High-strength insulating concrete for precast elements and method for the production thereof

Abstract

This invention relates to the field of concrete, specifically to a high-strength thermally insulating concrete for precast components and its preparation method. The concrete, by weight, comprises: 320-380 parts of composite cementitious material, 180-220 parts of modified composite thermally insulating aggregate, 8-12 parts of composite admixture, and 150-170 parts of water. The composite cementitious material and modified ceramsite extensively utilize granulated blast furnace slag powder, steel slag powder, fly ash, and other industrial solid wastes, with solid waste accounting for over 30%. This reduces dependence on natural resources and achieves resource utilization of industrial waste. Compared to traditional cement-based concrete, carbon emissions are reduced by more than 40%, and energy consumption is reduced by more than 35%. Furthermore, the raw materials for each component are readily available, the preparation process requires no special equipment, and it can be adapted to existing precast component production lines, balancing environmental benefits with industrial application costs.

Description

Technical Field

[0001] This invention relates to the field of concrete, and more specifically to a high-strength thermal insulation concrete for precast components and its preparation method. Background Technology

[0002] With the rapid development of prefabricated buildings, precast concrete components face stringent requirements regarding both the mechanical and thermal insulation properties of materials. To achieve low thermal conductivity, existing insulating concrete often incorporates lightweight insulating aggregates such as expanded perlite, vitrified microspheres, and ordinary ceramsite. However, these aggregates generally suffer from high porosity, low strength, and poor interfacial adhesion with cementitious materials, leading to a significant decrease in the compressive strength of the concrete and making it difficult to meet the load requirements during the transportation and installation of precast components.

[0003] To balance strength and insulation, existing technologies often employ a "cementing material reinforcement + single insulating aggregate" approach. This includes adding polypropylene fibers to improve strength and combining them with cenospheres or ceramic hollow microspheres to optimize insulation. However, this approach still has several limitations: First, the synergy between insulation and mechanical properties of a single insulating aggregate is insufficient. For example, cenospheres tend to float and separate, and ordinary ceramsite has limited insulation efficiency. Second, cementing materials often rely on increased cement usage, which not only increases costs but also leads to high carbon emissions. Some solutions using sulfur-aluminum based cementing materials suffer from raw material scarcity and high preparation costs. Third, the admixture system has poor compatibility; foam stabilizers, fibers, and water-reducing agents can easily antagonize each other, resulting in uneven distribution of pores within the concrete and further exacerbating the conflict between strength and insulation.

[0004] Furthermore, the comprehensive utilization rate of industrial solid waste (such as slag, steel slag, and fly ash) is low, and its large-scale stockpiling causes environmental pollution problems. Current technologies limit the amount of solid waste that can be incorporated into thermal insulation concrete, and it is difficult to achieve synergistic compatibility between solid waste components and insulation and reinforcement functions. Therefore, developing a concrete material that balances high strength, excellent insulation, low energy consumption, high solid waste utilization, and compatibility with precast component production processes has become a pressing technical problem for the industry. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to provide a high-strength thermal insulation concrete for precast components and its preparation method.

[0006] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a high-strength thermally insulating concrete for precast components, comprising, by weight parts: 320-380 parts of composite cementitious material, 180-220 parts of modified composite thermal insulation aggregate, 8-12 parts of composite admixture, and 150-170 parts of water.

[0007] Preferably, the composite gel material is a hydrated calcium silicate composite gel generated by a secondary hydration reaction of ordinary silicate cement, granulated blast furnace slag powder and steel slag powder.

[0008] Preferably, the composite gel material is composed of the following components in the indicated weight percentages: 55-65 parts of ordinary silicate cement, 15-20 parts of granulated blast furnace slag powder, 8-12 parts of steel slag powder, 5-8 parts of silica fume, and 3-5 parts of desulfurized gypsum.

[0009] Preferably, the preparation method of the composite gel material includes: Ordinary silicate cement, granulated blast furnace slag powder, steel slag powder, silica fume, and desulfurized gypsum are added to a mixer in proportion and dry-mixed for 3-5 minutes until uniform to obtain a composite cementitious material.

[0010] Preferably, the modified composite thermal insulation aggregate is a mixture of surface-modified cenospheres and modified ceramsite.

[0011] Preferably, the cenospheres are etched with hydrofluoric acid solution and then loaded with allyl hydroxyethyl ether. The modified ceramsite is prepared by compounding fly ash, bentonite, glass powder and boron carbide in a mass ratio of (55-60):(20-25):(8-10):(3-4) and then modifying it with vinyl silane agent.

[0012] Preferably, the composite admixture is composed of the following components in the indicated weight percentages: 40-50 parts of polycarboxylate-based high-efficiency water-reducing agent, 25-30 parts of basalt fiber, 10-15 parts of triterpenoid saponin foam stabilizer, and 10-15 parts of redispersible latex powder.

[0013] Preferably, the preparation method of the modified composite thermal insulation aggregate includes: S1: Place the cenospheres in a 5-8% hydrofluoric acid solution and etch them at room temperature for 20-30 minutes. After removing them, rinse them with deionized water until neutral, dry them, and then immerse them in a dispersion of allyl hydroxyethyl ether. Perform ultrasonic adsorption for 1-2 hours and dry them again to obtain modified cenospheres. S2: Pass fly ash, bentonite, glass powder, and boron carbide through a 300-mesh sieve, mix them in deionized water in a certain proportion, add silane coupling agent A-151, stir for 2-3 hours to obtain modified ceramsite solution. S3: Add the modified cenospheres to the modified ceramsite solution, then add the initiator, heat to 60-70℃, stir and react for 10-20 hours, granulate to form raw material balls with a particle size of 1-2 mm, and dry to obtain modified composite thermal insulation aggregate.

[0014] Preferably, the ratio of cenospheres, allyl hydroxyethyl ether, and hydrofluoric acid solution is 10g:(2-3)g:(40-60)mL.

[0015] Preferably, the weight ratio of modified cenospheres to modified ceramsite is 1:3-6.

[0016] Secondly, the present invention provides a method for preparing high-strength thermally insulating concrete for precast components, comprising the following steps: Step 1: Dissolve the polycarboxylate-based high-efficiency water-reducing agent in water to obtain an aqueous solution of the high-efficiency water-reducing agent; add the composite cementitious material, basalt fiber, and redispersible latex powder from the composite admixture into a mixer, dry mix for 2-3 minutes, pour in the aqueous solution of the high-efficiency water-reducing agent, and stir for 4-6 minutes to prepare a cementitious slurry; finally, add the modified composite thermal insulation aggregate and the triterpenoid saponin foam stabilizer from the composite admixture, and stir at low speed for 2-3 minutes until uniform to obtain a concrete mixture; Step 2: Pour the concrete mixture into the precast mold, vibrate to compact it, and then let it stand at room temperature for 12-24 hours before demolding. After demolding, cure it for 28 days at a temperature of 20±2℃ and a humidity of ≥90% to obtain high-strength thermal insulation precast concrete.

[0017] The beneficial effects of this invention are as follows: 1. This invention overcomes the technical bottleneck of the traditional incompatibility between high strength and low thermal conductivity in concrete by using a synergistic design of composite cementitious materials, modified composite insulating aggregates, and composite admixtures. In the composite cementitious material, ordinary silicate cement, granulated blast furnace slag powder, steel slag powder, silica fume, and desulfurized gypsum form a multi-element synergistic system. Through a secondary hydration reaction, a large amount of dense hydrated calcium silicate gel and etalinite crystals are generated, significantly improving the bonding strength and structural density. In the modified composite insulating aggregate, hydrofluoric acid-etched and silica-hydrophobic aerogel-loaded cenospheres possess extremely low thermal conductivity. When compounded with fly ash-based modified ceramsite, they retain the thermal insulation properties of the aggregate while surface modification treatment enhances the interfacial adhesion to the cementitious matrix, preventing strength loss due to delamination between the insulating aggregate and the matrix.

[0018] 2. The core advantage of modified composite insulating aggregate lies in the cross-linking of modified cenospheres and modified ceramsite, forming a functionally complementary composite system. Cenospheres, etched with hydrofluoric acid and loaded with silica hydrophobic aerogel, have a hollow internal structure and a porous, rough surface. This results in extremely low thermal conductivity for efficient insulation, while the porous structure enhances physical interlocking with the cementitious matrix. Simultaneously, the hydrophobic aerogel blocks moisture penetration. Fly ash-based modified ceramsite, with its high strength and high porosity, provides structural support for the aggregate system, compensating for the low strength and susceptibility to breakage of the cenospheres themselves. The two are cross-linked and polymerized through allyl hydroxyethyl ether and vinyl silane, forming a stable interfacial bonding layer, avoiding performance imbalances caused by a single insulating aggregate. This cross-linking synthesis design retains the core thermal insulation properties of the aggregate while significantly enhancing the interfacial adhesion to the cementitious matrix, completely solving the technical problems of delamination and strength reduction in traditional insulating aggregates.

[0019] 3. The basalt fiber in the composite admixture effectively inhibits the initiation and propagation of internal cracks in concrete, reduces 28-day shrinkage strain by approximately 15%, and simultaneously increases flexural strength by over 25%. The triterpenoid saponin foam stabilizer regulates the internal pore structure of concrete, forming uniformly distributed closed micropores, reducing the proportion of harmful pores, and lowering water absorption to below 8%. The modified aerogel loaded on the surface of the cenospheres and the silane coupling agent modification treatment significantly improve the water resistance and erosion resistance of the aggregate. These design features give the concrete excellent impermeability, crack resistance, and freeze-thaw resistance, making it suitable for precast component preparation in complex service environments.

[0020] 4. The composite cementitious materials and modified ceramsite extensively utilize granulated blast furnace slag powder, steel slag powder, fly ash, and other industrial solid wastes, with solid waste accounting for over 30%. This reduces dependence on natural resources and achieves resource utilization of industrial waste. Compared to traditional cement-based concrete, carbon emissions are reduced by more than 40%, and energy consumption is reduced by more than 35%. Furthermore, the raw materials for each component are readily available, the preparation process requires no special equipment, and it can be adapted to existing precast component production lines, balancing environmental benefits with industrial application costs. Detailed Implementation

[0021] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0022] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0023] The raw materials used in this invention include: ordinary Portland cement of P·O 42.5 grade; granulated blast furnace slag powder with a specific surface area of ​​450 m². 2 / kg; Specific surface area of ​​steel slag powder 400m² 2 / kg; SiO2 content of silica fume ≥95%; desulfurized gypsum is industrial grade; cenosphere bulk density is 180kg / m³ 3 The fly ash is Class F, Grade I; the basalt fiber is 12mm long and 13-15μm in diameter; the polycarboxylate-based high-efficiency water-reducing agent has a solid content of 40%; the triterpenoid saponin foam stabilizer is industrial grade; the redispersible latex powder is ethylene-vinyl acetate type; and the silane coupling agent is A-151.

[0024] The present invention will be further described below with reference to the following embodiments.

[0025] Example 1 A high-strength thermal insulation concrete for precast components, comprising, by weight parts: 350 parts of composite cementitious material (60 parts of ordinary silicate cement, 18 parts of granulated blast furnace slag powder, 10 parts of steel slag powder, 7 parts of silica fume, and 5 parts of desulfurized gypsum); 200 parts of modified composite thermal insulation aggregate; 10 parts of composite admixture (45 parts of polycarboxylate-based high-efficiency water-reducing agent, 28 parts of basalt fiber, 12 parts of triterpenoid saponin foam stabilizer, and 15 parts of redispersible latex powder); and 160 parts of water.

[0026] The preparation method of the modified composite thermal insulation aggregate includes: S1: Place 20g of cenospheres into 100mL of 6% hydrofluoric acid solution and etch at room temperature for 25min. After removing them, rinse them with deionized water until neutral, dry them, and then immerse them in a dispersion of 5g of allyl hydroxyethyl ether. Sonicate them for 1h and dry them again to obtain modified cenospheres. S2: Mix fly ash, bentonite, glass powder, and boron carbide in the following proportions of 58g, 20g, 9g, and 3g respectively. Pass the mixture through a 300-mesh sieve and mix it in deionized water. Add 6g of silane coupling agent A-151 and stir for 2 hours to obtain a modified ceramsite solution. S3: Add modified cenospheres to the modified ceramsite solution, then add an initiator, heat to 65℃, stir and react for 15 hours, granulate to form raw material balls with a particle size of 1-2 mm, and dry to obtain modified composite thermal insulation aggregate.

[0027] The method for preparing high-strength thermally insulating concrete for precast components includes the following steps: Step 1: Dissolve the polycarboxylate-based high-efficiency water-reducing agent in water to obtain an aqueous solution of the high-efficiency water-reducing agent; add the composite cementitious material, basalt fiber, and redispersible latex powder from the composite admixture into a mixer, dry mix for 2 minutes, pour in the aqueous solution of the high-efficiency water-reducing agent, and stir for 5 minutes to prepare a cementitious slurry; finally, add the modified composite thermal insulation aggregate and the triterpenoid saponin foam stabilizer from the composite admixture, and stir at low speed for 2 minutes until uniform to obtain a concrete mixture; Step 2: Pour the concrete mixture into the precast mold, vibrate it to compact it, and then let it stand at room temperature for 18 hours before demolding. After demolding, cure it for 28 days at a temperature of 20±2℃ and a humidity of ≥90% to obtain high-strength thermal insulation precast concrete.

[0028] Example 2 A high-strength thermal insulation concrete for precast components, comprising, by weight parts: 320 parts of composite cementitious material (55 parts of ordinary silicate cement, 15 parts of granulated blast furnace slag powder, 8 parts of steel slag powder, 5 parts of silica fume, and 3 parts of desulfurized gypsum); 180 parts of modified composite thermal insulation aggregate; 8 parts of composite admixture (40 parts of polycarboxylate-based high-efficiency water-reducing agent, 25 parts of basalt fiber, 10 parts of triterpenoid saponin foam stabilizer, and 15 parts of redispersible latex powder); and 150 parts of water.

[0029] The preparation method of the modified composite thermal insulation aggregate is the same as that in Example 1.

[0030] The preparation method of high-strength thermal insulation concrete for precast components is the same as that in Example 1.

[0031] Example 3 A high-strength thermal insulation concrete for precast components, comprising, by weight parts: 380 parts of composite cementitious material (65 parts of ordinary silicate cement, 20 parts of granulated blast furnace slag powder, 12 parts of steel slag powder, 8 parts of silica fume, and 5 parts of desulfurized gypsum); 220 parts of modified composite thermal insulation aggregate; 12 parts of composite admixture (50 parts of polycarboxylate-based high-efficiency water-reducing agent, 30 parts of basalt fiber, 15 parts of triterpenoid saponin foam stabilizer, and 5 parts of redispersible latex powder); and 170 parts of water.

[0032] The preparation method of the modified composite thermal insulation aggregate is the same as that in Example 1.

[0033] The preparation method of high-strength thermal insulation concrete for precast components is the same as that in Example 1.

[0034] Comparative Example 1 (Unmodified composite thermal insulation aggregate) Compared with Example 1, the modified composite thermal insulation aggregate was replaced with ordinary ceramsite and unmodified cenospheres (weight ratio 1:4), while the remaining components and dosages were the same as in Example 1.

[0035] Comparative Example 2 (Composite cementitious material without silica fume and desulfurized gypsum) Compared with Example 1, the composite cementitious material was adjusted to 75 parts of ordinary silicate cement, 18 parts of granulated blast furnace slag powder, and 10 parts of steel slag powder. Silica fume and desulfurization gypsum were removed, and the remaining components and dosages were the same as in Example 1.

[0036] Comparative Example 3 (Composite admixture without basalt fiber and triterpenoid saponin foam stabilizer) Compared with Example 1, the composite admixture was adjusted to 60 parts of polycarboxylate-based high-efficiency water-reducing agent and 40 parts of redispersible latex powder. Basalt fiber and triterpenoid saponin foam stabilizer were removed, and the remaining components and dosages were the same as in Example 1.

[0037] Performance testing was conducted in accordance with the following national standards: Compressive strength and flexural strength: GB / T 50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", test the performance at 7d and 28d age, specimen size 150mm×150mm×150mm (compressive strength) and 100mm×100mm×400mm (flexural strength). Thermal conductivity: GB / T 10294-2008 "Determination of steady-state thermal resistance and related properties of thermal insulation materials - protective hot plate method", specimen size 300mm×300mm×50mm, tested after drying to constant weight; Water absorption rate: GB / T 4111-2013 "Test Methods for Concrete Blocks and Bricks", test the water absorption rate after 24 hours; 28d shrinkage strain: GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", using the contact method for testing; Dry density: GB / T 50081-2002, calculated after the specimen is dried to constant weight.

[0038] The test results are shown below:

[0039] Example 1, as the preferred formulation, exhibits a 28-day compressive strength of 52.3 MPa, a flexural strength of 6.8 MPa, a thermal conductivity as low as 0.10 W / (m·K), a water absorption rate of only 6.2%, and a shrinkage strain of 420 × 10⁻⁶. -6All indicators were optimal, demonstrating the effectiveness of the synergistic effect of the components. Comparative Example 1, which did not use modified composite insulating aggregate, showed a 110% increase in thermal conductivity and a 26% decrease in compressive strength compared to Example 1, proving the dual contribution of modified aggregate to thermal insulation and strength. Comparative Example 2, lacking silica fume and desulfurized gypsum, had insufficient density in the cementitious system, resulting in a 21% decrease in compressive strength and a 53% increase in water absorption, indicating the optimizing effect of silica fume and desulfurized gypsum on cementitious strength and durability. Comparative Example 3, lacking basalt fiber and foam stabilizer, showed a 34% decrease in flexural strength, a 50% increase in shrinkage strain, and an 80% increase in thermal conductivity, verifying the regulatory effect of composite admixtures on toughness, pore structure, and thermal insulation performance.

[0040] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0041] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A high-strength thermal insulation concrete for precast components, characterized in that, Calculated by weight, including: 320-380 parts of composite cementitious material, 180-220 parts of modified composite thermal insulation aggregate, 8-12 parts of composite admixture, and 150-170 parts of water; The composite gel material is a hydrated calcium silicate composite gel generated by a secondary hydration reaction of ordinary silicate cement, granulated blast furnace slag powder and steel slag powder; the modified composite thermal insulation aggregate is a mixture of surface-modified cenospheres and modified ceramsite.

2. The high-strength thermal insulation concrete for precast components according to claim 1, characterized in that, The composite gel material is composed of the following components in the indicated weight percentages: 55-65 parts ordinary silicate cement, 15-20 parts granulated blast furnace slag powder, 8-12 parts steel slag powder, 5-8 parts silica fume, and 3-5 parts desulfurized gypsum.

3. The high-strength thermal insulation concrete for precast components according to claim 1, characterized in that, The preparation method of the composite gel material includes: Ordinary silicate cement, granulated blast furnace slag powder, steel slag powder, silica fume, and desulfurized gypsum are added to a mixer in proportion and dry-mixed for 3-5 minutes until uniform to obtain a composite cementitious material.

4. The high-strength thermal insulation concrete for precast components according to claim 1, characterized in that, The surface-modified cenospheres are etched with hydrofluoric acid solution and then loaded with allyl hydroxyethyl ether; the modified ceramsite is prepared by compounding fly ash, bentonite, glass powder and boron carbide in a mass ratio of (55-60):(20-25):(8-10):(3-4) and then modifying it with vinyl silane agent.

5. A high-strength thermal insulation concrete for precast components according to claim 1, characterized in that, The composite admixture is composed of the following components in the indicated weight percentages: 40-50 parts of polycarboxylate-based high-efficiency water-reducing agent, 25-30 parts of basalt fiber, 10-15 parts of triterpenoid saponin foam stabilizer, and 10-15 parts of redispersible latex powder.

6. The high-strength thermal insulation concrete for precast components according to claim 1, characterized in that, The preparation method of the modified composite thermal insulation aggregate includes: S1: Place the cenospheres in a 5-8% hydrofluoric acid solution and etch them at room temperature for 20-30 minutes. After removing them, rinse them with deionized water until neutral, dry them, and then immerse them in a dispersion of allyl hydroxyethyl ether. Perform ultrasonic adsorption for 1-2 hours and dry them again to obtain modified cenospheres. S2: Pass fly ash, bentonite, glass powder, and boron carbide through a 300-mesh sieve, mix them in deionized water in a certain proportion, add silane coupling agent A-151, stir for 2-3 hours to obtain modified ceramsite solution. S3: Add the modified cenospheres to the modified ceramsite solution, then add the initiator, heat to 60-70℃, stir and react for 10-20 hours, granulate to form raw material balls with a particle size of 1-2 mm, and dry to obtain modified composite thermal insulation aggregate.

7. A high-strength thermal insulation concrete for precast components according to claim 6, characterized in that, The ratio of cenospheres, allyl hydroxyethyl ether, and hydrofluoric acid solution is 10g:(2-3)g:(40-60)mL.

8. A high-strength thermal insulation concrete for precast components according to claim 6, characterized in that, The weight ratio of modified cenospheres to modified ceramsite is 1:3-6.

9. A method for preparing high-strength thermally insulating concrete for precast components as described in claim 1, comprising the following steps: Step 1: Dissolve the polycarboxylate-based high-efficiency water-reducing agent in water to obtain an aqueous solution of the high-efficiency water-reducing agent; add the composite cementitious material, basalt fiber, and redispersible latex powder from the composite admixture into a mixer, dry mix for 2-3 minutes, pour in the aqueous solution of the high-efficiency water-reducing agent, and stir for 4-6 minutes to prepare a cementitious slurry; finally, add the modified composite thermal insulation aggregate and the triterpenoid saponin foam stabilizer from the composite admixture, and stir at low speed for 2-3 minutes until uniform to obtain a concrete mixture; Step 2: Pour the concrete mixture into the precast mold, vibrate to compact it, and then let it stand at room temperature for 12-24 hours before demolding. After demolding, cure it for 28 days at a temperature of 20±2℃ and a humidity of ≥90% to obtain high-strength thermal insulation precast concrete.

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