Polymer-based anti-cracking concrete and method for preparing the same

Abstract

The application discloses polymer-based anti-cracking concrete and a preparation method thereof, and relates to the technical field of concrete. In the preparation of the polymer-based anti-cracking concrete, acrylic acid is grafted on the surface of pretreated polypropylene particles to prepare modified polypropylene particles; sodium alginate is used to coat sodium metasilicate to prepare self-repairing microcapsules; 3-glycidyl ether oxypropyl trimethoxysilane is hydrolyzed and grafted on the surface of silicon dioxide to prepare modified silicon dioxide; the modified polypropylene particles, basalt fibers and polyacrylonitrile fibers are mixed to prepare a solid functional component; and cement, slag powder, silica fume, an expanding agent, the solid functional component, the modified silicon dioxide, a water reducing agent, an air entraining agent, deionized water, river sand, crushed stone and pre-wetted self-repairing microcapsules are mixed to prepare the polymer-based anti-cracking concrete. The polymer-based anti-cracking concrete prepared by the application has excellent anti-cracking, anti-freezing and thawing and self-repairing properties.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, specifically to a polymer-based crack-resistant concrete and its preparation method. Background Technology

[0002] With infrastructure projects trending towards longer lifespan, higher durability, and adaptability to extreme environments, the crack resistance of concrete materials has become a core factor determining the service life and maintenance costs of structures such as bridges, roads, and tunnels.

[0003] Traditional cement-based concrete, with cement hydration products as its cementitious skeleton, remains the dominant material for infrastructure construction and is widely used in various engineering scenarios. However, the chemical shrinkage and drying shrinkage that occur during cement hydration easily form a large number of micron-sized microcracks inside the concrete. At the same time, concrete itself is a brittle material with a high elastic modulus and low fracture toughness. Under external stimuli such as load and temperature changes, these microcracks can quickly converge into macro-cracks, triggering a chain reaction of hazards such as steel corrosion, structural instability, and matrix spalling.

[0004] The introduction of polymer modification technology provides an effective way to solve the performance defects of traditional concrete: polymer molecular chains can bridge the two sides of cracks, block the further propagation of cracks, and greatly improve the fracture toughness of concrete. At the same time, when polymer-based microcapsules are incorporated into concrete, the microcapsules will rupture due to stress when cracks occur, and the released repair agent can be solidified at the crack, realizing the self-repair of damage, extending the service life of concrete, and reducing the later maintenance cost.

[0005] Therefore, developing a type of concrete that can improve its crack resistance and achieve self-healing by introducing polymers is key to transforming concrete into a functional and long-lasting material. Summary of the Invention

[0006] The purpose of this invention is to provide a polymer-based crack-resistant concrete and its preparation method to solve the problems existing in the prior art.

[0007] To solve the above-mentioned technical problems, the present invention provides the following solution:

[0008] A polymer-based crack-resistant concrete is prepared by grafting acrylic acid onto the surface of pretreated polypropylene particles to obtain modified polypropylene particles; coating sodium metasilicate with sodium alginate to obtain self-healing microcapsules; hydrolyzing 3-glycidoxypropyltrimethoxysilane and grafting it onto the surface of silica to obtain modified silica; mixing modified polypropylene particles, basalt fiber, and polyacrylonitrile fiber to obtain a solid functional component; and mixing cement, slag powder, silica fume, expansion agent, solid functional component, modified silica, water-reducing agent, air-entraining agent, deionized water, river sand, crushed stone, and pre-moistened self-healing microcapsules.

[0009] The pretreated polypropylene particles are prepared by reacting polypropylene particles with acetone.

[0010] The pre-wetted self-healing microcapsules are prepared by mixing self-healing microcapsules with deionized water.

[0011] A method for preparing polymer-based crack-resistant concrete, the method comprising the following preparation steps:

[0012] (1) Mix the pretreated polypropylene particles and the reaction solution at a mass ratio of 1:(2~3), irradiate with 245nm ultraviolet light at room temperature for 10~20 min under nitrogen protection, wash with 95 vol% ethanol aqueous solution and deionized water 2~4 times respectively, and vacuum dry at 35~45℃ for 4~6 h to obtain modified polypropylene particles.

[0013] (2) Mix liquid paraffin and Tween-80 at a mass ratio of 1:(50~60) and stir at room temperature for 5~7 min. Add an aqueous mixture of 0.15~0.25 times the mass of liquid paraffin at a uniform rate over 1~2 h and stir for 10~20 min. Add a 0.1 mol / L calcium chloride aqueous solution of 0.2~0.3 times the volume of the aqueous mixture at a uniform rate over 30~40 min and continue stirring for 30~40 min. Allow the mixture to stand and separate into layers. Wash the lower layer solution with anhydrous ethanol and deionized water 2~4 times respectively. Dry the solution under vacuum at 30~40℃ for 4~6 h to obtain self-healing microcapsules.

[0014] (3) Mix silica and silane hydrolysate at a mass ratio of 1:(5~7), stir and react at 60~70℃ for 3~4h under nitrogen protection, wash with anhydrous ethanol 2~4 times, and vacuum dry at 75~85℃ for 5~7h to obtain modified silica.

[0015] (4) By mass, mix 5-7 parts of modified polypropylene particles, 0.2-0.4 parts of basalt fiber, and 0.1-0.3 parts of polyacrylonitrile fiber evenly and stir at room temperature for 5-7 minutes to obtain a solid functional component; mix 0.6-1 parts of self-healing microcapsules and 7-9 parts of deionized water evenly and stir at room temperature for 3-5 minutes to obtain pre-wetted self-healing microcapsules; mix 60-70 parts of cement, 20-30 parts of slag powder, 8-12 parts of silica fume, and 4-6 parts of expansion agent evenly. Mix the ingredients evenly at room temperature for 2-4 minutes, add solid functional components, continue mixing for 4-6 minutes, add 1-1.4 parts modified silica, 0.7-0.9 parts water-reducing agent, 0.01-0.02 parts air-entraining agent, and 36-40 parts deionized water, continue mixing for 8-10 minutes, add 130-140 parts river sand and 200-240 parts crushed stone, continue mixing for 2-4 minutes, add pre-moistened self-healing microcapsules, and continue mixing for 1-3 minutes to obtain polymer-based crack-resistant concrete.

[0016] The purpose of this invention is to provide a polymer-based crack-resistant concrete and its preparation method to solve the problems existing in the prior art.

[0017] To solve the above-mentioned technical problems, the present invention provides the following solution:

[0018] A polymer-based crack-resistant concrete is prepared by grafting acrylic acid onto the surface of pretreated polypropylene particles to obtain modified polypropylene particles; coating sodium metasilicate with sodium alginate to obtain self-healing microcapsules; hydrolyzing 3-glycidoxypropyltrimethoxysilane and grafting it onto the surface of silica to obtain modified silica; mixing modified polypropylene particles, basalt fiber, and polyacrylonitrile fiber to obtain a solid functional component; and mixing cement, slag powder, silica fume, expansion agent, solid functional component, modified silica, water-reducing agent, air-entraining agent, deionized water, river sand, crushed stone, and pre-moistened self-healing microcapsules.

[0019] The pretreated polypropylene particles are prepared by reacting polypropylene particles with acetone.

[0020] The pre-wetted self-healing microcapsules are prepared by mixing self-healing microcapsules with deionized water.

[0021] A method for preparing polymer-based crack-resistant concrete, the method comprising the following preparation steps:

[0022] (1) Mix the pretreated polypropylene particles and the reaction solution at a mass ratio of 1:(2~3), irradiate with 245nm ultraviolet light at room temperature for 10~20 min under nitrogen protection, wash with 95 vol% ethanol aqueous solution and deionized water 2~4 times respectively, and vacuum dry at 35~45℃ for 4~6 h to obtain modified polypropylene particles.

[0023] (2) Mix liquid paraffin and Tween-80 at a mass ratio of 1:(50~60) and stir at room temperature for 5~7 min. Add an aqueous mixture of 0.15~0.25 times the mass of liquid paraffin at a uniform rate over 1~2 h and stir for 10~20 min. Add a 0.1 mol / L calcium chloride aqueous solution of 0.2~0.3 times the volume of the aqueous mixture at a uniform rate over 30~40 min and continue stirring for 30~40 min. Allow the mixture to stand and separate into layers. Wash the lower layer solution with anhydrous ethanol and deionized water 2~4 times respectively. Dry the solution under vacuum at 30~40℃ for 4~6 h to obtain self-healing microcapsules.

[0024] (3) Mix silica and silane hydrolysate at a mass ratio of 1:(5~7), stir and react at 60~70℃ for 3~4h under nitrogen protection, wash with anhydrous ethanol 2~4 times, and vacuum dry at 75~85℃ for 5~7h to obtain modified silica.

[0025] (4) By mass, mix 5-7 parts of modified polypropylene particles, 0.2-0.4 parts of basalt fiber, and 0.1-0.3 parts of polyacrylonitrile fiber evenly and stir at room temperature for 5-7 minutes to obtain a solid functional component; mix 0.6-1 parts of self-healing microcapsules and 7-9 parts of deionized water evenly and stir at room temperature for 3-5 minutes to obtain pre-wetted self-healing microcapsules; mix 60-70 parts of cement, 20-30 parts of slag powder, 8-12 parts of silica fume, and 4-6 parts of expansion agent evenly. Mix the ingredients evenly at room temperature for 2-4 minutes, add solid functional components, continue mixing for 4-6 minutes, add 1-1.4 parts modified silica, 0.7-0.9 parts water-reducing agent, 0.01-0.02 parts air-entraining agent, and 36-40 parts deionized water, continue mixing for 8-10 minutes, add 130-140 parts river sand and 200-240 parts crushed stone, continue mixing for 2-4 minutes, add pre-moistened self-healing microcapsules, and continue mixing for 1-3 minutes to obtain polymer-based crack-resistant concrete.

[0026] As an optimization, the specifications of the basalt fiber in step (4) are: diameter 17μm, elastic modulus ≥3500MPa, and density 2.6kg / m³. 3， The fiber, 12mm in length, was purchased from Taian Songze Composite Materials Co., Ltd. The specifications of the polyacrylonitrile fiber are: diameter 15μm, elastic modulus ≥6000MPa, density 1.18kg / m³. 3，6mm in length, purchased from Taian Hongtong New Materials Co., Ltd.

[0027] As an optimization, the cement in step (4) is: P·O 42.5 ordinary Portland cement, purchased from Huitai Building Materials Business Department of Lili Town, Wujiang District; the slag powder is: S95 blast furnace slag powder, purchased from Yiran Mineral Products Processing Plant of Lingshou County; the silica fume is: semi-dense microsilica powder with silicon content ≥95%, purchased from Laipeng Mineral Products Business Department of Lingshou County; the expansion agent is: AEA calcium sulfoaluminate expansion agent, purchased from Guzhen Mineral Products Co., Ltd. of Lujiang County, Anhui Province; the water reducing agent is: polycarboxylate high-performance water reducing agent with a water reduction rate of 25%, purchased from Hubei Tiewang Building Materials Co., Ltd.; the air entraining agent is: sodium rosinate air entraining agent, purchased from Henan Xinzhiyuan Chemical Products Co., Ltd.; the river sand specification is: medium sand of Zone II, with a particle size of 2mm, purchased from Yanteng Building Materials Co., Ltd. of Quyang County; the crushed stone particle size is: 15mm, purchased from Hebei Leijiang New Materials Technology Co., Ltd.

[0028] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0029] First, polypropylene granules are pretreated with acetone. Then, under the action of an initiator, acrylic acid is grafted onto the surface of the pretreated polypropylene granules through ultraviolet irradiation to obtain modified polypropylene granules. Polypropylene granules possess high tensile strength and good toughness. When used to replace medium-volume fine aggregate in concrete, they can directly bear and disperse the shrinkage tensile stress generated during the plastic stage before hardening and the drying stage after hardening, avoiding localized stress concentration and the formation of micron-level microcracks. Simultaneously, the carboxyl groups grafted onto the granule surface can undergo coordination reactions with calcium ions in cement hydration products, forming a chemical bond, making stress transfer between the granules and the matrix more efficient. This further enhances the dispersion effect of shrinkage stress, thereby endowing polymer-based crack-resistant concrete with excellent crack resistance. Polypropylene particles themselves have extremely poor water permeability, and when filled in the pores of concrete, they can directly block the water penetration path of gel pores and capillaries, effectively preventing capillary penetration of cold water during the freezing process, and significantly reducing the osmotic pressure inside the concrete. At the same time, the particles' inhibition of micro-cracks and improvement of density fundamentally reduce the space for water intrusion and retention inside the concrete, reducing the frost heave stress generated by the expansion of water during freezing and thawing cycles, thereby endowing polymer-based crack-resistant concrete with excellent freeze-thaw resistance.

[0030] Secondly, sodium alginate is coated onto sodium metasilicate to prepare self-healing microcapsules. When microcracks appear in the concrete, the sodium alginate wall material breaks and releases the sodium metasilicate core material. The sodium metasilicate core material reacts with the concrete pore fluid and calcium hydroxide in the cement hydration products to generate calcium silicate hydrate (CSH) gel. CSH gel is the core cementitious component of cement paste and can bond tightly to the concrete matrix to achieve chemical healing of cracks. After the broken sodium alginate wall material dissolves in water, the carboxyl groups on its molecular chain will undergo ionic cross-linking with calcium ions in the concrete to form water-insoluble calcium alginate gel. This gel has high water absorption and adhesion, which can quickly fill crack pores and form an organic-inorganic composite healing layer with the CSH gel, thereby giving the polymer-based crack-resistant concrete excellent self-healing properties.

[0031] Finally, 3-glycidyl etheroxypropyltrimethoxysilane was hydrolyzed and grafted onto the surface of silica to prepare modified silica, introducing epoxy groups onto the silica surface. The epoxy groups can undergo ring-opening esterification crosslinking reactions with the carboxyl groups of the modified polypropylene particles, the hydroxyl groups of the self-healing microcapsules, and the carboxyl groups in the system, and extensively crosslink with the cement matrix and organic components, forming an interpenetrating nanoscale three-dimensional chemical micronetwork inside the concrete. This effectively disperses the early plastic shrinkage and drying shrinkage stress of concrete, avoiding local stress concentration that could lead to microcracks. At the same time, it complements the macroscopic three-dimensional crack-resistant network formed by basalt fibers and polyacrylonitrile fibers, inhibiting the initiation and penetration of microcracks from multiple dimensions at the nanoscale, microscale, and macroscale, overcoming the limitations of single-scale crack resistance, and thus further improving the crack resistance of polymer-based crack-resistant concrete. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1: A method for preparing polymer-based crack-resistant concrete, the method comprising the following steps:

[0034] (1) Polypropylene particles and acetone were mixed evenly at a mass ratio of 1:4, ultrasonically cleaned at 35°C for 30 min, repeated twice, washed once with deionized water, and dried under reduced pressure at room temperature for 8 h to obtain pretreated polypropylene particles; benzophenone and acetone were mixed evenly at a mass ratio of 1:17, ultrasonically vibrated at room temperature for 20 min to obtain an initiator solution; 80 vol% acrylic acid aqueous solution and initiator solution were mixed at a volume ratio of 1:0.9, stirred at room temperature for 5 min to obtain a reaction solution; pretreated polypropylene particles and reaction solution were mixed evenly at a mass ratio of 1:2, irradiated with 245 nm ultraviolet light at room temperature for 20 min under nitrogen protection, washed twice with 95 vol% ethanol aqueous solution and deionized water respectively, and dried under vacuum at 35°C for 6 h to obtain modified polypropylene particles;

[0035] (2) Sodium metasilicate, sodium alginate and deionized water were mixed evenly at a mass ratio of 1:2:90 and stirred at room temperature for 25 min to obtain an aqueous phase mixture; liquid paraffin and Tween-80 were mixed evenly at a mass ratio of 1:50 and stirred at room temperature for 7 min; 0.15 times the mass of liquid paraffin aqueous phase mixture was added at a uniform rate over 2 h and stirred for 20 min; 0.2 times the volume of the aqueous phase mixture of 0.1 mol / L calcium chloride aqueous solution was added at a uniform rate over 40 min and stirred for another 40 min; the mixture was allowed to stand and separate into layers; the lower layer solution was washed twice with anhydrous ethanol and deionized water respectively; and dried under vacuum at 30℃ for 6 h to obtain self-healing microcapsules.

[0036] (3) Mix 3-glycidoxypropyltrimethoxysilane, anhydrous ethanol and deionized water at a mass ratio of 1:24:0.4, adjust the pH to 4 with acetic acid, stir and react at room temperature for 20 min to obtain silane hydrolysate; mix silica and silane hydrolysate at a mass ratio of 1:5, stir and react at 60°C for 4 h under nitrogen protection, wash twice with anhydrous ethanol, and vacuum dry at 75°C for 7 h to obtain modified silica;

[0037] (4) By mass, 5 parts of modified polypropylene particles, 0.2 parts of basalt fiber and 0.1 parts of polyacrylonitrile fiber are mixed evenly and stirred at room temperature for 7 min to obtain solid functional components; 0.6 parts of self-healing microcapsules and 7 parts of deionized water are mixed evenly and stirred at room temperature for 5 min to obtain pre-wetted self-healing microcapsules; 60 parts of cement, 20 parts of slag powder, 8 parts of silica fume and 4 parts of expansion agent are mixed evenly and stirred at room temperature for 4 min, solid functional components are added, and stirring is continued for 6 min, 1 part of modified silica, 0.7 parts of water-reducing agent, 0.01 parts of air-entraining agent and 36 parts of deionized water are added, and stirring is continued for 10 min, 130 parts of river sand and 200 parts of crushed stone are added, and stirring is continued for 4 min, pre-wetted self-healing microcapsules are added, and stirring is continued for 3 min to obtain polymer-based crack-resistant concrete.

[0038] Example 2: A method for preparing polymer-based crack-resistant concrete, the method comprising the following steps:

[0039] (1) Polypropylene particles and acetone were mixed evenly at a mass ratio of 1:4.5, ultrasonically cleaned at 40℃ for 25 min, repeated 3 times, washed twice with deionized water, and dried under reduced pressure at room temperature for 7 h to obtain pretreated polypropylene particles; benzophenone and acetone were mixed evenly at a mass ratio of 1:17.2, ultrasonically vibrated at room temperature for 15 min to obtain an initiator solution; 80 vol% acrylic acid aqueous solution and initiator solution were mixed at a volume ratio of 1:1, stirred and reacted at room temperature for 4 min to obtain a reaction solution; pretreated polypropylene particles and reaction solution were mixed evenly at a mass ratio of 1:2.5, irradiated with 245 nm ultraviolet light at room temperature for 15 min under nitrogen protection, washed 3 times with 95 vol% ethanol aqueous solution and deionized water respectively, and dried under vacuum at 40℃ for 5 h to obtain modified polypropylene particles;

[0040] (2) Sodium metasilicate, sodium alginate and deionized water were mixed evenly at a mass ratio of 1:2.5:95 and stirred at room temperature for 20 min to obtain an aqueous phase mixture; liquid paraffin and Tween-80 were mixed evenly at a mass ratio of 1:55 and stirred at room temperature for 6 min; 0.2 times the mass of liquid paraffin aqueous phase mixture was added at a uniform rate over 1.5 h and stirred for 15 min; 0.25 times the volume of the aqueous phase mixture of 0.1 mol / L calcium chloride aqueous solution was added at a uniform rate over 35 min and stirred for another 35 min; the reaction was continued for 35 min and allowed to stand for separation; the lower layer solution was washed three times with anhydrous ethanol and deionized water respectively; and vacuum dried at 35℃ for 5 h to obtain self-healing microcapsules.

[0041] (3) Mix 3-glycidoxypropyltrimethoxysilane, anhydrous ethanol and deionized water in a mass ratio of 1:25:0.5, adjust the pH to 4.5 with acetic acid, stir and react at room temperature for 15 min to obtain silane hydrolysate; mix silica and silane hydrolysate in a mass ratio of 1:6, stir and react at 65°C for 3.5 h under nitrogen protection, wash three times with anhydrous ethanol, and vacuum dry at 80°C for 6 h to obtain modified silica;

[0042] (4) By mass, 6 parts of modified polypropylene particles, 0.3 parts of basalt fiber and 0.2 parts of polyacrylonitrile fiber are mixed evenly and stirred at room temperature for 6 min to obtain solid functional components; 0.8 parts of self-healing microcapsules and 8 parts of deionized water are mixed evenly and stirred at room temperature for 4 min to obtain pre-wetted self-healing microcapsules; 65 parts of cement, 25 parts of slag powder, 10 parts of silica fume and 5 parts of expansion agent are mixed evenly and stirred at room temperature for 3 min, solid functional components are added, and stirring is continued for 5 min, 1.2 parts of modified silica, 0.8 parts of water-reducing agent, 0.015 parts of air-entraining agent and 38 parts of deionized water are added, and stirring is continued for 9 min, 135 parts of river sand and 220 parts of crushed stone are added, and stirring is continued for 3 min, pre-wetted self-healing microcapsules are added, and stirring is continued for 2 min to obtain polymer-based crack-resistant concrete.

[0043] Example 3: A method for preparing polymer-based crack-resistant concrete, the method comprising the following steps:

[0044] (1) Polypropylene particles and acetone were mixed evenly at a mass ratio of 1:5, ultrasonically cleaned at 45℃ for 20 min, repeated 4 times, washed 3 times with deionized water, and dried under reduced pressure at room temperature for 6 h to obtain pretreated polypropylene particles; benzophenone and acetone were mixed evenly at a mass ratio of 1:17.4, ultrasonically vibrated at room temperature for 10 min to obtain an initiator solution; 80 vol% acrylic acid aqueous solution and initiator solution were mixed at a volume ratio of 1:1.1, stirred and reacted at room temperature for 3 min to obtain a reaction solution; pretreated polypropylene particles and reaction solution were mixed evenly at a mass ratio of 1:3, irradiated with 245 nm ultraviolet light at room temperature for 10 min under nitrogen protection, washed 4 times with 95 vol% ethanol aqueous solution and deionized water respectively, and dried under vacuum at 45℃ for 4 h to obtain modified polypropylene particles;

[0045] (2) Sodium metasilicate, sodium alginate and deionized water were mixed evenly in a mass ratio of 1:3:100 and stirred at room temperature for 15 min to obtain an aqueous phase mixture; liquid paraffin and Tween-80 were mixed evenly in a mass ratio of 1:60 and stirred at room temperature for 5 min; 0.25 times the mass of liquid paraffin aqueous phase mixture was added at a uniform rate within 1 h and stirred for 10 min; 0.3 times the volume of the aqueous phase mixture of 0.1 mol / L calcium chloride aqueous solution was added at a uniform rate within 30 min and stirred for another 30 min; the mixture was allowed to stand and separate into layers; the lower layer solution was washed 4 times with anhydrous ethanol and deionized water respectively; and vacuum dried at 40℃ for 4 h to obtain self-healing microcapsules.

[0046] (3) Mix 3-glycidoxypropyltrimethoxysilane, anhydrous ethanol and deionized water in a mass ratio of 1:26:0.6, adjust the pH to 5 with acetic acid, stir and react at room temperature for 10 min to obtain silane hydrolysate; mix silica and silane hydrolysate in a mass ratio of 1:7, stir and react at 70°C for 3 h under nitrogen protection, wash 4 times with anhydrous ethanol, and vacuum dry at 85°C for 5 h to obtain modified silica;

[0047] (4) By mass, 7 parts of modified polypropylene particles, 0.4 parts of basalt fiber and 0.3 parts of polyacrylonitrile fiber are mixed evenly and stirred at room temperature for 5 min to obtain solid functional components; 1 part of self-healing microcapsule and 9 parts of deionized water are mixed evenly and stirred at room temperature for 3 min to obtain pre-wetted self-healing microcapsule; 70 parts of cement, 0 parts of slag powder, 12 parts of silica fume and 6 parts of expansion agent are mixed evenly and stirred at room temperature for 2 min, solid functional components are added, and stirring is continued for 4 min, 1.4 parts of modified silica, 0.9 parts of water-reducing agent, 0.02 parts of air-entraining agent and 40 parts of deionized water are added, and stirring is continued for 8 min, 140 parts of river sand and 240 parts of crushed stone are added, and stirring is continued for 2 min, pre-wetted self-healing microcapsule is added, and stirring is continued for 1 min to obtain polymer-based crack-resistant concrete.

[0048] Comparative Example 1:

[0049] The preparation method of the polymer-based crack-resistant concrete in Comparative Example 1 differs from that in Example 2 in that step (1) is omitted, and step (4) is changed as follows: 0.3 parts by mass of basalt fiber and 0.2 parts by mass of polyacrylonitrile fiber are mixed evenly and stirred at room temperature for 6 minutes to obtain a solid functional component; 0.8 parts by mass of self-healing microcapsules and 8 parts by mass of deionized water are mixed evenly and stirred at room temperature for 4 minutes to obtain pre-wetted self-healing microcapsules; 65 parts by mass of cement, 25 parts by mass of slag powder, 10 parts by mass of silica fume and 5 parts by mass of expansion agent are mixed evenly and stirred at room temperature for 3 minutes, the solid functional component is added, and stirring is continued for 5 minutes, 1.2 parts by mass of modified silica, 0.8 parts by mass of water-reducing agent, 0.015 parts by mass of air-entraining agent and 38 parts by mass of deionized water are added, and stirring is continued for 9 minutes, 141 parts by mass of river sand and 220 parts by mass of crushed stone are added, and stirring is continued for 3 minutes, the pre-wetted self-healing microcapsules are added, and stirring is continued for 2 minutes to obtain polymer-based crack-resistant concrete. The remaining steps are the same as in Example 2.

[0050] Comparative Example 2:

[0051] The preparation method of the polymer-based crack-resistant concrete in Comparative Example 2 differs from that in Example 2 in that step (2) is omitted, and step (4) is changed as follows: 6 parts by mass of modified polypropylene particles, 0.3 parts by mass of basalt fiber, and 0.2 parts by mass of polyacrylonitrile fiber are mixed evenly and stirred at room temperature for 6 minutes to obtain a solid functional component; 65 parts by mass of cement, 25 parts by mass of slag powder, 10 parts by mass of silica fume, and 5 parts by mass of expansion agent are mixed evenly and stirred at room temperature for 3 minutes; the solid functional component is added, and stirring is continued for 5 minutes; 1.2 parts by mass of modified silica, 0.8 parts by mass of water-reducing agent, 0.015 parts by mass of air-entraining agent, and 38 parts by mass of deionized water are added, and stirring is continued for 9 minutes; 135 parts by mass of river sand and 220 parts by mass of crushed stone are added, and stirring is continued for 3 minutes to obtain polymer-based crack-resistant concrete. The remaining steps are the same as in Example 2.

[0052] Comparative Example 3:

[0053] The preparation method of the polymer-based crack-resistant concrete in Comparative Example 3 differs from that in Example 2 in that step (3) is omitted, and step (4) is changed as follows: 6 parts by mass of modified polypropylene particles, 0.3 parts by mass of basalt fiber, and 0.2 parts by mass of polyacrylonitrile fiber are mixed evenly and stirred at room temperature for 6 minutes to obtain a solid functional component; 0.8 parts by mass of self-healing microcapsules and 8 parts by mass of deionized water are mixed evenly and stirred at room temperature for 4 minutes to obtain pre-wetted self-healing microcapsules; 65 parts by mass of cement, 25 parts by mass of slag powder, 10 parts by mass of silica fume, and 5 parts by mass of expansion agent are mixed evenly and stirred at room temperature for 3 minutes; the solid functional component is added, and stirring is continued for 5 minutes; 1.2 parts by mass of silica, 0.8 parts by mass of water-reducing agent, 0.015 parts by mass of air-entraining agent, and 38 parts by mass of deionized water are added, and stirring is continued for 9 minutes; 135 parts by mass of river sand and 220 parts by mass of crushed stone are added, and stirring is continued for 3 minutes; the pre-wetted self-healing microcapsules are added, and stirring is continued for 2 minutes to obtain polymer-based crack-resistant concrete. The remaining steps are the same as in Example 2.

[0054] Test Example 1

[0055] Crack resistance test

[0056] Test method: According to GB / T 50081-2019, standard specimens of polymer-based crack-resistant concrete from the examples and comparative examples were prepared, cured for 28 days, and the compressive strength of the specimens was determined using a servo hydraulic testing machine. f cu and splitting tensile strength f ts The results are shown in Table 1.

[0057] Table 1

[0058] ;

[0059] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-3 in Table 1 reveals that the polymer-based crack-resistant concrete prepared by this invention exhibits excellent crack resistance.

[0060] By comparison, the compressive strength and splitting tensile strength of Examples 1-3 are greater than those of Comparative Example 1. This indicates that pretreating polypropylene particles with acetone and then grafting acrylic acid onto the surface of the pretreated polypropylene particles under the action of an initiator and ultraviolet irradiation yields modified polypropylene particles. Polypropylene particles themselves possess high tensile strength and good toughness. When they replace medium-volume fine aggregates in concrete, they can directly bear and disperse the shrinkage tensile stress generated during the plastic stage before hardening and the drying stage after hardening, avoiding local stress concentration and the formation of micron-level microcracks. At the same time, the carboxyl groups grafted onto the particle surface can undergo coordination reactions with calcium ions in cement hydration products to form chemical bonds, making the stress transfer between particles and the matrix more efficient and further improving the dispersion effect of shrinkage stress, thereby endowing polymer-based crack-resistant concrete with excellent crack resistance.

[0061] By comparison, the compressive strength and splitting tensile strength of Examples 1-3 are greater than those of Comparative Example 3, indicating that the modified silica prepared by hydrolyzing 3-glycidoxypropyltrimethoxysilane and grafting it onto the silica surface introduces epoxy groups onto the silica surface. The epoxy groups can undergo ring-opening esterification crosslinking reactions with the carboxyl groups of the modified polypropylene particles and the hydroxyl and carboxyl groups of the self-healing microcapsules in the system, and extensively crosslink with the cement matrix and organic components, forming an interpenetrating nanoscale three-dimensional chemical micronetwork inside the concrete. This effectively disperses the early plastic shrinkage and drying shrinkage stress of the concrete, avoiding local stress concentration that can cause microcracks. At the same time, it complements the macroscopic three-dimensional crack-resistant network formed by basalt fibers and polyacrylonitrile fibers, inhibiting the initiation and penetration of microcracks from multiple dimensions at the nanoscale, microscale, and macroscale, overcoming the limitations of single-scale crack resistance, and thus further improving the crack resistance of polymer-based crack-resistant concrete.

[0062] Test Example 2

[0063] Freeze-thaw resistance test

[0064] Test Method: The polymer-based crack-resistant concrete samples from the examples and comparative examples were made into 100mm×100mm×400mm prism concrete blocks. After standard curing for 28 days, they were immersed in 20℃ water for 4 days, dried, and placed in a freeze-thaw chamber. Each freeze-thaw cycle lasted 3 hours, with the temperature range controlled between -18℃ and 5℃, for a total of 120 cycles. After drying, the blocks were weighed and tested using a servo hydraulic testing machine. The compressive strength and splitting tensile strength retention rates before and after the freeze-thaw cycles were calculated. The results are shown in Table 2.

[0065] Table 2

[0066] ;

[0067] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-3 in Table 2 reveals that the polymer-based crack-resistant concrete prepared by this invention has good freeze-thaw resistance.

[0068] By comparison, the compressive strength retention rate of Examples 1-3 is greater than that of Comparative Example 1, indicating that pretreating polypropylene particles with acetone and grafting acrylic acid onto the surface of the pretreated polypropylene particles under the action of an initiator and ultraviolet irradiation yields modified polypropylene particles. The polypropylene particles themselves have extremely poor water permeability, and when filled in the pores of concrete, they can directly block the water penetration path of gel pores and capillaries, effectively preventing capillary permeation of cold water during the freezing process, and significantly reducing the osmotic pressure inside the concrete. At the same time, the particles inhibit microcracks and improve density, fundamentally reducing the space for water intrusion and retention inside the concrete, and reducing the frost heave stress caused by the expansion of water during freezing and thawing cycles, thereby giving polymer-based crack-resistant concrete excellent freeze-thaw resistance.

[0069] Test Example 3

[0070] Self-repair performance test

[0071] Test Method: Polymer-based crack-resistant concrete specimens (100mm × 100mm × 100mm) from the examples and comparative examples were prepared and cured for 7 days. They were then pre-loaded with 80% of the failure load for 30 seconds, followed by standard curing for another 28 days. The compressive strength was tested using a servo-hydraulic testing machine and recorded as the repaired compressive strength M. Specimens cured to the same age without pre-loading were also tested for compressive strength and recorded as the unrepaired compressive strength N. The compressive strength repair rate was also recorded. The results are shown in Table 3.

[0072] ;

[0073] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-3 in Table 3 reveals that the polymer-based crack-resistant concrete prepared by this invention has good self-healing properties.

[0074] By comparison, the compressive strength repair rate of Examples 1-3 is greater than that of Comparative Example 2, indicating that the self-healing microcapsules prepared by coating sodium alginate with sodium metasilicate are obtained. When microcracks occur in concrete, the sodium alginate wall material ruptures and releases the sodium metasilicate core material. The sodium metasilicate core material reacts with the concrete pore fluid and calcium hydroxide in the cement hydration products to generate calcium silicate hydrate (CSH) gel. CSH gel is the core cementitious component of cement stone and can bond tightly with the concrete matrix to achieve chemical healing of cracks. After the ruptured sodium alginate wall material dissolves in water, the carboxyl groups on its molecular chain will undergo ionic cross-linking with calcium ions in the concrete to form water-insoluble calcium alginate gel. This gel has high water absorption and adhesion, which can quickly fill crack pores and form an organic-inorganic composite healing layer with CSH gel, thereby giving the polymer-based crack-resistant concrete excellent self-healing properties.

[0075] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polymer-based anti-cracking concrete, characterized in that, The polymer-based crack-resistant concrete is prepared by grafting acrylic acid onto the surface of pretreated polypropylene particles to obtain modified polypropylene particles; by coating sodium alginate with sodium metasilicate to obtain self-healing microcapsules; by hydrolyzing 3-glycidoxypropyltrimethoxysilane and grafting it onto the surface of silica to obtain modified silica; and by mixing 5-7 parts of modified polypropylene particles, 0.2-0.4 parts of basalt fiber, and 0.1-0.3 parts of polyacrylonitrile fiber to obtain a solid functional... Composition: The mixture consists of 60-70 parts cement, 20-30 parts slag powder, 8-12 parts silica fume, 4-6 parts expansion agent, 5.3-7.7 parts solid functional components, 1-1.4 parts modified silica, 0.7-0.9 parts water-reducing agent, 0.01-0.02 parts air-entraining agent, 36-40 parts deionized water, 130-140 parts river sand, 200-240 parts crushed stone, and 7.6-10 parts pre-moistened self-healing microcapsules. The pretreated polypropylene particles are prepared by reacting polypropylene particles with acetone. The specific preparation method of the modified polypropylene particles is as follows: the pretreated polypropylene particles and the reaction solution are mixed evenly at a mass ratio of 1:(2~3), and under nitrogen protection, the mixture is irradiated with 245nm ultraviolet light at room temperature for 10~20 min, washed 2~4 times with 95 vol% ethanol aqueous solution and deionized water respectively, and then vacuum dried at 35~45℃ for 4~6 h. The reaction solution is prepared by mixing benzophenone and acetone at a mass ratio of 1:(17~17.4) and ultrasonically vibrating at room temperature for 10~20 min to obtain an initiator solution; and by mixing 80 vol% acrylic acid aqueous solution and the initiator solution at a volume ratio of 1:(0.9~1.1) and stirring at room temperature for 3~5 min. The pre-wetted self-healing microcapsules are prepared by mixing self-healing microcapsules with deionized water.

2. A method of producing a polymer-based anti-cracking concrete, characterized by, The preparation method of the polymer-based crack-resistant concrete includes the following preparation steps: (1) Mix benzophenone and acetone at a mass ratio of 1:(17~17.4) and sonicate at room temperature for 10~20 min to obtain an initiator solution; mix 80 vol% acrylic acid aqueous solution and initiator solution at a volume ratio of 1:(0.9~1.1) and stir at room temperature for 3~5 min to obtain a reaction solution; mix pretreated polypropylene particles and reaction solution at a mass ratio of 1:(2~3) and irradiate at room temperature with 245 nm ultraviolet light for 10~20 min under nitrogen protection, wash with 95 vol% ethanol aqueous solution and deionized water 2~4 times respectively, and vacuum dry at 35~45℃ for 4~6 h to obtain modified polypropylene particles; (2) Sodium metasilicate, sodium alginate and deionized water are mixed evenly at a mass ratio of 1:(2~3):(90~100) and stirred at room temperature for 15~25 min to obtain an aqueous phase mixture; liquid paraffin and Tween-80 are mixed evenly at a mass ratio of 1:(50~60) and stirred at room temperature for 5~7 min; 0.15~0.25 times the mass of liquid paraffin is added evenly over 1~2 h and stirred for 10~20 min; 0.2~0.3 times the volume of the aqueous phase mixture is added evenly over 30~40 min and stirred for another 30~40 min; 0.1 mol / L calcium chloride aqueous solution is added evenly over 30~40 min and stirred for another 30~40 min; the mixture is allowed to stand and separate into layers; the lower layer is washed 2~4 times with anhydrous ethanol and deionized water respectively; and then dried under vacuum at 30~40℃ for 4~6 h to obtain self-healing microcapsules. (3) Mix silica and silane hydrolysate at a mass ratio of 1:(5~7), stir and react at 60~70℃ for 3~4h under nitrogen protection, wash with anhydrous ethanol 2~4 times, and vacuum dry at 75~85℃ for 5~7h to obtain modified silica. (4) By mass, mix 5-7 parts of modified polypropylene particles, 0.2-0.4 parts of basalt fiber, and 0.1-0.3 parts of polyacrylonitrile fiber evenly and stir at room temperature for 5-7 minutes to obtain a solid functional component; mix 0.6-1 parts of self-healing microcapsules and 7-9 parts of deionized water evenly and stir at room temperature for 3-5 minutes to obtain pre-wetted self-healing microcapsules; mix 60-70 parts of cement, 20-30 parts of slag powder, 8-12 parts of silica fume, and 4-6 parts of expansion agent evenly. Mix the ingredients evenly at room temperature for 2-4 minutes, add solid functional components, continue mixing for 4-6 minutes, add 1-1.4 parts modified silica, 0.7-0.9 parts water-reducing agent, 0.01-0.02 parts air-entraining agent, and 36-40 parts deionized water, continue mixing for 8-10 minutes, add 130-140 parts river sand and 200-240 parts crushed stone, continue mixing for 2-4 minutes, add pre-moistened self-healing microcapsules, and continue mixing for 1-3 minutes to obtain polymer-based crack-resistant concrete.

3. The method of claim 2, wherein the polymer-based anti-cracking concrete is prepared by mixing the polymer-based anti-cracking concrete mixture with water in a ratio of 1 : 0.5 to 1 : 1.

5. The preparation steps of the pretreated polypropylene particles in step (1) are as follows: mix polypropylene particles and acetone at a mass ratio of 1:(4~5), ultrasonically clean at 35~45℃ for 20~30min, repeat 2~4 times, wash with deionized water 1~3 times, and dry under reduced pressure at room temperature for 6~8h to obtain pretreated polypropylene particles.

4. The method for preparing polymer-based crack-resistant concrete according to claim 3, characterized in that, The polypropylene particles have a size of 2.5 mm in diameter and 3 mm in height, and a density of 910 kg / m 3 .

5. The method for preparing polymer-based crack-resistant concrete according to claim 2, characterized in that, The preparation steps of the silane hydrolysate in step (3) are as follows: 3-glycidoxypropyltrimethoxysilane, anhydrous ethanol and deionized water are mixed evenly at a mass ratio of 1:(24~26):(0.4~0.6), the pH is adjusted to 4~5 with acetic acid, and the mixture is stirred at room temperature for 10~20 min to obtain the silane hydrolysate.

6. The method for preparing polymer-based crack-resistant concrete according to claim 2, characterized in that, The silica used in step (3) is of type TH-6380.

7. The method for preparing polymer-based crack-resistant concrete according to claim 2, characterized in that, The basalt fiber of step (4) has a diameter of 17 μm, an elastic modulus of ≥ 3500 MPa, a density of 2.6 kg / m 3 , and a length of 12 mm; the polyacrylonitrile fiber has a diameter of 15 μm, an elastic modulus of ≥ 6000 MPa, a density of 1.18 kg / m 3 , and a length of 6 mm.

8. The method for preparing polymer-based crack-resistant concrete according to claim 2, characterized in that, The cement in step (4) is: P·O 42.5 ordinary Portland cement; the slag powder is: S95 blast furnace slag powder; the silica fume is: semi-dense microsilica powder with a silicon content ≥95%; the expansion agent is: AEA calcium sulfoaluminate expansion agent; the water reducing agent is: polycarboxylate high-performance water reducing agent with a water reduction rate of 25%; the air entraining agent is: sodium rosinate air entraining agent; the river sand specification is: zone II medium sand with a particle size of 2mm; the crushed stone particle size is: 15mm.