Lightweight high-strength high-durability concrete and preparation method thereof

Abstract

This invention relates to a lightweight, high-strength, and high-durability concrete and its preparation method, belonging to the field of concrete technology. The lightweight, high-strength, and high-durability concrete of this invention is mainly prepared from the following components: 730-850 parts by weight of cementitious materials, 840-920 parts by weight of aggregate system, 30-50 parts by weight of modified sepiolite, 3.0-4.0 parts by weight of polycarboxylate superplasticizer, 50-60 parts by weight of steel fiber, 10-20 parts by weight of polyethylene fiber, and 150-160 parts by weight of water. The concrete prepared by this invention can achieve high strength and high durability while maintaining lightweight properties, thus extending the service life of the concrete.

Description

Technical Field

[0001] This invention belongs to the field of concrete technology and relates to a lightweight, high-strength, and high-durability concrete and its preparation method. Background Technology

[0002] Concrete is a mixture made by mixing cementitious materials (organic, inorganic, or organic-inorganic composites), granular aggregates, water, and chemical admixtures and mineral admixtures in appropriate proportions, or a composite material with a cohesive structure after hardening. It is usually made of cementitious materials, water, fine aggregates, coarse aggregates, and admixtures and mineral admixtures added as needed, in appropriate proportions. It is the most important and widely used artificial civil engineering material in the world.

[0003] Concrete is characterized by its abundant and inexpensive raw materials and simple production process, leading to its ever-increasing usage. It also boasts high compressive strength, good durability, and a wide range of strength grades. These characteristics make it widely applicable, not only in various civil engineering projects but also in shipbuilding, machinery manufacturing, marine development, geothermal engineering, and other fields, where concrete plays a crucial role.

[0004] With the continuous development of concrete constituent materials, people's understanding of composite material technology is constantly improving. The performance requirements for concrete are no longer limited to compressive strength, but rather, based on strength, more attention is paid to the balance and coordination of comprehensive indicators such as concrete durability and deformation performance.

[0005] However, there is an inherent contradiction between lightweight, high strength, and high durability at the material level. The strength of concrete is usually positively correlated with its density, and reducing density (lightweight) is mainly achieved by introducing pores or using lightweight aggregates, which often comes at the cost of strength. To achieve high durability, a low water-cement ratio (i.e., a low ratio of water to cementitious materials) and a dense microstructure are usually required, but this will result in a viscous mixture with poor fluidity. The pores introduced to achieve lightweight will affect durability. Summary of the Invention

[0006] To address the above problems, this invention provides a lightweight, high-strength, and high-durability concrete. Through the compounding and optimization of components, this invention enables the concrete to improve its strength and durability while maintaining its lightweight properties.

[0007] The present invention employs the following technical solutions to achieve the above objectives: A lightweight, high-strength, and high-durability concrete is mainly prepared from the following components: The composition includes 730-850 parts by weight of cementitious materials, 840-920 parts by weight of aggregate system, 30-50 parts by weight of modified sepiolite, 3.0-4.0 parts by weight of polycarboxylate superplasticizer, 50-60 parts by weight of steel fiber, 10-20 parts by weight of polyethylene fiber, and 150-160 parts by weight of water.

[0008] Specifically, The cementitious material contains 400-450 parts by weight of silicate cement, 90-100 parts by weight of silica fume, 120-150 parts by weight of fly ash microspheres, 80-100 parts by weight of slag powder, and 40-50 parts by weight of metakaolin.

[0009] The aggregate system contains 400-420 parts by weight of ceramsite, 40-50 parts by weight of hollow glass microspheres, and 400-450 parts by weight of river sand.

[0010] Furthermore, the preparation method of the modified sepiolite includes the following steps: Step 1: Soak corn cobs in NaOH solution, then wash until neutral, and dry to obtain corn cob powder; place sepiolite in hydrochloric acid solution, heat at 70~100℃, then wash until neutral, and dry to obtain acidified sepiolite; mix γ-aminopropylmethyldiethoxysilane, water, and ethanol, and adjust the pH to 3.5~4.5 to obtain a hydrolyzable silane coupling agent; Step 2: Heat the acidified sepiolite to 90-100℃, add hydrolyzed silane coupling agent dropwise while stirring at 150-200 r / min, and stir to react to obtain pretreated sepiolite; mix the pretreated sepiolite and corn cob powder, heat to 100-110℃, add titanate coupling agent dropwise while stirring at 150-200 r / min, and stir to react to obtain secondary treated sepiolite; dissolve polylactic acid particles in acetone, add them to the secondary treated sepiolite, stir to react at 150-200 r / min, remove the solvent, and dry to obtain modified sepiolite.

[0011] Furthermore, In step 1, the NaOH solution has a mass fraction of 3%, the hydrochloric acid solution has a concentration of 0.5~1 mol / L, and the volume ratio of γ-aminopropylmethyldiethoxysilane, water, and ethanol is 1:1:10.

[0012] In step 2, the mass ratio of acidified sepiolite, hydrolyzed silane coupling agent, corn cob powder, titanate coupling agent, and polylactic acid particles is 1:0.06:0.03:0.01:0.06.

[0013] This invention provides a method for preparing the concrete, which mainly includes the following steps: Step A: Add the specified amounts of cementitious materials, aggregate system, and modified sepiolite to the concrete mixer and mix. Step B: Mix the polycarboxylate superplasticizer with 80% of the total water, slowly add it to the mixer, and stir to form a dense slurry; Step C: Add steel fiber, polyethylene fiber, and the remaining 20% ​​water while stirring. After stirring evenly, pour the mixture into a mold, vibrate it on a vibrating table to compact it, and then cure it according to standard.

[0014] The present invention has the following beneficial effects: Adding sepiolite to concrete, utilizing its filling and internal curing effects, can enhance its strength. However, directly adding sepiolite can lead to excessive water absorption due to its hydrophilic properties, resulting in poor concrete workability and agglomeration during mixing. Therefore, this invention involves appropriate modification of the sepiolite. A silane coupling agent acts as a molecular bridge to improve the interfacial affinity of the sepiolite. Polylactic acid forms a slow-release film on the sepiolite surface, and corn cob increases surface roughness and reactive sites. During the later stages of concrete hardening, this process slowly releases moisture, promoting cement hydration and increasing strength. Sepiolite's crystalline structure acts as a microfiber reinforcement in concrete. After modification, its affinity with cement paste is enhanced, effectively preventing, repairing, or hindering crack development. Hydrophobically modified sepiolite effectively reduces concrete water absorption, and the gel formation between its components fills voids, increasing resistance to water penetration and reducing the chloride ion diffusion coefficient. It also reduces the amount of freezeable water inside the concrete, effectively alleviating the hydrostatic pressure generated by ice crystal growth during freeze-thaw cycles, reducing cumulative freeze-thaw damage, and extending the service life of concrete under low-temperature conditions. Furthermore, modified sepiolite can solve the shrinkage cracking problem caused by water absorption and loss, improving concrete strength. Detailed Implementation

[0015] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope of protection of the claims of this application.

[0016] Example 1 Preparation of modified sepiolite: Step 1: Crush corn cobs to 100 μm, soak them in 3% NaOH solution for 1.5 h, filter, wash with water until neutral, and dry at 105 °C for 24 h. The corn cob powder is ready for use. Place 200 μm sepiolite powder in 0.5 mol / L hydrochloric acid solution, heat and stir at 70 °C under microwave conditions for 2 h, filter, wash with water until neutral, and dry to obtain acidified sepiolite. Mix γ-aminopropylmethyldiethoxysilane, water, and ethanol in a volume ratio of 1:1:10, adjust the pH to 3.5, and stir to obtain a hydrolyzed silane coupling agent. Step 2: Heat 1 kg of the above-mentioned acidified sepiolite to 100°C, add 60 g of hydrolyzed silane coupling agent dropwise to the acidified sepiolite at 200 r / min, and stir for 15 min to obtain pretreated sepiolite; mix the pretreated sepiolite and 30 g of corn cob powder, heat to 110°C, add 10 g of titanate coupling agent dropwise at 200 r / min (the titanate coupling agent and acetone are mixed in a 1:1 volume ratio beforehand), and stir for 10 min to obtain secondary treated sepiolite; dissolve 60 g of polylactic acid particles in an appropriate amount of acetone, stir until completely dissolved, add the secondary treated sepiolite, stir at 200 r / min for 30 min, evaporate the solvent, and dry to obtain modified sepiolite; Concrete preparation: Main components: cementitious materials (400kg silicate cement, 90kg silica fume, 150kg fly ash microspheres, 80kg slag powder, 50kg metakaolin), aggregate system (400kg 1~3mm ceramsite, 50kg hollow glass microspheres, 400kg river sand), 50kg modified sepiolite, 3.0kg polycarboxylate superplasticizer, 50kg steel fiber, 10kg polyethylene fiber, 160kg water; Step A: Add the formula amount of cementitious materials, aggregate system (of which the ceramsite is soaked for 24 hours in advance and drained before use), and modified sepiolite to the concrete mixer and mix at low speed for 2-3 minutes. Step B: Mix the polycarboxylate superplasticizer with 80% of the total water, slowly add it to the mixer, stir at low speed for 1-2 minutes and then stir at high speed for 3-4 minutes to form a dense slurry; Step C: Add steel fiber, polyethylene fiber, and the remaining 20% ​​water while stirring. After stirring evenly, pour the mixture into a mold, vibrate it on a vibrating table to compact it, and then cure it according to standard.

[0017] Example 2 Preparation of modified sepiolite: Step 1: Crush corn cobs to 150 μm, soak them in 3% NaOH solution for 2 hours, filter, wash with water until neutral, and dry at 105℃ for 24 hours. The corn cob powder is ready for use. Place 300 μm sepiolite powder in 1 mol / L hydrochloric acid solution, heat and stir at 100℃ for 1.5 hours under microwave conditions, filter, wash with water until neutral, and dry to obtain acidified sepiolite. Mix γ-aminopropylmethyldiethoxysilane, water, and ethanol in a volume ratio of 1:1:10, adjust the pH to 4.5, and stir to obtain a hydrolyzed silane coupling agent. Step 2: Heat 1 kg of the above-mentioned acidified sepiolite to 90°C, add 60 g of hydrolyzed silane coupling agent dropwise to the acidified sepiolite at 150 r / min, and stir for 20 min to obtain pretreated sepiolite; mix the pretreated sepiolite and 30 g of corn cob powder, heat to 100°C, add 10 g of titanate coupling agent dropwise at 150 r / min (the titanate coupling agent and acetone are mixed in a 1:1 volume ratio beforehand), and stir for 15 min to obtain secondary treated sepiolite; dissolve 60 g of polylactic acid particles in an appropriate amount of acetone, stir until completely dissolved, add the secondary treated sepiolite, stir at 150 r / min for 40 min, evaporate the solvent, and dry to obtain modified sepiolite; Concrete preparation: Main components: cementitious materials (450kg silicate cement, 100kg silica fume, 120kg fly ash microspheres, 100kg slag powder, 40kg metakaolin), aggregate system (420kg 1~3mm ceramsite, 40kg hollow glass microspheres, 450kg river sand), additives (30kg modified sepiolite, 4.2kg polycarboxylate superplasticizer, 60kg steel fiber, 20kg polyethylene fiber), 150kg water; Step A: Add the formula amount of cementitious materials, aggregate system (of which the ceramsite is soaked for 24 hours in advance and drained before use), and modified sepiolite to the concrete mixer and mix at low speed for 2-3 minutes. Step B: Mix the polycarboxylate superplasticizer with 80% of the total water, slowly add it to the mixer, stir at low speed for 1-2 minutes and then stir at high speed for 3-4 minutes to form a dense slurry; Step C: Add steel fiber, polyethylene fiber, and the remaining 20% ​​water while stirring. After stirring evenly, pour the mixture into a mold, vibrate it on a vibrating table to compact it, and then cure it according to standard.

[0018] Example 3 Preparation of modified sepiolite: Step 1: Crush corn cobs to 130 μm, soak them in 3% NaOH solution for 2 hours, filter, wash with water until neutral, and dry at 105℃ for 24 hours to obtain corn cob powder; place 250 μm sepiolite powder in 0.8 mol / L hydrochloric acid solution, heat and stir at 80℃ for 1 hour under microwave conditions, filter, wash with water until neutral, and dry to obtain acidified sepiolite; mix γ-aminopropylmethyldiethoxysilane, water, and ethanol in a volume ratio of 1:1:10, adjust the pH to 4.0, and stir to obtain hydrolyzed silane coupling agent; Step 2: Heat 1 kg of the above-mentioned acidified sepiolite to 100°C, add 60 g of hydrolyzed silane coupling agent dropwise to the acidified sepiolite at 180 r / min, and stir for 20 min to obtain pretreated sepiolite; mix the pretreated sepiolite and 30 g of corn cob powder, heat to 100°C, add 10 g of titanate coupling agent dropwise at 180 r / min (the titanate coupling agent and acetone are mixed in a 1:1 volume ratio beforehand), and stir for 15 min to obtain secondary treated sepiolite; dissolve 60 g of polylactic acid particles in an appropriate amount of acetone, stir until completely dissolved, add the secondary treated sepiolite, stir at 180 r / min for 40 min, evaporate the solvent, and dry to obtain modified sepiolite; Concrete preparation: Main components: cementitious materials (420kg silicate cement, 100kg silica fume, 130kg fly ash microspheres, 90kg slag powder, 40kg metakaolin), aggregate system (420kg 1~3mm ceramsite, 40kg hollow glass microspheres, 430kg river sand), additives (40kg modified sepiolite, 4.0kg polycarboxylate superplasticizer, 50kg steel fiber, 15kg polyethylene fiber), 150kg water; Step A: Add the formula amount of cementitious materials, aggregate system (of which the ceramsite is soaked for 24 hours in advance and drained before use), and modified sepiolite to the concrete mixer and mix at low speed for 2-3 minutes. Step B: Mix the polycarboxylate superplasticizer with 80% of the total water, slowly add it to the mixer, stir at low speed for 1-2 minutes and then stir at high speed for 3-4 minutes to form a dense slurry; Step C: Add steel fiber, polyethylene fiber, and the remaining 20% ​​water while stirring. After stirring evenly, pour the mixture into a mold, vibrate it on a vibrating table to compact it, and then cure it according to standard.

[0019] Comparative Example 1 Concrete preparation: Main components: cementitious materials (420kg silicate cement, 100kg silica fume, 130kg fly ash microspheres, 90kg slag powder, 40kg metakaolin), aggregate system (420kg 1~3mm ceramsite, 40kg hollow glass microspheres, 430kg river sand), additives (40kg modified sepiolite, 4.0kg polycarboxylate superplasticizer, 50kg steel fiber, 15kg polyethylene fiber), 150kg water; Step A: Add the formula amount of cementitious materials, aggregate system (of which the ceramsite is soaked for 24 hours in advance and drained before use), and sepiolite to the concrete mixer and mix at low speed for 2-3 minutes. Step B: Mix the polycarboxylate superplasticizer with 80% of the total water, slowly add it to the mixer, stir at low speed for 1-2 minutes and then stir at high speed for 3-4 minutes to form a dense slurry; Step C: Add steel fiber, polyethylene fiber, and the remaining 20% ​​water while stirring. After stirring evenly, pour the mixture into a mold, vibrate it on a vibrating table to compact it, and then cure it according to standard.

[0020] Comparative Example 2 Preparation of modified sepiolite: Step 1: Crush corn cobs to 130 μm, soak them in 3% NaOH solution for 2 hours, filter, wash with water until neutral, and dry at 105℃ for 24 hours to obtain corn cob powder; place 250 μm sepiolite powder in 0.8 mol / L hydrochloric acid solution, heat and stir at 80℃ for 1 hour under microwave conditions, filter, wash with water until neutral, and dry to obtain acidified sepiolite; mix γ-aminopropylmethyldiethoxysilane, water, and ethanol in a volume ratio of 1:1:10, adjust the pH to 4.0, and stir to obtain hydrolyzed silane coupling agent; Step 2: Heat 1 kg of the above-mentioned acidified sepiolite to 100°C, add 60 g of hydrolyzed silane coupling agent dropwise to the acidified sepiolite at 180 r / min, stir and react for 20 min to obtain pretreated sepiolite; mix the pretreated sepiolite and 30 g of corn cob powder, heat to 100°C, add 10 g of titanate coupling agent dropwise at 180 r / min (the titanate coupling agent and acetone were mixed in a 1:1 volume ratio beforehand), stir and react for 15 min, and after drying, obtain modified sepiolite; Concrete preparation: Main components: cementitious materials (420kg silicate cement, 100kg silica fume, 130kg fly ash microspheres, 90kg slag powder, 40kg metakaolin), aggregate system (420kg 1~3mm ceramsite, 40kg hollow glass microspheres, 430kg river sand), additives (40kg modified sepiolite, 4.0kg polycarboxylate superplasticizer, 50kg steel fiber, 15kg polyethylene fiber), 150kg water; Step A: Add the formula amount of cementitious materials, aggregate system (of which the ceramsite is soaked for 24 hours in advance and drained before use), and modified sepiolite to the concrete mixer and mix at low speed for 2-3 minutes. Step B: Mix the polycarboxylate superplasticizer with 80% of the total water, slowly add it to the mixer, stir at low speed for 1-2 minutes and then stir at high speed for 3-4 minutes to form a dense slurry; Step C: Add steel fiber, polyethylene fiber, and the remaining 20% ​​water while stirring. After stirring evenly, pour the mixture into a mold, vibrate it on a vibrating table to compact it, and then cure it according to standard.

[0021] Comparative Example 3 Preparation of modified sepiolite: Step 1: Place 250μm sepiolite powder in a 0.8mol / L hydrochloric acid solution, heat and stir at 80℃ for 1 hour under microwave conditions, filter, wash with water until neutral, and dry to obtain acidified sepiolite for later use; mix γ-aminopropylmethyldiethoxysilane, water, and ethanol in a volume ratio of 1:1:10, adjust the pH to 4.0, stir and mix to obtain a hydrolyzed silane coupling agent; Step 2: Heat 1 kg of the above-mentioned acidified sepiolite to 100°C, add 60 g of hydrolyzed silane coupling agent dropwise to the acidified sepiolite at 180 r / min, stir and react for 20 min to obtain pretreated sepiolite; dissolve 60 g of polylactic acid particles in an appropriate amount of acetone, stir until completely dissolved, add to the pretreated sepiolite, stir at 180 r / min for 40 min, evaporate and remove the solvent, and dry to obtain modified sepiolite; Concrete preparation: Main components: cementitious materials (420kg silicate cement, 100kg silica fume, 130kg fly ash microspheres, 90kg slag powder, 40kg metakaolin), aggregate system (420kg 1~3mm ceramsite, 40kg hollow glass microspheres, 430kg river sand), additives (40kg modified sepiolite, 4.0kg polycarboxylate superplasticizer, 50kg steel fiber, 15kg polyethylene fiber), 150kg water; Step A: Add the formula amount of cementitious materials, aggregate system (of which the ceramsite is soaked for 24 hours in advance and drained before use), and modified sepiolite to the concrete mixer and mix at low speed for 2-3 minutes. Step B: Mix the polycarboxylate superplasticizer with 80% of the total water, slowly add it to the mixer, stir at low speed for 1-2 minutes and then stir at high speed for 3-4 minutes to form a dense slurry; Step C: Add steel fiber, polyethylene fiber, and the remaining 20% ​​water while stirring. After stirring evenly, pour the mixture into a mold, vibrate it on a vibrating table to compact it, and then cure it according to standard.

[0022] Performance testing Concrete test blocks were prepared according to the formulation and method described in Examples 1-3 and Comparative Examples 1-3, and the relevant properties were tested. The results are shown in Table 1 below.

[0023] As can be seen from the results in Table 1, the concrete specimens prepared by this invention have a low dry apparent density but high compressive strength and flexural strength, which can ensure their mechanical properties while achieving lightweight.

[0024] Table 1 Concrete density and mechanical properties The concrete specimens prepared according to the formulations and methods described in Examples 1-3 and Comparative Examples 1-3 were tested for their memory durability (including freeze-thaw resistance, chloride ion penetration resistance, and carbonation resistance). The results are shown in Table 2.

[0025] As can be seen from the results in Table 2, the concrete specimens prepared in Examples 1-3 of this invention have stronger frost resistance, higher carbonation resistance, and lower electrical flux, indicating that they have better resistance to chloride ion penetration.

[0026] Table 2 Concrete durability results

Claims

1. A lightweight, high-strength, and high-durability concrete, characterized in that, It is mainly prepared from the following components: The composition includes 730-850 parts by weight of cementitious materials, 840-920 parts by weight of aggregate system, 30-50 parts by weight of modified sepiolite, 3.0-4.0 parts by weight of polycarboxylate superplasticizer, 50-60 parts by weight of steel fiber, 10-20 parts by weight of polyethylene fiber, and 150-160 parts by weight of water.

2. The concrete as described in claim 1, characterized in that, The cementitious material contains 400-450 parts by weight of silicate cement, 90-100 parts by weight of silica fume, 120-150 parts by weight of fly ash microspheres, 80-100 parts by weight of slag powder, and 40-50 parts by weight of metakaolin.

3. The concrete as described in claim 1, characterized in that, The aggregate system contains 400-420 parts by weight of ceramsite, 40-50 parts by weight of hollow glass microspheres, and 400-450 parts by weight of river sand.

4. The concrete according to any one of claims 1-3, characterized in that, The preparation method of the modified sepiolite includes the following steps: Step 1: Soak corn cobs in NaOH solution, then wash until neutral, and dry to obtain corn cob powder; place sepiolite in hydrochloric acid solution, heat at 70~100℃, then wash until neutral, and dry to obtain acidified sepiolite; mix γ-aminopropylmethyldiethoxysilane, water, and ethanol, and adjust the pH to 3.5~4.5 to obtain a hydrolyzable silane coupling agent; Step 2: Heat the acidified sepiolite to 90-100℃, add hydrolyzed silane coupling agent dropwise while stirring at 150-200 r / min, and stir to react to obtain pretreated sepiolite; mix the pretreated sepiolite and corn cob powder, heat to 100-110℃, add titanate coupling agent dropwise while stirring at 150-200 r / min, and stir to react to obtain secondary treated sepiolite; dissolve polylactic acid particles in acetone, add them to the secondary treated sepiolite, stir to react at 150-200 r / min, remove the solvent, and dry to obtain modified sepiolite.

5. The concrete as described in claim 4, characterized in that, In step 1, the NaOH solution has a mass fraction of 3%, the hydrochloric acid solution has a concentration of 0.5~1 mol / L, and the volume ratio of γ-aminopropylmethyldiethoxysilane, water, and ethanol is 1:1:

10.

6. The concrete as described in claim 4, characterized in that, In step 2, the mass ratio of acidified sepiolite, hydrolyzed silane coupling agent, corn cob powder, titanate coupling agent, and polylactic acid particles is 1:0.06:0.03:0.01:0.

06.

7. A method for preparing concrete as described in any one of claims 1-6, characterized in that, Includes the following steps: Step A: Add the specified amounts of cementitious materials, aggregate system, and modified sepiolite to the concrete mixer and mix. Step B: Mix the polycarboxylate superplasticizer with 80% of the total water, slowly add it to the mixer, and stir to form a dense slurry; Step C: Add steel fiber, polyethylene fiber, and the remaining 20% ​​water while stirring. After stirring evenly, pour the mixture into a mold, vibrate it on a vibrating table to compact it, and then cure it according to standard.

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