Low-thermal-conductivity lightweight concrete and preparation method thereof

Abstract

The invention discloses low-thermal-conductivity lightweight concrete and a preparation method thereof. The low-thermal-conductivity lightweight concrete is prepared from the following components in parts by weight and does not contain auxiliaries: 95-125 parts of water; 100 to 534 parts of ceramsite; 0-514 parts of fine aggregate; 315 to 500 parts of cement; 35 to 42 parts of silica fume; 3.15 to 4.2 parts of a water reducing agent; the EPS particles are added according to the volume mixing amount of 0.08 m < 3 > / m < 3 >; the fine aggregate is perlite. According to the low-heat-conductivity lightweight concrete formula provided by the invention, collaborative optimization of three properties of light weight, high strength and low heat conductivity is realized, the problem of strength loss when aggregate is replaced by perlite can be solved, and the 28d strength is not greatly reduced while the dry density is reduced by 10-15% by optimizing a replacement object (preferentially replacing sand instead of coarse aggregate) of the perlite and a doping proportion.

Description

Technical Field

[0001] This invention relates to building materials, and more specifically to concrete technology. Background Technology

[0002] Under the trend of building energy conservation and lightweight development, low thermal conductivity lightweight concrete is widely used in non-load-bearing walls, thermal insulation components, and prefabricated building envelopes. Its core requirements are to simultaneously meet three core indicators: "lightweight (low dry density), high strength (ensuring structural stability), and low thermal conductivity (improving thermal insulation performance)". Currently, the mainstream lightweight concrete in the industry is mainly divided into two categories: one is lightweight aggregate concrete with lightweight aggregates such as expanded clay, expanded perlite, and aerogel; the other is foam concrete and lightweight aggregate foam concrete, which achieve lightweighting by introducing foam.

[0003] For lightweight aggregate concrete, lightweight aggregates such as expanded perlite and aerogel are currently used. Performance is controlled by adjusting the proportions of cement, mineral admixtures (such as silica fume), and water-reducing agents. However, there are obvious limitations: it is difficult to balance the three major indicators of "lightweight, high strength and low thermal conductivity". Aggregate replacement can easily lead to a sharp drop in strength. Aggregates such as aerogel have poor compatibility with cement matrix, are prone to water absorption and do not form properly. The mix design lacks systematicity.

[0004] For foamed concrete and lightweight aggregate foamed concrete, foam is prepared through physical or chemical foaming, and then the foam is mixed with cement paste, lightweight aggregate, etc. to form a mold. This can significantly reduce the dry density (usually down to 600-1200 kg / m³). 3 However, it has fatal flaws: the process is extremely complex, requiring multiple key processes such as foam preparation (physical foaming requires high-speed stirring to produce foam, and chemical foaming requires precise control of the foaming agent reaction rate), foam mixing (ensuring that the foam is evenly dispersed in the cement paste to avoid defoaming), and foam stability control (requiring the addition of foam stabilizers and strict control of ambient temperature and humidity); it relies on specialized equipment, such as high-pressure foaming machines, foam stabilizers, and specialized foam mixing machines, resulting in high equipment purchase and maintenance costs; at the same time, the introduction of foam can easily lead to uneven pores inside the concrete, with the 28-day compressive strength generally being lower than 10MPa, and the water absorption rate being high (usually >15%), resulting in poor long-term durability, making it only suitable for non-load-bearing infill walls, thus limiting its application scenarios.

[0005] Currently, although there are optimization solutions in the industry for single performance (such as high strength or low density) (such as increasing the amount of cement to improve the strength of lightweight aggregate concrete and increasing the foam stabilizer to improve the stability of foamed concrete), none of them have solved the dual pain points of "poor performance synergy" of lightweight aggregate concrete and "complex process, reliance on special equipment, high cost and low strength" of foamed concrete, making it difficult to meet the comprehensive needs of modern buildings for high efficiency, energy saving, lightweight, high reliability and economy.

[0006] Therefore, existing low thermal conductivity lightweight concrete generally has the following problems: 1) Poor synergy of lightweight aggregate concrete performance: Existing lightweight concrete cannot simultaneously achieve the comprehensive performance of "lightweight (low dry density), high strength (ensuring structural stability), and low thermal conductivity (improving thermal insulation performance)". For example, when the density grade of traditional lightweight aggregate concrete is 1600, the strength grade is LC15~LC40, but the thermal conductivity at equilibrium moisture content reaches 0.77W / (m·K), resulting in insufficient thermal insulation effect.

[0007] 2) Foamed concrete and lightweight aggregate foamed concrete have complex processes and rely on specialized equipment: They require multiple complex processes such as foam preparation (physical foaming requires a special high-pressure foaming machine, and chemical foaming requires precise control of the foaming agent ratio), foam mixing (a special foam mixing mixer is required to ensure uniform foam dispersion), and foam stability control (a foam stabilizer needs to be added and the ambient temperature and humidity need to be controlled). Each step requires professional operation and has a low error tolerance. In addition, the purchase, installation and maintenance costs of specialized equipment are high, which is difficult for small and medium-sized construction companies to afford.

[0008] 3) Foamed concrete and lightweight aggregate foamed concrete are expensive: On the one hand, the investment in special equipment increases fixed costs; on the other hand, special additives such as foaming agents and foam stabilizers further increase material costs, making the comprehensive cost per cubic meter of foamed concrete (including equipment depreciation, materials and labor) 30-50% higher than that of ordinary lightweight concrete, resulting in poor economic efficiency.

[0009] 4) Foamed concrete and lightweight aggregate foamed concrete have obvious performance defects: the introduction of foam leads to high internal porosity and uneven distribution, and the 28-day compressive strength is generally lower than 10MPa, making it unsuitable for load-bearing or semi-load-bearing components; at the same time, foam rupture easily forms interconnected pores, the water absorption rate is >15%, the strength decay rate exceeds 30% under freeze-thaw cycle environment, and cracking and spalling are likely to occur, resulting in poor durability.

[0010] 5) Existing technologies have limited application scenarios: Due to their performance limitations, lightweight aggregate concrete can only meet the single requirements of load-bearing or thermal insulation; foamed concrete and lightweight aggregate foamed concrete are only suitable for non-load-bearing infill walls due to their low strength and high cost, and cannot cover core scenarios such as building load-bearing components and external wall insulation. Summary of the Invention

[0011] In view of the problems existing in the existing low thermal conductivity lightweight concrete solutions, the purpose of this invention is to provide a low thermal conductivity lightweight concrete solution that can achieve synergistic optimization of the three major properties of "lightweight, high strength and low thermal conductivity", thereby effectively overcoming the problems existing in the prior art.

[0012] To achieve the above objectives, the present invention provides a low thermal conductivity lightweight concrete, which is composed of the following components in parts by weight and does not contain any additives: 95-125 parts water; 100-534 parts of expanded clay aggregate; Fine aggregate 0-514 parts; 315-500 parts cement; 35-42 parts silica fume; Water-reducing agent: 3.15~4.2 parts; EPS particles are 0.08m 3 / m 3 Volumetric doping addition; The fine aggregate is perlite.

[0013] Furthermore, the water-cement ratio in the low thermal conductivity lightweight concrete is 0.28-0.35.

[0014] Furthermore, the ceramsite has a particle size distribution of 5-15mm and a bulk density of 600-700kg / m³. 3 The cylinder compressive strength is ≥5MPa.

[0015] Furthermore, up to 30% perlite is added to the ceramsite to replace the ceramsite.

[0016] Furthermore, the silica fume content is 10-12% of the cement mass.

[0017] To achieve the above objectives, the present invention also provides a method for preparing low thermal conductivity lightweight concrete, the method comprising the following steps in sequence: Step 1: Accurately weigh each material, weigh water, water-reducing agent, ceramsite, perlite, cement, and silica fume according to the formula, and mix the water-reducing agent with 50% of the total water to make an aqueous solution; Step 2: Aggregate pretreatment, soak the ceramsite for 20-26 hours and then filter out the water; Step 3: Dry mixing of aggregates. Put the treated ceramsite, perlite and EPS particles into the mixer and dry mix for 15-25 seconds to ensure that the ceramsite and perlite are evenly dispersed. Step 4: Mix the cementitious material and admixtures, add cement to the mixer, and at the same time slowly and evenly add the prepared water-reducing agent solution and 30% of the remaining water. Stir for 2-5 minutes to fully hydrate the cement and initially bond it to the surface of the ceramsite. Use the water-reducing agent to inhibit the ceramsite from floating. Step 5: Add mineral admixtures. Add silica fume and slowly add the remaining 20% ​​water. Continue stirring for 1-3 minutes to ensure that the silica fume is evenly dispersed in the cement paste and to avoid agglomeration.

[0018] Furthermore, during the pretreatment in the second step, the ceramsite is soaked in a clear water tank for 20-26 hours, and stirred once every 7-9 hours to ensure that the ceramsite absorbs water evenly. After soaking, the water is filtered through a filter screen to control the aggregate moisture content to be stable at 5-8%.

[0019] The low thermal conductivity lightweight concrete solution provided by this invention has the following advantages over existing technologies: (1) The low thermal conductivity lightweight concrete formula given by the present invention achieves synergistic optimization of the three major properties of "lightweight, high strength and low thermal conductivity", which can solve the strength loss problem when perlite is replaced with aggregate. By optimizing the replacement object of perlite (prioritizing the replacement of sand rather than coarse aggregate) and the dosage ratio, the dry density is reduced by 10~15% while ensuring that the 28-day strength is not significantly reduced.

[0020] (2) The low thermal conductivity lightweight concrete formula provided by the present invention, by screening compatible components such as optimizing the type of water-reducing agent and controlling the pre-wetting degree of aggregates, avoids water bleeding and segregation of the mixture, improves molding stability, and effectively overcomes the problem of water absorption molding of lightweight aggregates such as aerogel.

[0021] (3) The low thermal conductivity lightweight concrete preparation method given by the present invention forms a standardized preparation method, including raw material pretreatment (lightweight aggregate pre-wetting), mixing process (dry mixing-wet mixing in stages), and curing system, to ensure batch stability of concrete performance, while adapting to conventional concrete production equipment and improving industrial applicability.

[0022] (4) The method for preparing low thermal conductivity lightweight concrete provided by the present invention simplifies the production process and eliminates the dependence on special equipment: it eliminates the complex processes of foam preparation, mixing and stability control of foamed concrete and lightweight aggregate foamed concrete, and does not require high pressure foaming machine, special mixing mixer and other equipment. It can be produced by using conventional concrete mixing equipment, reducing the difficulty of operation and equipment investment.

[0023] (5) The method provided by the present invention significantly reduces costs. By selecting conventional raw materials (ceramsite, perlite, silica fume, etc., without the need for expensive additives such as foaming agents and foam stabilizers), simplifying the process, and reducing the investment in special equipment, the comprehensive cost of each cubic meter of concrete is controlled within the reasonable range of lightweight aggregate concrete, which is 30-50% lower than that of foamed concrete. Detailed Implementation

[0024] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further explained below with reference to specific examples.

[0025] Through thorough research into the problems faced by existing lightweight concrete (including lightweight aggregate concrete, foamed concrete, and lightweight aggregate foamed concrete), the inventors of this invention have developed a balanced formulation system by synergistically adapting "ceramsite-perlite-EPS particles" and optimizing cementitious materials and admixtures.

[0026] The resulting low thermal conductivity lightweight concrete formula achieves synergistic optimization of three major properties: lightweight, high strength, and low thermal conductivity. It innovatively adopts a perlite gradient replacement strategy: breaking away from the traditional approach of "preferentially replacing coarse aggregate with perlite", it proposes a solution of "preferentially replacing fine aggregate (sand)". At the same time, by optimizing the replacement target of perlite (preferentially replacing sand rather than coarse aggregate) and the dosage ratio, it can reduce strength loss while reducing dry density, thereby solving the strength loss problem when replacing aggregate with perlite. In addition, it eliminates the need for foaming to achieve lightweighting, thus saving the complex process of foam preparation from the source.

[0027] The low thermal conductivity lightweight concrete provided in this invention is specifically composed of the following components in parts by weight: 95-125 parts water; 100-534 parts of expanded clay aggregate; Fine aggregate 0-514 parts; 315-500 parts cement; 35-42 parts silica fume; Water-reducing agent: 3.15~4.2 parts; EPS particles (lightweight filler) at 0.08m 3 / m 3 Volumetric doping addition; In this formula, expanded clay aggregate is used as a lightweight coarse aggregate, while perlite is used as the fine aggregate. The components work synergistically to achieve a balance of performance, and no foaming agents, foam stabilizers or other additives are required in the entire formula.

[0028] Regarding the above-mentioned composition scheme for low thermal conductivity lightweight concrete, the specific synergistic formulation is given below.

[0029] In this low thermal conductivity lightweight concrete, the water content is dynamically adjusted according to the aggregate water absorption rate, and the water-cement ratio is controlled at 0.28-0.35 to ensure the workability and strength development of the mixture.

[0030] In this low thermal conductivity lightweight concrete, expanded clay aggregate is used as lightweight coarse aggregate, and further, a particle size distribution of 5-15mm and a bulk density of 600-700kg / m³ are adopted. 3 Ceramsite with a compressive strength ≥ 5 MPa.

[0031] Based on this, up to 30% perlite can be added to replace the expanded clay aggregate, thereby reducing the amount of expanded clay aggregate used. Since perlite is lighter than expanded clay aggregate, the density of the prepared concrete can be reduced.

[0032] In this low thermal conductivity lightweight concrete, perlite is used instead of conventional sand (such as river sand) as fine aggregate. The perlite needs to be surface modified to reduce water absorption, which can reduce strength loss while reducing dry density.

[0033] As further explanation, perlite with a particle size of 0.15-5mm is preferred in this scheme.

[0034] The preferred surface modification treatment here is to apply a waterproofing agent to reduce water absorption, thereby reducing density.

[0035] When calculating the mix proportions, the traditional concrete mix proportions can be calculated according to the specifications, and then the amount of sand can be replaced with the amount of perlite. In addition, when it is necessary to further reduce the concrete density, in addition to replacing sand with perlite, some of the expanded clay can be replaced with perlite, preferably 30% or 50%.

[0036] As a further explanation, this low thermal conductivity lightweight concrete incorporates highly precise aggregate pretreatment to address the high water absorption rate of the expanded clay and perlite used.

[0037] The present invention employs a standardized infiltration process to pretreat ceramsite and perlite, specifically including the following steps: First, soak the expanded clay and perlite separately in a clean water tank for 20-26 hours at a water temperature of 20±5℃, preferably for 24 hours; stir once every 7-9 hours during this period to ensure that the aggregates absorb water evenly. After soaking, use a 10mm mesh filter to filter the water and control the aggregate moisture content to be stable at 5-8%. This prevents the aggregate from absorbing too much water during mixing, which would lead to poor workability of the mixture. It also prevents the concrete from drying and shrinking and cracking later due to excessively low moisture content.

[0038] In this low thermal conductivity lightweight concrete, 52.5 grade ordinary Portland cement is preferred, but 42.5 grade ordinary Portland cement (compliant with GB 175 standard) can also be used to provide core cementitious strength. The amount used can be adjusted according to the strength requirements.

[0039] As a preferred option, the cement usage in this scheme is approximately 315-378 kg / m³. 3 This ensures the strength of the resulting concrete.

[0040] In this low thermal conductivity lightweight concrete, the silica fume content is 10-12% of the cement mass (compliant with GB / T 27690 standard), which fills the cement hydration gaps, enhances the interfacial bonding between aggregate and matrix, and improves strength and impermeability.

[0041] In this low thermal conductivity lightweight concrete, a polycarboxylate superplasticizer is used, with a water reduction efficiency of 25-30%.

[0042] In this low thermal conductivity lightweight concrete, EPS particles are used as lightweight filler, with a preferred particle size of 2-5 mm and an optimal volumetric admixture of 0.08 m³. 3 / m 3If the dosage is lower than this (e.g., 0.05 mg), 3 / m 3 If the dry density decreases by less than 10%, the insulation effect is not obvious; if the dosage is higher (e.g., 0.1m), the insulation effect is not significant. 3 / m 3 The strength drops below 5MPa after 28 days, which cannot meet the requirements for semi-load-bearing.

[0043] The low thermal conductivity lightweight concrete formulation proposed in this invention employs a perlite gradient replacement strategy: breaking away from the traditional approach of "preferentially replacing coarse aggregate with perlite," it proposes a scheme of "preferentially replacing fine aggregate (sand)," reducing both dry density and strength loss. This eliminates the need for foaming to achieve lightweighting, thus removing the complex processes of foam preparation at the source. For example, when perlite replaces 100% of sand, the dry density decreases from 1652.1 kg / m³. 3 Reduced to 1238.9 kg / m 3 The strength is reduced by 25%, while the 28-day strength remains at 16.3 MPa, meeting the requirements for non-load-bearing components.

[0044] This invention presents a low thermal conductivity lightweight concrete formulation that, compared to existing technologies that only use expanded clay and perlite particles, innovatively introduces a three-level synergistic aggregate system of "expanded clay-perlite-EPS particles." This system utilizes complementary particle sizes (expanded clay particles are approximately 5-15mm, perlite particles are approximately 0.15-5mm, and EPS particles are approximately 2-5mm) to define functional roles. Expanded clay, with its large particle size and high strength, but relatively poor thermal insulation, acts as a skeleton; the more expanded clay added, the higher the strength of the concrete product, but also the higher the density and the poorer the thermal insulation. Perlite, with its small particle size, lower strength, and lower density, has moderate thermal insulation, playing a supporting role in thermal insulation and density adjustment; the more perlite added, the lower the strength and density of the concrete product, but also the moderate thermal insulation. EPS particles, with their large particle size, low strength, and low density, have good thermal insulation, playing a supporting role in thermal insulation and density adjustment; the more EPS particles added, the lower the strength and density of the concrete product, and the better the thermal insulation. By balancing these three aspects, a balance can be achieved in strength, density, and thermal insulation performance, thus meeting different engineering needs.

[0045] This invention provides a corresponding preparation method for a low thermal conductivity lightweight concrete formulation.

[0046] The low thermal conductivity lightweight concrete preparation method provided in this invention is tailored to the specific characteristics of each component in the above-mentioned formula. It adopts a staged optimized mixing process, namely, a five-step standardized mixing process of "weighing - pretreatment - aggregate mixing - cementitious material mixing - mineral admixture replenishment" designed based on the characteristics of each component. This process is compatible with conventional concrete mixers, as detailed below: Step 1: Accurately weigh each material, including water, water-reducing agent (mix the water-reducing agent with 50% of the total water to prepare an aqueous solution), ceramsite, perlite, cement, and silica fume, according to the specified proportions, ensuring that the weighing error is ≤±1%. Step 2: Aggregate pretreatment. After soaking the ceramsite and perlite for 24 hours, filter them with clear water. The sand is passed through a 2.36mm sieve to remove impurities. Step 3: Dry mixing of aggregates. The treated ceramsite, perlite, and EPS particles are put into a conventional forced mixer for 15-25 seconds to ensure that the ceramsite and perlite are evenly dispersed and to prevent aggregate agglomeration during subsequent mixing. Step 4: Mix the cementitious material and admixture, add cement to the mixer, and at the same time slowly and evenly add the prepared water-reducing agent solution and 30% of the remaining water. Stir for 3 minutes to fully hydrate the cement and initially bond it to the surface of the aggregate. Use the water-reducing agent to inhibit the floating of lightweight aggregate. Step 5: Add mineral admixtures, add silica fume, and slowly add the remaining 20% ​​water. Continue stirring for 1-3 minutes to ensure that the silica fume is evenly dispersed in the cement paste, avoid agglomeration, and give full play to the interfacial reinforcement effect.

[0047] As can be seen from the above, the preparation method provided by this invention only requires conventional building material equipment such as forced mixers, filters, and weighing equipment, without the need for special foam concrete equipment such as high-pressure foaming machines and special foam mixing machines. The process achieves uniform mixing of each component through a staged mixing process, reducing the number of steps by more than 60% and equipment investment by 80% compared to foam concrete. Moreover, each step has clear time and operation standards, reducing dependence on the technical level of operators and improving the stability of industrial production.

[0048] Furthermore, the preparation method provided by this invention does not require expensive foaming agents (such as protein-based foaming agents) or foam stabilizers (such as polyacrylamide), and eliminates the need for depreciation costs of specialized equipment. Calculations show that the comprehensive cost (materials + equipment depreciation + labor) per cubic meter of concrete according to this invention is approximately 350-450 yuan, which is about 30% lower than that of foamed concrete, demonstrating significant economic advantages.

[0049] The present invention will be further illustrated below with reference to specific embodiments. These specific embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and operating procedures are provided. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally carried out under conventional conditions. Unless otherwise stated, proportions and percentages are by weight.

[0050] Example 1: Lightweight Concrete for Non-Load-Bearing Thermal Insulation 1) Raw material selection: All are conventional building materials, without special additives. Cement: P-O52.5 grade ordinary Portland cement (Shandong Shanshui Cement Group Co., Ltd.); Lightweight coarse aggregate: Lightweight and soft expanded clay aggregate (Sichuan Donghan Building Materials Co., Ltd., bulk density 300~400kg / m³) 3 (Water absorption rate 12%) The fine aggregate was replaced with 100% perlite.

[0051] Silica fume: Microsilica powder (Shenyang Xingfa Silica Fume Co., Ltd., SiO2 content 92%, specific surface area 20000 m²) 2 / kg); Thermal insulation particles: EPS particles Water-reducing agent: Polycarboxylate-based high-efficiency water-reducing agent (Sichuan Dongrun Baisheng New Material Co., Ltd., solid content 20%, water reduction efficiency ≥25%). Water: Tap water (pH=7.0).

[0052] 2) Proportion (kg / m³) 3 ): Water 54.8g, expanded clay 370.6g, perlite 24.0g, cement 378g, silica fume 42g, water-reducing agent 4.2g. EPS particle content is 0.08m³. 3 .

[0053] 3) Preparation process: Step 1: Weigh the materials and mix 4.20 kg of water-reducing agent with 27.44 kg of water (50% of the total water volume) to prepare an aqueous solution for later use; Step 2: Aggregate pretreatment. Ceramsite and perlite were soaked for 24 hours respectively. After filtering out the water, the moisture content was measured to be 6.5% and 7.2% respectively. Step 3: Dry mixing of aggregates, including 370.6 kg of ceramsite, 24.08 kg of perlite, and 0.08 m³ of... 3 Add EPS granules to the mixer and dry mix for 20 seconds; Step 4: Mix the cementitious material and admixtures, add 378 kg of cement, slowly add the water-reducing agent solution and 16.46 kg of water (30% of the remaining water), and stir for 3 minutes; Step 5: Add mineral admixtures, add 42kg silica fume, add 10.98kg water (20% of the remaining water), and stir for 1 minute; Step 6: Molding and curing. Pour the mixture into a 100mm×100mm×100mm steel mold, vibrate on a conventional vibrating table (frequency 50Hz) for 10 seconds, and smooth the surface. After standard curing (20℃, RH=95%) for 24 hours, demold and continue curing for 28 days.

[0054] 4) Performance test results: Dry density: 1180.7 kg / m³ 328-day compressive strength: 5.5 MPa; thermal conductivity: 0.53 W / (m·K).

[0055] Example 2: Lightweight Concrete for Non-Load-Bearing Thermal Insulation 1) The selection of raw materials and the preparation process are the same as in Example 1.

[0056] 2) Proportion (kg / m³) 3 ): Water 56.23, expanded clay 308.85, perlite 24.08, cement 378, silica fume 42, water-reducing agent 4.20. EPS particle content is 0.20m. 3 / m 3 .

[0057] Example 3: Lightweight Concrete for Non-Load-Bearing Thermal Insulation 1) The selection of raw materials and the preparation process are the same as in Example 1.

[0058] 2) Proportion (kg / m³) 3 ): Water 61.16, expanded clay 205.9, perlite 24.08, cement 378, silica fume 42, water-reducing agent 4.20. EPS particle content is 0.40m. 3 / m 3 .

[0059] Example 1: C30 grade lightweight load-bearing concrete 1) Raw material selection: Cement: P-O42.5 grade ordinary Portland cement (Shandong Shanshui Cement Group Co., Ltd.); Lightweight coarse aggregate: Shale ceramsite (Jining Zezhong Resources Comprehensive Utilization Co., Ltd., particle size distribution 5-15mm, bulk density 650kg / m³) 3 (Cylinder compressive strength 5.5 MPa, water absorption rate 8%) Sand: River sand (fineness modulus 2.5, mud content 2.5%); Silica fume: Microsilica powder (Shenyang Xingfa Silica Fume Co., Ltd., SiO2 content 92%, specific surface area 20000 m²) 2 / kg); Water-reducing agent: Polycarboxylate-based high-efficiency water-reducing agent (Sichuan Dongrun Baisheng New Material Co., Ltd., solid content 20%, water reduction efficiency ≥25%). Water: Tap water (pH=7.0).

[0060] 2) Proportion (kg / m³) 3 ): Water 122.5, expanded clay 533.7, sand 514.4, cement 315, silica fume 35, water-reducing agent 3.15.

[0061] 3) Preparation process: A phased optimization process is adopted, which is compatible with conventional equipment. Step 1: Weigh the materials. Accurately weigh each component according to the ratio. Mix 3.15 kg of water-reducing agent with 61.25 kg of water (50% of the total water volume) to prepare an aqueous solution for later use. Step 2: Aggregate pretreatment. The ceramsite was soaked in a clear water tank for 24 hours (water temperature 22℃), and stirred once every 8 hours. After soaking, the water was filtered through a 10mm filter screen and the moisture content was measured to be 7%. The sand was passed through a 2.36mm sieve to remove large particles of impurities. Step 3: Dry mixing of aggregates. Add 533.7 kg of expanded clay and 514.4 kg of sand to a forced mixer and dry mix for 20 seconds. Observe that the aggregates are mixed evenly and there is no obvious agglomeration. Step 4: Mix the cementitious materials and admixtures. Add 315 kg of cement to the mixer, and at the same time slowly add the water-reducing agent aqueous solution and 36.75 kg of water (30% of the remaining water) at a rate of 1 L / s. Start the mixer and mix for 3 minutes. During this period, observe the state of the mixture to ensure that there are no cement lumps and no obvious floating of aggregates. Step 5: Add mineral admixtures. Add 35 kg of silica fume and slowly add 24.5 kg of water (20% of the remaining water). Continue stirring for 1 minute until the silica fume is completely dispersed and the mixture is in a uniform and viscous state. Step 6: Molding and curing. Pour the mixture into a 100mm×100mm×100mm steel mold, vibrate on a conventional vibrating table (frequency 50Hz) for 10 seconds, and smooth the surface. After standard curing (20℃, RH=95%) for 24 hours, demold and continue curing for 28 days.

[0062] Comparative Example 2: Lightweight Concrete for Non-Load-Bearing Thermal Insulation 1) Raw material selection: Same as Comparative Example 1, but the fine aggregate was replaced with 100% perlite (Shandong Yuancheng New Material Technology Co., Ltd., bulk density ≤200kg / m³). 3 The water absorption rate is 15%, which is reduced to 9% after being treated with organosilane hydrophobic coating.

[0063] 2) Proportion (kg / m³) 3 ): Water 95.73, Ceramsite 411.8, Perlite 24.08, Cement 315, Silica Fume 35, Water Reducing Agent 3.15.

[0064] 3) Preparation process: Step 1: Weigh the materials and mix 3.15 kg of water-reducing agent with 47.87 kg of water (50% of the total water volume) to prepare an aqueous solution for later use; Step 2: Aggregate pretreatment. Ceramsite and perlite were soaked for 24 hours respectively. After filtering out the water, the moisture content was measured to be 6.5% and 7.2% respectively. Step 3: Dry mixing of aggregates. Add 411.8 kg of expanded clay and 24.08 kg of perlite to the mixer and dry mix for 20 seconds. Step 4: Mix the cementitious material and admixtures, add 315kg of cement, slowly add the water-reducing agent solution and 28.72kg of water (30% of the remaining water), and stir for 3 minutes; Step 5: Add mineral admixtures, add 35kg silica fume, add 19.14kg water (20% of the remaining water), stir for 1 minute, and measure the slump as 120mm; Step 6: Molding and curing, same as in Example 1.

[0065] Comparative Example 3: Traditional lightweight aggregate concrete (extensive process) 1) Raw materials and proportions: Same as Comparative Example 1, only the preparation process is different.

[0066] 2) Preparation process: The aggregate was not properly soaked (the ceramsite was only moistened with water, with a moisture content of 3%), and the mixing sequence was "all materials were put into the mixer at once and mixed for 5 minutes".

[0067] The density, compressive strength, and thermal conductivity of the samples obtained from Examples 1-3 and Comparative Examples 1-3 were tested respectively.

[0068] The density is based on JGJ / T 12-2019 standard, the compressive strength is based on GB / T 50081 standard, and the thermal conductivity is based on JGJ / T 12-2019 standard.

[0069] The specific test results are shown in Table 1. Table 1

[0070] As can be seen from the above, in Examples 1-3, as the EPS particle content increased from 0.08 μm... 3 / m 3 Increased to 0.40m 3 / m 3 The dry density continued to decrease to 946.4 kg / m³ 3 The thermal conductivity is reduced to 0.49 W / (m・K). Although the strength is reduced, it can still meet the non-load-bearing insulation requirements, giving priority to the performance regulation role of the three-stage synergistic aggregate system of "ceramsite-perlite-EPS" in the present invention.

[0071] Compared to Examples 1 to 3, the dry density of Example 1 (containing sand, but without perlite and EPS) is 1652.1 kg / m³. 3 With a compressive strength of 32.2 MPa and a thermal conductivity of 0.84 W / (m·K), it exhibits the high strength and high density characteristics required for load-bearing components. In contrast, in Example 2, replacing sand with perlite reduced the dry density to 1238.9 kg / m³. 3The thermal conductivity was reduced to 0.65 W / (m·K) while maintaining a strength of 16.3 MPa, verifying the effectiveness of the strategy of preferentially replacing fine aggregates with perlite.

[0072] Comparative Example 3, due to its crude preparation process, exhibited slight segregation, resulting in lower strength and thermal conductivity compared to Comparative Example 1, which employed a standardized process. This highlights the role of the pretreatment and staged stirring processes of the present invention in ensuring performance.

[0073] Based on the above examples, the synergistic optimization effect of the present invention on the three major indicators of "lightweight, high strength and low thermal conductivity" can be effectively demonstrated. Moreover, it does not require special equipment and expensive additives, and is economically significant.

[0074] As can be seen from the above examples, the low thermal conductivity lightweight concrete method provided by this invention has the following properties: 1) Excellent performance balance: The solution containing EPS particles (such as Example 1) has a dry density of 1180.7 kg / m³. 3 It has a 28-day strength of 5.5 MPa and a thermal conductivity of 0.53 W / (m·K), exhibiting relatively balanced performance.

[0075] 2) The preparation process is standardized and easy to operate: a five-step standardized process of "weighing-pretreatment-dry mixing of aggregates-stirring of cementitious materials-replenishment of silica fume" is established, clarifying the time and operation requirements of each step, which has low dependence on the technical level of operators and is easy to achieve industrial mass production.

[0076] 3) No special equipment required and simplified process: The complex foaming process of foamed concrete is eliminated, and only conventional forced mixer is required. There is no need to purchase special equipment, which lowers the threshold for enterprises to start production. The process is reduced by more than 60% compared with foamed concrete, and the production efficiency is increased by 30%.

[0077] 4) Significantly reduced costs: The raw materials are conventional building materials, without expensive foaming agents, foam stabilizers and other additives, and the equipment depreciation costs are low. The overall cost is 30-50% lower than that of foamed concrete and 10-15% lower than that of traditional lightweight aggregate concrete (extensive process), with outstanding economic advantages.

[0078] 5) Wide range of applications: The ratio can be adjusted according to needs (such as load-bearing, semi-load-bearing, and non-load-bearing insulation), and it is compatible with various components such as building beams, slabs, exterior walls, and interior partitions, solving the pain point of "single scenario" of existing technologies. It is especially suitable for fields with high requirements for the comprehensive performance of materials, such as prefabricated buildings and green buildings.

[0079] 6) Balancing environmental protection and economy: Using conventional building materials and general equipment reduces carbon emissions during the production of special additives and the manufacturing of special equipment; at the same time, the lightweight characteristics reduce the self-weight of the building structure, reduce the amount of foundation engineering and steel used, and further reduce the total life cycle cost of the building.

[0080] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A lightweight concrete with low thermal conductivity, characterized in that, It consists of the following components in parts by weight and does not contain any additives: 95-125 parts water; 100-534 parts of expanded clay aggregate; Fine aggregate 0-514 parts; 315-500 parts cement; 35-42 parts silica fume; Water-reducing agent: 3.15~4.2 parts; EPS particles are 0.08m 3 / m 3 Volumetric doping addition; The fine aggregate is perlite.

2. The low thermal conductivity lightweight concrete according to claim 1, characterized in that, The water-cement ratio in the low thermal conductivity lightweight concrete is 0.28-0.

35.

3. The low thermal conductivity lightweight concrete according to claim 1, characterized in that, The ceramsite has a particle size distribution of 5-15mm and a bulk density of 600-700kg / m³. 3 The cylinder compressive strength is ≥5MPa.

4. The low thermal conductivity lightweight concrete according to claim 1, characterized in that, Up to 30% perlite is added to replace the ceramsite.

5. The low thermal conductivity lightweight concrete according to claim 1, characterized in that, The silica fume content is 10-12% of the cement mass.

6. A method for preparing low thermal conductivity lightweight concrete, characterized in that, The preparation method consists of the following steps in sequence: Step 1: Accurately weigh each material, weigh water, water-reducing agent, ceramsite, perlite, cement, and silica fume according to the formula, and mix the water-reducing agent with 50% of the total water to make an aqueous solution; Step 2: Aggregate pretreatment, soak the ceramsite for 20-26 hours and then filter out the water; Step 3: Dry mixing of aggregates. Put the treated ceramsite, perlite and EPS particles into the mixer and dry mix for 15-25 seconds to ensure that the ceramsite and perlite are evenly dispersed. Step 4: Mix the cementitious material and admixtures, add cement to the mixer, and at the same time slowly and evenly add the prepared water-reducing agent solution and 30% of the remaining water. Stir for 2-5 minutes to fully hydrate the cement and initially bond it to the surface of the ceramsite. Use the water-reducing agent to inhibit the ceramsite from floating. Step 5: Add mineral admixtures. Add silica fume and slowly add the remaining 20% ​​water. Continue stirring for 1-3 minutes to ensure that the silica fume is evenly dispersed in the cement paste and to avoid agglomeration.

7. The method for preparing low thermal conductivity lightweight concrete according to claim 6, characterized in that, In the second step of pretreatment, the ceramsite is soaked in a clear water tank for 20-26 hours, and stirred once every 7-9 hours to ensure that the ceramsite absorbs water evenly. After soaking, the water is filtered through a filter screen to control the aggregate moisture content to be stable at 5-8%.

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