O2-CO2 composite chemical foaming-based high-performance solid waste-based foam concrete as well as preparation method and application thereof

Abstract

The invention discloses O2-CO2 composite chemical foaming-based high-performance solid waste-based foam concrete as well as a preparation method and application thereof, and belongs to the technical field of foam concrete. The high-performance solid waste based foam concrete provided by the invention is prepared from the following raw materials in parts by mass: 20-42 parts of solid waste based sulphoaluminate cement, 15-60 parts of semi-hydrated gypsum, 6-15 parts of Portland cement, 15-25 parts of mineral powder, 1-3 parts of steel slag micro powder, 1-2 parts of hydrogen peroxide, 2-4 parts of sodium bicarbonate, 3-6 parts of aluminum potassium sulfate, 0.2-0.4 part of a retarder, 0.02-0.2 part of a water reducing agent and 0.2-0.6 part of calcium stearate, wherein the water-cement ratio is 0.25-0.4. Wherein the hydrogen peroxide is decomposed to provide O2, and the sodium bicarbonate and the aluminum potassium sulfate react to provide CO2. The foam concrete material with high compressive strength and low dry density is prepared, and meanwhile, solid waste can be consumed in a high proportion.

Description

Technical Field

[0001] The present invention relates to the technical field of foamed concrete, and particularly to a high-performance solid waste-based foamed concrete based on O 2 -CO 2 composite chemical foaming, and its preparation method and application. Background Art

[0002] The information disclosed in the background art of the present invention is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an indication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] As a lightweight and porous building material, foamed concrete has important value in the fields of building energy conservation and solid waste resource utilization due to its light weight and excellent thermal insulation performance. The existing preparation methods of foamed concrete mainly include two categories: physical foaming and chemical foaming. Among them, chemical foaming directly generates gas in the slurry through chemical reactions, eliminating the need for special foaming equipment and complex foam stabilization processes required for physical foaming, and significantly reducing equipment costs and energy consumption, especially suitable for small-scale or on-site construction scenarios.

[0004] Currently, chemical foaming still mainly uses a single foaming agent. For example, the patent with the publication number CN108298944A discloses a phosphate cement foamed concrete and its preparation method, which uses hydrogen peroxide as the foaming agent and manganese dioxide as the catalyst. However, the cost of the phosphate cement used in this patent is relatively high, and manganese dioxide with a relatively high cost is used as the catalyst, resulting in poor economy. The patent with the publication number CN119330674A discloses a CO 2 foamed concrete material based on a solid waste-based multi-component cementitious system and its preparation method, which releases CO 2 gas by the reaction of potassium alum solution and sodium bicarbonate, and uses solid waste-based sulphoaluminate cement, hemihydrate gypsum and other cementitious materials to achieve the efficient utilization of solid waste resources. However, the pore structure formed by single CO 2 foaming is mainly composed of micropores. When its dry density is above 700 kg / m 3 , it can maintain a relatively high compressive strength (above 6 MPa); but when its dry density is as low as about 650 kg / m 3 , its compressive strength drops below 6 MPa.

[0005] At present, there is little research on the composite chemical foaming process. The composite chemical foaming may face the following problems. For example, the decomposition conditions of different foaming agents vary significantly. If the foaming sequence and time are not properly controlled, it may be difficult to form an ideal pore structure. Moreover, the foaming process needs to be strictly matched with the setting time of the slurry. Foaming too early will result in insufficient slurry consistency, causing the bubbles to float and burst, leading to form collapse. Foaming too late, the slurry has already started to set, and the gas cannot expand effectively, resulting in a decrease in porosity. At the same time, in the double-gas-source foaming, the small bubbles may merge into the large bubbles due to the difference in bubble size, resulting in a high dispersion degree of the pore size distribution and a decrease in compressive strength. In addition, the complexity of the concrete raw materials will also have an unpredictable impact on the composite foaming process. The particle morphology and surface activity of the raw materials may interfere with the bubble stability.

[0006] Therefore, how to provide a method for preparing foam concrete materials with high compressive strength and low dry density using solid waste as the main cementitious material and O 2 and CO 2 as the composite foaming gas is an urgent problem to be solved. Summary of the Invention

[0007] In view of this, the present invention provides a high-performance solid waste-based foam concrete based on O 2 -CO 2 composite chemical foaming, its preparation method and application. In the present invention, the initial pore skeleton is constructed by the staged oxygen release of hydrogen peroxide catalyzed by steel slag micro-powder, and it is synergistically foamed with CO 2 to form micropore filling, and finally a foam concrete material with both high compressive strength and low dry density is obtained, and at the same time, a high proportion of solid waste can be consumed.

[0008] In the first aspect, the present invention provides a high-performance solid waste-based foam concrete based on O 2 -CO 2 composite chemical foaming, which is made from raw materials including the following parts by mass: 20-42 parts of solid waste-based sulphoaluminate cement, 15-60 parts of hemihydrate gypsum, 6-15 parts of Portland cement, 15-25 parts of mineral powder, 1-3 parts of steel slag micro-powder, 1-2 parts of hydrogen peroxide, 2-4 parts of sodium bicarbonate, 3-6 parts of potassium alum, 0.2-0.4 part of retarder, 0.02-0.2 part of water reducer, 0.2-0.6 part of calcium stearate, and the water-cement ratio is 0.25-0.4; Among them, hydrogen peroxide decomposes to provide O 2 , and sodium bicarbonate and potassium alum react to provide CO 2 ; The preparation method of the high-performance solid waste-based foam concrete based on O 2 -CO 2 composite chemical foaming includes the following steps: S1. Premix solid waste-based sulphoaluminate cement, hemihydrate gypsum, Portland cement, blast furnace slag powder, steel slag powder and sodium bicarbonate evenly; then add a retarder, a water reducer and calcium stearate, and stir and mix evenly to obtain a mixture; S2. Add water to the mixture in step S1, and stir at a speed of 400 - 800 r / min for 1 - 10 min; S3. Adjust the stirring speed to 50 - 150 r / min, then add hydrogen peroxide, and after adding, stir at a speed of 400 - 800 r / min for 20 - 40 s; S4. Add an aqueous solution of potassium alum to the slurry in step S3, stir at a speed of 400 - 800 r / min for 20 - 40 s, pour it into a mold for static forming, and perform curing after demolding to obtain the product.

[0009] Preferably, the solid waste-based sulphoaluminate cement is prepared from raw materials including the following parts by mass: 80 - 90 parts of sulphoaluminate cement clinker, 15 - 20 parts of desulphurized gypsum, and 5 - 10 parts of stone powder.

[0010] Further, the preparation method of the solid waste-based sulphoaluminate cement is as follows: Dry and mix the sulphoaluminate cement clinker, desulphurized gypsum and stone powder evenly, and then heat up to 1250 - 1350 °C for heat preservation and calcination for 20 - 40 min to obtain the product.

[0011] Preferably, the retarder is selected from one or both of boric acid and tartaric acid; the water reducer is a polycarboxylate-based water reducer or a naphthalene-based water reducer.

[0012] Preferably, the specific surface area of the steel slag powder ≥ 600 m 2 / kg; the mass fraction of the hydrogen peroxide is 25 - 40%.

[0013] In a second aspect, the present invention provides a preparation method of the above-mentioned high-performance solid waste-based foam concrete based on O 2 -CO 2 composite chemical foaming, comprising the following steps: S1. Premix solid waste-based sulphoaluminate cement, hemihydrate gypsum, Portland cement, blast furnace slag powder, steel slag powder and sodium bicarbonate evenly; then add a retarder, a water reducer and calcium stearate, and stir and mix evenly to obtain a mixture; S2. Add water to the mixture in step S1, and stir at a speed of 400 - 800 r / min for 1 - 10 min; S3. Adjust the stirring speed to 50 - 150 r / min, then add hydrogen peroxide, and after adding, stir at a speed of 400 - 800 r / min for 20 - 40 s; S4. Add an aqueous solution of potassium alum to the slurry in step S3, stir at a speed of 400 - 800 r / min for 20 - 40 s, pour it into a mold for static forming, and perform curing after demolding to obtain the product.

[0014] Preferably, in step S1, in the step of stirring and mixing to obtain the mixture, the stirring speed is 50 - 150 r / min, and the stirring time is 1 - 10 min.

[0015] Preferably, in the aqueous solution of potassium alum, the mass fraction of potassium alum is 30 - 60%.

[0016] Preferably, in step S4, the time for static forming is 2 - 3 d, and the curing is carried out under standard conditions.

[0017] In a third aspect, the present invention provides the above-mentioned high-performance waste-based foam concrete based on O 2 -CO 2 composite chemical foaming or the application of the high-performance waste-based foam concrete prepared by the above preparation method based on O 2 -CO 2 composite chemical foaming in building thermal insulation materials.

[0018] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) The present invention adopts a staged foaming process of hydrogen peroxide (O 2 source) and sodium bicarbonate (CO 2 source). Utilizing the alkaline catalytic effect of steel slag micro-powder, the decomposition of hydrogen peroxide is triggered preferentially before the initial setting of the slurry to form a pore structure framework through a slow reaction. Subsequently, potassium alum is used to stimulate sodium bicarbonate to release CO 2 to form CO 2 micropores, thereby forming a "macropore - micropore" gradient nested structure, making the overall form a uniform pore structure, breaking through the porosity - strength bottleneck of a single foaming agent. When the dry density is as low as nearly 600 kg / m 3 , the compressive strength can still be maintained above 6 MPa; (2) The present invention uses waste-based sulphoaluminate cement and hemihydrate gypsum as the main cementitious materials, combines steel slag micro-powder and mineral powder, and through the pozzolanic effect and nucleation effect of active components (Al 2 O 3 , Fe 2 O 3 ), the growth of hydration products (ettringite, C-S-H gel) is directionally regulated to achieve pore densification and mechanical property improvement; the present invention can realize a high proportion utilization of waste-based materials, and the preparation method is very simple, without the need to use expensive or complex equipment, which is environmentally friendly and low in cost, meeting the requirements of industrial production. Description of the Drawings

[0019] The accompanying drawings forming a part of this invention are used to provide a further understanding of the invention. The schematic embodiments of the invention and their descriptions are used to explain the invention and do not unduly limit the invention. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is a schematic process flow diagram of the preparation of high-performance solid waste-based foam concrete in Embodiments 1 to 3 of the present invention; Figure 2 It is a macroscopic picture of the high-performance solid waste-based foam concrete in Embodiment 1 of the present invention; Figure 3 It is a macroscopic picture of the high-performance solid waste-based foam concrete in Embodiment 2 of the present invention; Figure 4 It is a macroscopic picture of the high-performance solid waste-based foam concrete in Embodiment 3 of the present invention; Figure 5 It is a macroscopic picture of the high-performance solid waste-based foam concrete in Comparative Example 2 of the present invention. Detailed Description of the Invention

[0021] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0022] The present invention provides a high-performance solid waste-based foam concrete based on O 2 -CO 2 composite chemical foaming, which is made from raw materials including the following parts by mass: 20 - 42 parts of solid waste-based sulphoaluminate cement, 15 - 60 parts of hemihydrate gypsum, 6 - 15 parts of portland cement, 15 - 25 parts of mineral powder, 1 - 3 parts of steel slag powder, 1 - 2 parts of hydrogen peroxide, 2 - 4 parts of sodium bicarbonate, 3 - 6 parts of potassium alum, 0.2 - 0.4 parts of retarder, 0.02 - 0.2 parts of water reducer, 0.2 - 0.6 parts of calcium stearate, and the water-cement ratio is 0.25 - 0.4; Among them, hydrogen peroxide decomposes to provide O 2 , and sodium bicarbonate and potassium alum react to provide CO 2 .

[0023] In the present invention, solid waste-based sulphoaluminate cement and hemihydrate gypsum are used as the main cementitious materials, and portland cement is used as the auxiliary cementitious material. Among them, the solid waste-based sulphoaluminate cement provides early strength, and the main hydration products are ettringite (AFt) and C-S-H gel, endowing the material with rapid hardening characteristics and high impermeability. Hemihydrate gypsum reacts with sulphoaluminate cement to form ettringite, optimizing the pore structure density and generating a lapping effect to enhance the performance; at the same time, it can adjust the setting time to avoid insufficient foaming caused by too fast hardening of the paste. Portland cement provides a calcium source (CaO therein will react with CO 2 to form calcium carbonate to enhance the performance), and hydrates later to provide strength for the specimen (mainly C-S-H gel), making up for the defect of insufficient long-term strength growth of sulphoaluminate cement; at the same time, it can adjust the alkalinity of the system and stabilize the decomposition rate of hydrogen peroxide.

[0024] In the present invention, the active SiO 2 and Al 2 O 3 in the mineral powder can react with the cement hydration product Ca(OH) 2 to generate additional C-S-H gel, improving the compactness and durability; at the same time, the fine particles of the mineral powder fill the pores, which can reduce the proportion of connected pores to a certain extent. The steel slag powder is rich in basic components such as Fe 2 O 3 , CaO, etc., which can catalyze the decomposition of hydrogen peroxide (accelerating the release of O 2 ); at the same time, Fe 2 O 3 in the steel slag powder and Al 2 O 3 promote the directional growth of the hydration product (ettringite) of sulphoaluminate cement, thereby optimizing the pore distribution.

[0025] In the present invention, hydrogen peroxide (O 2 source) is used as the main foaming agent, which decomposes in an alkaline environment (OH - provided by the steel slag powder) to generate O 2 gas, forming an initial macroporous framework. Sodium bicarbonate (CO 2 source) is used as the auxiliary foaming agent, which reacts with potassium alum to release CO 2 gas, generating micropores to fill the macroporous gaps and improving the pore uniformity. Potassium alum, on the one hand, acts as an acidic activator, and its hydrolysis provides H + , triggering the decomposition of sodium bicarbonate (NaHCO 3 + H + → CO 2 ↑ + H 2 O + Na + ); on the other hand, the Al 3+ it provides can also promote the rapid formation of ettringite, shorten the setting time, and stabilize the foaming structure.

[0026] In the present invention, the setting retarder, water reducer and calcium stearate are functional additives. Among them, the setting retarder can delay the early hydration of sulfoaluminate cement, ensure that hydrogen peroxide is fully decomposed before entering the setting stage, and avoid form collapse. The water reducer can reduce the viscosity of the slurry at a specific water-cement ratio, thereby improving the uniformity of bubble distribution. The hydrophobic group of calcium stearate adsorbs on the surface of the bubbles, inhibits coalescence and rupture, and can also assist in reducing the water absorption rate of the material.

[0027] In the present invention, the water-cement ratio refers to the ratio of the total mass of water to the total mass of the added cementitious material powder (i.e., waste-based sulfoaluminate cement, hemihydrate gypsum, portland cement and mineral powder).

[0028] In the present invention, the waste-based sulfoaluminate cement is prepared from raw materials including the following parts by mass: 80-90 parts of sulfoaluminate cement clinker, 15-20 parts of desulfurized gypsum, and 5-10 parts of stone powder. Further, the preparation method of the waste-based sulfoaluminate cement is as follows: dry and mix the sulfoaluminate cement clinker, desulfurized gypsum and stone powder, and then heat up to 1250-1350 °C and keep it warm for calcination for 20-40 min to obtain it. The use of waste-based sulfoaluminate cement can reduce costs and improve environmental protection.

[0029] In the present invention, the setting retarder is selected from one or two of boric acid or tartaric acid; the water reducer is a polycarboxylate-based water reducer or a naphthalene-based water reducer.

[0030] In the present invention, the specific surface area of the steel slag powder ≥ 600 m² / kg; the mass fraction of the hydrogen peroxide is 25-40%.

[0031] The present invention provides the preparation method of the above-mentioned high-performance waste-based foamed concrete based on O 2 -CO 2 composite chemical foaming, including the following steps: S1. Premix the waste-based sulfoaluminate cement, hemihydrate gypsum, portland cement, mineral powder, steel slag powder and sodium bicarbonate evenly; then add the setting retarder, water reducer and calcium stearate, and stir and mix evenly to obtain a mixture; S2. Add water to the mixture in step S1, and stir at a speed of 400-800 r / min for 1-10 min; S3. Adjust the stirring speed to 50-150 r / min, then add hydrogen peroxide, and after adding, stir at a speed of 400-800 r / min for 20-40 s; S4. Add an aqueous solution of potassium alum to the slurry in step S3, stir at a speed of 400-800 r / min for 20-40 s, pour it into a mold, cure it statically, demold it and then cure it to obtain the product.

[0032] The decomposition reaction of hydrogen peroxide is relatively slow. In the case of using hydrogen peroxide alone for foaming, the phenomenon of slurry stratification may occur, which is not conducive to the formation of a uniform pore structure. CO 2 has a relatively fast foaming reaction. When using CO 2 alone for foaming, dry shrinkage and collapse may occur due to the absorption and mineralization of CO 2 . In the present invention, when introducing hydrogen peroxide, low-speed premixing (50 - 150 r / min) is adopted to reduce the shear force and prevent the out-of-control escape of O 2 caused by the too-fast decomposition of hydrogen peroxide. Then, a short-term high-speed stirring at 400 - 800 r / min is adopted to promote the uniform dispersion of hydrogen peroxide, and O 2 is rapidly released under the catalysis of steel slag micro-powder to form a macroporous framework, effectively reducing the dry density of the material. Subsequently, potassium alum is added, and it reacts with sodium bicarbonate to release CO 2 to form micropores, fill the macropore gaps, refine the pore size distribution, and continue foaming until the slurry coagulates, which is beneficial to improving the strength and pore uniformity. In addition, the CO 2 gas reacts with the gelling components (Ca(OH) 2 , C-S-H) inside the pores to generate CaCO 3 precipitate, filling the pore wall defects and further improving the density of the interfacial transition zone. In the solution of the present invention, the foaming of hydrogen peroxide and sodium bicarbonate complements each other, synergistically improving the stability of the foaming process and the macroscopic uniformity of the foamed concrete.

[0033] In step S1 of the present invention, in the step of stirring and mixing to obtain the mixture, the stirring speed is 50 - 150 r / min, and the stirring time is 1 - 10 min.

[0034] In the present invention, in the potassium alum aqueous solution, the mass fraction of potassium alum is 30 - 60%. It should be noted that in the present invention, potassium alum preferably adopts potassium alum dodecahydrate. In the potassium alum aqueous solution, potassium alum does not need to be completely dissolved. Its pre-mixing with water is to make it more easily dispersed uniformly, thus being beneficial to the subsequent CO 2 foaming.

[0035] In the present invention, in step S4, the static forming time is 2 - 3 d, and the curing is carried out under standard conditions. The standard conditions are specifically as follows: the environmental temperature needs to be strictly controlled within the range of 20 ± 2 °C to ensure the stable progress of the concrete hydration reaction; the relative humidity needs to be maintained above 95% to prevent cracking caused by the too-fast evaporation of water; the curing time is 28 days, and at this time, the concrete strength basically reaches more than 90% of the design value.

[0036] The present invention provides the high-performance solid waste-based foamed concrete based on O 2 -CO 2 composite chemical foaming or the high-performance solid waste-based foamed concrete prepared by the above preparation method based on O 2-CO 2 Application of High-performance Solid Waste-based Foamed Concrete with Composite Chemical Foaming in Building Thermal Insulation Materials

[0037] The thermal conductivity of the high-performance solid waste-based foamed concrete prepared by the present invention is below 0.2 W / m·K, and the water absorption rate in 24 hours is lower than 10%, so it can be used as a building thermal insulation material.

[0038] The technical solution of the present invention will be further described below in conjunction with specific embodiments. In the following embodiments, the specific surface area of steel slag powder ≥ 600m 2 / kg, the retarder is boric acid, the water reducer is a polycarboxylate-based high-performance water reducer, and the water used is tap water; the potassium alum used is potassium alum dodecahydrate.

[0039] In the following embodiments, the preparation method of the solid waste-based sulphoaluminate cement is as follows: Mix 85 parts of sulphoaluminate cement clinker, 18 parts of desulphurized gypsum and 8 parts of stone powder after drying, and then heat them up to 1300 °C at a heating rate of 8 °C / min in an oxygen atmosphere and keep them calcined for 30 min to obtain it.

[0040] Example 1 This example provides a high-performance solid waste-based foamed concrete based on O 2 -CO 2 Composite chemical foaming, which is made of the following components in parts by mass: 40 parts of solid waste-based sulphoaluminate cement, 30 parts of hemihydrate gypsum, 10 parts of Portland cement, 20 parts of mineral powder, 2 parts of steel slag powder, 1 part of hydrogen peroxide, 2 parts of sodium bicarbonate, 3 parts of potassium alum, 0.2 part of retarder, 0.2 part of water reducer, 0.4 part of calcium stearate, 30 parts of water.

[0041] The specific preparation method is as follows: S1. Premix the solid waste-based sulphoaluminate cement, hemihydrate gypsum, Portland cement, mineral powder, steel slag powder and sodium bicarbonate evenly; then add the retarder, water reducer and calcium stearate, and stir and mix evenly at a speed of 100 r / min for 2 min to obtain a mixture; S2. Add 27 parts of water to the mixture in step S1, and stir at a speed of 600 r / min for 1.5 min; S3. Adjust the stirring speed to 100 r / min, then add hydrogen peroxide, and stir at a speed of 600 r / min for 25 s after adding; S4. Add an aqueous solution of potassium alum (3 parts of potassium alum, 3 parts of water) to the slurry in step S3, stir at a speed of 600 r / min for 25 s, pour it into a mold, cure and form for 3 d, and cure it under standard conditions (20 ± 2 °C, humidity ≥ 95%) for 28 d to obtain it.

[0042] The process flow diagram of the preparation of the high-performance solid waste-based foamed concrete in this embodiment is as Figure 1 shown, and the macroscopic picture of the high-performance solid waste-based foamed concrete prepared in this embodiment is as Figure 2 shown. The pore structure formed by the specimen has both large pores, and micropores are supplemented between the large pores to make the overall pores more uniform.

[0043] Example 2 This embodiment provides a high-performance solid waste-based foamed concrete based on O 2 -CO 2 compound chemical foaming, which is made of the following components in parts by mass: 40 parts of solid waste-based sulphoaluminate cement, 30 parts of hemihydrate gypsum, 10 parts of Portland cement, 20 parts of mineral powder, 2 parts of steel slag micropowder, 2 parts of hydrogen peroxide, 2 parts of sodium bicarbonate, 3 parts of potassium alum, 0.2 part of retarder, 0.2 part of water reducer, 0.4 part of calcium stearate, and 30 parts of water.

[0044] The specific preparation method is as follows: S1. Premix the solid waste-based sulphoaluminate cement, hemihydrate gypsum, Portland cement, mineral powder, steel slag micropowder and sodium bicarbonate evenly; then add the retarder, water reducer and calcium stearate, and stir and mix evenly at a speed of 100 r / min for 2 min to obtain a mixture; S2. Add 27 parts of water to the mixture in step S1, and stir at a speed of 600 r / min for 1.5 min; S3. Adjust the stirring speed to 100 r / min, then add hydrogen peroxide, and stir at a speed of 600 r / min for 25 s after adding; S4. Add an aqueous solution of potassium alum (3 parts of potassium alum and 3 parts of water) to the slurry in step S3, stir at a speed of 600 r / min for 25 s, pour it into a mold, cure and form for 3 d, and cure under standard conditions (20 ± 2 °C, humidity ≥ 95%) for 28 d to obtain.

[0045] The process flow diagram of the preparation of the high-performance solid waste-based foamed concrete in this embodiment is as Figure 1 shown, and the macroscopic picture of the high-performance solid waste-based foamed concrete prepared in this embodiment is as Figure 3 shown. It can be seen that on the basis of Example 1, the amount of oxygen is increased, and the large pores are significantly increased, which is beneficial to reducing the density.

[0046] Example 3 This embodiment provides a high-performance solid waste-based foamed concrete based on O 2 -CO 2 compound chemical foaming, which is made of the following components in parts by mass: 40 parts of solid waste-based sulphoaluminate cement, 30 parts of hemihydrate gypsum, 10 parts of portland cement, 20 parts of mineral powder, 2 parts of steel slag powder, 1 part of hydrogen peroxide, 4 parts of sodium bicarbonate, 3 parts of potassium alum, 0.2 part of retarder, 0.2 part of water reducer, 0.4 part of calcium stearate, 30 parts of water.

[0047] The specific preparation method is as follows: S1. Premix the solid waste-based sulphoaluminate cement, hemihydrate gypsum, portland cement, mineral powder, steel slag powder and sodium bicarbonate evenly; then add the retarder, water reducer and calcium stearate, and stir and mix evenly at a speed of 100 r / min for 2 min to obtain a mixture; S2. Add 27 parts of water to the mixture in step S1, and stir at a speed of 600 r / min for 1.5 min; S3. Adjust the stirring speed to 100 r / min, then add hydrogen peroxide, and stir at a speed of 600 r / min for 25 s after adding; S4. Add an aqueous solution of potassium alum (3 parts of potassium alum, 3 parts of water) to the slurry in step S3, stir at a speed of 600 r / min for 25 s, pour it into a mold, cure and form for 3 d, and cure under standard conditions (20±2 °C, humidity ≥95%) for 28 d to obtain.

[0048] The process flow diagram of the preparation of the high-performance solid waste-based foam concrete in this example is as Figure 1 shown, and the macroscopic picture of the high-performance solid waste-based foam concrete prepared in this example is as Figure 4 shown.

[0049] Comparative Example 1 Compared with Example 1, the difference in this comparative example is that hydrogen peroxide is not added in this comparative example.

[0050] The specific preparation method is as follows: S1. Premix the solid waste-based sulphoaluminate cement, hemihydrate gypsum, portland cement, mineral powder, steel slag powder and sodium bicarbonate evenly; then add the retarder, water reducer and calcium stearate, and stir and mix evenly at a speed of 100 r / min for 2 min to obtain a mixture; S2. Add 27 parts of water to the mixture in step S1, and stir at a speed of 600 r / min for 1.5 min; S3. Add an aqueous solution of potassium alum (3 parts of potassium alum, 3 parts of water) to the slurry in step S2, stir at a speed of 600 r / min for 25 s, pour it into a mold, cure and form for 3 d, and cure under standard conditions (20±2 °C, humidity ≥95%) for 28 d to obtain.

[0051] Comparative Example 2 This comparative example is different from Example 1 in that sodium bicarbonate and potassium alum are not added in this comparative example.

[0052] The specific preparation method is as follows: S1. Premix solid waste-based sulphoaluminate cement, hemihydrate gypsum, portland cement, mineral powder and steel slag powder evenly; then add a retarder, a water reducer and calcium stearate, and stir and mix evenly at a speed of 100 r / min for 2 min to obtain a mixture; S2. Add 27 parts of water to the mixture in step S1, and stir at a speed of 600 r / min for 1.5 min; S3. Adjust the stirring speed to 100 r / min, then add hydrogen peroxide, and stir at a speed of 600 r / min for 25 s after adding; pour into a mold and cure statically for 3 d, and cure under standard conditions (20 ± 2 °C, humidity ≥ 95%) for 28 d to obtain.

[0053] The macroscopic picture of the foamed concrete material prepared in this comparative example is as Figure 4 shown. It can be seen that at this time, the density of the specimen increases significantly, and the uniformity of its pore distribution is poor, and there will be some sunken holes in the specimen.

[0054] Comparative Example 3 This comparative example is different from Example 1 in that steel slag powder is not added in this comparative example, and the missing part is supplemented by mineral powder.

[0055] The specific preparation method is as follows: S1. Premix solid waste-based sulphoaluminate cement, hemihydrate gypsum, portland cement, mineral powder and sodium bicarbonate evenly; then add a retarder, a water reducer and calcium stearate, and stir and mix evenly at a speed of 100 r / min for 2 min to obtain a mixture; S2. Add 27 parts of water to the mixture in step S1, and stir at a speed of 600 r / min for 1.5 min; S3. Adjust the stirring speed to 100 r / min, then add hydrogen peroxide, and stir at a speed of 600 r / min for 25 s after adding; S4. Add an aqueous solution of potassium alum (3 parts of potassium alum, 3 parts of water) to the slurry in step S3, stir at a speed of 600 r / min for 25 s, pour into a mold and cure statically for 3 d, and cure under standard conditions (20 ± 2 °C, humidity ≥ 95%) for 28 d to obtain.

[0056] Comparative Example 4 This comparative example is different from Example 1 in that this comparative example first performs CO 2 foaming, and then performs O 2 foaming. The specific preparation process is as follows: S1. Premix solid waste-based sulphoaluminate cement, hemihydrate gypsum, portland cement, blast furnace slag powder, steel slag powder and sodium bicarbonate evenly; then add a retarder, a water reducer and calcium stearate, and stir and mix evenly at a speed of 100 r / min for 2 min to obtain a mixture; S2. Add 27 parts of water to the mixture in step S1, and stir at a speed of 600 r / min for 1.5 min; S3. Add an aqueous solution of potassium alum (3 parts of potassium alum, 3 parts of water) to the slurry in step S2, and stir at a speed of 600 r / min for 25 s, S4. Adjust the stirring speed to 100 r / min, then add hydrogen peroxide, and stir at a speed of 600 r / min for 25 s after adding; pour it into a mold and cure statically for 3 d, and then cure under standard conditions (20±2℃, humidity≥95%) for 28 d to obtain the product.

[0057] Test example Measure the dry density, compressive strength, thermal conductivity and 24-hour water absorption rate of the foamed concrete specimens of Examples 1 to 3 and Comparative Examples 1 to 4, and the results are summarized in Table 1.

[0058] The test method for 24-hour water absorption rate is as follows: Take the specimens of the examples and comparative examples (n = 3), dry them at 40±5℃ to constant weight and weigh the mass, denoted as m 1 , then completely immerse the specimens in distilled water at 20±2℃, ensure that the water surface is at least 20 mm higher than the surface of the specimens, soak for 24 h, dry the water on the surface of the specimens and weigh the saturated mass after soaking, denoted as m 2 . The calculation formula for the water absorption rate W is as follows: .

[0059] Table 1 Test data of foamed concrete specimens of Examples 1 to 3 and Comparative Examples 1 to 4

[0060] On the basis of Example 1, Example 2 increases the amount of oxygen, and significantly more macropores are formed. At this time, the formation of macropores makes the density of the concrete lower than that of Example 1 on the same raw material basis, and also makes the mechanical properties decline. On the basis of Example 1, Example 3 increases the amount of carbon dioxide. At this time, carbon dioxide is generated rapidly, and its generation speed is much faster than the speed of oxygen forming the skeleton. The density at this time is lower on the same raw material basis, resulting in a decrease in mechanical properties. However, the internal reaction to generate calcium carbonate is beneficial to the improvement of mechanical properties. Under the synergistic effect, the strength does not decrease too much compared with Example 1.

[0061] In Comparative Example 1, only carbon dioxide gas was used for chemical foaming, which would cause carbonization shrinkage, the density increased somewhat, the compressive strength was higher than that of Examples 2 and 3, but the specific strength did not increase. In Comparative Example 2, only hydrogen peroxide was used for chemical foaming, and no carbon dioxide was generated. Its strength increase was limited, and the strength improvement relied only on the hydration effect. In Comparative Example 3, steel slag powder was not added, and the decomposition rate of hydrogen peroxide was very slow. Therefore, the dry density of the finally prepared foam concrete was relatively high, which was not much different from that of Comparative Example 1. In Comparative Example 4, the foaming sequence of oxygen and carbon dioxide was changed. At this time, carbon dioxide was generated first. Because its reaction was rapid, carbon dioxide would overflow during the stirring process, resulting in limited enhancement of the carbonization of carbon dioxide and the synergy of hydration.

[0062] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming, characterized in that: Made from the following raw materials in parts by weight: 20-42 parts of solid waste-based sulphoaluminate cement, 15-60 parts of hemihydrate gypsum, 6-15 parts of Portland cement, 15-25 parts of mineral powder, 1-3 parts of steel slag powder, 1-2 parts of hydrogen peroxide, 2-4 parts of sodium bicarbonate, 3-6 parts of potassium aluminum sulfate, 0.2-0.4 parts of retarder, 0.02-0.2 parts of water reducer, 0.2-0.6 parts of calcium stearate, and a water-cement ratio of 0.25-0.4; Among them, hydrogen peroxide decomposes to provide O2, and sodium bicarbonate and potassium aluminum sulfate react to provide CO2; The method for preparing high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming comprises the following steps: S1. Premix solid waste-based sulphoaluminate cement, hemihydrate gypsum, silicate cement, mineral powder, steel slag powder and sodium bicarbonate; then add retarder, water reducer and calcium stearate, stir and mix to obtain a mixture; S2, adding water to the mixture of step S1, stirring at a speed of 400-800 r / min for 1-10 min; S3, adjust the stirring speed to 50-150 r / min, then add hydrogen peroxide, and stir at a speed of 400-800 r / min for 20-40 seconds after the addition is completed; S4. Add potassium aluminum sulfate aqueous solution to the slurry in step S3, stir at a speed of 400-800 r / min for 20-40 s, pour into a mold and let it stand for shaping, and perform curing after demoulding to obtain the slurry.

2. The high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming according to claim 1, characterized in that: The solid waste-based sulphoaluminate cement is prepared from the following raw materials in parts by weight: 80-90 parts of sulphoaluminate cement clinker, 15-20 parts of desulfurized gypsum, and 5-10 parts of stone powder.

3. The high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming according to claim 2, characterized in that: The preparation method of the solid waste-based sulphoaluminate cement is as follows: sulphoaluminate cement clinker, desulfurized gypsum and stone powder are dried and mixed, and then the temperature is raised to 1250-1350° C. and calcined for 20-40 min to obtain the cement.

4. The high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming according to claim 1, characterized in that: The retarder is selected from one or both of boric acid and tartaric acid; the water reducer is a polycarboxylic acid water reducer or a naphthalene water reducer.

5. The high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming according to claim 1, characterized in that: The specific surface area of ​​the steel slag powder is ≥600m 2 / kg; the mass fraction of the hydrogen peroxide is 25~40%.

6. The method for preparing high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming according to any one of claims 1 to 5, characterized in that: The steps include: S1. Premix solid waste-based sulphoaluminate cement, hemihydrate gypsum, silicate cement, mineral powder, steel slag powder and sodium bicarbonate; then add retarder, water reducer and calcium stearate, stir and mix to obtain a mixture; S2, adding water to the mixture of step S1, stirring at a speed of 400-800 r / min for 1-10 min; S3, adjust the stirring speed to 50-150 r / min, then add hydrogen peroxide, and stir at a speed of 400-800 r / min for 20-40 seconds after the addition is completed; S4. Add potassium aluminum sulfate aqueous solution to the slurry in step S3, stir at a speed of 400-800 r / min for 20-40 s, pour into a mold and let it stand for shaping, and perform curing after demoulding to obtain the slurry.

7. The preparation method according to claim 6, characterized in that: In step S1, in the step of stirring and mixing to obtain a mixture, the stirring speed is 50-150 r / min, and the stirring time is 1-10 min.

8. The preparation method according to claim 6, characterized in that: In the potassium aluminum sulfate aqueous solution, the mass fraction of potassium aluminum sulfate is 30-60%.

9. The preparation method according to claim 6, characterized in that: In step S4, the static culture time is 2 to 3 days, and the curing is performed under standard conditions.

10. Use of the high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming as described in any one of claims 1 to 5 or the high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming prepared by the preparation method according to any one of claims 6 to 9 in building insulation materials.

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