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

Abstract

The invention discloses a preparation method and product of fiber-reinforced recycled aggregate concrete with high impermeability, belonging to the technical field of building materials. The invention uses cement, silica fume, polypropylene fiber, calcined coal gangue fine aggregate, recycled coarse bone, water glass and sodium hydroxide as raw materials to prepare the fiber-reinforced recycled aggregate concrete with high impermeability. The concrete can not only have high impermeability, but also improve the early strength of the concrete, so that the concrete can achieve ultra-high strength.

Description

Technical Field

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

[0002] With the rapid development of industries like petroleum and chemical engineering, the emission and infiltration of harmful gases and industrial wastewater have caused significant 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 its impermeability is insufficient, it can cause pollution, leakage, and other accidents, directly affecting the use and safety of the building.

[0003] Concrete permeability refers to its ability to resist pressure (water or oil) penetration. Factors influencing concrete permeability include the water-cement ratio, the degree of cement hydration, the size of the coarse aggregate, the gradation of the aggregate, and the interface between the aggregate and the cement paste. Ordinary concrete materials have poor resistance to pressure water penetration. Once pressurized water penetrates the concrete, it causes expansion and cracking. It also acts as a carrier for the corrosive medium, accelerating its diffusion into the concrete, thereby accelerating the deterioration of concrete performance. As concrete is subjected to dry-wet cycles, freeze-thaw cycles, brine erosion, and the action of alkali aggregates, its durability continues to decline, and water penetration plays a significant role in the process of reaching destruction and failure. Therefore, improving the impermeability of concrete has become an indispensable part of improving concrete durability.

[0004] Impermeable concrete refers to concrete with an impermeability rating equal to or greater than P6. Impermeable concrete is generally categorized as P6, P8, or P12 based on the level of impermeability. Highly impermeable concrete refers to achieving extremely high impermeability, effectively controlling invisible cracks and pores in the concrete, as required by actual projects. For large-scale industrial buildings in industries like the petrochemical industry, which place extremely stringent requirements, the goal is to achieve zero millimeter penetration, or even complete watertightness.

[0005] Concrete prepared with aggregates with small pores, large bulk density and good gradation does not necessarily have good water-resistance. This is because no matter whether it is continuous gradation or discontinuous gradation, the high-density concrete obtained only reduces the possibility of pore penetration between cement aggregates after increasing the sand and gravel to a certain level. 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 water-resistance performance of concrete is still very poor.

[0006] Existing methods for improving the anti-permeability of concrete fail to control the pores between cement, sand, and the contact surfaces of cement and aggregate, resulting in poor anti-permeability 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, calculated 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. The particle sizes of the recycled coarse aggregate are as follows: 4.75-6.15 mm, accounting for 20-35%, 6.15-8.5 mm, accounting for 40-60%, and 8.5-11 mm, accounting 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 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 important factors affecting the impermeability of concrete. The present invention can improve the rheological properties of concrete, the cohesive structure of cement slurry, and the density after hardening 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 that concrete with good impermeability can be obtained. The aggregate gradation of the present invention is moderate, the porosity is small, and the concrete density is large, so its impermeability is better.

[0013] The polypropylene fiber is a monofilament polypropylene fiber. The present invention changes the internal structure of concrete by adding polypropylene fiber, further ensuring the high impermeability of concrete. After polypropylene fiber is mixed into concrete and stirred, since polypropylene fiber has extremely strong bonding force with aggregate, it can be quickly and easily mixed with other components and evenly distributed, and can form a uniform random support system inside the concrete. During the concrete hardening process, due to the chemical shrinkage of cement paste, tensile stress is generated at the bonding surface between cement paste and aggregate, so there are a large number of extremely fine micro cracks in the concrete. These micro cracks are very likely to cause stress concentration and cause damage when the concrete is stressed. After adding 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 micro cracks caused by concrete shrinkage, and in addition to improving the impermeability of 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 a holding time of 3-4 hours. Unburned gangue has a stable crystal structure, and its atoms, ions, molecules and other particles are arranged in an orderly manner according to a certain rule. Even after being ground, the gelling effect is very weak. The present invention performs a thermal activation treatment on the gangue, and the kaolin component therein is dehydrated and decomposed to produce metakaolin and amorphous silicon oxide and aluminum oxide. The original crystalline phase is decomposed and destroyed, greatly improving 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 solution A, adding cocamidopropyl betaine and polyethylene glycol to the solution A, and performing ultrasonic treatment. After the ultrasonic treatment is completed, the polypropylene fiber is taken out and dried to obtain 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] Treating polypropylene fibers with a sodium carbonate solution increases their surface activation energy. Subsequent heat treatment further increases this activation energy, facilitating the subsequent binding of the polypropylene fibers with cocamidopropyl betaine and polyethylene glycol. During the binding process with cocamidopropyl betaine and polyethylene glycol, ultrasound reduces the aggregation of polypropylene fibers within the dispersed system, promoting their effective dispersion and preventing the formation of flocculent or hairy aggregates. The polypropylene fibers form hydrogen bonds or covalent bonds with the active groups of the two, spreading across the polypropylene fiber surface to form a continuous new surface layer, repairing, filling, and encapsulating surface defects, further increasing 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, uniformly mixing cement, silica fume and water, adding polypropylene fiber, and mixing uniformly, then adding calcined coal gangue fine aggregate, recycled coarse aggregate, water glass and sodium hydroxide, mixing uniformly, and curing to obtain the above-mentioned 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 pozzolanic effect, reacting with calcium hydroxide (Ca(OH)2) in cement hydration products to produce more calcium silicate hydrate (CSH) gel, thereby filling the pores and making the concrete structure denser. At the same time, due to its small particle size, silica fume can fill the large pores in concrete, optimize the pore structure distribution, and reduce the proportion of harmful pores, thereby improving the concrete's impermeability and early strength. The addition of silica fume can also provide "nucleation" sites for cement hydration, promoting the early hydration reaction of cement and significantly improving the early strength of concrete. Calcined coal gangue aggregate has a certain degree of activity and can undergo chemical reactions in an alkaline environment to form 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 aggregate, promote their synergistic reaction with cement, and produce more cementitious 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 aggregate. 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, and 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 improving the early strength and microstructure. The concrete prepared by the present invention has a P12 level of impermeability. The concrete of the present invention has high compressive and flexural strength and high early strength. 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 rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

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

[0026] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice 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 any conflict with any incorporated document, the contents 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 described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative 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, comprising the following raw materials, calculated 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 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 discarded concrete test blocks. Calculated by mass percentage, the particle sizes of the recycled coarse aggregate are: 4.75-6.15 mm, accounting for 20-35%, 6.15-8.5 mm, accounting for 40-60%, and 8.5-11 mm, accounting for 20-25%. The particle size of the recycled coarse aggregate is not 4.75 mm.

[0033] Calculated by mass percentage, the particle size of the calcined 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 important factors affecting the impermeability of concrete. The present invention can improve the rheological properties of concrete, the cohesive structure of cement slurry, and the density after hardening 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 that concrete with good impermeability can be obtained. The aggregate gradation of the present invention is moderate, the porosity is small, and the concrete density is large, so its impermeability is better.

[0035] Polypropylene fiber is a monofilament polypropylene fiber. The present invention changes the internal structure of concrete by adding polypropylene fiber, further ensuring the high impermeability of concrete. After polypropylene fiber is mixed into concrete and stirred, since polypropylene fiber has extremely strong bonding force with aggregate, it can be quickly and easily mixed with other components, evenly distributed, and can form a uniform random support system inside the concrete. During the concrete hardening process, due to the chemical shrinkage of cement paste, tensile stress is generated at the bonding surface between cement paste and aggregate, so there are a large number of extremely fine micro cracks in the concrete. These micro cracks are very likely to cause stress concentration and cause damage when the concrete is stressed. After adding 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 micro cracks caused by concrete shrinkage, and in addition to improving the impermeability of concrete, also greatly improve the crack resistance and toughness of the concrete after hardening.

[0036] In an embodiment of the present invention, a method for preparing calcined gangue fine aggregate comprises calcining undisturbed gangue at a temperature of 850-950°C for 3-4 hours. Unburned gangue has a stable crystal structure, with its atoms, ions, molecules, and other particles arranged in an orderly manner according to a certain pattern. Even after grinding, its gelling effect is very weak. The present invention thermally activates the gangue, causing the kaolin component therein to dehydrate and decompose, generating metakaolin and amorphous silicon oxide and aluminum oxide. The original crystalline phase is decomposed and destroyed, greatly enhancing 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 increase the concrete's compressive and flexural strengths.

[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 impermeability, acid resistance and strength.

[0039] In other embodiments of the present invention, 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, 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] Treating polypropylene fibers with a sodium carbonate solution increases their surface activation energy. Subsequent heat treatment further increases this activation energy, facilitating the subsequent binding of the polypropylene fibers with cocamidopropyl betaine and polyethylene glycol. During the binding process with cocamidopropyl betaine and polyethylene glycol, ultrasound reduces the aggregation of polypropylene fibers within the dispersed system, promoting their effective dispersion and preventing the formation of flocculent or hairy aggregates. The polypropylene fibers form hydrogen bonds or covalent bonds with the active groups of the two, spreading across the polypropylene fiber surface to form a continuous new surface layer, repairing, filling, and encapsulating surface defects, further increasing 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, with a mass ratio of basalt fibers to sophorolipids of 1:3, and reacting at 35°C for 20 minutes to obtain the modified basalt fibers. Sophorolipids are both lipophilic and hydrophilic. Sophorolipids can reduce the surface energy of basalt fibers, improve the wettability and dispersion of basalt fibers, which helps basalt fibers better bond with the matrix and improve interfacial compatibility. After sophorolipid treatment, a protective film will form on the surface of the basalt fibers, thereby improving the impermeability, wear resistance and toughness of the basalt fibers, and can also improve the dispersion and interfacial bonding properties of the basalt fibers in the matrix. The composition of the basalt fibers treated with sophorolipids is changed, which can better form calcium silicate compounds (CSH) in concrete, which is the main substance that improves concrete strength. 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 present invention can prepare high-strength and high-impermeability concrete without adding a water reducer 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 examples and comparative examples of the present invention, the cement is Lafarge ordinary silicate 42.5 grade cement; the 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 conventional operating means in this 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 examples.

[0057] Example 1

[0058] This embodiment provides a fiber-reinforced recycled aggregate concrete with high impermeability, which is composed of the following raw materials, calculated 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 of 1.3), and 35 parts of sodium hydroxide, with a water-cement ratio of 0.43.

[0059] The recycled coarse aggregate is obtained by crushing discarded concrete test blocks. Calculated by mass percentage, the particle sizes of the recycled coarse aggregate are: 4.75-6.15 mm, accounting for 30%, 6.15-8.5 mm, accounting for 50%, and 8.5-11 mm, accounting for 20%. The particle size of the recycled coarse aggregate is not 4.75 mm.

[0060] Calculated by mass percentage, the particle size of the calcined 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 gangue fine aggregate is as follows: crushing the original gangue to a particle size of ≤5mm, calcining at a temperature of 900°C for 3 hours, and sieving to obtain calcined 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 the raw materials 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] This embodiment provides a fiber-reinforced recycled aggregate concrete with high impermeability, which is composed of the following raw materials, calculated 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 of 1.4), and 40 parts of sodium hydroxide, with a water-cement ratio of 0.45.

[0065] The recycled coarse aggregate is obtained by crushing discarded concrete test blocks. Calculated by mass percentage, the particle sizes of the recycled coarse aggregate are: 4.75-6.15 mm, accounting for 35%, 6.15-8.5 mm, accounting for 40%, and 8.5-11 mm, accounting for 25%. The particle size of the recycled coarse aggregate is not 4.75 mm.

[0066] Calculated by mass percentage, the particle size of the calcined 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: crushing the original gangue to a particle size of ≤5mm, calcining at a temperature of 850°C for 4 hours, and sieving 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] This embodiment provides a fiber-reinforced recycled aggregate concrete with high impermeability, which is composed of the following raw materials, calculated 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 1.2), and 30 parts of sodium hydroxide, with a water-cement ratio of 0.4;

[0071] The recycled coarse aggregate is obtained by crushing discarded concrete test blocks. Calculated by mass percentage, the particle sizes of the recycled coarse aggregate are: 4.75-6.15 mm, accounting for 20%, 6.15-8.5 mm, accounting for 60%, and 8.5-11 mm, accounting for 20%. The particle size of the recycled coarse aggregate is not 4.75 mm.

[0072] Calculated by mass percentage, the particle size of the calcined 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: crushing the original gangue to a particle size of ≤5mm, calcining at a temperature of 950°C for 4 hours, and sieving 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] This embodiment provides a fiber-reinforced recycled aggregate concrete with high impermeability, which is composed of the following raw materials, calculated 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 of 1.3), and 35 parts of sodium hydroxide, with a water-cement ratio of 0.43.

[0077] The recycled coarse aggregate is obtained by crushing discarded concrete test blocks. Calculated by mass percentage, the particle sizes of the recycled coarse aggregate are: 4.75-6.15 mm, accounting for 30%, 6.15-8.5 mm, accounting for 50%, and 8.5-11 mm, accounting for 20%. The particle size of the recycled coarse aggregate is not 4.75 mm.

[0078] Calculated by mass percentage, the particle size of the calcined 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: polypropylene fiber is placed in a sodium carbonate solution with a concentration of 12wt%, heated to 80°C and kept warm for 5 minutes, cocamidopropyl betaine and polyethylene glycol (mass ratio is 1:1) are added, and ultrasonic treatment is carried out at 250W for 5 minutes. After the ultrasonic treatment, the polypropylene fiber is taken out and dried to obtain 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 the raw materials 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] This embodiment provides a fiber-reinforced recycled aggregate concrete with high impermeability, which is composed of the following raw materials, calculated 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 of 1.3), and 35 parts of sodium hydroxide, with a water-cement ratio of 0.43.

[0084] The recycled coarse aggregate is obtained by crushing discarded concrete test blocks. Calculated by mass percentage, the particle sizes of the recycled coarse aggregate are: 4.75-6.15 mm, accounting for 30%, 6.15-8.5 mm, accounting for 50%, and 8.5-11 mm, accounting for 20%. The particle size of the recycled coarse aggregate is not 4.75 mm.

[0085] Calculated by mass percentage, the particle size of the calcined 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 to the basalt fiber, with the mass ratio of basalt fiber to sophorolipid being 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 the raw materials 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, calculated 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 of 0.3-0.6 mm), 900 parts of recycled coarse aggregate (particle size of 6.15-8.5 mm), 65 parts of water glass (modulus of 1.3), and 35 parts of sodium hydroxide, with a water-cement ratio of 0.43;

[0094] The preparation method of the 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, calculated 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 of 6.15-8.5 mm), 65 parts of water glass (modulus of 1.3), and 35 parts of sodium hydroxide, with a water-cement ratio of 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 in Example 1;

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

[0099] Comparative Example 3

[0100] The same as Example 5, except that the basalt fiber is not modified, that is, unmodified basalt fiber is directly added during the preparation of concrete.

[0101] The mechanical properties of the concrete prepared in each embodiment and comparative example were measured in accordance with GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete"; the frost resistance of the concrete specimens was tested in accordance with the "Test Procedure for Hydraulic Concrete" (DL / T5150-2001). The test specimens were prisms of concrete with a length × width × height of 150 mm × 150 mm × 400 mm. The specimens were subjected to 300 freeze-thaw cycles continuously, and the durability index was calculated using the following formula: 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 cycles, Hz. The results are shown in Table 2.

[0102] Table 2

[0103]

[0104] As shown in 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 140 MPa, achieving 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 150.2 MPa. As can be seen from the ratio of 3d compressive strength to 28d compressive strength, 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 merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A fiber-reinforced recycled aggregate concrete with high impermeability, characterized in that: The raw materials include, 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. 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 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 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; performing ultrasonic treatment; and taking out the polypropylene fiber after the ultrasonic treatment is completed, and drying it to obtain 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, 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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