High-toughness anti-cracking lightweight concrete and preparation method thereof

Abstract

The invention belongs to the technical field of building materials, and discloses high-toughness anti-cracking lightweight concrete and a preparation method thereof. The high-toughness anti-cracking lightweight concrete is prepared from the following raw materials in parts by mass: 90 to 160 parts of cement, 22 to 45 parts of silica fume, 55 to 120 parts of fly ash, 140 to 260 parts of fine aggregate, 120 to 230 parts of coarse aggregate, 35 to 65 parts of modified waste rubber particles, 80 to 140 parts of modified composite fiber gel, 20 to 45 parts of polycarboxylate superplasticizer, 10 to 30 parts of CaCO3 whisker and 60 to 120 parts of water. According to the formula, on the premise that the compressive strength is guaranteed, the toughness and cracking resistance of the lightweight concrete can be synergistically improved, the apparent densities of the lightweight concrete obtained in the embodiment are 1758 kg / m < 3 > and 1671 kg / m < 3 > respectively, and the lightweight concrete is excellent in performance.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a high-toughness, crack-resistant lightweight concrete and a preparation method thereof. Background Art

[0002] As an indispensable base material for contemporary construction projects, concrete is widely used in various construction fields. Concrete can form a solid structure similar to stone by mixing cementitious materials, coarse and fine aggregates and chemical admixtures in precise proportions, and through mixing, vibrating and curing and hardening processes. The reason why concrete can dominate the engineering world is attributed to its series of significant advantages, including: customizable high compressive strength range (from C20 to C100 grades), excellent environmental adaptability and durability, easy access to raw materials, low economic cost, and mature production technology. However, the inherent brittle nature of concrete leads to its poor flexural strength and deformation capacity, which is prone to cracks caused by stress concentration and even overall structural failure, posing a major threat to the safe service of buildings. For lightweight concrete, due to the addition of lightweight aggregates, the strength of the aggregates is relatively low, and cracks are likely to occur inside starting from the lightweight aggregates, and the cracks expand rapidly, making the brittle characteristics of lightweight concrete more significant than ordinary concrete.

[0003] However, traditional toughening methods mainly rely on adding discrete fibers (such as polypropylene, PVA fiber, glass fiber, etc.) for reinforcement. Although it can improve the toughness index to a certain extent, it faces problems such as uneven fiber distribution and decreased interface bonding strength. It is difficult to effectively curb the expansion of microcracks, let alone effectively control the crack width. Summary of the invention

[0004] The purpose of the present invention is to provide a high-toughness crack-resistant lightweight concrete and a preparation method thereof, so as to solve the problem that the existing toughening methods are still unable to effectively curb the expansion of microcracks in lightweight concrete.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a high-toughness, crack-resistant lightweight concrete, comprising the following raw materials in parts by mass:

[0007] 90-160 parts of cement, 22-45 parts of silica fume, 55-120 parts of fly ash, 140-260 parts of fine aggregate, 120-230 parts of coarse aggregate, 35-65 parts of modified waste rubber particles, 80-140 parts of modified composite fiber gel, 20-45 parts of polycarboxylic acid water reducer, 10-30 parts of CaCO3 whiskers, and 60-120 parts of water.

[0008] Preferably, in the high-toughness crack-resistant lightweight concrete, the cement includes one or more of portland cement, slag portland cement, and pozzolanic portland cement.

[0009] Preferably, in the high-toughness crack-resistant lightweight concrete, the particle size conditions of the silica fume include: D 50 ≤0.3 μm, D 90 ≤1 μm;

[0010] The particle size condition of the fly ash is that the residue on a 45-μm sieve is ≤ 30 wt%.

[0011] Preferably, in the high-toughness crack-resistant lightweight concrete, the fine aggregate includes ceramsite fine aggregate; the particle size of the fine aggregate ≤ 5 mm;

[0012] The coarse aggregate includes ceramsite coarse aggregate; the particle size of the coarse aggregate is 10 - 20 mm.

[0013] Preferably, in the high-toughness crack-resistant lightweight concrete, the preparation method of the modified waste rubber particles includes the following steps:

[0014] Mix waste rubber with a particle size of 80 - 200 mesh with hydrogen peroxide solution and conduct surface oxidation treatment to obtain activated waste rubber;

[0015] Mix lignin, silane coupling agent, and solvent and conduct modification treatment to obtain silane-modified lignin;

[0016] Mix silane-modified lignin, activated waste rubber, and dispersant and conduct mixing and kneading to obtain modified waste rubber particles;

[0017] Among them, the temperature of the surface oxidation treatment is 45 - 75 °C, and the time of the surface oxidation treatment is 4 - 10 h;

[0018] The silane coupling agent includes one or more of KH-550, KH-570, and KH-590;

[0019] The pH of the modification treatment is 4 - 6, the temperature of the modification treatment is 60 - 80 °C, and the time of the modification treatment is 2 - 4 h;

[0020] The mass ratio of the silane-modified lignin to the activated waste rubber is 1:5 - 10;

[0021] The temperature of the mixing and kneading is 120 - 150 °C, the shear rotation speed of the mixing and kneading is 100 - 400 rpm, and the time of the mixing and kneading is 0.2 - 1 h.

[0022] Preferably, in the high-toughness anti-cracking lightweight concrete, the preparation method of the modified composite fiber gel comprises the following steps:

[0023] Mix plant fiber, basalt fiber, and aqueous polyurethane emulsion, and carry out modification to obtain modified plant fiber and modified basalt fiber; disperse the modified plant fiber, modified basalt fiber, and sodium alginate solution, and carry out vacuum defoaming to obtain the modified composite fiber gel;

[0024] Wherein, the mass ratio of the plant fiber to the basalt fiber is 6-8:4-2;

[0025] The temperature of the modification is 50-60°C, and the time of the modification is 2-4h;

[0026] The mass concentration of the sodium alginate solution is 3-5%;

[0027] The sum of the masses of the modified plant fiber and the modified basalt fiber is 5-20% of the mass of the sodium alginate solution;

[0028] The rotation speed of the dispersion is 5000-6000 rpm, and the time of the dispersion is 10-30 min;

[0029] The pressure of the vacuum defoaming is -0.01 to -0.1 MPa, and the time of the vacuum defoaming is 10-60 min.

[0030] Preferably, in the high-toughness anti-cracking lightweight concrete, the water reduction rate of the polycarboxylate water reducer is ≥25%.

[0031] Preferably, in the high-toughness anti-cracking lightweight concrete, the aspect ratio of the CaCO3 whiskers is 20-30, and the length of the CaCO3 whiskers is 20-30 μm.

[0032] The present invention also provides a preparation method of high-toughness anti-cracking lightweight concrete, comprising the following steps:

[0033] Mix cement, silica fume, fly ash, fine aggregate, coarse aggregate, modified waste rubber particles, and CaCO3 whiskers by mass to obtain a dry mix;

[0034] Mix the modified composite fiber gel and a partial amount of water by mass to obtain a dispersion slurry;

[0035] Mix the polycarboxylate water reducer and the remaining amount of water by mass to obtain a water reducer solution;

[0036] Mix the dry mix, the water reducer solution, and the dispersion slurry to obtain high-toughness anti-cracking lightweight concrete.

[0037] As can be seen from the above technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0038] In this application, modified waste rubber particles are added, which can produce elastic deformation to absorb energy. When microcracks expand to the interface, the plastic deformation of the modified rubber particles can blunt the crack tip, thereby inhibiting crack propagation and improving the anti-cracking performance of lightweight concrete. The modified composite fiber gel in this application contains plant fibers modified by waterborne polyurethane and basalt fibers. Through gelation treatment, the modified fibers are evenly dispersed to form a dense fiber network, ensuring the uniform distribution of the modified fiber material in the concrete and improving the toughness of the lightweight concrete. The CaCO3 whiskers added in this application can promote the densification of hydration products. Moreover, the modified composite fiber gel and CaCO3 whiskers synergistically toughen, and the whiskers can effectively combine the bridging effect of the fibers, reducing the late cracking of lightweight concrete. The coarse aggregate, fine aggregate and powders such as fly ash in this application can form a particle size grading. The spherical fine particles act as a lubricating phase, reducing the frictional resistance between the aggregates, improving the density, and effectively compensating for the strength loss caused by the addition of plant fibers, ensuring that the mechanical strength can meet the performance requirements of lightweight concrete in the construction industry. The polycarboxylate water reducer added in this application can further improve the dispersibility of the composite fiber gel in the concrete, and at the same time make up for the pore defects introduced by the fiber material by reducing the water-binder ratio. This shows that this application significantly improves the toughness, mechanical strength and other properties of lightweight concrete through multi-scale synergistic effects (macro rubber particle energy consumption, mesoscopic fiber bridging, microscopic whisker deflection, nanoscale pore optimization), providing a theoretical support for the design of high-performance lightweight concrete. Detailed implementation mode

[0039] The present invention provides a high-toughness anti-cracking lightweight concrete, which comprises the following raw materials in parts by mass:

[0040] 90 - 160 parts of cement, 22 - 45 parts of silica fume, 55 - 120 parts of fly ash, 140 - 260 parts of fine aggregate, 120 - 230 parts of coarse aggregate, 35 - 65 parts of modified waste rubber particles, 80 - 140 parts of modified composite fiber gel, 20 - 45 parts of polycarboxylate water reducer, 10 - 30 parts of CaCO3 whiskers, and 60 - 120 parts of water.

[0041] In the present invention, the cement preferably includes one or more of Portland cement, slag Portland cement, and pozzolanic Portland cement, further preferably includes Portland cement, slag Portland cement or pozzolanic Portland cement, and more preferably is pozzolanic Portland cement.

[0042] In the present invention, the particle size conditions of the silica fume preferably include: D 50 ≤0.3 μm, D 90 ≤1 μm.

[0043] In the present invention, the particle size condition of the fly ash is preferably that the residue on a 45-μm sieve is ≤ 30 wt%.

[0044] In the present invention, the fine aggregate preferably includes ceramsite fine aggregate.

[0045] In the present invention, the particle size of the fine aggregate is preferably ≤ 5 mm.

[0046] In the present invention, the coarse aggregate preferably includes ceramsite coarse aggregate.

[0047] In the present invention, the particle size of the coarse aggregate is preferably 10 - 20 mm, more preferably 10 - 15 mm, and still more preferably 12 - 15 mm.

[0048] In the present invention, the preparation method of the modified waste rubber particles preferably includes the following steps:

[0049] Mix waste rubber with a particle size of 80 - 200 mesh and hydrogen peroxide solution, and perform surface oxidation treatment to obtain activated waste rubber;

[0050] Mix lignin, silane coupling agent and solvent, and perform modification treatment to obtain silane-modified lignin;

[0051] Mix silane-modified lignin, activated waste rubber and dispersant, and perform mixing and kneading to obtain modified waste rubber particles.

[0052] In the present invention, for the particle size of the waste rubber, it can be crushed to the required mesh number.

[0053] In the present invention, the waste rubber is preferably pretreated before the modification treatment, and the pretreatment process preferably includes: soaking the waste rubber in an inorganic base solution, and then successively washing and drying.

[0054] In the present invention, the mass concentration of the inorganic base solution is preferably 2 - 10%, more preferably 4 - 7%, and still more preferably 5%; the inorganic base in the inorganic base solution is preferably NaOH.

[0055] In the present invention, the soaking time is preferably 12 - 24 h, more preferably 18 - 24 h, and still more preferably 24 h.

[0056] In the present invention, the sources of the waste rubber preferably include but are not limited to waste tires, waste rubber tubes, waste latex products, and waste rubber shoes.

[0057] In the present invention, the mass concentration of the hydrogen peroxide solution is preferably 20 - 40%, more preferably 20 - 30%, and still more preferably 25%.

[0058] In the present invention, the temperature of the surface oxidation treatment is preferably 45-75°C, more preferably 55-70°C, and still more preferably 65°C; the time of the surface oxidation treatment is preferably 4-10 h, more preferably 5-7 h, and still more preferably 6 h.

[0059] In the present invention, the silane coupling agent preferably includes one or more of KH-550, KH-570, and KH-590, more preferably includes KH-550, KH-570 or KH-590, and still more preferably is KH-550.

[0060] In the present invention, the solvent is preferably a mixed solution of ethanol and water.

[0061] In the present invention, the volume ratio of ethanol to water is preferably 4:1 to 2, more preferably 4:1 to 1.5, and still more preferably 4:1.

[0062] In the present invention, the mass ratio of lignin to the silane coupling agent is preferably 1:0.02 to 0.2, more preferably 1:0.08 to 0.15, and still more preferably 1:0.1.

[0063] In the present invention, the ratio of the mass of lignin to the volume of the solvent is preferably 1 g:15-30 mL, more preferably 1 g:15-20 mL, and still more preferably 1 g:15 mL.

[0064] In the present invention, the pH of the modification treatment is preferably 4-6, more preferably 4.5-5.5, and still more preferably 5; the temperature of the modification treatment is preferably 60-80°C, more preferably 65-75°C, and still more preferably 70°C; the time of the modification treatment is preferably 2-4 h, more preferably 3-4 h, and still more preferably 4 h.

[0065] In the present invention, the reagent for adjusting the pH of the modification treatment is preferably acetic acid.

[0066] In the present invention, the mass ratio of the silane-modified lignin to the activated waste rubber is preferably 1:5 to 10, more preferably 1:6 to 8, and still more preferably 1:8.

[0067] In the present invention, the dispersant is preferably zinc stearate.

[0068] In the present invention, the mass ratio of the silane-modified lignin to the dispersant is preferably 1:0.1 to 0.3, more preferably 1:0.15 to 0.25, and still more preferably 1:0.2.

[0069] In the present invention, the temperature of the kneading is preferably 120 to 150 °C, more preferably 130 to 145 °C, and even more preferably 140 °C; the shear speed of the kneading is preferably 100 to 400 rpm, more preferably 150 to 300 rpm, and even more preferably 250 rpm; the time of the kneading is preferably 0.2 to 1 h, more preferably 0.4 to 0.8 h, and even more preferably 0.5 h.

[0070] In the present invention, after the kneading, it further includes crushing and screening; the screening is preferably through a 100-mesh sieve.

[0071] In the present invention, the preparation method of the modified composite fiber gel preferably includes the following steps:

[0072] Mix plant fibers, basalt fibers, and aqueous polyurethane emulsion, and carry out modification to obtain modified plant fibers and modified basalt fibers; disperse the modified plant fibers, modified basalt fibers, and sodium alginate solution, and perform vacuum defoaming to obtain the modified composite fiber gel.

[0073] In the present invention, the sources of the plant fibers preferably include but are not limited to flax fibers, bamboo fibers, and jute fibers.

[0074] In the present invention, the plant fibers are preferably pretreated before modification; the specific operation of the pretreatment is preferably: immersing the plant fibers in an alkali solution for water bath heating, and successively performing washing, drying, and pulverizing.

[0075] In the present invention, the mass concentration of the alkali solution is preferably 2 to 10%, more preferably 4 to 7%, and even more preferably 5%; the alkali in the alkali solution is preferably NaOH.

[0076] In the present invention, the temperature of the water bath heating is preferably 70 to 90 °C, more preferably 75 to 85 °C, and even more preferably 80 °C; the time of the water bath heating is preferably 1 to 3 h, more preferably 1.5 to 2.5 h, and even more preferably 2 h.

[0077] In the present invention, the length of the plant fibers is preferably 1 to 10 mm, more preferably 2 to 9 mm, and even more preferably 4 to 8 mm.

[0078] In the present invention, the basalt fibers are preferably pretreated before modification; the specific operation of the pretreatment is preferably: immersing the basalt fibers in a silane coupling agent solution for ultrasonic treatment, and then drying.

[0079] In the present invention, the silane coupling agent solution is preferably a mixture of KH-550 and ethanol.

[0080] In the present invention, the mass concentration of the silane coupling agent solution is preferably 0.2 to 2%, more preferably 0.6 to 1.2%, and still more preferably 1%.

[0081] In the present invention, the time of the ultrasonic treatment is preferably 20 to 60 min, more preferably 25 to 40 min, and still more preferably 30 min.

[0082] In the present invention, the length of the basalt fiber is preferably 1 to 3 mm.

[0083] In the present invention, the mass ratio of the plant fiber to the basalt fiber is preferably 6 to 8:4 to 2, more preferably 6.5 to 7.5:3.5 to 2.5, and still more preferably 7:3.

[0084] In the present invention, the mass concentration of the aqueous polyurethane emulsion is preferably 10 to 30%, more preferably 15 to 25%, and still more preferably 20%.

[0085] In the present invention, the sum of the masses of the plant fiber and the basalt fiber is preferably 20 to 50% of the mass of the aqueous polyurethane emulsion, more preferably 20 to 30%, and still more preferably 25%.

[0086] In the present invention, the temperature of the modification is preferably 50 to 60 °C, more preferably 50 to 55 °C, and still more preferably 50 °C; the time of the modification is preferably 2 to 4 h, more preferably 2.5 to 3.5 h, and still more preferably 3 h.

[0087] In the present invention, after the modification, it preferably further includes: centrifuging and drying in sequence.

[0088] In the present invention, the mass concentration of the sodium alginate solution is preferably 3 to 5%, more preferably 3.5 to 4.5%, and still more preferably 4%.

[0089] In the present invention, the sum of the masses of the modified plant fiber and the modified basalt fiber is preferably 5 to 20% of the mass of the sodium alginate solution, more preferably 8 to 15%, and still more preferably 10%.

[0090] In the present invention, the rotation speed of the dispersion is preferably 5000 to 6000 rpm, more preferably 5000 to 5500 rpm, and still more preferably 5000 rpm; the time of the dispersion is preferably 10 to 30 min, more preferably 10 to 20 min, and still more preferably 10 min.

[0091] In the present invention, the pressure of the vacuum degassing is preferably -0.01 to -0.1 MPa, more preferably -0.05 to -0.1 MPa, and still more preferably -0.1 MPa; the time of the vacuum degassing is preferably 10 to 60 min, more preferably 10 to 30 min, and still more preferably 20 min.

[0092] In the present invention, the water reducing rate of the polycarboxylate water reducer is preferably ≥25%.

[0093] In the present invention, the aspect ratio of the CaCO3 whisker is preferably 20 to 30; the length of the CaCO3 whisker is preferably 20 to 30 μm.

[0094] In the present invention, the mass parts of the cement are preferably 100 to 150 parts, more preferably 110 to 130 parts, and still more preferably 120 parts.

[0095] In the present invention, the mass parts of the silica fume are preferably 25 to 40 parts, more preferably 30 to 40 parts, and still more preferably 35 parts.

[0096] In the present invention, the mass parts of the fly ash are preferably 60 to 100 parts, more preferably 75 to 90 parts, and still more preferably 85 parts.

[0097] In the present invention, the mass parts of the fine aggregate are preferably 160 to 240 parts, more preferably 175 to 200 parts, and still more preferably 185 parts.

[0098] In the present invention, the mass parts of the coarse aggregate are preferably 150 to 220 parts, more preferably 170 to 210 parts, and still more preferably 203 parts.

[0099] In the present invention, the mass parts of the modified waste rubber particles are preferably 40 to 65 parts, more preferably 45 to 60 parts, and still more preferably 60 parts.

[0100] In the present invention, the mass parts of the modified composite fiber gel are preferably 90 to 130 parts, more preferably 90 to 100 parts, and still more preferably 90 parts.

[0101] In the present invention, the mass parts of the polycarboxylate water reducer are preferably 25 to 40 parts, more preferably 28 to 35 parts, and still more preferably 32 parts.

[0102] In the present invention, the mass parts of the CaCO3 whisker are preferably 15 to 30 parts, more preferably 25 to 30 parts, and still more preferably 30 parts.

[0103] In the present invention, the mass parts of water are preferably 80 - 115 parts, more preferably 95 - 110 parts, and still more preferably 102 parts.

[0104] The present invention also provides a preparation method of high - toughness anti - cracking lightweight concrete, comprising the following steps:

[0105] Mix cement, silica fume, fly ash, fine aggregate, coarse aggregate, modified waste rubber particles, and CaCO3 whiskers according to mass parts to obtain a dry - mix material;

[0106] Mix the modified composite fiber gel and a partial amount of water according to mass parts to obtain a dispersion slurry;

[0107] Mix the polycarboxylate water - reducing agent and the remaining amount of water according to mass parts to obtain a water - reducing agent solution;

[0108] Mix the dry - mix material, the water - reducing agent solution, and the dispersion slurry to obtain high - toughness anti - cracking lightweight concrete.

[0109] In the present invention, the specific preferred method for mixing cement, silica fume, fly ash, fine aggregate, coarse aggregate, modified waste rubber particles, and CaCO3 whiskers is: mix the coarse aggregate and the fine aggregate, and sequentially add cement, silica fume, fly ash, CaCO3 whiskers, and modified waste rubber particles for mixing respectively.

[0110] In the present invention, the rotation speed for mixing the modified composite fiber gel and a partial amount of water is preferably 500 - 2000 rpm, more preferably 700 - 1000 rpm, and still more preferably 800 rpm; the time is preferably 5 - 25 min, more preferably 10 - 20 min, and still more preferably 15 min.

[0111] In the present invention, the parameters for mixing in the preparation method are not limited, as long as the mixture is uniform.

[0112] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0113] Preparation Example 1

[0114] This preparation example provides a preparation method of modified waste rubber particles, comprising the following steps:

[0115] Immerse waste tires with a mesh size of 80 - 200 in an NaOH aqueous solution (5 wt%) for 24 h, and then wash and dry to obtain pretreated waste rubber;

[0116] The pretreated waste rubber is immersed in an aqueous hydrogen peroxide solution (25 wt%), and undergoes a surface oxidation reaction at 65 °C for 6 h to obtain activated waste rubber;

[0117] 1 g of lignin (enzymatic hydrolysis lignin (LIG-I type), manufactured by Shandong Longli Biotechnology Co., Ltd.), 0.1 g of silane coupling agent KH-550 and 15 mL of ethanol-water mixed solvent (ethanol: water = 4:1 v:v) are mixed evenly, acetic acid is added to adjust the pH to 5, and the mixture is modified at 70 °C for 4 h, centrifuged and dried to obtain silane-modified lignin;

[0118] The silane-modified lignin, activated waste rubber and dispersant zinc stearate are mixed. The mass ratio of silane-modified lignin to activated waste rubber is 1:8, and the mass ratio of silane-modified lignin to dispersant is 1:0.2. The mixture is kneaded in a mixer at 140 °C and 250 rpm for 0.5 h, crushed and sieved through a 100-mesh sieve to obtain modified waste rubber particles.

[0119] Preparation Example 2

[0120] This preparation example provides a method for preparing a modified composite fiber gel, which includes the following steps:

[0121] The Dendrocalamus membranaceus fiber (manufactured by Sichuan Changsheng New Material Technology Co., Ltd.) is immersed in an aqueous NaOH solution (5 wt%), heated in a water bath at 80 °C for 2 h, washed, dried and pulverized in sequence to obtain plant fibers of 4 - 8 mm;

[0122] The basalt fiber (manufactured by Shandong Liangpin New Material Co., Ltd.) is immersed in a silane coupling agent KH550-ethanol mixed solution (1 wt%) and ultrasonically treated for 30 min, then dried to obtain basalt fibers of 1 - 3 mm;

[0123] The plant fibers, basalt fibers and aqueous polyurethane emulsion (AH-K100-1, manufactured by Anhui Dawei Huatai New Material Technology Co., Ltd., diluted to 20 wt%) are mixed. The mass ratio of plant fibers to basalt fibers is 7:3, and the sum of the masses of plant fibers + basalt fibers is 25% of the mass of the aqueous polyurethane emulsion. The mixture is modified at 50 °C for 3 h, centrifuged and dried to obtain modified plant fibers and modified basalt fibers;

[0124] The modified plant fibers, modified basalt fibers and sodium alginate solution (sodium alginate is manufactured by Suzhou Zhuoxin Biotechnology Co., Ltd., and is mixed with water to prepare a 4 wt% solution) are mixed and dispersed at 5000 rpm for 10 min. The sum of the masses of modified plant fibers + modified basalt fibers is 10% of the mass of the sodium alginate solution, and vacuum degassing is carried out at -0.1 MPa for 20 min to obtain a modified composite fiber gel.

[0125] In Examples 1-2 and Comparative Examples 1-4, the cement was pozzolanic Portland cement (Guangzhou Fanshan Cement P.P32.5R);

[0126] The silica fume was special silica fume for concrete, SF-85 as-received ash, and the manufacturer was Wuxi Yiwente New Materials Co., Ltd.;

[0127] The fly ash was secondary fly ash, and the manufacturer was Dongguan Lihui Mineral Products Co., Ltd.;

[0128] The particle size of the fine ceramsite aggregate was 2-5 mm, and the manufacturer was Hubei Huiteng Lightweight Aggregate Environmental Protection Products Co., Ltd.;

[0129] The particle size of the coarse ceramsite aggregate was 12-15 mm, and the manufacturer was Hubei Huiteng Lightweight Aggregate Environmental Protection Products Co., Ltd.;

[0130] The polycarboxylate superplasticizer was TD-JSS2 polycarboxylate superplasticizer, and the manufacturer was Shaanxi Longhan Chuanghong New Building Materials Co., Ltd.;

[0131] The manufacturer of the CaCO3 whiskers was Jinan Xinsenyuan Chemical Co., Ltd.

[0132] Example 1

[0133] This example provides a high-toughness and crack-resistant lightweight concrete, which comprises the following raw materials in parts by mass: 120 parts of cement, 35 parts of silica fume, 85 parts of fly ash, 185 parts of fine aggregate, 203 parts of coarse aggregate, 60 parts of the modified waste rubber particles of Preparation Example 1, 90 parts of the modified composite fiber gel of Preparation Example 2, 32 parts of polycarboxylate superplasticizer, 30 parts of CaCO3 whiskers, and 102 parts of water.

[0134] This example also provides a preparation method of the aforementioned high-toughness and crack-resistant lightweight concrete, which comprises the following steps:

[0135] According to the parts by mass, the coarse aggregate and the fine aggregate were mixed for 3 min, and then cement, silica fume, fly ash, CaCO3 whiskers, and the modified waste rubber particles were sequentially added and mixed for 3 min respectively to obtain a dry mix;

[0136] According to the parts by mass, the modified composite fiber gel and 1 / 3 of the total amount of water were mixed at 800 rpm for 15 min to obtain a dispersion slurry;

[0137] According to the parts by mass, the polycarboxylate superplasticizer and the remaining water were mixed for 5 min to obtain a superplasticizer solution;

[0138] The superplasticizer solution and the dispersion slurry were sequentially added to the dry mix and mixed for 3 min respectively to obtain the high-toughness and crack-resistant lightweight concrete.

[0139] Example 2

[0140] This embodiment provides a high-toughness and crack-resistant lightweight concrete, which comprises raw materials in the following parts by mass: 150 parts of cement, 25 parts of silica fume, 100 parts of fly ash, 160 parts of fine aggregate, 170 parts of coarse aggregate, 45 parts of modified waste rubber particles of Preparation Example 1, 130 parts of modified composite fiber gel of Preparation Example 2, 28 parts of polycarboxylate water reducer, 22 parts of CaCO3 whiskers, and 111 parts of water. The preparation method refers to Example 1.

[0141] Comparative Example 1

[0142] This comparative example provides a lightweight concrete. Compared with Example 1, the modified waste rubber particles are deleted, and other parameter conditions are the same as those in Example 1.

[0143] Comparative Example 2

[0144] This comparative example provides a lightweight concrete. Compared with Example 1, the modified composite fiber gel is deleted, and other parameter conditions are the same as those in Example 1.

[0145] Comparative Example 3

[0146] This comparative example provides a lightweight concrete. Compared with Example 1, the CaCO3 whiskers are deleted, and other parameter conditions are the same as those in Example 1.

[0147] Comparative Example 4

[0148] This comparative example provides a lightweight concrete. Compared with Example 1, the basalt fiber during modification in Preparation Example 2 is replaced with pretreated plant fiber, that is, the modified composite fiber gel is replaced with modified plant fiber gel, and other parameter conditions are the same as those in Example 1.

[0149] After curing the lightweight concretes prepared in Examples 1-2 and Comparative Examples 1-4 for 28 days in an environment with a temperature of 20°C and a relative humidity of more than 95%, the flexural strength and compressive strength are tested according to the national standard GB / T 50107-2019 "Standard for Inspection and Evaluation of Concrete Strength". The total cracking area per unit area is measured and calculated 24 hours after the concrete is poured. The test results are shown in Table 1.

[0150] Table 1. Test results of Examples 1-2 and Comparative Examples 1-4

[0151]

[0152] As can be seen from Table 1, after removing the modified rubber particles in Comparative Example 1, the aggregate system became denser. Although its compressive strength increased to some extent, the elastic buffering effect of the rubber particles was lost, greatly reducing the toughness, resulting in the disappearance of the crack bridging ability of the rubber and an increase in the cracking area of the concrete. In Comparative Example 2, after removing the composite fiber gel, the toughening effect of the fibers was lost, and the flexural strength decreased significantly. Moreover, due to the loss of the ability of the fiber network to inhibit crack propagation, the cracking area increased sharply. In Comparative Example 3, after removing the CaCO3 whiskers, the compressive and flexural strengths decreased slightly because of the loss of the synergistic toughening effect of the whiskers, and at the same time, the cracking area increased slightly. In Comparative Example 4, after replacing the basalt fibers with plant fibers, since the modulus and strength of the plant fibers were lower than those of the basalt fibers, the compressive and flexural strengths both decreased. Moreover, due to the weak alkali resistance and interfacial bonding of the plant fibers, the cracking area increased and the crack resistance effect decreased. This shows that each component in this application is indispensable, and can synergistically improve the toughness and crack resistance performance of lightweight concrete on the premise of ensuring the compressive strength. Finally, the apparent densities of the lightweight concretes in Examples 1 to 2 were measured to be 1658 kg / m 3 and 1571 kg / m 3 , respectively, which is a lightweight concrete with excellent performance.

[0153] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A high-toughness and crack-resistant lightweight concrete, characterized in that, The raw materials include the following parts by mass: 90 - 160 parts of cement, 22 - 45 parts of silica fume, 55 - 120 parts of fly ash, 140 - 260 parts of fine aggregate, 120 - 230 parts of coarse aggregate, 35 - 65 parts of modified waste rubber particles, 80 - 140 parts of modified composite fiber gel, 20 - 45 parts of polycarboxylate superplasticizer, 10 - 30 parts of CaCO3 whiskers, and 60 - 120 parts of water.

2. The high-toughness anti-cracking lightweight concrete according to claim 1, characterized in that, The cement includes one or more of portland cement, slag portland cement, and pozzolanic portland cement.

3. A highly ductile and crack-resistant lightweight concrete according to claim 1, wherein, The particle size conditions of the silica fume include: D 50 ≤ 0.3 μm, D 90 ≤ 1 μm; The particle size condition of the fly ash is that the residue on a 45μm sieve is ≤ 30wt%.

4. A high-toughness and crack-resistant lightweight concrete according to claim 1, characterized in that, The fine aggregate includes ceramsite fine aggregate; the particle size of the fine aggregate is ≤ 5mm; The coarse aggregate includes ceramsite coarse aggregate; the particle size of the coarse aggregate is 10 - 20mm.

5. A highly ductile and crack-resistant lightweight concrete according to claim 1, characterized in that, The preparation method of the modified waste rubber particles includes the following steps: Mix waste rubber with a particle size of 80 - 200 meshes and hydrogen peroxide solution for surface oxidation treatment to obtain activated waste rubber; Mix lignin, silane coupling agent, and solvent for modification treatment to obtain silane-modified lignin; Mix silane-modified lignin, activated waste rubber, and dispersant for mixing and kneading to obtain modified waste rubber particles; Among them, the temperature of the surface oxidation treatment is 45 - 75°C, and the time of the surface oxidation treatment is 4 - 10h; The silane coupling agent includes one or more of KH-550, KH-570, and KH-590; The pH of the modification treatment is 4 - 6, the temperature of the modification treatment is 60 - 80°C, and the time of the modification treatment is 2 - 4h; The mass ratio of the silane-modified lignin to the activated waste rubber is 1:5 - 10; The temperature of the mixing and kneading is 120 - 150°C, the shear rotation speed of the mixing and kneading is 100 - 400rpm, and the time of the mixing and kneading is 0.2 - 1h.

6. A high-toughness and crack-resistant lightweight concrete according to claim 1, characterized in that, The preparation method of the modified composite fiber gel includes the following steps: Mix plant fiber, basalt fiber, and aqueous polyurethane emulsion for modification to obtain modified plant fiber and modified basalt fiber; disperse the modified plant fiber, modified basalt fiber, and sodium alginate solution, and perform vacuum degassing to obtain modified composite fiber gel; Among them, the mass ratio of the plant fiber to the basalt fiber is 6 - 8:4 - 2; The temperature of the modification is 50 - 60°C, and the time of the modification is 2 - 4h; The mass concentration of the sodium alginate solution is 3 - 5%; The sum of the masses of the modified plant fiber and the modified basalt fiber is 5 - 20% of the mass of the sodium alginate solution; The rotation speed of the dispersion is 5000 - 6000rpm, and the time of the dispersion is 10 - 30min; The pressure of the vacuum degassing is -0.01 - -0.1MPa, and the time of the vacuum degassing is 10 - 60min.

7. A high-toughness anti-cracking lightweight concrete according to claim 1, characterized in that, The water reducing rate of the polycarboxylate superplasticizer is ≥ 25%.

8. A highly ductile and crack-resistant lightweight concrete according to claim 1, characterized in that, The aspect ratio of the CaCO3 whiskers is 20 - 30, and the length of the CaCO3 whiskers is 20 - 30μm.

9. The preparation method of a highly tough and crack-resistant lightweight concrete according to any one of claims 1 to 8, characterized in that, It includes the following steps: Mix cement, silica fume, fly ash, fine aggregate, coarse aggregate, modified waste rubber particles, and CaCO3 whiskers by mass parts to obtain a dry mix; Mix the modified composite fiber gel with a partial amount of water by mass parts to obtain a dispersion slurry; Mix the polycarboxylate water reducer with the remaining amount of water by mass parts to obtain a water reducer solution; Mix the dry mix, the water reducer solution, and the dispersion slurry to obtain high-toughness crack-resistant lightweight concrete.

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