined material;

[0042] 5) It has significant economic and environmental benefits. The present invention can consume a large amount of molding sand solid waste and reduce the consumption of lime. In addition, medium-pressure steam generated during the cooling process of the calcined material can be used to replace part of the boiler steam for curing aerated concrete, reducing steam consumption; taking a B03 grade aerated concrete production line with an annual output of 300,000 cubic meters as an example, it can process more than 50,000 tons of molding sand and high-calorific value solid waste per year, reduce lime consumption by more than 15,000 tons, and reduce steam consumption by more than 10,000 tons;

[0043] 6) The aerated concrete prepared by this method has excellent performance, and the product quality meets the requirements of A1.5B03 grade, and performance indicators such as appearance quality and dry shrinkage all meet the standard requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the production process flow of low-density aerated concrete. Detailed Embodiments

[0045] 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.

[0046] In the following examples and comparative examples, the high-calorie solid wastes used include two types: coal gangue and coal slime. The main chemical composition of coal gangue is: SiO2 56%, Al2O3 14%, CaO 3%, Fe2O3 5.9%, loss on ignition is 18%, calorific value is 5.5 MJ / kg, slime content is 6%, moisture content is 4%, potassium and sodium content is 1.6%; the main chemical composition of coal slime is: SiO2 52%, Al2O3 19%, CaO 6%, Fe2O3 4%, loss on ignition is 15%, calorific value is 8.1 MJ / kg, slime content is 21%, moisture content is 5%, potassium and sodium content is 2.1%.

[0047] The main chemical composition of the molding sand used is: SiO2 72 wt%, Al2O3 11 wt%, CaO 2 wt%, Fe2O3 2.9 wt%, loss on ignition is 9%; the main mineral components are: quartz 68 wt%, feldspar 5 wt%, kaolin 7 wt%, montmorillonite 3 wt%, illite 3 wt%; the moisture content in the molding sand is 3%, the slime content is 13%, and the calorific value is 1.3 MJ / kg.

[0048] The limestone materials include limestone and marble powder. Among them, the calcium carbonate content in limestone is 91 wt%, the magnesium-containing mineral content is 4 wt%, and the moisture content is 2%; the calcium carbonate content in marble powder is 88 wt%, the magnesium-containing mineral content is 6 wt%, and the moisture content is 3 wt%.

[0049] The hemihydrate gypsum used contains 88 wt% of hemihydrate calcium sulfate, the initial setting time is 13 min, and the final setting time is 19 min. P·O42.5 cement is used as the cement. The water-reducing agent used is a polycarboxylate superplasticizer with a water-reducing rate of 35%. The physical foaming agent uses a protein-based foaming agent provided by Henan Huatai New Material Technology Co., Ltd., and the dilution liquid is prepared by diluting 60 times with water. The foam bleeding amount of the prepared foam is 42 ml, the settlement distance is 6 mm, and the density is 41 kg / m 3 。

[0050] Example 1

[0051] A molding sand-based high-activity slurry and the low-density autoclaved sand aerated concrete prepared by using the same, the preparation process includes the following steps:

[0052] 1) Weigh each raw material according to the ratio, and prepare a mixture after crushing and mixing. Among them, the raw materials in the mixture and their mass percentages are: molding sand 65%, limestone 25%, and coal gangue 10%. The particle size of the molding sand is controlled within 0 - 1 mm, the particle size of the limestone is controlled within 0 - 8 mm, and the particle size of the coal gangue is controlled within 0 - 2 mm;

[0053] 2) Keep the mixture at 900 °C for 25 min to obtain a low-temperature calcined material;

[0054] 3) After the constant-temperature stage of the calcined material, spray condensed water (92 °C). By controlling the spraying amount of the condensed water and the ventilation volume, the condensed water consumption is controlled at 45% of the mass of the low-temperature calcined material, and the high-pressure spraying time is controlled at 45 s. Cool the low-temperature calcined material to 200 °C at a rate of 600 °C / min to obtain a water-cooled calcined material;

[0055] 4) Add water to the obtained water-cooled calcined material and ball mill (the ball mill rate is 30 r / min and the time is 15 min) to prepare a high-activity slurry. Among them, the water content in the slurry is 32 wt%, the residue on an 80 μm sieve of the solid content is 21%, and the slurry temperature is 43 °C;

[0056] 5) Use the high-activity slurry to prepare sand aerated concrete. Take 80 parts of the high-activity slurry, 17 parts of cement, 3 parts of hemihydrate gypsum, and 0.2 parts of water reducer, stir evenly to prepare a mixed slurry. Take 0.2 parts of physical foaming agent, dilute it 60 times to prepare foam, and stir the foam and the mixed slurry evenly to obtain a finished slurry. Pour the finished slurry into a mold frame, demold and cut after the blank hardens, and put the cut blank into an autoclave for autoclave curing. Among them, during autoclave curing, the temperature and pressure during the constant-temperature process are controlled at 185 °C and 1.2 MPa respectively and remain unchanged, and the durations are 4 h (#1), 6 h (#2), and 8 h (#3) respectively.

[0057] Refer to the standard GB / T11969 - 2008 to detect the performance of the autoclaved aerated concrete obtained in this example. The specific detection results are shown in Table 1.

[0058] Table 1 Performance detection results of the low-density aerated concrete obtained in Example 1

[0059]

[0060] Example 2

[0061] A kind of low-density aerated concrete, whose preparation method is roughly the same as that of Example 1, the difference is that: the high-calorific value solid waste uses coal slime, during autoclave curing, the temperature and pressure during the constant-temperature process are controlled at 170 °C and 0.8 MPa respectively and remain unchanged, and the constant-temperature duration during the autoclave curing process of the prepared blank is 6 h; the specific performance test results are shown in Table 2.

[0062] Table 2 Performance detection results of the low-density aerated concrete obtained in Example 2

[0063]

[0064] Example 3

[0065] A low-density aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that: the mass fraction of medium sand in the mixture is 60%, marble powder is 30%, and coal gangue is 10%; the particle size of marble powder is controlled within 0 - 0.5 mm; when preparing the mixed slurry, 83 parts of slurry, 14 parts of cement, 3 parts of hemihydrate gypsum, 0.2 part of water reducing agent, and 0.2 part of foaming agent are used; during the autoclave curing process of the prepared green body, the constant temperature duration is 4 h. Detection is carried out with reference to the standard GB / T11969 - 2008, and the performance is as follows.

[0066] Table 3 Performance test results of the low-density aerated concrete obtained in Example 3

[0067]

[0068] Comparative Example 1

[0069] A low-density aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that: after limestone and coal gangue are calcined and cooled and digested, they are mixed evenly with uncalcined medium sand and ball-milled to prepare a slurry, wherein the ball-milling rate is 35 r / min, the time is 23 min, the water content in the slurry is 32 wt%, the solid content 80 μm sieve residue is 23%, and the slurry temperature is 43 °C;

[0070] During the autoclave curing process of the prepared green body, the constant temperature durations are 4 h (#6), 6 h (#7), and 8 h (#8) respectively. Detection is carried out with reference to the standard GB / T11969 - 2008, and the performance is as follows.

[0071] Table 4 Performance test results of the low-density aerated concrete obtained in Comparative Example 1

[0072]

[0073] Comparative Example 2

[0074] A low-density aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that: limestone, medium sand, and coal gangue are first calcined and cooled and digested separately, and then mixed evenly and ball-milled to prepare a slurry, wherein the ball-milling rate is 30 r / min, the time is 15 min, the mass fraction of water in the slurry is 33.5%, the solid content 80 μm sieve residue is 22%, and the slurry temperature is 44 °C. During the autoclave curing process of the prepared green body, the constant temperature durations are 4 h (#9), 6 h (#10), and 8 h (#11) respectively. Detection is carried out with reference to the standard GB / T11969 - 2008, and the performance is as follows.

[0075] Table 5 Performance test results of the low-density aerated concrete obtained in Comparative Example 2

[0076]

[0077] Comparative Example 3

[0078] A low-density aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that: after the constant temperature stage of the calcined material ends, the temperature of the low-temperature calcined material is reduced to 200 °C at a rate of 10 °C / min, and then ball milled to prepare a slurry, where the ball milling rate is 35 r / min, the time is 21 min, the mass fraction of water in the slurry is 33%, the residue on an 80-μm sieve of the solid content is 22.6%, and the slurry temperature is 42 °C. During the autoclave curing process of the prepared green body, the constant temperature duration is 4 h (#12), 6 h (#13), and 8 h (#14) respectively. Detection is carried out with reference to the standard GB / T11969-2008, and the performance is as follows.

[0079] Table 6 Performance test results of the low-density aerated concrete obtained in Comparative Example 3

[0080]

[0081] Comparative Example 4

[0082] A low-density aerated concrete, the preparation method of which is substantially the same as that of Example 1, except that: it is heated to the target calcination temperature of 1400 °C and kept warm for 25 min; the water content in the obtained slurry is 32 wt%, the residue on an 80-μm sieve of the solid content is 15%, and the slurry temperature is 43 °C; during the autoclave curing process of the prepared green body, the constant temperature duration is 8 h (#15). Detection is carried out with reference to the standard GB / T11969-2008, and the performance is as follows.

[0083] Table 7 Performance test results of the low-density aerated concrete obtained in Comparative Example 4

[0084]

[0085] The present invention is not limited to the above embodiments. For those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and retouches can be made, and these improvements and retouches are also regarded as within the protection scope of the present invention. The content not described in detail in this specification belongs to the prior art well-known to those of ordinary skill in the art.

Claims

1. A molding sand-based highly active slurry, characterized in that, Its raw materials include water-cooled calcined materials and water; among them, the water-cooled calcined materials are obtained by mixing molding sand, limestone materials and high-calorific solid waste as the main raw materials, followed by low-temperature calcination and rapid cooling. The raw materials used in the water-cooled calcined materials and their mass percentages are as follows: molding sand 65 - 80%, limestone materials 20 - 35%, high-calorific solid waste 0 - 10%. The molding sand is a high-carbon high-silicon industrial waste, with a quartz content of more than 65 wt%, a clay content of less than 20 wt%, a calorific value of not less than 1 MJ / kg, and a water content of less than 5%. The target temperature for the low-temperature calcination is 850 - 950 °C, and the holding time is 10 - 30 min; the cooling rate for the rapid cooling is 500 - 800 °C / min, and the target temperature for the cooling step is 200 - 300 °C.

2. The molding sand-based highly active slurry according to claim 1, characterized in that, The water content in the molding sand-based highly active slurry is 30 - 35 wt%.

3. The molding sand-based highly active slurry according to claim 1, characterized in that, The particle size of the molding sand is 0 - 2 mm.

4. The molding sand-based highly active slurry according to claim 1, characterized in that, The limestone materials include limestone or marble, with a calcium carbonate content of more than 80 wt%, a magnesium-containing mineral content of less than 10 wt%, a water content of less than 3%; the particle size is 0 - 10 mm.

5. The molding sand-based highly active slurry according to claim 1, characterized in that, The high-calorific solid waste includes coal gangue, coal slime, sawdust or waste wood boards, with a calorific value of not less than 5.5 MJ / kg, a water content of not exceeding 5%, and a potassium and sodium content of not exceeding 3%; the particle size is 0 - 2 mm.

6. A preparation method of the molding sand-based highly active slurry according to claim 1, characterized in that, It includes the following steps: 1) Mix the weighed molding sand, limestone materials and high-calorific solid waste evenly, and subject the obtained mixture to low-temperature calcination to obtain low-temperature calcined materials. Use the means of high-pressure injection of condensed water to rapidly cool the obtained low-temperature calcined materials to 200 - 300 °C to obtain water-cooled calcined materials. 2) Add water to the obtained water-cooled calcined materials and ball mill to obtain the molding sand-based highly active slurry.

7. A low-density autoclaved sand aerated concrete of the molding sand-based highly active slurry prepared based on any one of claims 1 to 5 or the preparation method according to claim 6, characterized in that, The components and their weight parts are as follows: 80 - 85 parts of molding sand-based highly active slurry, 13 - 17 parts of cement, 2.5 - 4 parts of hemihydrate gypsum, 0.1 - 0.3 parts of water reducer, and 0.1 - 0.2 parts of foaming agent.

8. The low-density autoclaved sand aerated concrete according to claim 7, characterized in that, The autoclave curing system adopted by it includes: steam temperature 160 - 190 °C, pressure 0.6 - 1.3 MPa, and constant temperature and pressure time 4 - 8 h.

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