Preparation method of high-impermeability fiber-reinforced recycled aggregate concrete and product

Abstract

The invention discloses a preparation method of high-impermeability fiber-reinforced recycled aggregate concrete and a product, and belongs to the technical field of building materials, and the high-impermeability fiber-reinforced recycled aggregate concrete is prepared by taking cement, silica fume, polypropylene fiber, calcined coal gangue fine aggregate, recycled coarse bone, water glass and sodium hydroxide as raw materials. The concrete can have high anti-permeability performance, and the early strength performance of the concrete can be improved, so that the concrete has ultrahigh strength performance.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a preparation method and a product of fiber-reinforced recycled aggregate concrete with high impermeability. Background Art

[0002] With the rapid development of industries such as petroleum and chemical industry, the emission and infiltration of harmful gases and industrial wastewater have caused great pollution to the air, rivers, lakes and even groundwater resources, causing serious damage to the environment. Therefore, the permeability of concrete used in large industrial buildings is particularly important. Once the concrete is damaged or the anti-permeability is insufficient, it will cause pollution, leakage and other accidents, directly affecting the use and safety of the building.

[0003] The permeability of concrete refers to the ability of concrete to resist the penetration of pressure (water or oil). Factors that affect the permeability of concrete include water-cement ratio, degree of cement hydration, size of coarse aggregate, gradation of aggregate, and the interface bonding between aggregate and cement paste. Ordinary concrete materials have poor resistance to the penetration of pressure water. After the pressure water penetrates into the concrete, it causes the concrete to expand and crack, and as a carrier of the corrosive medium, it accelerates its diffusion into the concrete, thereby accelerating the deterioration of the concrete performance. The durability of concrete continues to decline under the action of dry-wet cycles, freeze-thaw cycles, brine erosion and alkali aggregates. In the process of reaching destruction and failure, the penetration of water plays a very important role. Therefore, improving the impermeability of concrete has become an indispensable part of improving the durability of concrete.

[0004] Impermeable concrete refers to concrete with an impermeability grade equal to or greater than P6. Generally, impermeable concrete is divided into P6, P8, and P12 according to different impermeability pressures. The so-called high impermeability of concrete means that the concrete has extremely high impermeability performance in accordance with actual engineering requirements, and the invisible cracks and invisible pores of concrete are most effectively controlled. For large industrial buildings in industries such as petrochemicals that have extremely strict requirements, in terms of penetration height, we strive to achieve zero millimeter penetration, or even complete water isolation.

[0005] Concrete made from aggregates with small pores, large bulk density and good grading may not necessarily have good impermeability. This is because no matter it is continuous grading or discontinuous grading, the high-density concrete obtained only increases the sand and gravel to a certain extent to reduce the possibility of pore penetration between cement aggregates. There are still many capillary pores between cement and sand, and there are also a large number of cracks between the contact surface of cement and aggregate. Therefore, the impermeability of concrete is still very poor.

[0006] The existing methods for improving the impermeability of concrete do not control the pores between cement, sand and the contact surface between cement and aggregate, resulting in poor impermeability of concrete. Summary of the invention

[0007] In order to solve the above technical problems, the present invention proposes a preparation method and product of fiber-reinforced recycled aggregate concrete with high impermeability.

[0008] To achieve the above object, the present invention provides a fiber-reinforced recycled aggregate concrete with high impermeability, which comprises the following raw materials by weight: 300-400 parts of cement, 10-50 parts of silica fume, 0.5-3 parts of polypropylene fiber, 600-800 parts of calcined coal gangue fine aggregate, 800-1000 parts of recycled coarse aggregate, 60-70 parts of water glass, and 30-40 parts of sodium hydroxide;

[0009] The raw materials of the high impermeability fiber reinforced recycled aggregate concrete also include water, and the water-cement ratio is 0.4-0.45;

[0010] The recycled coarse aggregate is obtained by crushing waste concrete test blocks. According to the mass percentage, the particle size of the recycled coarse aggregate is: 4.75-6.15 mm accounts for 20-35%, 6.15-8.5 mm accounts for 40-60%, and 8.5-11 mm accounts for 20-25%. The particle size of the recycled coarse aggregate is not 4.75 mm;

[0011] Calculated by mass percentage, the particle size of the calcined coal gangue fine aggregate is: 0.075-0.15mm accounts for 5-20%, 0.15-0.3mm accounts for 5-15%, 0.3-0.6mm accounts for 15-45%, 0.6-1.0mm accounts for 20-30%, 1.0-2.5mm accounts for 10-20%, and 2.5-4.75mm accounts for 10-15%.

[0012] The structure and porosity of concrete are one of the important factors affecting the anti-seepage ability of concrete. The present invention can make the rheological properties of concrete, the cohesive structure of cement slurry and the density after hardening better by controlling the water-cement ratio. Too large or too small a water-cement ratio will affect the strength of concrete. The present invention adjusts the gradation of fine aggregate and coarse aggregate to minimize the cracks generated at the interface between aggregate and cement slurry and the holes formed under the larger aggregate. At the same time, the addition of calcined coal gangue, water glass and sodium hydroxide can make the cement hydration more complete and the internal structure more dense, so as to obtain concrete with good anti-seepage performance. The aggregate gradation of the present invention is moderate, the porosity is small, and the concrete density is large, so its anti-seepage ability is good.

[0013] The polypropylene fiber is a monofilament polypropylene fiber. The present invention changes the internal structure of concrete by adding polypropylene fiber, and further ensures the high impermeability of concrete. After the polypropylene fiber is added into the concrete and stirred, the polypropylene fiber can be quickly and easily mixed with other components and evenly distributed because of its strong binding force with aggregate, so that a uniform random support system can be formed inside the concrete. During the concrete hardening process, due to the chemical shrinkage of the cement paste, tensile stress is generated at the bonding surface between the cement paste and the aggregate, so there are a large number of extremely fine micro cracks in the concrete, which are very likely to cause stress concentration and cause damage when the concrete is stressed. After adding the polypropylene fiber, when the cement matrix shrinks, the polypropylene fiber plays a role of fine reinforcement and consumes energy, which can inhibit the process of concrete cracking, effectively reduce the tiny cracks caused by the shrinkage of the concrete, and in addition to improving the impermeability of the concrete, also greatly improve the crack resistance and toughness of the hardened concrete.

[0014] The preparation method of the calcined gangue fine aggregate is as follows: calcining the original gangue at a temperature of 850-950°C for 3-4 hours. Unburned gangue has a stable crystal structure, and its atoms, ions, molecules and other particles are arranged in order according to certain rules, and the gelling effect is very weak even after being ground. The present invention performs thermal activation treatment on the gangue, and the kaolin component therein will be dehydrated and decomposed to generate metakaolin and amorphous silicon oxide and aluminum oxide, and the original crystalline phase will be decomposed and destroyed, which greatly improves the activity of the gangue. Adding the calcined gangue fine aggregate to concrete can not only improve the early strength of the concrete, but also significantly improve the compressive and flexural strength of the concrete.

[0015] Furthermore, the original coal gangue is crushed to a particle size of ≤5 mm before calcination.

[0016] The modulus of the water glass is 1.2-1.4.

[0017] Furthermore, the polypropylene fiber is a modified polypropylene fiber. The preparation method of the modified polypropylene fiber is: placing the polypropylene fiber in a sodium carbonate solution, heating it to 80° C. and keeping it warm for 5 minutes to obtain a solution A, adding cocamidopropyl betaine and polyethylene glycol to the solution A, and performing ultrasonic treatment. After the ultrasonic treatment, taking out the polypropylene fiber, drying it, and obtaining the modified polypropylene fiber.

[0018] The concentration of the sodium carbonate solution is 10-15 wt %.

[0019] The mass ratio of the cocamidopropyl betaine to the polyethylene glycol is 1:1.

[0020] The polypropylene fiber is treated with sodium carbonate solution to increase the surface activation energy of the polypropylene fiber, and then heat-treated to further increase the activation energy, which is beneficial to improve the subsequent binding ability of the polypropylene fiber with cocamidopropyl betaine and polyethylene glycol. In the process of binding with cocamidopropyl betaine and polyethylene glycol, ultrasound can reduce the aggregation of polypropylene fibers in the dispersion system, promote the effective dispersion of polypropylene fibers, and prevent the generation of flocculent or hair-ball-like aggregated fibers. The polypropylene fiber can form hydrogen bonds or covalent bonds with the active groups of the two, spread on the surface of the polypropylene fiber and form a continuous new surface layer, repair, fill, and wrap the defects on the surface of the polypropylene fiber, and further increase the uniformity and impermeability of the concrete.

[0021] The present invention also provides a method for preparing the above-mentioned high impermeability fiber-reinforced recycled aggregate concrete, which comprises accurately weighing each raw material by weight, mixing cement, silica fume and water evenly, adding polypropylene fiber, mixing evenly, then adding calcined coal gangue fine aggregate, recycled coarse aggregate, water glass and sodium hydroxide, mixing evenly, and curing to obtain the high impermeability fiber-reinforced recycled aggregate concrete.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] Silica fume has a volcanic ash effect and can react with calcium hydroxide (Ca(OH)2) in cement hydration products to generate more calcium silicate hydrate (CSH) gel, thereby filling the pores and making the concrete structure more compact. At the same time, due to the small particle size of silica fume, it can fill the large pores in the concrete, optimize the pore structure distribution, and reduce the proportion of harmful pores, thereby improving the impermeability and early strength of the concrete. The addition of silica fume can also provide "nucleation" sites for cement hydration, promote the early hydration reaction of cement, and significantly improve the early strength of concrete. Calcined coal gangue aggregate has a certain activity and can react chemically in an alkaline environment to generate a dense gel layer, thereby improving the strength and impermeability of concrete. Water glass and sodium hydroxide, as alkaline activators, can further activate the activity of silica fume and coal gangue aggregates, promote their synergistic reaction with cement, and generate more gelling substances, thereby improving the early strength and density of concrete. The use of recycled coarse aggregate not only reduces costs, but also reduces dependence on natural aggregates. At the same time, the present invention improves the performance of concrete by optimizing the gradation of coarse aggregate and fine aggregate. Polypropylene fiber and / or modified basalt fiber can play a crack-blocking role in concrete, by bridging cracks, preventing the expansion of cracks, improving the microstructure of concrete, thereby further improving the toughness and impermeability of concrete. The synergistic effect between the raw materials of the present invention makes the pore structure of concrete more compact and the hydration reaction more sufficient, thereby significantly improving the early strength and impermeability of concrete. The addition of silica fume, calcined coal gangue fine aggregate and polypropylene fiber plays a key role in the improvement of early strength and microstructure. The concrete impermeability level prepared by the present invention can reach P12 level. The concrete of the present invention has high compressive and flexural strength and high early strength, and the 3d compressive strength can reach 130.2MPa, the 3d flexural strength can reach 18.1MPa, the 28d compressive strength can reach 150.2MPa, and the 28d flexural strength can reach 31.2MPa. DETAILED DESCRIPTION

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0026] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0027] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0028] Unless otherwise specified, the room temperature in the present invention is 25±2°C.

[0029] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0030] Some embodiments of the present invention provide a fiber-reinforced recycled aggregate concrete with high impermeability, which includes the following raw materials in parts by weight: 300-400 parts of cement, 10-50 parts of silica fume, 0.5-3 parts of polypropylene fiber, 600-800 parts of calcined coal gangue fine aggregate, 800-1000 parts of recycled coarse aggregate, 60-70 parts of water glass, and 30-40 parts of sodium hydroxide;

[0031] The raw materials of high impermeability fiber-reinforced recycled aggregate concrete also include water, with a water-cement ratio of 0.4-0.45;

[0032] The recycled coarse aggregate is obtained by crushing the waste concrete test blocks. According to the mass percentage, the particle size of the recycled coarse aggregate is: 4.75-6.15mm accounts for 20-35%, 6.15-8.5mm accounts for 40-60%, 8.5-11mm accounts for 20-25%. The particle size of the recycled coarse aggregate is not 4.75mm;

[0033] Calculated by mass percentage, the particle size of calcined coal gangue fine aggregate is: 0.075-0.15mm accounts for 5-20%, 0.15-0.3mm accounts for 5-15%, 0.3-0.6mm accounts for 15-45%, 0.6-1.0mm accounts for 20-30%, 1.0-2.5mm accounts for 10-20%, and 2.5-4.75mm accounts for 10-15%.

[0034] The structure and porosity of concrete are one of the important factors affecting the anti-seepage ability of concrete. The present invention can make the rheological properties of concrete, the cohesive structure of cement slurry and the density after hardening better by controlling the water-cement ratio. Too large or too small a water-cement ratio will affect the strength of concrete. The present invention adjusts the gradation of fine aggregate and coarse aggregate to minimize the cracks generated at the interface between aggregate and cement slurry and the holes formed under the larger aggregate. At the same time, the addition of calcined coal gangue, water glass and sodium hydroxide can make the cement hydration more complete and the internal structure more dense, so as to obtain concrete with good anti-seepage performance. The aggregate gradation of the present invention is moderate, the porosity is small, and the concrete density is large, so its anti-seepage ability is good.

[0035] The polypropylene fiber is a monofilament polypropylene fiber. The present invention changes the internal structure of the concrete by adding the polypropylene fiber, and further ensures the high impermeability of the concrete. After the polypropylene fiber is added into the concrete and stirred, the polypropylene fiber can be quickly and easily mixed with other components and evenly distributed because of its strong binding force with the aggregate, and can form a uniform random support system inside the concrete. During the concrete hardening process, due to the chemical shrinkage of the cement slurry, tensile stress is generated at the bonding surface between the cement slurry and the aggregate, so there are a large number of extremely fine micro cracks in the concrete, and these micro cracks are very likely to cause stress concentration and cause damage when the concrete is stressed. After adding the polypropylene fiber, when the cement matrix shrinks, the polypropylene fiber plays a role of fine reinforcement and consumes energy, which can inhibit the process of concrete cracking, effectively reduce the tiny cracks caused by the shrinkage of the concrete, and in addition to improving the impermeability of the concrete, also greatly improve the crack resistance and toughness of the hardened concrete.

[0036] In an embodiment of the present invention, the preparation method of calcined gangue fine aggregate is: calcining the original gangue at a temperature of 850-950°C for 3-4 hours. Unburned gangue has a stable crystal structure, and its atoms, ions, molecules and other particles are arranged in order according to a certain rule, and the gelling effect is very weak even after grinding. The present invention performs thermal activation treatment on the gangue, and the kaolin component therein will be dehydrated and decomposed to generate metakaolin and amorphous silicon oxide and aluminum oxide, and the original crystalline phase will be decomposed and destroyed, which greatly improves the activity of the gangue. Adding the calcined gangue fine aggregate to concrete can not only improve the early strength of the concrete, but also significantly improve the compressive and flexural strength of the concrete.

[0037] In the embodiment of the present invention, the original coal gangue is crushed to a particle size of ≤5 mm before calcination.

[0038] In the embodiment of the present invention, the modulus of water glass is 1.2-1.4. When the modulus of water glass is low, the strength of concrete increases as the modulus decreases, but after exceeding a certain range, the strength decreases. When the modulus of water glass is 1.2-1.4, the concrete has the best performance in terms of impermeability, acid resistance and strength.

[0039] In other embodiments of the present invention, the polypropylene fiber is a modified polypropylene fiber, and the preparation method of the modified polypropylene fiber is: placing the polypropylene fiber in a sodium carbonate solution, heating to 80° C. and keeping warm for 5 minutes, adding cocamidopropyl betaine and polyethylene glycol, and performing ultrasonic treatment. After the ultrasonic treatment, the polypropylene fiber is taken out and dried to obtain the modified polypropylene fiber.

[0040] In an embodiment of the present invention, the concentration of the sodium carbonate solution is 10-15 wt %.

[0041] In an embodiment of the present invention, the mass ratio of cocamidopropyl betaine to polyethylene glycol is 1:1.

[0042] The polypropylene fiber is treated with sodium carbonate solution to increase the surface activation energy of the polypropylene fiber, and then heat-treated to further increase the activation energy, which is beneficial to improve the subsequent binding ability of the polypropylene fiber with cocamidopropyl betaine and polyethylene glycol. In the process of binding with cocamidopropyl betaine and polyethylene glycol, ultrasound can reduce the aggregation of polypropylene fibers in the dispersion system, promote the effective dispersion of polypropylene fibers, and prevent the generation of flocculent or hair-ball-like aggregated fibers. The polypropylene fiber can form hydrogen bonds or covalent bonds with the active groups of the two, spread on the surface of the polypropylene fiber and form a continuous new surface layer, repair, fill, and wrap the defects on the surface of the polypropylene fiber, and further increase the uniformity and impermeability of the concrete.

[0043] Some embodiments of the present invention also provide a method for preparing the above-mentioned high impermeability fiber-reinforced recycled aggregate concrete, which comprises accurately weighing each raw material by weight, mixing cement, silica fume and water evenly, adding polypropylene fiber, mixing evenly, then adding calcined coal gangue fine aggregate, recycled coarse aggregate, water glass and sodium hydroxide, mixing evenly, and curing to obtain high impermeability fiber-reinforced recycled aggregate concrete.

[0044] In the following examples of the present invention and comparative examples, "curing" refers to standard curing.

[0045] In some embodiments of the present invention, the raw materials of the high impermeability fiber-reinforced recycled aggregate concrete further include 0.2-0.8 parts of modified basalt fiber.

[0046] The preparation method of the modified basalt fiber is as follows: adding sophorolipids to basalt fibers, the mass ratio of basalt fibers to sophorolipids is 1:3, reacting at 35°C for 20 minutes, and obtaining modified basalt fibers. Sophorolipids are both lipophilic and hydrophilic. Sophorolipids can reduce the surface energy of basalt fibers, improve the wettability and dispersibility of basalt fibers, which helps basalt fibers to better combine with the matrix and improve interfacial compatibility. A protective film will be formed on the surface of basalt fibers treated with sophorolipids, thereby improving the impermeability, wear resistance and toughness of basalt fibers, and also improving the dispersibility and interfacial bonding properties of basalt fibers in the matrix. The composition of basalt fibers treated with sophorolipids has changed, and calcium silicate compounds (CSH) can be better formed in concrete, which is the main substance for improving the strength of concrete. Therefore, adding modified basalt fibers can further improve the strength and impermeability of concrete.

[0047] When the raw materials of the fiber-reinforced recycled aggregate concrete with high impermeability of the present invention contain modified basalt fibers, the modified basalt fibers are added together with polypropylene fibers during the preparation of the concrete.

[0048] The invention can prepare high-strength and high-impermeability concrete without adding a water reducing agent by adjusting the gradation of coarse and fine aggregates, and by adjusting the type, proportion and water-cement ratio of each component.

[0049] The term "fine aggregate" refers to aggregate with a particle size less than 4.75 mm, and the term "coarse aggregate" refers to aggregate with a particle size greater than 4.75 mm.

[0050] In the following embodiments and comparative examples of the present invention, cement is Lafarge ordinary silicate 42.5 grade cement; polypropylene fiber is Shandong Taian Tongban brand TB19 monofilament polypropylene fiber; silica fume is purchased from Lingshou County Jinyuan Mining Processing Plant; basalt fiber is purchased from Hunan Bangbei Basalt Co., Ltd., and its single fiber tensile strength is 2.25×10 3 MPa; cocamidopropyl betaine was purchased from Shandong Yousuo Chemical Technology Co., Ltd.; polyethylene glycol was purchased from Aladdin Reagent (Shanghai) Co., Ltd.

[0051] In the following examples and comparative examples of the present invention, the main chemical components (%) of the original coal gangue are shown in Table 1.

[0052] Table 1

[0053] <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[SO3]]> Loss on ignition 60.23 15.75 6.13 3.58 3.43 0.71 0.78

[0054] In the following examples and comparative examples of the present invention, unless otherwise specified, "parts" refer to parts by weight.

[0055] It should be pointed out that the matters not described in detail in the present invention are all conventional operating means in the field and are not the focus of the present invention. For example, specific methods such as crushing of original coal gangue are all completed by conventional methods.

[0056] The technical solution of the present invention is further illustrated by the following embodiments.

[0057] Example 1

[0058] This embodiment provides a fiber-reinforced recycled aggregate concrete with high impermeability, which is composed of the following raw materials by weight: 350 parts of cement, 30 parts of silica fume, 2 parts of polypropylene fiber, 700 parts of calcined coal gangue fine aggregate, 900 parts of recycled coarse aggregate, 65 parts of water glass (modulus is 1.3), 35 parts of sodium hydroxide, and the water-cement ratio is 0.43;

[0059] The recycled coarse aggregate is obtained by crushing the waste concrete test blocks. According to the mass percentage, the particle size of the recycled coarse aggregate is: 4.75-6.15mm accounts for 30%, 6.15-8.5mm accounts for 50%, 8.5-11mm accounts for 20%, and the particle size of the recycled coarse aggregate is not 4.75mm;

[0060] Calculated by mass percentage, the particle size of calcined coal gangue fine aggregate is: 0.075-0.15mm accounts for 5%, 0.15-0.3mm accounts for 5%, 0.3-0.6mm accounts for 38%, 0.6-1.0mm accounts for 25%, 1.0-2.5mm accounts for 15%, and 2.5-4.75mm accounts for 12%.

[0061] The preparation method of calcined coal gangue fine aggregate is as follows: crushing the original coal gangue to a particle size of ≤5mm, calcining at a temperature of 900°C for 3h, and sieving to obtain calcined coal gangue fine aggregate of corresponding particle size.

[0062] The preparation method of the above-mentioned high impermeability fiber-reinforced recycled aggregate concrete is as follows: accurately weigh each raw material according to the weight ratio, mix the cement, silica fume and water evenly, add polypropylene fiber, mix evenly, then add calcined coal gangue fine aggregate, recycled coarse aggregate, water glass and sodium hydroxide, mix evenly, and cure to obtain high impermeability fiber-reinforced recycled aggregate concrete.

[0063] Example 2

[0064] The present embodiment provides a fiber-reinforced recycled aggregate concrete with high impermeability, which is composed of the following raw materials by weight: 300 parts of cement, 50 parts of silica fume, 0.5 parts of polypropylene fiber, 600 parts of calcined coal gangue fine aggregate, 1000 parts of recycled coarse aggregate, 70 parts of water glass (modulus is 1.4), 40 parts of sodium hydroxide, and the water-cement ratio is 0.45;

[0065] The recycled coarse aggregate is obtained by crushing the waste concrete test blocks. According to the mass percentage, the particle size of the recycled coarse aggregate is: 4.75-6.15mm accounts for 35%, 6.15-8.5mm accounts for 40%, 8.5-11mm accounts for 25%, and the particle size of the recycled coarse aggregate is not 4.75mm;

[0066] Calculated by mass percentage, the particle size of calcined coal gangue fine aggregate is: 0.075-0.15mm accounts for 5%, 0.15-0.3mm accounts for 5%, 0.3-0.6mm accounts for 35%, 0.6-1.0mm accounts for 20%, 1.0-2.5mm accounts for 20%, and 2.5-4.75mm accounts for 15%.

[0067] The preparation method of calcined gangue fine aggregate is as follows: crush the original gangue to a particle size of ≤5 mm, calcine at a temperature of 850° C., keep warm for 4 hours, and sieve to obtain calcined gangue fine aggregate of corresponding particle size.

[0068] The preparation method of the above-mentioned high impermeability fiber reinforced recycled aggregate concrete is the same as that of Example 1.

[0069] Example 3

[0070] The present embodiment provides a fiber-reinforced recycled aggregate concrete with high impermeability, which is composed of the following raw materials by weight: 400 parts of cement, 10 parts of silica fume, 3 parts of polypropylene fiber, 800 parts of calcined coal gangue fine aggregate, 800 parts of recycled coarse aggregate, 60 parts of water glass (modulus is 1.2), 30 parts of sodium hydroxide, and the water-cement ratio is 0.4;

[0071] The recycled coarse aggregate is obtained by crushing the waste concrete test blocks. According to the mass percentage, the particle size of the recycled coarse aggregate is: 4.75-6.15mm accounts for 20%, 6.15-8.5mm accounts for 60%, 8.5-11mm accounts for 20%, and the particle size of the recycled coarse aggregate is not 4.75mm;

[0072] Calculated by mass percentage, the particle size of calcined coal gangue fine aggregate is: 0.075-0.15mm accounts for 20%, 0.15-0.3mm accounts for 15%, 0.3-0.6mm accounts for 25%, 0.6-1.0mm accounts for 20%, 1.0-2.5mm accounts for 10%, and 2.5-4.75mm accounts for 10%.

[0073] The preparation method of calcined gangue fine aggregate is as follows: crush the original gangue to a particle size of ≤5 mm, calcine at a temperature of 950° C., keep warm for 4 hours, and sieve to obtain calcined gangue fine aggregate of corresponding particle size.

[0074] The preparation method of the above-mentioned high impermeability fiber reinforced recycled aggregate concrete is the same as that of Example 1.

[0075] Example 4

[0076] The present embodiment provides a fiber-reinforced recycled aggregate concrete with high impermeability, which is composed of the following raw materials by weight: 350 parts of cement, 30 parts of silica fume, 2 parts of modified polypropylene fiber, 700 parts of calcined coal gangue fine aggregate, 900 parts of recycled coarse aggregate, 65 parts of water glass (modulus is 1.3), 35 parts of sodium hydroxide, and the water-cement ratio is 0.43;

[0077] The recycled coarse aggregate is obtained by crushing the waste concrete test blocks. According to the mass percentage, the particle size of the recycled coarse aggregate is: 4.75-6.15mm accounts for 30%, 6.15-8.5mm accounts for 50%, 8.5-11mm accounts for 20%, and the particle size of the recycled coarse aggregate is not 4.75mm;

[0078] Calculated by mass percentage, the particle size of calcined coal gangue fine aggregate is: 0.075-0.15mm accounts for 5%, 0.15-0.3mm accounts for 5%, 0.3-0.6mm accounts for 38%, 0.6-1.0mm accounts for 25%, 1.0-2.5mm accounts for 15%, and 2.5-4.75mm accounts for 12%.

[0079] The preparation method of modified polypropylene fiber is as follows: placing polypropylene fiber in a sodium carbonate solution with a concentration of 12wt%, heating to 80°C for 5 minutes, adding cocamidopropyl betaine and polyethylene glycol (mass ratio is 1:1), ultrasonic treatment at 250W for 5 minutes, taking out the polypropylene fiber after the ultrasonic treatment, drying, and obtaining modified polypropylene fiber.

[0080] The preparation method of calcined coal gangue fine aggregate is the same as that in Example 1.

[0081] The preparation method of the above-mentioned high impermeability fiber-reinforced recycled aggregate concrete is as follows: accurately weigh each raw material according to the weight ratio, mix the cement, silica fume and water evenly, add modified polypropylene fiber, mix evenly, then add calcined coal gangue fine aggregate, recycled coarse aggregate, water glass and sodium hydroxide, mix evenly, and cure to obtain high impermeability fiber-reinforced recycled aggregate concrete.

[0082] Example 5

[0083] The present embodiment provides a fiber-reinforced recycled aggregate concrete with high impermeability, which is composed of the following raw materials in parts by weight: 350 parts of cement, 30 parts of silica fume, 2 parts of polypropylene fiber, 0.5 parts of modified basalt fiber, 700 parts of calcined coal gangue fine aggregate, 900 parts of recycled coarse aggregate, 65 parts of water glass (modulus is 1.3), 35 parts of sodium hydroxide, and the water-cement ratio is 0.43;

[0084] The recycled coarse aggregate is obtained by crushing the waste concrete test blocks. According to the mass percentage, the particle size of the recycled coarse aggregate is: 4.75-6.15mm accounts for 30%, 6.15-8.5mm accounts for 50%, 8.5-11mm accounts for 20%, and the particle size of the recycled coarse aggregate is not 4.75mm;

[0085] Calculated by mass percentage, the particle size of calcined coal gangue fine aggregate is: 0.075-0.15mm accounts for 5%, 0.15-0.3mm accounts for 5%, 0.3-0.6mm accounts for 38%, 0.6-1.0mm accounts for 25%, 1.0-2.5mm accounts for 15%, and 2.5-4.75mm accounts for 12%.

[0086] The preparation method of the modified basalt fiber is as follows: adding sophorolipid into the basalt fiber, the mass ratio of the basalt fiber to the sophorolipid is 1:3, reacting at 35° C. for 20 minutes, and obtaining the modified basalt fiber.

[0087] The preparation method of the above-mentioned high impermeability fiber-reinforced recycled aggregate concrete is as follows: accurately weigh each raw material according to the weight ratio, mix the cement, silica fume and water evenly, add polypropylene fiber and modified basalt fiber, mix evenly, then add calcined coal gangue fine aggregate, recycled coarse aggregate, water glass and sodium hydroxide, mix evenly, and cure to obtain high impermeability fiber-reinforced recycled aggregate concrete.

[0088] Example 6

[0089] Same as Example 5, except that the weight portion of the modified basalt fiber is 0.2 parts.

[0090] Example 7

[0091] Same as Example 5, except that the weight portion of the modified basalt fiber is 0.8 parts.

[0092] Comparative Example 1

[0093] This comparative example provides a fiber-reinforced recycled aggregate concrete, which is composed of the following raw materials in parts by weight: 350 parts of cement, 30 parts of silica fume, 2 parts of polypropylene fiber, 700 parts of calcined coal gangue fine aggregate (particle size is 0.3-0.6mm), 900 parts of recycled coarse aggregate (particle size is 6.15-8.5mm), 65 parts of water glass (modulus is 1.3), 35 parts of sodium hydroxide, and the water-cement ratio is 0.43;

[0094] The preparation method of the above fiber reinforced recycled aggregate concrete is the same as that in Example 1.

[0095] Comparative Example 2

[0096] This comparative example provides a fiber-reinforced recycled aggregate concrete, which is composed of the following raw materials in parts by weight: 350 parts of cement, 30 parts of silica fume, 2 parts of polypropylene fiber, 700 parts of coal gangue fine aggregate, 900 parts of recycled coarse aggregate (particle size is 6.15-8.5mm), 65 parts of water glass (modulus is 1.3), 35 parts of sodium hydroxide, and the water-cement ratio is 0.43;

[0097] The preparation method of coal gangue fine aggregate is as follows: crushing the original coal gangue to a particle size of ≤5 mm, sieving to obtain coal gangue fine aggregate of corresponding particle size, and the gradation of the coal gangue fine aggregate is the same as that of Example 1;

[0098] The preparation method of the above fiber reinforced recycled aggregate concrete is the same as that in Example 1.

[0099] Comparative Example 3

[0100] The same as Example 5, the only difference is that the basalt fiber is not modified, that is, unmodified basalt fiber is directly added in the preparation process of concrete.

[0101] The mechanical properties of the concrete prepared in each embodiment and comparative example were measured according to GB / T50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete"; the frost resistance of the concrete specimens was tested according to the "Test Procedure for Hydraulic Concrete" (DL / T5150-2001). The test specimens were prisms of 150 mm × 150 mm × 400 mm in length × width × height. The freeze-thaw cycles were repeated 300 times, and the durability index was calculated. The formula is as follows: Durability index = p n × freeze-thaw cycles / 300, where p n is the relative dynamic elastic modulus of the specimen, p n =f 2 n / f 2 1×100, f n is the natural frequency of the specimen after freeze-thaw cycles, Hz, f 2 1 is the natural frequency of the specimen before freeze-thaw cycle, Hz. The results are shown in Table 2.

[0102] Table 2

[0103]

[0104] As can be seen from Table 2, the high impermeability fiber reinforced recycled aggregate concrete prepared by the present invention has excellent mechanical properties. The 28-day compressive strength exceeds 140MPa, reaching ultra-high strength, and the impermeability grade of the concrete prepared by the present invention can reach P12. The mechanical properties of the concrete in Example 5 are the most superior, and its 28d compressive strength reaches 150.2MPa. It can be seen from the ratio of 3d compressive strength / 28d compressive strength that the ratio exceeds 0.7, indicating that the concrete prepared by the method of the present invention has early strength characteristics.

[0105] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A fiber-reinforced recycled aggregate concrete with high impermeability, characterized in that: According to weight, the raw materials include: 300-400 parts of cement, 10-50 parts of silica fume, 0.5-3 parts of polypropylene fiber, 600-800 parts of calcined coal gangue fine aggregate, 800-1000 parts of recycled coarse aggregate, 60-70 parts of water glass, and 30-40 parts of sodium hydroxide; The raw materials of the high impermeability fiber reinforced recycled aggregate concrete also include water, and the water-cement ratio is 0.4-0.45; The recycled coarse aggregate is obtained by crushing waste concrete test blocks. In terms of mass percentage, the particle size of the recycled coarse aggregate is: 4.75-6.15mm accounts for 20-35%, 6.15-8.5mm accounts for 40-60%, 8.5-11mm accounts for 20-25%, and the particle size of the recycled coarse aggregate is not 4.75mm; Calculated by mass percentage, the particle size of the calcined coal gangue fine aggregate is: 0.075-0.15mm accounts for 5-20%, 0.15-0.3mm accounts for 5-15%, 0.3-0.6mm accounts for 15-45%, 0.6-1.0mm accounts for 20-30%, 1.0-2.5mm accounts for 10-20%, and 2.5-4.75mm accounts for 10-15%.

2. The high impermeability fiber reinforced recycled aggregate concrete according to claim 1, characterized in that: The polypropylene fiber is a monofilament polypropylene fiber.

3. The high impermeability fiber reinforced recycled aggregate concrete according to claim 1, characterized in that: The preparation method of the calcined coal gangue fine aggregate is as follows: calcining the original coal gangue at a temperature of 850-950° C. for a heat preservation time of 3-4 hours.

4. The high impermeability fiber reinforced recycled aggregate concrete according to claim 1, characterized in that: The modulus of the water glass is 1.2-1.

4.

5. The high impermeability fiber-reinforced recycled aggregate concrete according to claim 1, characterized in that: The polypropylene fiber is a modified polypropylene fiber. The preparation method of the modified polypropylene fiber is as follows: placing the polypropylene fiber in a sodium carbonate solution, heating it to 80° C. and keeping it warm for 5 minutes to obtain a solution A, adding cocamidopropyl betaine and polyethylene glycol to the solution A, and performing ultrasonic treatment. After the ultrasonic treatment, taking out the polypropylene fiber, drying it, and obtaining the modified polypropylene fiber.

6. The high impermeability fiber reinforced recycled aggregate concrete according to claim 5, characterized in that: The concentration of the sodium carbonate solution is 10-15 wt %.

7. The high impermeability fiber-reinforced recycled aggregate concrete according to claim 5, characterized in that: The mass ratio of the cocamidopropyl betaine to the polyethylene glycol is 1:

1.

8. A method for preparing the high impermeability fiber reinforced recycled aggregate concrete according to any one of claims 1 to 7, characterized in that: Accurately weigh the raw materials according to their weight proportions, mix cement, silica fume and water evenly, add polypropylene fiber, mix evenly, then add calcined coal gangue fine aggregate, recycled coarse aggregate, water glass and sodium hydroxide, mix evenly, and cure to obtain the fiber-reinforced recycled aggregate concrete with high impermeability.

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