High-strength, crack-resistant foam concrete

Abstract

The application discloses high-strength anti-cracking foam concrete and belongs to the technical field of concrete. The concrete is prepared from the following raw materials in parts by weight: cement 200-300 parts, silica ash 10-20 parts, fly ash 20-40 parts, foaming agent 1-2 parts, fine aggregate 5-15 parts, foam stabilizer 1-3 parts, modified bamboo fiber-carbon nanotube composite material 5-10 parts, water reducing agent 0.5-1 part and water 120-130 parts. The high-strength anti-cracking foam concrete obtained by mixing and stirring the modified bamboo fiber-carbon nanotube composite material prepared by a specific method and other raw materials has the characteristics of low dry density, high strength, excellent anti-cracking performance and the like, and has a good market application prospect.

Description

Technical Field

[0001] This invention belongs to the field of concrete technology, specifically relating to a high-strength, crack-resistant foamed concrete. Background Technology

[0002] Foamed concrete is a special type of building material with micropores. It has attracted much attention due to its advantages such as self-leveling, low thermal conductivity, low raw material requirements, and light weight, as well as its excellent properties such as lightness, environmental protection, sound absorption, and fire resistance. It is widely used in the exterior walls and roof insulation of residential buildings, tunnel filling and pipe filling in underground engineering, and sculptures and decorative elements in the decoration field. Its flexibility and versatility have made it a popular material choice in the construction industry.

[0003] As is well known, foamed concrete possesses high porosity and strong pore connectivity, giving it excellent insulation and heat insulation properties. However, this also results in relatively low compressive and flexural strength, and a high moisture content, making it prone to cracking and leakage, which seriously hinders its widespread application. Therefore, research on improving the performance of foamed concrete has become a hot topic in the building materials field. Currently, specific measures to improve the performance of foamed concrete can be divided into three categories: first, changing the foaming method to alter the internal structure of the foamed concrete, filling and reinforcing voids; second, incorporating fibers to inhibit shrinkage and cracking; and third, incorporating mineral admixtures such as fly ash, slag, and silica fume to improve the pore structure of the foamed concrete through their pozzolanic effect and micro-aggregate filling effect. Numerous studies have shown that incorporating appropriate amounts of fibers (organic or inorganic fibers) as reinforcing agents during the preparation of foamed concrete can improve its overall performance. However, the effect of incorporating a single type of fiber on improving the performance of foamed concrete is limited. How to prepare a foamed concrete with better overall performance has become an urgent technical problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength, crack-resistant foamed concrete, which has excellent compressive strength, crack resistance and good thermal insulation properties.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] A high-strength, crack-resistant foamed concrete is made from the following raw materials in parts by weight: 200-300 parts cement, 10-20 parts silica fume, 10-20 parts fly ash, 1-2 parts foaming agent, 5-15 parts fine aggregate, 1-3 parts foam stabilizer, 5-10 parts modified bamboo fiber-carbon nanotube composite material, 0.5-1 part water-reducing agent, and 120-130 parts water.

[0007] The modified bamboo fiber-carbon nanotube composite material was prepared using the following method:

[0008] (1) Mix distilled water, silane coupling agent and anhydrous ethanol in a mass ratio to obtain a silane coupling agent solution;

[0009] (2) Carbon nanotubes were added to a silane coupling agent solution and ultrasonically dispersed for 30 min to obtain a carbon nanotube suspension;

[0010] (3) Mix bamboo fiber with 0.2 mol / L CaCl2 solution and stir at 400 r / min for a period of time. After the reaction is completed, add equal amounts of Na2CO3 solution and dispersant EDTA-2Na, and continue stirring at 300 r / min for 25 min. After the reaction is completed, rinse with tap water using a 200 mesh nylon net until there are no obvious particles in the suspension. Air dry to obtain modified bamboo fiber.

[0011] (4) The modified bamboo fiber was immersed in stearic acid ethanol solution at 75°C for 30 min, and then immersed in sodium hydroxide solution for 30 min. After taking it out, it was dried to obtain pretreated modified bamboo fiber.

[0012] (5) The pretreated modified bamboo fiber was added to the prepared carbon nanotube suspension and stirred magnetically for 12 hours. After filtration, the modified bamboo fiber-carbon nanotube composite material was obtained.

[0013] Preferably, the mass ratio of distilled water, silane coupling agent, and anhydrous ethanol in the silane coupling agent solution is 1:5:50, and the silane coupling agent is KH550.

[0014] Preferably, the carbon nanotube concentration in the carbon nanotube suspension is 0.5 wt%.

[0015] Preferably, in step (3), the ratio of bamboo fiber to CaCl2 solution is 1g:50ml, and the stirring reaction time is 30min.

[0016] Preferably, in step (3), the ratio of EDTA-2Na to CaCl2 solution is 0.01g:1ml.

[0017] Preferably, the concentration of the stearic acid ethanol solution is 2 wt%, and the concentration of the sodium hydroxide solution is 0.5 mol / L; the ratio of the modified bamboo fiber, stearic acid ethanol solution, and sodium hydroxide solution is 1 g: 20 ml: 20 ml.

[0018] Preferably, the ratio of the pretreated modified bamboo fiber to the carbon nanotube suspension is 1g:50ml.

[0019] Preferably, the foam stabilizer is composed of dodecyl dimethylamine oxide and polyacrylamide in a 1:1 mass ratio.

[0020] Preferably, the foaming agent is composed of plant protein foaming agent FP50A and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.3.

[0021] Preferably, the cement is ordinary Portland cement P·O42.5; and the water-reducing agent is a polycarboxylate water-reducing agent.

[0022] The preparation method of the high-strength crack-resistant foamed concrete of the present invention is as follows:

[0023] (1) Prepare modified bamboo fiber-carbon nanotube composite material according to the above steps;

[0024] (2) Mix the foaming agent and water at a volume ratio of 1:50 to obtain a foaming liquid, and then use an air compressor to introduce compressed air into the foaming liquid to form foam;

[0025] (3) Mix cement, silica fume, fly ash, fine aggregate, modified bamboo fiber-carbon nanotube composite material and water-reducing agent according to the proportion, then add the remaining water, stir at 200 r / min for 10 min, add foam stabilizer, and continue stirring for 5 min to make slurry;

[0026] (4) Add the foam obtained in step (2) to the slurry prepared in step (3), stir thoroughly to obtain a mixed slurry, pour, demold and cure the mixed slurry to obtain the high-strength crack-resistant foam concrete.

[0027] Existing research has demonstrated that incorporating appropriate amounts of fiber as a reinforcing material during the preparation of foamed concrete can improve its overall performance. The type, quantity, and method of fiber incorporation all significantly impact the properties of foamed concrete. This invention prepares a modified bamboo fiber-carbon nanotube composite material using a specific method. First, bamboo fibers are modified with nano-calcium carbonate. Then, the modified bamboo fibers undergo surface treatment and are connected to carbon nanotubes via a silane coupling agent. The silanol groups chemically bond with numerous active hydroxyl groups on the surface of the carbon nanotube molecules and the active hydroxyl groups on the surface of the modified bamboo fibers to form the modified bamboo fiber-carbon nanotube composite material. This fiber composite material forms a stable three-dimensional network structure within the concrete, promoting the uniform distribution of internal air bubbles. This effectively reduces the drying shrinkage rate of foamed concrete and improves its compressive strength, crack resistance, and thermal insulation properties. Furthermore, the modified bamboo fiber-carbon nanotube composite material contains bamboo fibers modified with nano-calcium carbonate. The nano-calcium carbonate promotes cement hydration, refines the crystal structure, and improves the interfacial structure of the concrete. This helps reduce porosity and cracks in the concrete, lowering its permeability and water absorption, further enhancing its durability. Simultaneously, the fiber composite material prepared in this invention improves the compatibility and adhesion between the fiber material and the cement matrix, further enhancing the crack resistance of the concrete.

[0028] The foam stabilizer used in this invention is composed of dodecyl dimethylamine oxide and polyacrylamide in a 1:1 mass ratio. The adhesive and thickening properties of polyacrylamide enhance the viscosity of concrete, making the bubbles more stable and less prone to breakage; while the foaming and stabilizing properties of dodecyl dimethylamine oxide further increase the number of bubbles in the concrete and improve their stability. The combined effect of these two components achieves excellent foam stabilization. Furthermore, it works synergistically with the modified bamboo fiber-carbon nanotube composite material used in this invention to ensure uniform distribution and size of closed pores in the foamed concrete, reducing the probability of cracking under pressure and thus improving the overall performance of the concrete.

[0029] This invention simultaneously adds silica fume and fly ash. The active SiO2 in the silica fume reacts with the calcium hydroxide produced during cement hydration, increasing the volume of CSH gel in the cement paste, reducing porosity, and improving the pore structure, thereby increasing the strength of the concrete. Meanwhile, the active SiO2 and Al2O3 in the fly ash react with the Ca(OH)2 produced during cement hydration to generate a large amount of hydrated silica gel. These gels can fill the voids, disrupt the preferred orientation of Ca(OH)2 in the interface region, greatly improve the interface region, and promote the growth of the concrete's later strength.

[0030] The beneficial effects of this invention are as follows:

[0031] Foamed concrete made by using specially modified bamboo fiber-carbon nanotube composite material as fiber reinforcement, selecting appropriate foam stabilizers and other raw materials, and optimizing the raw material ratio has excellent compressive strength, flexural strength, crack resistance and thermal insulation performance. It has good comprehensive performance and has excellent market application prospects. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to specific embodiments, but is not limited thereto. Unless otherwise specified, all raw materials used in the present invention are commercially available.

[0033] Example 1

[0034] A high-strength, crack-resistant foamed concrete is made from the following raw materials in parts by weight: 200 parts cement, 10 parts silica fume, 10 parts fly ash, 1 part foaming agent, 5 parts fine aggregate, 1 part foam stabilizer, 5 parts modified bamboo fiber-carbon nanotube composite material, 0.5 parts water-reducing agent, and 120 parts water.

[0035] The foam stabilizer is composed of dodecyl dimethylamine oxide and polyacrylamide in a 1:1 mass ratio.

[0036] The foaming agent is composed of plant protein foaming agent FP50A and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.3.

[0037] The cement is ordinary Portland cement P·O42.5; the water-reducing agent is polycarboxylate water-reducing agent.

[0038] The modified bamboo fiber-carbon nanotube composite material was prepared using the following method:

[0039] (1) Mix distilled water, silane coupling agent and anhydrous ethanol in a mass ratio to obtain a silane coupling agent solution;

[0040] (2) Carbon nanotubes were added to a silane coupling agent solution and ultrasonically dispersed for 30 min to obtain a carbon nanotube suspension with a concentration of 0.5 wt%.

[0041] (3) Mix bamboo fiber with 0.2 mol / L CaCl2 solution at a ratio of 1 g: 50 ml, stir at 400 r / min for 30 min, add equal amounts of Na2CO3 solution and dispersant EDTA-2Na after the reaction, continue stirring at 300 r / min for 25 min, rinse with tap water using a 200 mesh nylon net until there are no obvious particles in the suspension, air dry, and obtain modified bamboo fiber; wherein the ratio of EDTA-2Na to CaCl2 solution is 0.01 g: 1 ml;

[0042] (4) The modified bamboo fiber is immersed in stearic acid ethanol solution at 75°C for 30 min, and then immersed in sodium hydroxide solution for 30 min. After removal, it is dried to obtain pretreated modified bamboo fiber. The concentration of stearic acid ethanol solution is 2 wt%, and the concentration of sodium hydroxide solution is 0.5 mol / L. The ratio of the amount of modified bamboo fiber, stearic acid ethanol solution and sodium hydroxide solution is 1 g: 20 ml: 20 ml.

[0043] (5) The pretreated modified bamboo fiber was added to the prepared carbon nanotube suspension and magnetically stirred for 12 hours. After filtration, the modified bamboo fiber-carbon nanotube composite material was obtained. The ratio of the pretreated modified bamboo fiber to the carbon nanotube suspension was 1 g: 50 ml.

[0044] The specific preparation method of the above-mentioned high-strength crack-resistant foamed concrete is as follows:

[0045] (1) Prepare modified bamboo fiber-carbon nanotube composite material according to the above steps;

[0046] (2) Mix the foaming agent and water at a volume ratio of 1:50 to obtain a foaming liquid, and then use an air compressor to introduce compressed air into the foaming liquid to form foam;

[0047] (3) Mix cement, silica fume, fly ash, fine aggregate, modified bamboo fiber-carbon nanotube composite material and water-reducing agent according to the proportion, then add the remaining water, stir at 200 r / min for 10 min, add foam stabilizer, and continue stirring for 5 min to make slurry;

[0048] (4) Add the foam obtained in step (2) to the slurry prepared in step (3), stir thoroughly to obtain a mixed slurry, pour, demold and cure the mixed slurry to obtain the high-strength crack-resistant foam concrete.

[0049] Example 2

[0050] A high-strength, crack-resistant foamed concrete is made from the following raw materials in parts by weight: 250 parts cement, 15 parts silica fume, 15 parts fly ash, 1.5 parts foaming agent, 10 parts fine aggregate, 2 parts foam stabilizer, 8 parts modified bamboo fiber-carbon nanotube composite material, 0.8 parts water-reducing agent, and 125 parts water.

[0051] The foam stabilizer is composed of dodecyl dimethylamine oxide and polyacrylamide in a 1:1 mass ratio.

[0052] The foaming agent is composed of plant protein foaming agent FP50A and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.3.

[0053] The cement is ordinary Portland cement P·O42.5; the water-reducing agent is polycarboxylate water-reducing agent.

[0054] The modified bamboo fiber-carbon nanotube composite material was prepared using the following method:

[0055] (1) Mix distilled water, silane coupling agent and anhydrous ethanol in a mass ratio to obtain a silane coupling agent solution;

[0056] (2) Carbon nanotubes were added to a silane coupling agent solution and ultrasonically dispersed for 30 min to obtain a carbon nanotube suspension with a concentration of 0.5 wt%.

[0057] (3) Mix bamboo fiber with 0.2 mol / L CaCl2 solution at a ratio of 1 g: 50 ml, stir at 400 r / min for 30 min, add equal amounts of Na2CO3 solution and dispersant EDTA-2Na after the reaction, continue stirring at 300 r / min for 25 min, rinse with tap water using a 200 mesh nylon net until there are no obvious particles in the suspension, air dry, and obtain modified bamboo fiber; wherein the ratio of EDTA-2Na to CaCl2 solution is 0.01 g: 1 ml;

[0058] (4) The modified bamboo fiber is immersed in stearic acid ethanol solution at 75°C for 30 min, and then immersed in sodium hydroxide solution for 30 min. After removal, it is dried to obtain pretreated modified bamboo fiber. The concentration of stearic acid ethanol solution is 2 wt%, and the concentration of sodium hydroxide solution is 0.5 mol / L. The ratio of the amount of modified bamboo fiber, stearic acid ethanol solution and sodium hydroxide solution is 1 g: 20 ml: 20 ml.

[0059] (5) The pretreated modified bamboo fiber was added to the prepared carbon nanotube suspension and magnetically stirred for 12 hours. After filtration, the modified bamboo fiber-carbon nanotube composite material was obtained. The ratio of the pretreated modified bamboo fiber to the carbon nanotube suspension was 1 g: 50 ml.

[0060] The specific preparation method of the above-mentioned high-strength crack-resistant foamed concrete is as follows:

[0061] (1) Prepare modified bamboo fiber-carbon nanotube composite material according to the above steps;

[0062] (2) Mix the foaming agent and water at a volume ratio of 1:50 to obtain a foaming liquid, and then use an air compressor to introduce compressed air into the foaming liquid to form foam;

[0063] (3) Mix cement, silica fume, fly ash, fine aggregate, modified bamboo fiber-carbon nanotube composite material and water-reducing agent according to the proportion, then add the remaining water, stir at 200 r / min for 10 min, add foam stabilizer, and continue stirring for 5 min to make slurry;

[0064] (4) Add the foam obtained in step (2) to the slurry prepared in step (3), stir thoroughly to obtain a mixed slurry, pour, demold and cure the mixed slurry to obtain the high-strength crack-resistant foam concrete.

[0065] Example 3

[0066] A high-strength, crack-resistant foamed concrete is made from the following raw materials in parts by weight: 300 parts cement, 20 parts silica fume, 20 parts fly ash, 2 parts foaming agent, 15 parts fine aggregate, 3 parts foam stabilizer, 10 parts modified bamboo fiber-carbon nanotube composite material, 1 part water-reducing agent, and 130 parts water.

[0067] The foam stabilizer is composed of dodecyl dimethylamine oxide and polyacrylamide in a 1:1 mass ratio.

[0068] The foaming agent is composed of plant protein foaming agent FP50A and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.3.

[0069] The cement is ordinary Portland cement P·O42.5; the water-reducing agent is polycarboxylate water-reducing agent.

[0070] The modified bamboo fiber-carbon nanotube composite material was prepared using the following method:

[0071] (1) Mix distilled water, silane coupling agent and anhydrous ethanol in a mass ratio to obtain a silane coupling agent solution;

[0072] (2) Carbon nanotubes were added to a silane coupling agent solution and ultrasonically dispersed for 30 min to obtain a carbon nanotube suspension with a concentration of 0.5 wt%.

[0073] (3) Mix bamboo fiber with 0.2 mol / L CaCl2 solution at a ratio of 1 g: 50 ml, stir at 400 r / min for 30 min, add equal amounts of Na2CO3 solution and dispersant EDTA-2Na after the reaction, continue stirring at 300 r / min for 25 min, rinse with tap water using a 200 mesh nylon net until there are no obvious particles in the suspension, air dry, and obtain modified bamboo fiber; wherein the ratio of EDTA-2Na to CaCl2 solution is 0.01 g: 1 ml;

[0074] (4) The modified bamboo fiber is immersed in stearic acid ethanol solution at 75°C for 30 min, and then immersed in sodium hydroxide solution for 30 min. After removal, it is dried to obtain pretreated modified bamboo fiber. The concentration of stearic acid ethanol solution is 2 wt%, and the concentration of sodium hydroxide solution is 0.5 mol / L. The ratio of the amount of modified bamboo fiber, stearic acid ethanol solution and sodium hydroxide solution is 1 g: 20 ml: 20 ml.

[0075] (5) The pretreated modified bamboo fiber was added to the prepared carbon nanotube suspension and magnetically stirred for 12 hours. After filtration, the modified bamboo fiber-carbon nanotube composite material was obtained. The ratio of the pretreated modified bamboo fiber to the carbon nanotube suspension was 1 g: 50 ml.

[0076] The specific preparation method of the above-mentioned high-strength crack-resistant foamed concrete is as follows:

[0077] (1) Prepare modified bamboo fiber-carbon nanotube composite material according to the above steps;

[0078] (2) Mix the foaming agent and water at a volume ratio of 1:50 to obtain a foaming liquid, and then use an air compressor to introduce compressed air into the foaming liquid to form foam;

[0079] (3) Mix cement, silica fume, fly ash, fine aggregate, modified bamboo fiber-carbon nanotube composite material and water-reducing agent according to the proportion, then add the remaining water, stir at 200 r / min for 10 min, add foam stabilizer, and continue stirring for 5 min to make slurry;

[0080] (4) Add the foam obtained in step (2) to the slurry prepared in step (3), stir thoroughly to obtain a mixed slurry, pour, demold and cure the mixed slurry to obtain the high-strength crack-resistant foam concrete.

[0081] Comparative Example 1

[0082] A high-strength, crack-resistant foamed concrete is made from the following raw materials in parts by weight: 300 parts cement, 20 parts silica fume, 20 parts fly ash, 2 parts foaming agent, 15 parts fine aggregate, 3 parts foam stabilizer, 10 parts bamboo fiber, 1 part water-reducing agent, and 130 parts water.

[0083] The foam stabilizer is composed of dodecyl dimethylamine oxide and polyacrylamide in a 1:1 mass ratio.

[0084] The foaming agent is composed of plant protein foaming agent FP50A and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.3.

[0085] The cement is ordinary Portland cement P·O42.5; the water-reducing agent is polycarboxylate water-reducing agent.

[0086] The specific preparation method of the above-mentioned high-strength crack-resistant foamed concrete is as follows:

[0087] (1) Soak bamboo fiber in a 1 mol / L sodium hydroxide solution for 30 min, then remove and dry it;

[0088] (2) Mix the foaming agent and water at a volume ratio of 1:50 to obtain a foaming liquid, and then use an air compressor to introduce compressed air into the foaming liquid to form foam;

[0089] (3) Mix cement, silica fume, fly ash, fine aggregate, alkali-treated bamboo fiber and water-reducing agent according to the proportion, then add the remaining water, stir at 200r / min for 10min, add foam stabilizer, and continue stirring for 5min to make slurry;

[0090] (4) Add the foam obtained in step (2) to the slurry prepared in step (3), stir thoroughly to obtain a mixed slurry, pour, demold and cure the mixed slurry to obtain the high-strength crack-resistant foam concrete.

[0091] This comparative example is basically the same as Example 3, except that bamboo fiber is used to replace the modified bamboo fiber-carbon nanotube composite material.

[0092] Comparative Example 2

[0093] A high-strength, crack-resistant foamed concrete is made from the following raw materials in parts by weight: 300 parts cement, 20 parts silica fume, 20 parts fly ash, 2 parts foaming agent, 15 parts fine aggregate, 3 parts foam stabilizer, 10 parts carbon nanotubes, 1 part water-reducing agent, and 130 parts water.

[0094] The foam stabilizer is composed of dodecyl dimethylamine oxide and polyacrylamide in a 1:1 mass ratio.

[0095] The foaming agent is composed of plant protein foaming agent FP50A and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.3.

[0096] The cement is ordinary Portland cement P·O42.5; the water-reducing agent is polycarboxylate water-reducing agent.

[0097] The specific preparation method of the above-mentioned high-strength crack-resistant foamed concrete is as follows:

[0098] (1) Mix the foaming agent and water at a volume ratio of 1:50 to obtain a foaming liquid, and then use an air compressor to introduce compressed air into the foaming liquid to form foam;

[0099] (2) Mix cement, silica fume, fly ash, fine aggregate, carbon nanotubes and water-reducing agent in proportion, then add the remaining water, stir at 200 r / min for 10 min, add foam stabilizer, and continue stirring for 5 min to make slurry;

[0100] (4) Add the foam obtained in step (1) to the slurry prepared in step (2), stir thoroughly to obtain a mixed slurry, pour, demold and cure the mixed slurry to obtain the high-strength crack-resistant foam concrete.

[0101] This comparative example is basically the same as Example 3, except that ordinary carbon nanotubes are used to replace the modified bamboo fiber-carbon nanotube composite material.

[0102] Comparative Example 3

[0103] A high-strength, crack-resistant foamed concrete is made from the following raw materials in parts by weight: 300 parts cement, 20 parts silica fume, 20 parts fly ash, 2 parts foaming agent, 15 parts fine aggregate, 10 parts modified bamboo fiber-carbon nanotube composite material, 1 part water-reducing agent, and 130 parts water.

[0104] The foaming agent is composed of plant protein foaming agent FP50A and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.3.

[0105] The cement is ordinary Portland cement P·O42.5; the water-reducing agent is polycarboxylate water-reducing agent.

[0106] The modified bamboo fiber-carbon nanotube composite material was prepared using the following method:

[0107] (1) Mix distilled water, silane coupling agent and anhydrous ethanol in a mass ratio to obtain a silane coupling agent solution;

[0108] (2) Carbon nanotubes were added to a silane coupling agent solution and ultrasonically dispersed for 30 min to obtain a carbon nanotube suspension with a concentration of 0.5 wt%.

[0109] (3) Mix bamboo fiber with 0.2 mol / L CaCl2 solution at a ratio of 1 g: 50 ml, stir at 400 r / min for 30 min, add equal amounts of Na2CO3 solution and dispersant EDTA-2Na after the reaction, continue stirring at 300 r / min for 25 min, rinse with tap water using a 200 mesh nylon net until there are no obvious particles in the suspension, air dry, and obtain modified bamboo fiber; wherein the ratio of EDTA-2Na to CaCl2 solution is 0.01 g: 1 ml;

[0110] (4) The modified bamboo fiber is immersed in stearic acid ethanol solution at 75°C for 30 min, and then immersed in sodium hydroxide solution for 30 min. After removal, it is dried to obtain pretreated modified bamboo fiber. The concentration of stearic acid ethanol solution is 2 wt%, and the concentration of sodium hydroxide solution is 0.5 mol / L. The ratio of the amount of modified bamboo fiber, stearic acid ethanol solution and sodium hydroxide solution is 1 g: 20 ml: 20 ml.

[0111] (5) The pretreated modified bamboo fiber was added to the prepared carbon nanotube suspension and magnetically stirred for 12 hours. After filtration, the modified bamboo fiber-carbon nanotube composite material was obtained. The ratio of the pretreated modified bamboo fiber to the carbon nanotube suspension was 1 g: 50 ml.

[0112] The specific preparation method of the above-mentioned high-strength crack-resistant foamed concrete is as follows:

[0113] (1) Prepare modified bamboo fiber-carbon nanotube composite material according to the above steps;

[0114] (2) Mix the foaming agent and water at a volume ratio of 1:50 to obtain a foaming liquid, and then use an air compressor to introduce compressed air into the foaming liquid to form foam;

[0115] (3) Mix cement, silica fume, fly ash, fine aggregate, modified bamboo fiber-carbon nanotube composite material and water-reducing agent in proportion, then add the remaining water, stir at 200 r / min for 10 min, and continue stirring for 5 min to make slurry;

[0116] (4) Add the foam obtained in step (2) to the slurry prepared in step (3), stir thoroughly to obtain a mixed slurry, pour, demold and cure the mixed slurry to obtain the high-strength crack-resistant foam concrete.

[0117] This comparative example is identical to Example 3 except that it does not contain a foam stabilizer.

[0118] Performance testing

[0119] Samples: The concrete slurry prepared in Examples 1-3 and Comparative Examples 1-3 was poured into molds with dimensions of 100mm × 100mm × 100mm. After molding for 24 hours, the samples were demolded and placed in a standard curing chamber with a temperature of (20±2)℃ and a relative humidity of >95% for 28 days. The dry density (kg / m³) of the foamed concrete was measured using the method in JG / T266-2011 Foamed Concrete. 3The 28-day compressive strength (MPa) and 28-day flexural strength (MPa) were determined. Thermal conductivity was tested according to GB10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Insulation Materials - Protective Hot Plate Method," including transient and flat plate methods. The cracking area of ​​the concrete specimens (excluding the bottom surface) was measured according to GB / T 50081-2019 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete," and the cracking area per unit area was calculated. Specific test results are shown in Table 1.

[0120] Table 1 Performance Test Results

[0121]

[0122] As shown in Table 1, compared with Comparative Examples 1-3, the foamed concrete prepared in Examples 1-3 exhibits superior compressive strength, flexural strength, and crack resistance, while also possessing excellent thermal insulation properties. It is a high-strength, crack-resistant foamed concrete with excellent overall performance. This is because the modified bamboo fiber-carbon nanotube composite material used in this invention works synergistically with other raw materials. The modified bamboo fiber-carbon nanotube composite material forms a stable three-dimensional network structure within the concrete, promoting the uniform distribution of internal air bubbles. Simultaneously, the nano-calcium carbonate within it can promote cement hydration, refine the crystal structure, improve the interfacial structure of the concrete, reduce porosity and cracks, decrease the permeability and water absorption of the concrete, and also improve the compatibility and adhesion between the fiber material and the cement matrix, thereby better enhancing the overall performance of the concrete, such as crack resistance and compressive strength.

[0123] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A high-strength, crack-resistant foamed concrete, characterized in that, It is made from the following raw materials in parts by weight: 200-300 parts cement, 10-20 parts silica fume, 10-20 parts fly ash, 1-2 parts foaming agent, 5-15 parts fine aggregate, 1-3 parts foam stabilizer, 5-10 parts modified bamboo fiber-carbon nanotube composite material, 0.5-1 part water reducing agent, and 120-130 parts water. The modified bamboo fiber-carbon nanotube composite material was prepared using the following method: (1) Mix distilled water, silane coupling agent and anhydrous ethanol in a mass ratio to obtain a silane coupling agent solution; (2) Carbon nanotubes were added to a silane coupling agent solution and ultrasonically dispersed for 30 min to obtain a carbon nanotube suspension; (3) Mix bamboo fiber with 0.2 mol / L CaCl2 solution and stir at 400 r / min for a period of time. After the reaction is completed, add equal amounts of Na2CO3 solution and dispersant EDTA-2Na, and continue stirring at 300 r / min for 25 min. After the reaction is completed, rinse with tap water using a 200 mesh nylon net until there are no obvious particles in the suspension. Air dry to obtain modified bamboo fiber. (4) The modified bamboo fiber was immersed in stearic acid ethanol solution at 75°C for 30 min, and then immersed in sodium hydroxide solution for 30 min. After taking it out, it was dried to obtain pretreated modified bamboo fiber. (5) Add the pretreated modified bamboo fiber obtained in step (4) into the prepared carbon nanotube suspension and stir magnetically for 12 hours. After filtration, the modified bamboo fiber-carbon nanotube composite material is obtained.

2. The high-strength, crack-resistant foamed concrete according to claim 1, characterized in that, The mass ratio of distilled water, silane coupling agent, and anhydrous ethanol in the silane coupling agent solution is 1:5:50, and the silane coupling agent is KH550.

3. The high-strength, crack-resistant foamed concrete according to claim 1, characterized in that, The carbon nanotube concentration in the carbon nanotube suspension is 0.5 wt%.

4. The high-strength, crack-resistant foamed concrete according to claim 1, characterized in that, In step (3), the ratio of bamboo fiber to CaCl2 solution is 1g:50ml, and the stirring reaction time is 30min.

5. The high-strength, crack-resistant foamed concrete according to claim 1, characterized in that, In step (3), the ratio of EDTA-2Na to CaCl2 solution is 0.01g:1ml.

6. The high-strength, crack-resistant foamed concrete according to claim 1, characterized in that, In step (5), the ratio of the amount of pretreated modified bamboo fiber to carbon nanotube suspension is 1g:50ml.

7. The high-strength, crack-resistant foamed concrete according to claim 1, characterized in that, The foam stabilizer is composed of dodecyl dimethylamine oxide and polyacrylamide in a 1:1 mass ratio.

8. The high-strength, crack-resistant foamed concrete according to claim 1, characterized in that, The foaming agent is composed of plant protein foaming agent FP50A and sodium dodecylbenzenesulfonate in a mass ratio of 1:0.

3.

9. The high-strength, crack-resistant foamed concrete according to claim 1, characterized in that, In step (4), the concentration of stearic acid ethanol solution is 2wt% and the concentration of sodium hydroxide solution is 0.5mol / L; the ratio of modified bamboo fiber, stearic acid ethanol solution and sodium hydroxide solution is 1g:20ml:20ml.

10. The high-strength, crack-resistant foamed concrete according to claim 1, characterized in that, The cement is ordinary Portland cement P·O42.5, and the water-reducing agent is polycarboxylate water-reducing agent.

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