CO2 inflation foaming preparation method of ternary solid waste foam cement thermal insulation material

Abstract

The invention discloses a CO2 inflation foaming preparation method of a ternary solid waste foam cement thermal insulation material, which comprises the following steps: step 1, weighing desulfurized gypsum, fly ash, mineral powder and an additive, and uniformly stirring for later use; step 2, weighing water with required weight, and uniformly stirring the uniformly mixed dry material and water to form uniform slurry; step 3, stirring the uniform slurry at a high speed, and filling CO2 gas while stirring, so as to prepare inflatable foaming slurry; step 4, pouring the inflatable foaming slurry into a mold, weighing a sample, loading the sample into a self-sealing bag, sealing, and curing in a natural environment; and step 5, after curing to the age, taking out the sample, and drying to constant weight to prepare the ternary solid waste foam cement thermal insulation material. The ternary solid waste foamed cement thermal insulation material which takes CO2 as foaming gas, the desulfurized gypsum as a main cementing material and the fly ash and the mineral powder as auxiliary cementing materials is prepared, and meets the A08 grade requirement specified by the standard of foam concrete.

Description

Technical Field

[0001] The present invention relates to the building materials industry and belongs to building materials. Specifically, it is a method for preparing a ternary solid waste foam cement thermal insulation material by CO2 gas injection foaming. Background Art

[0002] The construction field is accelerating its transformation towards low-carbon energy conservation. Foamed concrete, with its adjustable pore structure, while retaining the fire safety of inorganic thermal insulation materials, also has lightweight thermal insulation properties similar to those of organic thermal insulation materials. It has become an optimal choice for building energy-saving materials with fire safety, low-carbon performance, and cost advantages. Foamed concrete has higher flexibility in the selection of foaming gas and can utilize CO2 captured from high-carbon emission industries as the foaming gas. The CO2 gas injection foaming process seals the captured CO2 in the pore structure of foamed concrete, realizing the fixation and utilization of carbon resources; and the extremely low thermal conductivity of CO2 (0.0143 W / (m·K)) can further optimize the thermal insulation performance of the material. In addition, compared with physical foaming and chemical foaming, the gas injection foaming process does not require the use of foaming agents, which can reduce production costs and avoid potential environmental pollution problems caused by chemical foaming agents. Using neutral or weakly alkaline industrial solid wastes compatible with acidic CO2 gas to replace traditional cement as the cementitious material not only provides a new option for CO2 capture and utilization but also realizes the resource utilization of solid wastes, while avoiding energy consumption and carbon emissions during cement production, forming a synergistic effect of resource recycling and process carbon reduction. This development model integrating performance optimization, resource recycling, and technological innovation provides a practical technical path for the low-carbon transformation of the building materials industry. Summary of the Invention

[0003] Based on the low thermal conductivity of CO2 and the low-cost advantage of the gas injection foaming process, the object of the present invention is to provide a method for preparing a ternary solid waste foam cement thermal insulation material by CO2 gas injection foaming, with desulfurized gypsum as the main cementitious material and combining multiple auxiliary cementitious materials such as fly ash and slag powder.

[0004] The present invention is implemented by the following technical solutions:

[0005] A method for preparing a ternary solid waste foam cement thermal insulation material by CO2 gas injection foaming, comprising the following steps:

[0006] Step 1: Weigh desulfurized gypsum, fly ash, slag powder, and additives, and stir evenly for standby;

[0007] Step 2: Weigh the required amount of water, and stir the uniformly mixed dry materials in Step 1 with water to form a uniform slurry for standby;

[0008] Step 3: Further stir the uniform slurry at a high speed, adjust the rotation speed of the mixer to 3000 revolutions per minute, and inject CO2 gas while stirring to prepare an inflated foaming slurry;

[0009] Step 4: Pour the inflatable foaming slurry into the mold. After solidification, remove the mold to form a specimen. Weigh the specimen, record the data, then put the specimen into a self-sealing bag, seal it, and place it in the natural environment for curing.

[0010] Step 5: After curing to the specified age, take out the specimen from the airtight self-sealing bag and dry it to a constant weight, thus preparing the ternary solid waste foam cement thermal insulation material.

[0011] Further preferably, in Step 1, the mass ratio of desulfurized gypsum: fly ash: slag powder is 580:210:210. The desulfurized gypsum is desulfurized building gypsum, and its particle size range is: D10 is 2.50 μm, D50 is 35.67 μm, D90 is 65.45 μm; the particle size range of the fly ash is: D10 is 3.48 μm, D50 is 21.79 μm, D90 is 116.60 μm; the particle size range of the slag powder is: D10 is 1.65 μm, D50 is 9.46 μm, D90 is 26.58 μm.

[0012] The admixtures include: foam stabilizer, pore modifier, and retarder. The foam stabilizer includes: polyvinyl alcohol, hydroxypropyl guar gum, or hydroxypropyl methylcellulose; the pore modifier includes: styrene-acrylic emulsion, epoxy resin, or nano-inorganic modifier 720D and early strength agent 31B.

[0013] The foam stabilizer is selected as hydroxypropyl methylcellulose, and the dosage is: 3‰ of the total mass of desulfurized gypsum, fly ash, and slag powder. The pore modifier is selected as nano-inorganic modifier 720D and early strength agent 31B, and the mass ratio of nano-inorganic modifier 720D to early strength agent 31B is 1:2. The dosage of nano-inorganic modifier 720D is 4‰ of the total mass of desulfurized gypsum, fly ash, and slag powder, and the dosage of early strength agent 31B is 8‰ of the total mass of desulfurized gypsum, fly ash, and slag powder.

[0014] The dosage of the retarder is 2.27‰ of the total mass of desulfurized gypsum, fly ash, and slag powder.

[0015] Further preferably, in Step 2, the water-solid ratio is 0.8; during stirring, first stir slowly for 1 min to mix the water and dry materials, and then stir quickly for 2 min to form a uniform slurry without lumps.

[0016] Further preferably, in Step 3, the bottom of the air inlet pipe is wrapped with gauze so that the bubbles are filled into the slurry in a small pore diameter state.

[0017] (1) Through preliminary experiments, it is proved that CO2-inflated, air-inflated and physically foamed foams are prepared using PVA, HPG, and HPMC as foam stabilizers respectively. The foam drop height and water bleeding height experiments are used to study the effects of the type and dosage of foam stabilizers on the foam stability and pore structure characteristics. The results show that HPMC is the best foam stabilizer. When its dosage is 3‰, the water bleeding rate of the foam is 0.358 mm / min, which is 43.7% and 86.5% lower than that of PVA and HPG respectively. The HPMC foam is mostly regular circular structure, and the pore size distribution is relatively uniform. Compared with the physical foaming process, the gas-inflated foaming process can improve the foaming ability, and through the synergistic regulation of thickening and stabilizing, interfacial modification and water retention and water bleeding inhibition of the HPMC foam stabilizer, the stability of CO2 foam can be improved, which proves the feasibility of the CO2-inflated foaming process.

[0018] (2) Through preliminary experiments, it is proved that the CO2-inflated foaming process is optimized by the single factor experiment method, and a pore modifier is introduced to optimize the pore structure. The mechanical and thermal insulation properties of desulfurized gypsum (single cementitious system) foam cement thermal insulation materials are studied by compressive strength, thermal conductivity, CO2 escape amount calculation and microscopic characterization methods. The results show that the optimal CO2-inflated foaming process is a water-solid ratio of 0.8, an HPMC dosage of 2‰, an inflation time of 5 min, and an inflation flow rate of 15 L / min. Styrene-acrylic emulsion constructs a dense pore wall and a low-connected pore network through the interfacial bonding effect, slows down the escape of CO2 gas, and the thermal insulation performance optimization efficiency is higher than that of epoxy resin and nano-inorganic modification material 720D. Due to the synergistic regulation mechanism of 720D to enhance the foam strength through heterogeneous nucleation and early strength, the specimen has a more uniform pore structure. When 1% styrene-acrylic emulsion is incorporated, the thermal conductivity is the lowest, which is 0.1362 W / (m·K); while when 4‰ of 720D and 8‰ of 31B are incorporated, the dry density is the lowest, which is 789.04 kg / m 3 .

[0019] (3) In order to improve the performance of a single gelling system, the optimal ratio of a ternary solid waste gelling system (desulfurized gypsum, fly ash, and slag powder) was determined based on orthogonal experiments and range analysis. By means of single-factor experiments, the difference in the paste viscosity between the ternary solid waste system and the pure desulfurized gypsum system was regulated to determine the dosage of HPMC, and a pore modifier was incorporated. The mechanical and thermal insulation properties of the ternary solid waste foam cement thermal insulation material were studied by means of compressive strength, thermal conductivity, CO2 emission calculation, and microscopic characterization methods. The results show that the optimal ratio of the ternary solid waste gelling system is desulfurized gypsum:fly ash:slag powder = 580:210:210. When the dosage of HPMC is 3‰, the paste has both good foaming ability and foam stability. The ternary solid waste system can form a uniform pore structure without adding a pore modifier through multi-scale particle gradation filling and the pore closing effect of hydration products, and its thermal conductivity is almost the same as that of the system with a pore modifier added. When the dosage of 720D is 4‰ and the dosage of 31B is 8‰, the thermal conductivity of the CO2-inflated ternary solid waste foam cement thermal insulation material is the lowest, which is 0.1042 W / (m·K), and its dry density is 754.38 kg / m 3 , the compressive strength is 3.23 MPa, meeting the requirements of Grade A08 specified in the "Foamed Concrete" (JG / T 266—2011) standard, and having a CO2 emission reduction effect similar to that of styrene-acrylic emulsion.

[0020] In summary, the present invention is reasonably designed. A CO2-inflated foaming process for the ternary solid waste foam cement thermal insulation material is obtained with CO2 as the foaming gas, desulfurized gypsum as the main gelling material, and fly ash and slag powder as the auxiliary gelling materials. The regulation mechanism of CO2 gas on the performance of the ternary solid waste foam cement thermal insulation material is revealed, and it is confirmed that CO2 as the foaming gas can reduce the thermal conductivity of the foam cement thermal insulation material, providing a feasible method for the development of CO2 green and low-carbon building materials and having good practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments in line with the present invention and used together with the specification to explain the principles of the present invention.

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0023] Figure 1 It shows the range analysis diagram of the ternary solid waste gelling system; in the figure, a) is the compressive strength and b) is the thermal conductivity.

[0024] Figure 2Cross-sections (40 mm × 40 mm) of ternary solid waste foam cement thermal insulation materials with different HPMC dosages.

[0025] Figure 3 Showing the influence of HPMC dosage on the properties of ternary solid waste foam cement thermal insulation materials at 7 days; in the figure, a) is the compressive strength and b) is the thermal conductivity.

[0026] Figure 4 Showing the influence of HPMC dosage on the properties of ternary solid waste foam cement thermal insulation materials at 28 days; in the figure, a) is the compressive strength and b) is the thermal conductivity.

[0027] Figure 5 Showing the influence of adding pore modifiers on the properties of ternary solid waste foam cement thermal insulation materials before and after; in the figure, a) is 7 days and b) is 28 days.

[0028] Figure 6 Showing the comparison diagram of the phase composition of ternary solid waste foam cement thermal insulation materials before and after adding pore modifiers; in the figure, a) is 7 days and b) is 28 days.

[0029] Figure 7 Showing the comparison diagram of the microscopic morphology of ternary solid waste foam cement thermal insulation materials before and after adding pore modifiers at 28 days; in the figure: 1 is desulfurized gypsum; 2 is fly ash; 3 is slag powder; 4 is ettringite; 5 is C-S-H gel.

[0030] Figure 8 Showing the EDS peak diagram of C-S-H hydration products of ternary solid waste foam cement thermal insulation materials.

[0031] Figure 9 Showing the differential pore volume of ternary solid waste foam cement thermal insulation materials before and after adding pore modifiers; in the figure: a) and b) are 7 days, c) and d) are 28 days.

[0032] Figure 10 Showing the cross-sections (40 mm × 40 mm) of ternary solid waste foam cement thermal insulation materials before and after adding pore modifiers.

[0033] Figure 11 Showing the pore size distribution of the cross-sections of ternary solid waste foam cement thermal insulation materials before and after adding pore modifiers.

[0034] Figure 12 Showing the infrared spectra of CO2-inflated ternary solid waste foam cement thermal insulation materials at different ages.

[0035] Note: 720D in the figure actually represents 720D + 31B, which is simply written as 720D in the figure. Detailed implementation method

[0036] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the solution of the present invention will be further described below.

[0037] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0038] A method for preparing a ternary solid waste foam cement thermal insulation material by CO2 gas inflation foaming comprises the following steps:

[0039] Step 1: Weigh desulfurized gypsum, fly ash, mineral powder and additives (including: foam stabilizer, pore modifier and retarder), and stir evenly for standby;

[0040] Step 2: Weigh the required weight of water, pour the uniformly mixed dry materials in Step 1 and water into a stirring pot together, first stir slowly for 1 min to mix the water and dry materials, and then stir quickly for 2 min to form a uniform and lump-free slurry. Pour the uniformly stirred slurry into a beaker for standby;

[0041] Step 3: Place the beaker containing the uniform slurry on a high-speed stirrer, adjust the rotation speed to 3000 revolutions per minute, and prepare an inflated foaming slurry while stirring and inflating CO2 gas. The bottom of the gas injection pipe is wrapped with gauze to make the bubbles enter the slurry in a small-aperture state;

[0042] Step 4: Pour the inflated foaming slurry into a 40mm×40mm×160mm mold, wait for 3 h for the specimen to have a certain strength, then remove the mold. Weigh the demolded weight of the specimen with a balance, record the data, then put the specimen into a self-sealing bag, seal it and place it in a natural environment for curing, avoiding the influence of CO2 in the air on the specimen;

[0043] Step 5: After curing to the age, take out the specimen from the airtight self-sealing bag and place it in a blast drying oven at 40 °C to dry to a constant weight (weigh at intervals of 24 h, and the difference in weight between two weighings is less than 0.2% to be the constant weight). Record the dried weight of the specimen and conduct subsequent physical and mechanical property tests and microscopic test characterizations.

[0044] Based on the low thermal conductivity of CO2 and the low-cost advantage of the gas-inflated foaming process, this invention uses desulfurized gypsum as the main cementitious material, combined with multiple auxiliary cementitious materials such as fly ash and slag powder, and adopts the CO2 gas-inflated foaming process to prepare ternary solid waste foam cement thermal insulation materials. At the same time, it reveals the influence mechanism of pore modifiers, gas types, and the synergistic effect of solid wastes on the performance of foam cement thermal insulation materials. It includes: (1) The influence of the type and dosage of foam stabilizers on the stability and pore structure of CO2 gas-inflated foamed foam, and compare the stability performance and pore structure of CO2 gas-inflated foamed foam, air-inflated foamed foam, and physical foamed foam to obtain the most suitable foam stabilizer for the CO2 gas-inflated foaming process. (2) To improve the performance of single cementitious materials, fly ash and slag powder are added to prepare ternary solid waste foam cement thermal insulation materials. The orthogonal experiment is used to optimize the solid waste ratio, and the influence of the dosage of HPMC, pore modifiers, and CO2 escape amount on the physical and mechanical properties and pore structure of ternary solid waste foam cement thermal insulation materials is studied. Through the analysis of phase composition, microstructure, and pore size structure, the influence mechanism of pore modifiers, gas types, and the synergistic effect of ternary solid wastes on the performance of foam cement thermal insulation materials is revealed.

[0045] I. Raw materials

[0046] 1.1. The desulfurized gypsum used in the embodiments of this invention is desulfurized building gypsum, taken from a certain resource recycling company in Taiyuan. It is building gypsum calcined from the desulfurized gypsum generated by the wet flue gas desulfurization of power plants, and the powder thermal conductivity is 0.1109 W / (m·K). Its basic properties are shown in Table 1, meeting the requirements of Grade 3 specified in the "Building Gypsum" (GB / T 9776-2022) standard. The particle size analysis is shown in Table 2, and the main chemical components are shown in Table 3. It can be seen that the particle size of the desulfurized gypsum used in this embodiment is relatively uniform; the main elements are Ca and S, containing a small amount of elements such as Mg, Al, Si, and K; the main component is hemihydrate calcium sulfate (CaSO4·0.5H2O), and the gypsum crystal shapes are diverse, with different sizes, mostly columnar crystals.

[0047] Table 1 Basic properties of desulfurized gypsum

[0048]

[0049] Table 2 Particle size analysis of desulfurized gypsum

[0050]

[0051] Table 3 Chemical composition of desulfurized gypsum

[0052]

[0053] 1.2. The fly ash is taken from a certain resource recycling company in Taiyuan. The powder thermal conductivity is 0.1430 W / (m·K), meeting the requirements of Class C, Grade II fly ash specified in the standard of Fly Ash Used in Cement and Concrete (GB / T 1596 - 2017). Its particle size analysis is shown in Table 4, and the main chemical components are shown in Table 5. It can be seen that the main elements of the fly ash used in the embodiments of the present invention are Si and Al, with a total amount of 71.98%; its main mineral phases are mullite and quartz; because it contains a large amount of vitreous body, there are diffraction peaks in the amorphous state at 15 - 30°; it is mainly spherical microspheres, with a small amount of porous fragments.

[0054] Table 4 Fly Ash Particle Size Analysis

[0055]

[0056] Table 5 Fly Ash Chemical Composition

[0057]

[0058] 1.3. The slag powder is taken from a certain resource recycling company in Taiyuan. The powder thermal conductivity is 0.1080 W / (m·K), meeting the requirements of S95 grade specified in the standard of Ground Granulated Blast - Furnace Slag for Use in Cement, Mortar and Concrete (GB / T 18046 - 2017). Its particle size analysis is shown in Table 6, and the main chemical components are shown in Table 7. It can be seen that the main elements of the slag powder used in this embodiment are Ca, Si, and Al; due to the rapid cooling of the water - quenching process inhibiting crystal growth, the slag powder is usually mainly amorphous vitreous body, containing a small amount of calcium silicate and calcium aluminofeldspar; irregular angular particles, with a relatively rough surface.

[0059] Table 6 Slag Powder Particle Size Analysis

[0060]

[0061] Table 7 Slag Powder Chemical Composition

[0062]

[0063] 1.4. Foam stabilizers: Polyvinyl Alcohol (PVA), Hydroxypropyl Guar Gum (HPG), Hydroxypropyl Methylcellulose (HPMC, 100000 mPa), all purchased from a certain group in Shandong. The retarder is purchased from a certain technology company in Beijing.

[0064] 1.5. Pore modifiers: Styrene - acrylic emulsion, epoxy resin (epoxy resin emulsion A: curing agent B = 1:1) are purchased from a certain company in Taiyuan. Nano - inorganic modification material 720D (specific surface area 528 m2 Both the foaming agent 720D (with a main component of NaCl and Na₂SO₄, 2.0 g per 1000 g of water) and the early-strength agent 31B (with a main component of Al₂(SO₄)₃) were purchased from a new building material additive company in Henan. 720D can adsorb on the surface of the liquid film to improve the foam stability, and 31B can enhance the strength of the liquid film. The two acting synergistically can significantly improve the pore uniformity of the foamed concrete.

[0065] 1.6. The CO₂ gas was purchased from a certain technology development company in Taiyuan, with a purity of over 99%, and was used to simulate the CO₂ gas captured by high-carbon emission industries.

[0066] II. Optimization of the proportion of ternary solid waste cementitious materials

[0067] 2.1. To achieve the performance goals of low thermal conductivity and high compressive strength for the ternary solid waste cementitious materials, the embodiments of the present invention adopt the orthogonal experiment method to optimize the cementitious material system. The dosages of fly ash and slag powder were selected as the research factors, each with four levels of 120 g, 150 g, 180 g, and 210 g, and the total amount of the cementitious system was controlled to be constant at 1000 g (the amount of desulfurized gypsum = 1000 g - the amount of fly ash - the amount of slag powder). Based on the L16(4⁴) orthogonal table, a total of 16 groups of experiments were designed (groups 1 - 16 in Table 8), and at the same time, a control group of pure desulfurized gypsum was added (group 17: 1000 g of desulfurized gypsum, 0 g of both fly ash and slag powder) to systematically study the synergistic effect of the desulfurized gypsum - fly ash - slag powder ternary solid waste cementitious system and quantify the beneficial effects of adding fly ash and slag powder on the performance.

[0068] Table 8 Orthogonal experiment table of ternary solid waste cementitious system

[0069]

[0070] Table 9 is the range analysis table of the ternary solid waste cementitious system. Figure 1 is the range analysis diagram, where the Ki value represents the average value of the response index of each factor at different levels. R is the range, which can quantitatively evaluate the influence degree of each factor on the experimental result. The larger the R value, the more significant the main effect of the factor on the index, and the higher the influence weight of its change on the system. Its calculation formula is shown as follows. The blank column is used to estimate the influence of experimental error or random fluctuation. When the R value of a certain factor is greater than the R value of the blank column, this factor is considered a significant factor.

[0071] R = max(Ki) - min(Ki)

[0072] In the formula: R is the range;

[0073] max(Ki) is the maximum value corresponding to the average value of the experimental results at the i level of a certain factor;

[0074] min(Ki) is the minimum value corresponding to the average value of the experimental results obtained at a certain level of factor i.

[0075] Table 9 Range analysis table of ternary solid waste cementitious system

[0076]

[0077] Orthogonal experiments and range analysis were used to explore the different effects of desulfurized gypsum, fly ash, and slag powder on the mechanical properties and thermal insulation properties in the ternary solid waste cementitious system. By adjusting the mix ratio, it is possible to increase the compressive strength while reducing the thermal conductivity.

[0078] Fly ash can improve the compressive strength of the specimens, and the range values of the 7-day and 28-day compressive strengths are 4.46 and 8.24 respectively. Fly ashes with different particle sizes (D10 is 3.48 μm, D50 is 21.79 μm, D90 is 116.60 μm) fill each other in the specimens, which may form a denser structure. When the dosage of fly ash increases from 120 g to 210 g, the 28-day compressive strength increases by about 17%. Although the thermal conductivity of the raw fly ash powder is relatively high, at 0.1430 W / (m·K), the hollow cenosphere structure inside it can block heat transfer, reducing the thermal conductivity by 0.0026 W / (m·K) at 28 days, showing its dual role in strength enhancement and thermal insulation optimization.

[0079] Although the contribution of slag powder to strength improvement is second only to that of fly ash, it is still significant, with range values of 3.49 and 5.75 for 7 days and 28 days respectively. Its ultra-fine particle size (D10 is 1.65 μm, D50 is 9.46 μm, D90 is 26.58 μm) can effectively fill the micro-pores. When the dosage of slag powder increases from 120 g to 210 g, the 28-day compressive strength increases by about 13%. The thermal insulation performance of slag powder is particularly prominent. The thermal conductivity of its raw material powder is 0.1080 W / (m·K), and the high vitreous content can reduce the solid-phase heat conduction efficiency, further reducing the thermal conductivity. The range value is 0.0253, and the 28-day thermal conductivity reduction is 6.49%. It is the core control component for the thermal insulation performance of this cementitious system.

[0080] As the matrix cementitious material, the regulation of the dosage of desulfurized gypsum is crucial for performance balance. When the dosage of desulfurized gypsum is reduced to 580 g, the dosage space of fly ash and slag powder increases to 40%. The synergistic effect of the ternary solid waste increases the 28-day strength to 50.21 MPa. At the same time, for every 100 g reduction in the dosage of desulfurized gypsum, the thermal conductivity can be reduced by 0.0189 W / (m·K), which is 37.42% less than the reduction rate for every 100 g reduction in the dosage of slag powder. The framework support provided by the relatively wide particle size distribution of desulfurized gypsum is the basis for strength development, but the proportion needs to be strictly controlled to avoid the disadvantage of heat conduction.

[0081] When the dosages of fly ash and slag powder are both 210 g and that of desulfurized gypsum is 580 g, the compressive strength of the system is the highest and the thermal conductivity is the lowest. Fly ash improves the density through gradation optimization, slag powder reduces the porosity through ultra-fine particle filling, and desulfurized gypsum ensures the matrix strength through skeleton support. Under this ratio, the 28-day compressive strength is 50.21 MPa and the thermal conductivity is 0.3873 W / (m·K). Compared with the pure desulfurized gypsum paste, the 28-day strength is increased by 59.54% and the 28-day thermal conductivity is reduced by 16.08%, verifying the feasibility of the synergistic optimization of the mechanical and thermal insulation properties of the ternary solid waste system.

[0082] 2.2 Influence of HPMC Dosage on the Properties of Ternary Solid Waste Foamed Cement Thermal Insulation Materials

[0083] Due to the significant difference in the particle size distribution of fly ash, slag powder and desulfurized gypsum, under the same water-solid ratio condition, the rheological properties of the ternary solid waste paste are significantly different from those of the pure desulfurized gypsum paste. In the examples of the present invention, by studying the influence law of HPMC dosage on the foam stability of the ternary solid waste paste, the optimal HPMC dosage range is determined, so as to optimize the preparation process of the ternary solid waste foamed cement thermal insulation materials. Table 10 shows the mix proportions of the ternary solid waste foamed cement thermal insulation materials with different HPMC dosages.

[0084] Table 10 Mix Proportions of Ternary Solid Waste Foamed Cement Thermal Insulation Materials with Different HPMC Dosages

[0085]

[0086] Figure 2 The cross-sectional morphologies of the ternary solid waste and desulfurized gypsum foamed cement thermal insulation materials with different HPMC dosages were compared. The results show that the macroscopic pore size of the ternary solid waste specimens becomes smaller, the uniformity of pore distribution is improved, and the number of pores increases compared with the desulfurized gypsum-based specimens. This difference is mainly attributed to the synergistic incorporation of fly ash and slag powder in the ternary solid waste system. By reconstructing the particle size distribution of the cementitious material (D50 changes from 35.67 μm to 25.09 μm), the rheological properties of the paste are optimized, promoting the nucleation and stability of bubbles during the foaming process and forming a more uniform pore structure. When the HPMC dosage is 1‰, the viscosity of the paste is too low, resulting in obvious bubble escape, and the proportion of the number and area of pores is small; when the dosage is increased to 2‰, the viscosity increase promotes the foaming ability, but the entanglement of polymer chains is insufficient to effectively fix the bubble interface, and macroscopically, local bubbles float up and small bubbles merge into large bubbles; when the dosage is 3‰ and above, the thickening and foam stabilizing synergistic effect of HPMC makes the viscosity of the paste and the surface tension of bubbles reach a dynamic balance, ultimately achieving a significant improvement in the uniform distribution of pores and structural stability.

[0087] Through Figure 3It can be observed that the addition amount of HPMC shows a non-monotonic regulation law of first decreasing and then increasing on the dry density of the specimen. When the addition amount increases from 1‰ to 2‰, the insufficient viscosity of the slurry leads to intensified bubble coalescence, an increase in the proportion of the pore area, and a consequent decrease in the dry density. After the addition amount exceeds 3‰, the foam-stabilizing effect of HPMC enhances, promoting the homogenization of the pore distribution, but the number of bubble nucleation sites decreases, resulting in an increase in the dry density. The compressive strength is significantly positively correlated with the dry density. The enhanced continuity of the solid-phase skeleton in the high-density state is the main reason for the improvement of its mechanical properties. The thermal conductivity is co-regulated by the dry density and the pore morphology and also shows a trend of first decreasing and then increasing. When the addition amount of HPMC is 3‰, although the dry density is at a relatively low level, due to the large number of pores and uniform size distribution, the superimposed effect of the gas-solid interface thermal resistance reaches the peak value, ultimately reducing the thermal conductivity to the lowest value.

[0088] The ternary solid waste cementitious system has a longer strength growth period compared to the pure desulfurized gypsum system. For this, the study analyzed the effects of different HPMC addition amounts on the specimen properties at the 28-day age, as Figure 4 shown. With the increase in age, the dry density of the CO2-inflated foamed ternary solid waste foam cement thermal insulation material is relatively less affected, while the dry density of the air-foamed specimen increases significantly, with an average increase of 8.84%. The reason for this difference may be that during the foaming process, part of the CO2 dissolves in the slurry and participates in the chemical reaction. After the reaction ends, the system structure tends to be stable, and it is difficult for the growth of subsequent ages to have an obvious impact on its dry density. In contrast, for the air-foamed specimen during the age growth stage, the internal hydration reaction continues, and the newly formed hydration products continuously fill the pores, making the internal structure of the specimen more dense, thus leading to an increase in the dry density. The change in the dry density directly affects the mechanical and thermal insulation properties. The compressive strength of the CO2-inflated foamed thermal insulation material increases by 7.38% with the increase in age; while for the air-foamed specimen, due to the continuous filling of pores by hydration products during the curing stage, the compressive strength increases significantly by 55.85%. For the CO2 specimen, due to the slow escape of gas in the pores, the gas-solid interface thermal resistance decreases, resulting in a 5.80% increase in the thermal conductivity; while for the air-foamed specimen, due to the bridging of pores by hydration products to form a continuous heat transfer path, the final increase in the thermal conductivity is 8.83%.

[0089] Through the above tests, it is obtained that when the addition amount of HPMC is 3‰, the thermal conductivity of the CO2-inflated foamed thermal insulation material is the lowest, the 7-day dry density is 733.79 kg / m 3 ; the 7-day compressive strength is 3.49 MPa, and the 7-day thermal conductivity is 0.0992 W / (m·K); compared with the desulfurized gypsum system, they are reduced by 11.11%, 43.80%, and 35.50% respectively. The 28-day dry density of this CO2-inflated foamed ternary solid waste foam cement thermal insulation material is 735.29 kg / m 3, the 28-day compressive strength is 3.81 MPa and the 28-day thermal conductivity is 0.1043 W / (m·K).

[0090] 2.3. Influence of pore modifiers on the properties of ternary solid waste foam cement thermal insulation materials

[0091] By adjusting the dosage of HPMC, the foaming and foam stability of the ternary solid waste cementitious system slurry are at the best level. On this basis, according to the optimal dosage of pore modifiers determined by the single-factor test of pore modifiers for desulfurized gypsum foam cement thermal insulation materials, the pore modifiers are added to the ternary solid waste cementitious system to study the influence of pore modifiers on the ternary solid waste foam cement thermal insulation materials. Table 11 shows the mix ratios of different pore modifiers in the ternary solid waste foam cement thermal insulation materials.

[0092] Table 11 Mix ratios of different pore modifiers in the ternary solid waste foam cement thermal insulation materials

[0093]

[0094] 2.3.1 Influence of pore modifiers on the macroscopic properties of ternary solid waste foam cement thermal insulation materials

[0095] The influence of pore modifiers on the properties of ternary solid waste foam cement thermal insulation materials at 7 days and 28 days is as Figure 5 shown. The incorporation of pore modifiers shows that the dry density and compressive strength of the ternary solid waste and desulfurized gypsum system have a similar change trend, while the change trend of thermal conductivity is different. For example, incorporating styrene-acrylic emulsion into desulfurized gypsum can significantly reduce its thermal conductivity, while incorporating styrene-acrylic into ternary solid waste increases the thermal conductivity. This may be related to the multi-scale particle size distribution and synergistic effect of hydration products in ternary solid waste, which optimize the bubble nucleation, stabilization, and pore wall strengthening processes, enabling the formation of a uniform pore structure in the specimen without adding pore modifiers, making the interfacial modification effect of styrene-acrylic emulsion offset the inherent optimization mechanism in terms of performance.

[0096] With the increase of curing age, styrene-acrylic emulsion and epoxy resin have no significant influence on the performance evolution trend of the ternary solid waste system, indicating that their modification effect mainly focuses on optimizing the pore structure in the early stage rather than regulating the hydration process. However, the air-inflated foamed thermal insulation material incorporated with early strength agent 720D shows unique behavioral characteristics. Since the early strength agent accelerates the hydration reaction and inhibits the further influence of late hydration micro-expansion and pore reconstruction on the performance, that is, the dry density, compressive strength, and thermal conductivity tend to be stable in the later stage. This phenomenon reveals the differential regulation of the catalytic mechanism of chemical pore modifiers and the surface modification effect of physical pore modifiers on the curing age of the system. Styrene-acrylic emulsion and epoxy resin only affect the interfacial energy and cannot block the hydration process, while the early strength component of 720D directly terminates the microstructure evolution by reconstructing the reaction path, forming a strength development platform effect.

[0097] Through multi-scale particle gradation filling, the ternary solid waste system synergistically optimizes interface stability and pore size distribution, realizes a uniform pore structure without adding pore modifiers, and obtains a thermal conductivity similar to that after adding modifiers. When the dosage of 720D is 4‰ and the dosage of 31B is 8‰, the ternary solid waste foam cement thermal insulation material prepared by the CO2 gas foaming process has the lowest thermal conductivity at 28 days, which is 0.1042 W / (m·K), 0.10% lower than that of the CO2 sample without adding pore modifiers, and 21.60% lower than that of the air sample with the lowest thermal conductivity. At this time, the dry density is 754.38 kg / m 3 , and the compressive strength is 3.23 MPa.

[0098] 2.3.2 Influence of Pore Modifiers on the Microscopic Properties of Ternary Solid Waste Foam Cement Thermal Insulation Materials

[0099] Phase Composition: The main phases of the ternary solid waste foam cement thermal insulation material are gypsum dihydrate, with a small amount of ettringite, quartz, and mullite. In the neutral and weakly alkaline environment of the ternary solid waste system, the formation of ettringite depends on the synergistic reaction of multiple components. The dissolution of desulfurized gypsum (CaSO4·2H2O) provides Ca 2+ and SO4 2- , and the amorphous glass in the mineral powder partially dissolves and releases Al 3+ and SiO4 4- under weakly alkaline conditions. Among them, Al 3+ combines with SO4 2- and Ca 2+ to form ettringite (3CaO·Al2O3·3CaSO4·32H2O); the mullite and quartz in fly ash have limited dissolution under neutral conditions due to their high inertness and mainly participate in the densification of the system as fine aggregates. As can be seen from Figure 6 , ettringite phase exists only in the air-inflated foam insulation material, and its content increases with the increase of age. The reason is that the slow release of aluminate with age and the stable supply of sulfate form a continuous reaction window, and the air environment does not introduce acidic interference, and the local micro-area alkaline fluctuation provides conditions for the dissolution of the aluminum phase. After adding 720D, it inhibits the formation of ettringite through three mechanisms: (1) It preferentially complexes with Al 3+ to form a stable compound, blocking the participation of aluminum source in the synthesis of ettringite; (2) It accelerates the silicate reaction and consumes Ca 2+ , resulting in an imbalance in the molar ratio of SO4 2- / Ca 2+ ; (3) It induces the rapid hardening of the slurry, restricting the diffusion and contact of Al 3+ with SO4 2- .

[0100] Microscopic Morphology: The microscopic morphology of the ternary solid waste foam cement thermal insulation material is shown in Figure 7。The desulfurized gypsum crystals are mainly columnar or flaky crystals, distributed in an interlaced network structure. The crystal surface is smooth, and layered growth lines can be seen in some areas. Most of the fly ash particles are spherical or ellipsoidal, with a smooth surface or a microporous structure. Small mineral phases (such as mullite and quartz) adhere to the surface of some particles. The shape of the mineral powder particles is irregular, the surface is rough, with a flaky or angular structure, and the vitreous characteristics of an amorphous smooth surface are shown in some areas. In the CO2-inflated foamed thermal insulation material and the air-inflated foamed thermal insulation material doped with 720D, the desulfurized gypsum, fly ash and mineral powder are mostly physically stacked, and there are no obvious reaction products at the interface, and there are many pores, which is one of the reasons for the low compressive strength of the CO2 specimens. In the air-inflated foamed thermal insulation material (except doped with 720D), the interface of the desulfurized gypsum, fly ash and mineral powder is filled with C-S-H gel, and flocculent C-S-H gel also adheres to the surface of some fly ash particles. A small amount of ettringite is generated by the synergistic hydration of the ternary solid waste. This multi-scale densification effect stems from the continuous hydration reaction in the air environment. The amorphous vitreous body in the mineral powder slowly releases active SiO4 4- , which combines with the Ca 2+ dissolved from the desulfurized gypsum to form a gel with a low calcium-silicon ratio (Ca / Si≈1.33) ( Figure 8 ). It reduces the porosity and improves the solid-phase continuity through nanoparticle bridging, ultimately driving the increase in dry density. In contrast, the acidic environment of CO2 (pH<7) inhibits the dissociation of silicate, and the early-strength agent 720D blocks the gel nucleation path by complexing Ca 2+ , resulting in the lack of an interface cementation strengthening mechanism in the two types of specimens.

[0101] Pore size structure: Through the differential volume distribution analysis of Figure 9 , it can be seen that the pore structure of the CO2-inflated foamed thermal insulation material changes little with the age. During the age from 7d to 28d, its porosity only decreases by about 2.33%, and the order of the most probable pore sizes is CO2+epoxy (3.88μm)<CO2 (5.0μm)<CO2+styrene-acrylic (5.5μm)<CO2+720D (5.8μm), which is negatively correlated with the compressive strength. This stability stems from the fact that the acidic gas CO2 inhibits the dissolution of silicate in the mineral, reducing the formation of C-S-H, thus making the gel structure loose and having a limited contribution to the compressive strength. In contrast, the porosity of the air-inflated foamed thermal insulation material (except doped with 720D) decreases significantly with the age. It decreases by 14.29% at 28d compared with 7d. The proportion of mesopores with a size of 2-10μm decreases significantly, which is attributed to the continuous formation of C-S-H gel and the slow dissociation of active silicate in the mineral powder to release SiO4 4- , which combines with the Ca 2+Combining to form a gel, filling the pores and bridging the particle gaps, which promotes a 55.8% increase in compressive strength. At the same time, due to the enhanced continuity of the solid-phase skeleton, the thermal conductivity synchronously increases by 8.83%. For the specimen doped with 720D, the early-strength agent blocks the long-term dissociation path of silicate, and the porosity and pore size distribution basically maintain the initial state, verifying the dominant role of the hydration reaction in the microstructure evolution.

[0102] Through the analysis of the 28d ternary solid waste foam cement thermal insulation material ( Figure 10 ) and pore size ( Figure 11 ), it can be seen that compared with the pure desulfurized gypsum system, the ternary solid waste system has a better pore size uniformity distribution. The coarse particles of desulfurized gypsum (D50 is 35.67μm) build a rigid skeleton to limit the excessive expansion of bubbles. The medium particles of fly ash (D50 is 21.79μm) fill the coarse pores to reduce the expansion stress of the slurry. The ultra-fine particles of slag powder (D50 is 9.46μm) stabilize the gas-liquid interface through the physical adsorption and interfacial wetting effects of ultra-fine particles, inhibiting the coalescence of bubbles. The three work together to achieve a uniform pore structure without adding pore modifiers. After adding styrene-acrylic emulsion, the interfacial interference effect of the polymer chain destroys the bubble-stabilizing mechanism of particle gradation, resulting in the coalescence and floating of bubbles. The CO2+epoxy system reduces the gas diffusion path due to the early cross-linking of epoxy resin, and the pore-forming efficiency decreases by 78.04%. In contrast, the pore structure of the air foaming environment remains stable under the interference of pore modifiers. The ternary system can replace the collaborative pore size regulation functions of part of 720D and 31B by synergistically optimizing the interfacial stability and pore size distribution through multi-scale particle gradation filling and the pore closure effect of hydration products.

[0103] In the ternary solid waste system, the porosity is stably maintained at about 60%, and its fluctuation range is not sufficient to be the main controlling factor for the difference in thermal conductivity. For the CO2-inflated foamed thermal insulation material, the porosity difference of the four groups of specimens is only 4.04%. At this time, the change in thermal conductivity is mainly regulated by the pore structure parameters. When the pore density and the proportion of pore area are similar, the regulating effect of the pore size distribution on the thermal conductivity becomes prominent. For example, the specimens with a lower proportion of pores with a diameter of 100-500μm and a higher proportion of pores with a diameter of 500-1000μm (such as CO2 and CO2+720D at 28d) have a thermal conductivity reduced to 0.104W / (m·K), and this rule also holds in the air foaming group. When the pore density and the proportion of pore area change significantly, the two play a dominant role in the thermal conductivity, and the influence of the pore size distribution weakens. For example, in the ternary solid waste system, the CO2+epoxy group has the largest thermal conductivity due to the smallest proportion of pore area, while the air+720D group has the smallest thermal conductivity due to the largest proportion of pore area. The experimental data of the air+720D group in the desulfurized gypsum system further verifies this rule.

[0104] 2.4. Influence of CO2 Escape Amount on Thermal Conductivity of Ternary Solid Waste Foam Cement Thermal Insulation Material

[0105] By statistically comparing the specimens prepared by the CO2 and air inflation foaming processes in this embodiment, it can be found that the average dry density of the CO2 inflation foaming specimens is 777.68 kg / m 3 , and the average thermal conductivity is 0.1127 W / (m·K); the average dry density of the air inflation foaming specimens is 751.76 kg / m 3 , and the average thermal conductivity is 0.1440 W / (m·K). The dry density of the CO2 inflation foaming specimens is 3.45% higher than that of the air inflation foaming specimens, but the thermal conductivity is 21.71% lower. CO2 gas has certain advantages in improving the thermal insulation performance. At the same time, the dry density and thermal conductivity of the ternary solid waste foam cement thermal insulation material are both lower than those of the desulfurized gypsum foam cement thermal insulation material. It is necessary to study the influence of the CO2 escape amount on the thermal conductivity of the ternary solid waste foam cement thermal insulation material.

[0106] 2.4.1 Experimental calculation of the influence of CO2 escape amount on the thermal conductivity of ternary solid waste foam cement thermal insulation material

[0107] Select the CO2 inflation foaming ternary solid waste foam cement thermal insulation material with the lowest thermal conductivity at 28d in the above experimental results to conduct an experiment on the influence of CO2 escape amount on the thermal conductivity. Table 11 shows the experimental mix ratio and experimental results. The infrared spectra of the CO2 inflation ternary solid waste foam cement thermal insulation material at different ages are as Figure 12 shown.

[0108] With the increase of age, the thermal conductivity of the CO2 inflation foaming ternary solid waste specimens shows an upward trend. The thermal conductivity at 28d is 1.58% higher than that at 0d. The synergistic incorporation of fly ash and mineral powder and the addition of the 720D pore modifier form fine particles during the hydration process to fill the pore wall defects, reduce the number of CO2 gas diffusion channels, and improve the overall airtightness of the specimen pore structure. At the same time, the CO2 inflation foaming ternary solid waste specimens have a higher porosity, and the high porosity provides more storage space for CO2. These two factors make the CO2 content of the CO2 inflation foaming ternary solid waste specimens between the CO2 contents of the gypsum CO2 inflation foaming specimens without and with the addition of styrene-acrylic emulsion. The carbon fixation amount in the open pores of the CO2 inflation foaming ternary solid waste specimens is 11.61 kg / m 3 . From the perspective of gas escape, the CO2 escape amount of the ternary solid waste system specimens at 28d is 268 ml, and the escape rate is 28.72%, which is similar to the escape rate of the desulfurized gypsum CO2 inflation foaming specimens added with styrene-acrylic reagent, with a difference of 2.47%. This indicates that the relatively complex pore structure of the ternary solid waste system increases the CO2 gas diffusion path and resistance, reduces its CO2 escape rate, and realizes the equivalent gas sequestration performance to that of styrene-acrylic emulsion within 28d.

[0109] Table 12 Experimental design table of CO2 emission of CO2-inflated ternary solid waste foam cement thermal insulation material at different ages

[0110]

[0111] 2.4.2 Influence of theoretical calculation of CO2 emission on thermal conductivity of ternary solid waste foam cement thermal insulation material

[0112] Select the CO2-inflated foamed ternary solid waste foam cement thermal insulation material with 4‰ addition at 720D for theoretical calculation. Its dry density is 754.38 kg / m 3 The dry density of the unfoamed ternary solid waste sample is 1498.59 kg / m 3 The thermal conductivity is 0.3873 W / (m·K). Use the relationship between thermal conductivity and density to calculate the thermal conductivity of the thermal insulation material. The experimental design and calculation results are shown in Table 12

[0113] Table 13 Calculation results of thermal conductivity of ternary solid waste foam cement thermal insulation material with different CO2 volume fractions

[0114]

[0115] Similar to the pure gypsum system, the theoretical calculated value is larger than the measured thermal conductivity of 0.1042 W / (m·K). As the CO2 emission increases, the thermal conductivity of the sample shows an upward trend. For every 20% of CO2 emission, the thermal conductivity increases by 2.12%. When CO2 is completely replaced by air, the thermal conductivity increases by 10.62%, which is 51.07% more than that of the pure desulfurized gypsum system. The high porosity of the ternary solid waste system enables it to capture more CO2 gas. When CO2 begins to escape, the space originally occupied by CO2 is gradually occupied by air with a relatively high thermal conductivity. As this process continues, the content of CO2 replaced in the ternary solid waste is more than that of the pure desulfurized gypsum system, resulting in a greater impact of CO2 emission on the ternary solid waste system

[0116] 2.5. In order to solve the problems of poor pore tightness and high thermal conductivity of the single desulfurized gypsum cementitious system, in this embodiment, an orthogonal experiment is used to determine the formula of the ternary solid waste cementitious material. The performance of the ternary solid waste foam cement thermal insulation material is optimized by the addition amount of HPMC and the incorporation of pore modifiers. And the influence of CO2 emission on the thermal conductivity of the ternary solid waste foam cement thermal insulation material is analyzed by experiments and theoretical calculations. The main conclusions are as follows

[0117] (1) When the ratio of desulfurized gypsum: fly ash: slag powder is 580:210:210, the 28-day compressive strength of the ternary solid waste cementitious system is 50.21 MPa, and the thermal conductivity is 0.3873 W / (m·K). Compared with the pure desulfurized gypsum system, the compressive strength increases by 59.54%; the thermal conductivity decreases by 16.08%.

[0118] (2) The dosage of HPMC significantly affects the properties of the specimens by regulating the viscosity of the slurry. When the dosage is 3‰, the rheological properties and bubble stability of the slurry reach the optimal balance. The 7-day thermal conductivity of the CO2-inflated specimen is 0.0992 W / (m·K), which is 35.50% lower than that of the desulfurized gypsum system.

[0119] (3) The ternary solid waste system synergistically optimizes the interface stability and pore size distribution through multi-scale particle gradation filling and pore closure effect of hydration products, realizing a uniform pore structure without adding pore modifiers. The difference between its thermal conductivity and the lowest thermal conductivity of the added pore modifier is only 0.10%. When the dosage of 720D is 4‰ and the dosage of 31B is 8‰, the 28-day thermal conductivity of the ternary solid waste foam cement thermal insulation material prepared by the CO2-inflated foaming process is the lowest, which is 0.1042 W / (m·K), and its dry density is 754.38 kg / m 3 , and the compressive strength is 3.23 MPa, meeting the requirements of Grade A08 specified in the standard of "Foamed Concrete" (JG / T 266—2011).

[0120] (4) The CO2 system inhibits the silicate reaction due to the acidic environment, and the pore structure cannot be filled by hydration products; while in the air system, the densification filling of pores by C-S-H gel reduces the porosity. The porosity of the CO2 system is higher than that of the air system. Due to the loose structure and high porosity of the CO2 system, its compressive strength and thermal conductivity are both lower than those of the air system.

[0121] (5) When the dry density of the CO2 specimen is 3.45% higher than that of the air specimen, its thermal conductivity is 21.71% lower. Compared with the pure desulfurized gypsum system, the high porosity of the ternary solid waste foam cement thermal insulation material makes its thermal conductivity more affected by the CO2 escape amount, and it has the effect of slowing down the CO2 diffusion rate similar to that of styrene-acrylic emulsion.

[0122] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Although the above embodiments have been described in detail with reference to the foregoing, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the above embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A method for preparing a ternary solid waste foam cement thermal insulation material by CO2 gas injection foaming, characterized in that: It includes the following steps: Step 1: Weigh desulfurized gypsum, fly ash, mineral powder and admixtures, and stir them evenly for standby; Step 2: Weigh the required amount of water, and stir the uniformly mixed dry materials in Step 1 with water to form a uniform slurry for standby; Step 3: Stir the uniform slurry at a high speed again. Adjust the rotation speed of the mixer to 3000 r / min, and charge CO2 gas while stirring to prepare an aerated foamed slurry; Step 4: Pour the aerated foamed slurry into a mold. After solidification, remove the mold to form a specimen. Weigh the specimen, record the data, then put the specimen into a self-sealing bag, seal it and cure it in a natural environment; Step 5: After curing to the specified age, take out the specimen from the airtight self-sealing bag and dry it to a constant weight, then the ternary solid waste foam cement thermal insulation material is prepared.

2. The CO2 inflation foaming preparation method of a ternary solid waste foam cement thermal insulation material according to claim 1, characterized in that: In Step 2, the water-solid ratio is 0.8; when stirring, first stir slowly for 1 min to mix the water and dry materials, and then stir quickly for 2 min to form a uniform slurry without lumps.

3. The CO2 inflation foaming preparation method of a ternary solid waste foam cement thermal insulation material according to claim 1 or 2, characterized in that: In Step 3, the bottom of the gas charging pipe is wrapped with gauze to make the bubbles enter the slurry in a small pore diameter state.

4. The CO2 gas injection foaming preparation method of a ternary solid waste foam cement thermal insulation material according to claim 3, characterized in that: In Step 1, the admixtures include: foam stabilizer, pore modifier and retarder.

5. The method for preparing a ternary solid waste foam cement thermal insulation material by CO2 inflation foaming according to claim 4, characterized in that: The foam stabilizer includes: polyvinyl alcohol, hydroxypropyl guar gum or hydroxypropyl methyl cellulose; The pore modifier includes: styrene-acrylic emulsion, epoxy resin, or nano-inorganic modifier 720D and early strength agent 31B.

6. The CO2 gas injection foaming preparation method of a ternary solid waste foam cement thermal insulation material according to claim 5, characterized in that: The mass ratio of desulfurized gypsum:fly ash:mineral powder is 580:210:

210.

7. The method for preparing a ternary solid waste foam cement thermal insulation material by CO2 gas injection foaming according to claim 6, characterized in that: The desulfurized gypsum is desulfurized building gypsum, and its particle size range is: D10 is 2.50 μm, D50 is 35.67 μm, D90 is 65.45 μm; The particle size range of the fly ash is: D10 is 3.48 μm, D50 is 21.79 μm, D90 is 116.60 μm; The particle size range of the mineral powder is: D10 is 1.65 μm, D50 is 9.46 μm, D90 is 26.58 μm.

8. The CO2 gas injection foaming preparation method of a ternary solid waste foam cement thermal insulation material according to claim 7, characterized in that: The foam stabilizer is selected as hydroxypropyl methyl cellulose, and the dosage is: 3‰ of the total mass of desulfurized gypsum, fly ash and mineral powder.

9. The method for preparing a ternary solid waste foam cement thermal insulation material by CO2 inflation foaming according to claim 8, characterized in that: The pore modifier is selected as nano-inorganic modifier 720D and early strength agent 31B. The mass ratio of nano-inorganic modifier 720D and early strength agent 31B is 1:

2. The dosage of nano-inorganic modifier 720D is 4‰ of the total mass of desulfurized gypsum, fly ash and mineral powder, and the dosage of early strength agent 31B is 8‰ of the total mass of desulfurized gypsum, fly ash and mineral powder.

10. The method for preparing a ternary solid waste foam cement thermal insulation material by CO2 gas inflation foaming according to claim 9, characterized in that: The dosage of the retarder is 2.27‰ of the total mass of desulfurized gypsum, fly ash and mineral powder.

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