A high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming, and its preparation method and application

Abstract

The present invention discloses a high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming, a preparation method and an application thereof, and belongs to the field of foamed concrete technology. The high-performance solid waste-based foamed concrete provided by the present invention is made of the following raw materials in parts by mass: 20 to 42 parts of solid waste-based sulfoaluminate cement, 15 to 60 parts of hemihydrate gypsum, 6 to 15 parts of Portland cement, 15 to 25 parts of mineral powder, 1 to 3 parts of steel slag powder, 1 to 2 parts of hydrogen peroxide, 2 to 4 parts of sodium bicarbonate, 3 to 6 parts of potassium aluminum sulfate, 0.2 to 0.4 parts of retarder, 0.02 to 0.2 parts of water reducer, 0.2 to 0.6 parts of calcium stearate, and a water-cement ratio of 0.25 to 0.4; wherein, hydrogen peroxide decomposes to provide O2, and sodium bicarbonate and potassium aluminum sulfate react to provide CO2. The present invention prepares a foamed concrete material with both high compressive strength and low dry density, while being able to consume solid waste in a high proportion.

Description

Technical Field

[0001] The present invention relates to the technical field of foamed concrete, and in particular to a high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming, and a preparation method and application thereof. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] As a lightweight, porous building material, foamed concrete holds significant value in building energy conservation and solid waste resource utilization due to its light weight and excellent thermal insulation properties. Existing methods for preparing foamed concrete primarily include physical foaming and chemical foaming. Chemical foaming, in particular, produces gas directly within the slurry through a chemical reaction, eliminating the specialized foaming equipment and complex foam stabilization processes required for physical foaming. This significantly reduces equipment costs and energy consumption, making it particularly suitable for small-scale or on-site construction scenarios.

[0004] At present, chemical foaming is still mainly based on a single foaming agent. For example, the patent with publication number CN108298944A discloses a phosphate cement foam concrete and its preparation method, which uses hydrogen peroxide as a foaming agent and manganese dioxide as a catalyst. However, the cost of the phosphate cement used in this patent is relatively high, and the use of manganese dioxide with a relatively high cost as a catalyst has poor economic efficiency. The patent with publication number CN119330674A discloses a CO2 foam concrete material and preparation method based on a solid waste-based multi-component cementing system, which releases CO2 gas for foaming through the reaction of potassium aluminum sulfate solution with sodium bicarbonate, and uses solid waste-based sulfoaluminate cement, semi-hydrated gypsum and other cementing materials to achieve efficient utilization of solid waste resources. However, the pore structure formed by the single CO2 foaming in this patent is mainly micropores, and its dry density is 700kg / m 3 Above 6MPa, it can maintain relatively high compressive strength (above 6MPa); but when its dry density is as low as 650kg / m 3 When it is around 3000 psi, its compressive strength drops below 6 MPa.

[0005] Currently, there is little research on composite chemical foaming processes. Composite chemical foaming may face the following problems. For example, the decomposition conditions of different foaming agents vary significantly. If the foaming sequence and timing are not properly controlled, it may be difficult to form an ideal pore structure. Moreover, the foaming process must be strictly matched with the slurry setting time. Premature foaming will lead to insufficient slurry consistency, causing bubbles to float and burst, resulting in mold collapse. If foaming is too late, the slurry will have initially set, and the gas cannot expand effectively, resulting in reduced porosity. At the same time, dual-gas source foaming may cause small bubbles to merge into large bubbles due to differences in bubble size, resulting in a high degree of dispersion in the pore size distribution and reduced compressive strength. In addition, the complexity of concrete raw materials can have unpredictable effects on the composite foaming process. The raw material particle morphology and surface activity may interfere with 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 O2 and CO2 as composite foaming gases 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 foamed concrete based on O2-CO2 composite chemical foaming, as well as a preparation method and application thereof. The present invention uses steel slag micropowder to catalyze the staged release of hydrogen peroxide to construct an initial pore skeleton, and cooperates with CO2 foaming to form micropore filling, ultimately obtaining a foamed concrete material with both high compressive strength and low dry density, while being able to absorb solid waste in high proportion.

[0008] In a first aspect, the present invention provides a high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming, which is made from the following raw materials in parts by mass:

[0009] 20-42 parts of solid waste-based sulfoaluminate 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;

[0010] Among them, hydrogen peroxide decomposes to provide O2, and sodium bicarbonate and potassium aluminum sulfate react to provide CO2;

[0011] The method for preparing high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming comprises the following steps:

[0012] S1. Premix solid waste-based sulfoaluminate cement, hemihydrate gypsum, Portland cement, mineral powder, steel slag powder, and sodium bicarbonate; then add retarder, water reducer, and calcium stearate, and stir to obtain a mixture;

[0013] S2. Add water to the mixture of step S1 and stir at a speed of 400-800 r / min for 1-10 min;

[0014] S3. Adjust the stirring speed to 50-150 r / min, then add hydrogen peroxide. After the addition is complete, stir at a speed of 400-800 r / min for 20-40 seconds;

[0015] S4. Add potassium aluminum sulfate aqueous solution to the slurry in step S3, stir at a speed of 400-800 r / min for 20-40s, pour into a mold and let it stand for shaping, and perform curing after demoulding to obtain the slurry.

[0016] Preferably, 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.

[0017] Furthermore, 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 heated to 1250-1350° C. and calcined for 20-40 min to obtain the solid waste-based sulphoaluminate cement.

[0018] Preferably, the retarder is selected from one or both of boric acid and tartaric acid; and the water reducer is a polycarboxylic acid water reducer or a naphthalene water reducer.

[0019] Preferably, the specific surface area of ​​the steel slag powder is ≥600m 2 / kg; the mass fraction of the hydrogen peroxide is 25~40%.

[0020] In a second aspect, the present invention provides a method for preparing the above-mentioned high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming, comprising the following steps:

[0021] S1. Premix solid waste-based sulfoaluminate cement, hemihydrate gypsum, Portland cement, mineral powder, steel slag powder, and sodium bicarbonate; then add retarder, water reducer, and calcium stearate, and stir to obtain a mixture;

[0022] S2. Add water to the mixture of step S1 and stir at a speed of 400-800 r / min for 1-10 min;

[0023] S3. Adjust the stirring speed to 50-150 r / min, then add hydrogen peroxide. After the addition is complete, stir at a speed of 400-800 r / min for 20-40 seconds;

[0024] S4. Add potassium aluminum sulfate aqueous solution to the slurry in step S3, stir at a speed of 400-800 r / min for 20-40s, pour into a mold and let it stand for shaping, and perform curing after demoulding to obtain the slurry.

[0025] Preferably, 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.

[0026] Preferably, the mass fraction of potassium aluminum sulfate in the potassium aluminum sulfate aqueous solution is 30-60%.

[0027] Preferably, in step S4, the static culture time is 2 to 3 days, and the curing is performed under standard conditions.

[0028] In a third aspect, the present invention provides the application of the above-mentioned high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming or the high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming prepared by the above-mentioned preparation method in building insulation materials.

[0029] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0030] (1) The present invention adopts a staged foaming process of hydrogen peroxide (O2 source) and sodium bicarbonate (CO2 source), and utilizes the alkaline catalytic effect of steel slag powder to preferentially trigger the slow decomposition reaction of hydrogen peroxide to form a pore structure skeleton before the initial setting of the slurry. Then, potassium aluminum sulfate is used to stimulate sodium bicarbonate to release CO2 to form CO2 micropores, thereby forming a "macropore-micropore" gradient nested structure, so that the overall pore structure is uniform, breaking through the porosity-strength bottleneck of a single foaming agent, and achieving a dry density as low as nearly 600 kg / m 3 Under the condition of , it can still maintain a compressive strength of more than 6MPa;

[0031] (2) The present invention uses solid waste-based sulfoaluminate cement and hemihydrate gypsum as the main cementitious materials, combined with steel slag powder and mineral powder, and through the volcanic ash effect and crystal nucleation effect of the active components (Al2O3, Fe2O3), directionally regulates the growth of hydration products (calcium aluminate, CSH gel), thereby achieving pore densification and mechanical property improvement; the present invention can achieve a high proportion of solid waste-based materials, and the preparation method is very simple, without the need for expensive or complex equipment, environmentally friendly and low cost, and meets the needs of industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute undue limitations thereon. It is obvious that one of ordinary skill in the art could derive other drawings based on these drawings without inventive effort.

[0033] Figure 1 1 is a schematic flow chart of the preparation process of high-performance solid waste-based foamed concrete according to Examples 1 to 3 of the present invention;

[0034] Figure 2 This is a macroscopic picture of the high-performance solid waste-based foamed concrete of Example 1 of the present invention;

[0035] Figure 3 This is a macroscopic picture of the high-performance solid waste-based foamed concrete of Example 2 of the present invention;

[0036] Figure 4 This is a macroscopic picture of the high-performance solid waste-based foamed concrete of Example 3 of the present invention;

[0037] Figure 5 This is a macroscopic picture of the high-performance solid waste-based foamed concrete of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0038] It should be noted that the following detailed descriptions are exemplary and 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 skilled in the art to which the present invention belongs.

[0039] The present invention provides a high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming, which is made from the following raw materials in parts by mass:

[0040] 20-42 parts of solid waste-based sulfoaluminate 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;

[0041] Among them, hydrogen peroxide decomposes to provide O2, and sodium bicarbonate and potassium aluminum sulfate react to provide CO2.

[0042] This invention uses solid waste-based sulfoaluminate cement and hemihydrate gypsum as the primary cementitious materials, with Portland cement as the auxiliary cementitious material. The solid waste-based sulfoaluminate cement provides early strength, and its primary hydration products are ettringite (AFt) and CSH gel, imparting rapid hardening and high impermeability to the material. Hemihydrate gypsum reacts with sulfoaluminate cement to form ettringite, which optimizes pore structure density and creates a bridging effect to enhance performance. It also regulates the setting time, preventing excessive hardening of the slurry and insufficient foaming. Portland cement provides a calcium source (CaO reacts with CO2 to form calcium carbonate, enhancing performance). Later hydration provides strength to the sample (primarily from CSH gel), compensating for the lack of long-term strength growth associated with sulfoaluminate cement. It also regulates the system's alkalinity and stabilizes the decomposition rate of hydrogen peroxide.

[0043] In this invention, the active SiO2 and Al2O3 in the mineral powder react with the cement hydration product Ca(OH)2 to form additional CSH gel, improving compactness and durability. Furthermore, the fine particles of the mineral powder fill pores, reducing the proportion of interconnected pores to a certain extent. Steel slag powder is rich in alkaline components such as Fe2O3 and CaO, which catalyze the decomposition of hydrogen peroxide (accelerating the release of O2). Furthermore, the Fe2O3 and Al2O3 in the steel slag powder promote the directional growth of sulfoaluminate cement hydration products (ettringite), thereby optimizing pore distribution.

[0044] In the present invention, hydrogen peroxide (O2 source) is used as the main foaming agent, which is in an alkaline environment (steel slag powder provides OH - ) decomposes to generate O2 gas, forming the initial macroporous skeleton. Sodium bicarbonate (CO2 source) acts as an auxiliary foaming agent, which reacts with potassium aluminum sulfate to release CO2 gas, generating micropores, filling the macropore gaps and improving the pore uniformity. Potassium aluminum sulfate acts as an acidic activator, and its hydrolysis provides H + , triggering the decomposition of sodium bicarbonate (NaHCO3+ H + → CO2↑ + H2O + Na + ); On the other hand, the Al 3+ It can also promote the rapid formation of ettringite, shorten the setting time and stabilize the foaming structure.

[0045] In this invention, the retarder, water reducer, and calcium stearate are functional additives. The retarder delays the early hydration of sulfoaluminate cement, ensuring that hydrogen peroxide fully decomposes before setting, thus preventing mold collapse. The water reducer reduces the slurry viscosity at a specific water-cement ratio, thereby improving the uniformity of bubble distribution. The hydrophobic groups in calcium stearate adsorb on the bubble surface, inhibiting coalescence and rupture, and also helping to reduce the material's water absorption rate.

[0046] 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 (ie, solid waste-based sulphoaluminate cement, hemihydrate gypsum, Portland cement and mineral powder).

[0047] In the present invention, the solid waste-based sulfoaluminate cement is prepared from the following raw materials in parts by weight: 80-90 parts sulfoaluminate cement clinker, 15-20 parts desulfurized gypsum, and 5-10 parts stone powder. Furthermore, the solid waste-based sulfoaluminate cement is prepared by drying the sulfoaluminate cement clinker, desulfurized gypsum, and stone powder, mixing them uniformly, and then heating them to 1250-1350°C and calcining them for 20-40 minutes. The use of solid waste-based sulfoaluminate cement can reduce costs and improve environmental performance.

[0048] In the present invention, the retarder is selected from one or both of boric acid and tartaric acid; and the water reducer is a polycarboxylic acid water reducer or a naphthalene water reducer.

[0049] In the present invention, the specific surface area of ​​the steel slag powder is ≥600 m² / kg; and the mass fraction of the hydrogen peroxide is 25-40%.

[0050] The present invention provides a method for preparing the above-mentioned high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming, comprising the following steps:

[0051] S1. Premix solid waste-based sulfoaluminate cement, hemihydrate gypsum, Portland cement, mineral powder, steel slag powder, and sodium bicarbonate; then add retarder, water reducer, and calcium stearate, and stir to obtain a mixture;

[0052] S2. Add water to the mixture of step S1 and stir at a speed of 400-800 r / min for 1-10 min;

[0053] S3. Adjust the stirring speed to 50-150 r / min, then add hydrogen peroxide. After the addition is complete, stir at a speed of 400-800 r / min for 20-40 seconds;

[0054] S4. Add potassium aluminum sulfate aqueous solution to the slurry in step S3, stir at a speed of 400-800 r / min for 20-40s, pour into a mold and let it stand for shaping, and perform curing after demoulding to obtain the slurry.

[0055] Hydrogen peroxide decomposes slowly, and using it alone in a foaming process can result in slurry stratification, hindering the formation of a uniform pore structure. CO2 foaming reacts rapidly, and using it alone can lead to shrinkage and collapse due to CO2 absorption and mineralization. This method uses low-speed premixing (50-150 rpm) to reduce shear forces when introducing hydrogen peroxide, preventing rapid decomposition of hydrogen peroxide and uncontrolled O2 release. A brief high-speed stirring process at 400-800 rpm promotes uniform dispersion of hydrogen peroxide. Catalyzed by steel slag powder, O2 rapidly releases, forming a macroporous skeleton and effectively reducing the material's dry density. Potassium aluminum sulfate is then added, reacting with sodium bicarbonate to release CO2, forming micropores that fill the macropore gaps and refine the pore size distribution. Continuing foaming until the slurry solidifies helps improve strength and pore uniformity. Furthermore, the CO2 gas reacts with the gelling components (Ca(OH)2 and CSH) within the pores to form CaCO3 precipitates, which fill pore wall defects and increase the density of the interfacial transition zone. In the solution of the present invention, hydrogen peroxide and sodium bicarbonate foaming complement each other and synergistically improve the stability of the foaming process and the macroscopic uniformity of the foamed concrete.

[0056] In step S1 of the present invention, 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.

[0057] In the present invention, the mass fraction of potassium aluminum sulfate in the potassium aluminum sulfate aqueous solution is 30-60%. It should be noted that the potassium aluminum sulfate of the present invention is preferably potassium aluminum sulfate dodecahydrate. In the potassium aluminum sulfate aqueous solution, potassium aluminum sulfate does not need to be completely dissolved. It is pre-mixed with water to make it easier to disperse evenly, thereby facilitating subsequent CO2 foaming.

[0058] In the present invention, in step S4, the static curing period is 2-3 days, and the curing is performed under standard conditions. Specifically, the standard conditions include: the ambient temperature must be strictly controlled within the range of 20±2°C to ensure stable hydration of the concrete; the relative humidity must be maintained above 95% to prevent rapid evaporation of water and cracking; and the curing period is 28 days, at which point the concrete strength essentially reaches above 90% of the design value.

[0059] The present invention provides the use of the above-mentioned high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming or the high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming prepared by the above-mentioned preparation method in building insulation materials.

[0060] The high-performance solid waste-based foamed concrete prepared by the present invention has a thermal conductivity of less than 0.2 W / m·K and a 24-hour water absorption rate of less than 10%, and can be used as a building insulation material.

[0061] The technical solution of the present invention is further described below in conjunction with specific examples. In the following examples, the specific surface area of ​​the steel slag powder is ≥600m 2 / kg, the retarder is boric acid, the water reducer is a polycarboxylic acid-based high-performance water reducer, the water used is tap water; the potassium aluminum sulfate used is potassium aluminum sulfate dodecahydrate.

[0062] In the following examples, the preparation method of solid waste-based sulphoaluminate cement is as follows: 85 parts of sulphoaluminate cement clinker, 18 parts of desulfurized gypsum and 8 parts of stone powder are dried and mixed, and then heated to 1300°C at a heating rate of 8°C / min in an oxygen atmosphere and calcined for 30 minutes to obtain the product.

[0063] Example 1

[0064] This embodiment provides a high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming, which is made of the following components in parts by weight:

[0065] 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 aluminum sulfate, 0.2 parts of retarder, 0.2 parts of water reducer, 0.4 parts of calcium stearate, and 30 parts of water.

[0066] The specific preparation method is as follows:

[0067] S1. Premix solid waste-based sulfoaluminate cement, hemihydrate gypsum, silicate cement, mineral powder, steel slag powder and sodium bicarbonate; then add retarder, water reducer and calcium stearate, and stir at a speed of 100 r / min for 2 min to obtain a mixture;

[0068] S2. Add 27 parts of water to the mixture of step S1 and stir at a speed of 600 r / min for 1.5 min;

[0069] S3. Adjust the stirring speed to 100 r / min, then add hydrogen peroxide, and stir at 600 r / min for 25 seconds after the addition is complete;

[0070] S4. Add an aqueous solution of potassium aluminum sulfate (3 parts of potassium aluminum sulfate and 3 parts of water) to the slurry of step S3, stir at a speed of 600 r / min for 25 seconds, pour into a mold and let it stand for 3 days. After demolding, cure under standard conditions (20±2°C, humidity ≥95%) for 28 days to obtain the product.

[0071] The process flow diagram of the preparation of high performance solid waste-based foamed concrete in this embodiment is as follows: Figure 1 As shown in the macroscopic picture of the high performance solid waste-based foamed concrete prepared in this embodiment, Figure 2As shown in the figure, the pore structure formed by the sample consists of macropores, and micropores are added between the macropores to make the overall pores more uniform.

[0072] Example 2

[0073] This embodiment provides a high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming, which is made of the following components in parts by weight:

[0074] 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, 2 parts of hydrogen peroxide, 2 parts of sodium bicarbonate, 3 parts of potassium aluminum sulfate, 0.2 parts of retarder, 0.2 parts of water reducer, 0.4 parts of calcium stearate, and 30 parts of water.

[0075] The specific preparation method is as follows:

[0076] S1. Premix solid waste-based sulfoaluminate cement, hemihydrate gypsum, silicate cement, mineral powder, steel slag powder and sodium bicarbonate; then add retarder, water reducer and calcium stearate, and stir at a speed of 100 r / min for 2 min to obtain a mixture;

[0077] S2. Add 27 parts of water to the mixture of step S1 and stir at a speed of 600 r / min for 1.5 min;

[0078] S3. Adjust the stirring speed to 100 r / min, then add hydrogen peroxide, and stir at 600 r / min for 25 seconds after the addition is complete;

[0079] S4. Add an aqueous solution of potassium aluminum sulfate (3 parts of potassium aluminum sulfate and 3 parts of water) to the slurry of step S3, stir at a speed of 600 r / min for 25 seconds, pour into a mold and let it stand for 3 days. After demolding, cure under standard conditions (20±2°C, humidity ≥95%) for 28 days to obtain the product.

[0080] The process flow diagram of the preparation of high performance solid waste-based foamed concrete in this embodiment is as follows: Figure 1 As shown in the macroscopic picture of the high performance solid waste-based foamed concrete prepared in this embodiment, Figure 3 As shown, it can be seen that by increasing the amount of oxygen on the basis of Example 1, the number of macropores increases significantly, which is beneficial to reducing the density.

[0081] Example 3

[0082] This embodiment provides a high-performance solid waste-based foamed concrete based on O2-CO2 composite chemical foaming, which is made of the following components in parts by weight:

[0083] 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 aluminum sulfate, 0.2 parts of retarder, 0.2 parts of water reducer, 0.4 parts of calcium stearate, and 30 parts of water.

[0084] The specific preparation method is as follows:

[0085] S1. Premix solid waste-based sulfoaluminate cement, hemihydrate gypsum, silicate cement, mineral powder, steel slag powder and sodium bicarbonate; then add retarder, water reducer and calcium stearate, and stir at a speed of 100 r / min for 2 min to obtain a mixture;

[0086] S2. Add 27 parts of water to the mixture of step S1 and stir at a speed of 600 r / min for 1.5 min;

[0087] S3. Adjust the stirring speed to 100 r / min, then add hydrogen peroxide, and stir at 600 r / min for 25 seconds after the addition is complete;

[0088] S4. Add an aqueous solution of potassium aluminum sulfate (3 parts of potassium aluminum sulfate and 3 parts of water) to the slurry of step S3, stir at a speed of 600 r / min for 25 seconds, pour into a mold and let it stand for 3 days. After demolding, cure under standard conditions (20±2°C, humidity ≥95%) for 28 days to obtain the product.

[0089] The process flow diagram of the preparation of high performance solid waste-based foamed concrete in this embodiment is as follows: Figure 1 As shown in the macroscopic picture of the high performance solid waste-based foamed concrete prepared in this embodiment, Figure 4 shown.

[0090] Comparative Example 1

[0091] The difference between this comparative example and Example 1 is that no hydrogen peroxide is added in this comparative example.

[0092] The specific preparation method is as follows:

[0093] S1. Premix solid waste-based sulfoaluminate cement, hemihydrate gypsum, silicate cement, mineral powder, steel slag powder and sodium bicarbonate; then add retarder, water reducer and calcium stearate, and stir at a speed of 100 r / min for 2 min to obtain a mixture;

[0094] S2. Add 27 parts of water to the mixture of step S1 and stir at a speed of 600 r / min for 1.5 min;

[0095] S3. Add an aqueous solution of potassium aluminum sulfate (3 parts of potassium aluminum sulfate and 3 parts of water) to the slurry of step S2, stir at a speed of 600 r / min for 25 seconds, pour into a mold and statically cure for 3 days. After demolding, cure under standard conditions (20±2°C, humidity ≥95%) for 28 days to obtain the product.

[0096] Comparative Example 2

[0097] The difference between this comparative example and Example 1 is that sodium bicarbonate and potassium aluminum sulfate are not added in this comparative example.

[0098] The specific preparation method is as follows:

[0099] S1. Premix solid waste-based sulfoaluminate cement, hemihydrate gypsum, Portland cement, mineral powder, and steel slag powder; then add retarder, water reducer, and calcium stearate, and stir at a speed of 100 r / min for 2 min to obtain a mixture;

[0100] S2. Add 27 parts of water to the mixture of step S1 and stir at a speed of 600 r / min for 1.5 min;

[0101] S3. Adjust the stirring speed to 100 r / min, then add hydrogen peroxide, and stir at a speed of 600 r / min for 25 seconds after the addition is completed; pour into a mold and let it stand for 3 days. After demolding, cure under standard conditions (20±2℃, humidity ≥95%) for 28 days.

[0102] The macroscopic picture of the foamed concrete material prepared in this comparative example is as follows Figure 4 As shown, it can be seen that the density of the sample is significantly increased at this time, and its pore distribution is less uniform, and some sunken holes appear in the sample.

[0103] Comparative Example 3

[0104] The difference between this comparative example and Example 1 is that no steel slag powder is added in this comparative example, and the missing part is supplemented by mineral powder.

[0105] The specific preparation method is as follows:

[0106] S1. Premix solid waste-based sulfoaluminate cement, hemihydrate gypsum, Portland cement, mineral powder and sodium bicarbonate; then add retarder, water reducer and calcium stearate, and stir at a speed of 100 r / min for 2 min to obtain a mixture;

[0107] S2. Add 27 parts of water to the mixture of step S1 and stir at a speed of 600 r / min for 1.5 min;

[0108] S3. Adjust the stirring speed to 100 r / min, then add hydrogen peroxide, and stir at 600 r / min for 25 seconds after the addition is complete;

[0109] S4. Add an aqueous solution of potassium aluminum sulfate (3 parts of potassium aluminum sulfate and 3 parts of water) to the slurry of step S3, stir at a speed of 600 r / min for 25 seconds, pour into a mold and let it stand for 3 days. After demolding, cure under standard conditions (20±2°C, humidity ≥95%) for 28 days to obtain the product.

[0110] Comparative Example 4

[0111] Compared with Example 1, this comparative example is different in that CO2 foaming is performed first and then O2 foaming is performed. The specific preparation process is as follows:

[0112] S1. Premix solid waste-based sulfoaluminate cement, hemihydrate gypsum, silicate cement, mineral powder, steel slag powder and sodium bicarbonate; then add retarder, water reducer and calcium stearate, and stir at a speed of 100 r / min for 2 min to obtain a mixture;

[0113] S2. Add 27 parts of water to the mixture of step S1 and stir at a speed of 600 r / min for 1.5 min;

[0114] S3, add potassium aluminum sulfate aqueous solution (3 parts potassium aluminum sulfate, 3 parts water) to the slurry of step S2, and stir at a speed of 600 r / min for 25 seconds.

[0115] S4. Adjust the stirring speed to 100 r / min, then add hydrogen peroxide, and stir at a speed of 600 r / min for 25 seconds after the addition is completed; pour into a mold and let it stand for 3 days. After demolding, cure under standard conditions (20±2℃, humidity ≥95%) for 28 days.

[0116] Test example

[0117] The dry density, compressive strength, thermal conductivity and 24h water absorption of the foamed concrete samples of Examples 1-3 and Comparative Examples 1-4 were measured. The results are summarized in Table 1.

[0118] The 24-hour water absorption test method is as follows: Take the samples of the examples and comparative examples (n=3), dry them at 40±5°C to constant weight, and weigh the mass, recorded as m1. Then, completely immerse the sample in distilled water at 20±2°C, ensuring that the water level is at least 20 mm above the sample surface. Soak for 24 hours. Wipe the sample surface dry and weigh the saturated mass after immersion, recorded as m2. The water absorption rate W is calculated as follows:

[0119] .

[0120] Table 1 Test data of foamed concrete samples of Examples 1 to 3 and Comparative Examples 1 to 4

[0121]

[0122] In Example 2, the amount of oxygen was increased based on Example 1, resulting in a significant increase in macropores. The formation of macropores resulted in a lower density of the concrete than in Example 1 based on the same raw materials, and also resulted in a decrease in mechanical properties. In Example 3, the amount of carbon dioxide was increased based on Example 1. Carbon dioxide was rapidly generated, at a rate much greater than the rate at which oxygen formed the skeleton. Based on the same raw materials, the density was lower, resulting in a decrease in mechanical properties. However, the internal reaction to form calcium carbonate was beneficial to the improvement of mechanical properties, and the synergistic effect prevented a significant decrease in strength compared to Example 1.

[0123] Comparative Example 1 uses only carbon dioxide gas for chemical foaming, which causes carbonization shrinkage and increases density. The compressive strength is higher than that of Examples 2 and 3, but the specific strength does not increase. Comparative Example 2 uses only hydrogen peroxide for chemical foaming. No carbon dioxide is generated, and its strength increase is limited. It relies solely on hydration to achieve strength improvement. Comparative Example 3 does not add steel slag powder, and the decomposition rate of hydrogen peroxide is very slow. Therefore, the dry density of the foamed concrete finally prepared is relatively high, which is not much different from Comparative Example 1. Comparative Example 4 changes the foaming order of oxygen and carbon dioxide. At this time, carbon dioxide is generated first. Because of its rapid reaction, carbon dioxide will overflow during the stirring process, which limits the degree of carbonization enhancement and hydration synergistic enhancement of carbon dioxide.

[0124] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection 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 mass: 20-42 parts of solid waste-based sulfoaluminate 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 sulfoaluminate cement, hemihydrate gypsum, Portland cement, mineral powder, steel slag powder, and sodium bicarbonate; then add retarder, water reducer, and calcium stearate, and stir to obtain a mixture; S2. Add water to the mixture of 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. After the addition is complete, stir at a speed of 400-800 r / min for 20-40 seconds; S4. Add potassium aluminum sulfate aqueous solution to the slurry in step S3, stir at a speed of 400-800 r / min for 20-40s, 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 heated to 1250-1350° C. and calcined for 20-40 minutes 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; and 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 sulfoaluminate cement, hemihydrate gypsum, Portland cement, mineral powder, steel slag powder, and sodium bicarbonate; then add retarder, water reducer, and calcium stearate, and stir to obtain a mixture; S2. Add water to the mixture of step S1 and stir at a speed of 400-800 rpm for 1-10 min; S3. Adjust the stirring speed to 50-150 r / min, then add hydrogen peroxide. After the addition is complete, stir at a speed of 400-800 r / min for 20-40 seconds; S4. Add potassium aluminum sulfate aqueous solution to the slurry in step S3, stir at a speed of 400-800 r / min for 20-40s, 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, wherein 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, wherein In the aqueous solution of potassium aluminum sulfate, the mass fraction of potassium aluminum sulfate is 30-60%.

9. The preparation method according to claim 6, wherein In step S4, the static growth 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 according to 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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