Fiber reinforced self-healing concrete and method of making the same

Abstract

The present application relates to the technical field of self-healing concrete, and particularly relates to a fiber-reinforced self-healing concrete and a preparation method thereof.The fiber-reinforced self-healing concrete comprises the following raw materials in parts by mass: 5-10 parts of silica sol, 1-2 parts of calcium sulfate, 10-20 parts of ethylene-vinyl acetate copolymer, 5-15 parts of TPE resin, 0.1-1 part of sodium chloride, 1-3 parts of urease bacteria liquid, 1-3 parts of dopamine hydrochloride, 40-60 parts of coarse aggregate, 20-40 parts of fine aggregate, 1-5 parts of chopped basalt fiber, 5-15 parts of kaolin, 1-4 parts of urea, 40-60 parts of fly ash, 40-50 parts of cement and 1-2 parts of water reducing agent.The present application effectively improves the strength and durability of concrete, and even if the concrete structure is locally damaged and leaks, it can be self-repaired and healed, thereby fundamentally changing the crack and leakage caused by the unstable volume of ordinary concrete structure.

Description

Technical Field

[0001] This invention relates to the field of self-healing concrete technology, and in particular to a fiber-reinforced self-healing concrete and its preparation method. Background Technology

[0002] As a core material in modern construction, concrete cracking directly impacts structural safety and durability. Once cracks form, external moisture and corrosive media can penetrate, leading to steel reinforcement corrosion, freeze-thaw damage, and chemical erosion, significantly reducing structural load-bearing capacity and service life.

[0003] Traditional concrete is prone to penetrating cracks under dynamic loads. While fiber-reinforced concrete can improve toughness, uneven fiber dispersion can lead to stress concentration, which in turn reduces compressive strength. Furthermore, weak areas at the fiber-matrix interface can easily become crack propagation paths. Additionally, in freeze-thaw cycles, ordinary concrete experiences a significant increase in mass loss after 100 cycles, with limited improvement in freeze-thaw resistance, thus restricting its application in extremely cold regions.

[0004] Microbial remediation relies on the activity of urease bacteria, but the high alkalinity of concrete leads to insufficient bacterial survival rate; while chemical remediation agents (such as sodium silicate gel) have low bonding strength with the substrate, resulting in poor restoration of impermeability after repair; physical remediation requires the pre-embedding of hollow fiber tubes, but the rupture threshold of the tubes is difficult to match the actual engineering requirements.

[0005] Existing technologies, whether by improving pore structure with mineral admixtures or by using fiber toughening to suppress cracking, have failed to simultaneously solve the problems of strength development, durability improvement, and self-repair, which urgently need to be addressed. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a fiber-reinforced self-healing concrete and its preparation method.

[0007] A fiber-reinforced self-healing concrete comprises the following raw materials by weight: 5-10 parts silica sol, 1-2 parts calcium sulfate, 10-20 parts ethylene-vinyl acetate copolymer, 5-15 parts TPE resin, 0.1-1 parts sodium chloride, 1-3 parts urease bacterium solution, 1-3 parts dopamine hydrochloride, 40-60 parts coarse aggregate, 20-40 parts fine aggregate, 1-5 parts chopped basalt fiber, 5-15 parts kaolin, 1-4 parts urea, 40-60 parts fly ash, 40-50 parts cement, and 1-2 parts water-reducing agent.

[0008] Preferably, the urease-producing bacteria are Bacillus pasteurellii and / or Micrococcus urealyticum.

[0009] Preferably, the urease activity in the urease-producing bacteria solution is 50. 60 mmol / (L·min).

[0010] Preferably, the coarse aggregate is crushed stone with a diameter of 15-25 mm, a water absorption rate of 2.5-4.5%, and an apparent density of 2200-2450 kg / m³. 3 .

[0011] Preferably, the fine aggregate is natural river sand with a fineness modulus of 2-3 and an apparent density of 2.25-2.55 g / cm³. 3 .

[0012] Preferably, the length of the chopped basalt fiber is 20-25 mm, and the diameter of the single filament is 5-15 μm.

[0013] Preferably, the water-reducing agent is at least one of lignin sulfonate, sulfonated melamine-formaldehyde resin, and aromatic aminosulfonate polymer.

[0014] The preparation method of the above-mentioned fiber-reinforced self-healing concrete includes the following steps:

[0015] S1. Mix ethylene-vinyl acetate copolymer, TPE resin and sodium chloride evenly, melt spin at 180-200℃, cut to obtain blended fibers; soak in water and ultrasonically vibrate for 10-30 minutes, filter, wash and vacuum dry to obtain porous fibers.

[0016] S2. Add the porous fiber to water, add urease bacteria solution and stir for 1-2 hours. Adjust the pH of the system to 7.5-8, add dopamine hydrochloride and continue stirring for 10-20 hours. Filter and vacuum dry to obtain organic porous fiber.

[0017] S3. Mix coarse aggregate, fine aggregate, and chopped basalt fiber evenly, then add fly ash, kaolin, cement, and urea and mix evenly to obtain a premix.

[0018] S4. Stir the silica sol and organic porous fibers evenly, sonicate for 1-2 hours, add premix, water-reducing agent, calcium sulfate and water, stir evenly, pour, dry and cure.

[0019] Preferably, in S1, the ultrasonic oscillation frequency is 70-90kHz.

[0020] Preferably, in S4, the ultrasonic processing frequency is 50-70kHz.

[0021] Beneficial effects:

[0022] This invention employs a leaching and pore-forming process using EVA / TPE resin and sodium chloride to form a fiber carrier with controllable pore size. The combination of polydopamine coating and silica sol effectively immobilizes the bacteria and forms a protective shell, significantly improving the survival rate of urease-producing bacteria in concrete. Furthermore, when cracks extend into the fiber region, the CO3 produced by urease catalyzing the hydrolysis of urea... 2-With Ca in concrete 2+ Directional deposition of calcium carbonate on the fiber surface results in high interfacial bonding strength between the repair and the matrix, and excellent self-healing properties.

[0023] Meanwhile, the porous fibers obtained by this invention increase the friction coefficient between the fibers and aggregates and form a uniform multidirectional branched system in concrete. Combined with the effect of short-cut basalt fibers, a three-dimensional strengthening effect can be produced in concrete, thereby improving the integrity of concrete and enhancing its resistance to cracking and drying shrinkage deformation.

[0024] The organic porous fibers obtained in this invention have polydopamine deposited on their surface and compounded with silica sol, which can effectively enhance the interfacial bonding with fly ash, kaolin, and cement. Further compounding with short-cut basalt fibers allows concrete to dissipate energy through plastic deformation of composite fibers in the early stages of crack development. As the crack width continues to expand, the microbial repair of porous fibers is initiated, and the calcium carbonate deposits are compounded with the fiber structure to achieve a dynamic balance between strength and self-healing function. Moreover, even after freeze-thaw cycles, the mass loss rate is low and the self-repair effect is good.

[0025] This invention effectively improves the strength and durability of concrete. Even if the concrete structure is locally damaged and leaks, it will self-repair and heal, thus fundamentally changing the problem of cracking and seepage caused by the instability of ordinary concrete structures. This invention optimizes the concrete mix proportion, which not only strengthens the overall structure but also reduces production costs, resulting in concrete with excellent comprehensive performance. Moreover, the preparation method is simple and suitable for large-scale application. Attached Figure Description

[0026] Figure 1 The curves show the change in compressive strength of the concrete samples obtained in Example 5 and Comparative Examples 1-3 as the number of freeze-thaw cycles increases.

[0027] Figure 2 The curves show the changes in splitting tensile strength of concrete samples obtained in Example 5 and Comparative Examples 1-3 as the number of freeze-thaw cycles increases.

[0028] Figure 3 The curves show the overall repair rate of the concrete samples obtained in Example 5 and Comparative Examples 1-3 after prefabrication damage, as a function of repair and curing time. Detailed Implementation

[0029] The present invention will be further explained below with reference to specific embodiments.

[0030] The ethylene-vinyl acetate copolymer used below is sourced from Formosa Plastics Group (Taiwan), and its grade is 7470M. The thermoplastic polyester elastomer used below is sourced from DuPont (USA), and its grade is 4056. The coarse aggregate used below is crushed stone with a diameter of 15-25 mm, a water absorption rate of 3.5%, and an apparent density of 2370 kg / m³. 3The fine aggregate used below is natural river sand with a fineness modulus of 2.5 and an apparent density of 2.42 g / cm³. 3 The short-cut basalt fibers used below are 25 mm in length and 10 μm in diameter.

[0031] Example 1

[0032] A fiber-reinforced self-healing concrete comprises the following raw materials: 50g silica sol, 10g calcium sulfate, 100g ethylene-vinyl acetate copolymer, 50g thermoplastic polyester elastomer, 1g sodium chloride, 10g Pasteurella multocida bacterial solution with urease activity of 50mmol / (L·min), 10g dopamine hydrochloride, 400g coarse aggregate, 200g fine aggregate, 10g chopped basalt fiber, 50g kaolin, 10g urea, 400g fly ash, 400g PO42.5 silicate cement, and 10g sulfonated melamine-formaldehyde resin.

[0033] The preparation method of the above-mentioned fiber-reinforced self-healing concrete includes the following steps:

[0034] S1. Ethylene-vinyl acetate copolymer, thermoplastic polyester elastomer, and sodium chloride are mixed evenly and fed into an extruder for melt spinning at a spinning temperature of 180℃. The resulting blended fibers are cut to a length of 6mm and a fineness of 5μm. The fibers are then immersed in water and ultrasonically vibrated for 10 minutes at an ultrasonic frequency of 70kHz. After filtration, washing, and vacuum drying, porous fibers are obtained.

[0035] S2. Add the porous fiber to 300g of deionized water, add Bacillus pasteurellium bacterial solution, stir at 100r / min for 1h, adjust the pH of the system to 7.5-8, add dopamine hydrochloride, continue stirring for 10h, filter, and vacuum dry to obtain organic porous fiber.

[0036] S3. Mix coarse aggregate, fine aggregate, and chopped basalt fiber evenly, then add fly ash, kaolin, cement, and urea and mix evenly to obtain a premix.

[0037] S4. Stir the silica sol and organic porous fiber evenly, sonicate for 1 hour at a frequency of 50kHz, add the premix, sulfonated melamine-formaldehyde resin, calcium sulfate and 100g of water and stir evenly. Pour into the mold, vibrate and dry, demold and cure at 25℃.

[0038] Example 2

[0039] A fiber-reinforced self-healing concrete comprises the following raw materials: 100g silica sol, 20g calcium sulfate, 200g ethylene-vinyl acetate copolymer, 150g thermoplastic polyester elastomer, 10g sodium chloride, 30g urea-containing Micrococcus urealyticum solution with a urease activity of 60 mmol / (L·min), 30g dopamine hydrochloride, 600g coarse aggregate, 400g fine aggregate, 50g chopped basalt fiber, 150g kaolin, 40g urea, 600g fly ash, 500g PO42.5 silicate cement, and 20g aromatic aminosulfonate polymer.

[0040] The preparation method of the above-mentioned fiber-reinforced self-healing concrete includes the following steps:

[0041] S1. Ethylene-vinyl acetate copolymer, thermoplastic polyester elastomer, and sodium chloride are mixed evenly and fed into an extruder for melt spinning at a spinning temperature of 200℃. The resulting blended fibers are cut to a length of 20mm and a fineness of 15μm. The fibers are then soaked in water and ultrasonically vibrated for 30min at a frequency of 90kHz. After filtration, washing, and vacuum drying, porous fibers are obtained.

[0042] S2. Add the porous fiber to 600g of deionized water, add urea-containing micrococcus bacteria solution, stir at 300r / min for 2h, adjust the pH of the system to 7.5-8, add dopamine hydrochloride, continue stirring for 20h, filter, and vacuum dry to obtain organic porous fiber.

[0043] S3. Mix coarse aggregate, fine aggregate, and chopped basalt fiber evenly, then add fly ash, kaolin, cement, and urea and mix evenly to obtain a premix.

[0044] S4. Stir the silica sol and organic porous fiber evenly, sonicate for 2 hours at a frequency of 70kHz, add the premix, aromatic aminosulfonate polymer, calcium sulfate and 200g water and stir evenly. Pour into the mold, vibrate and dry, demold and cure at 25℃.

[0045] Example 3

[0046] A fiber-reinforced self-healing concrete comprises the following raw materials: 70g silica sol, 12g calcium sulfate, 120g ethylene-vinyl acetate copolymer, 120g thermoplastic polyester elastomer, 3g sodium chloride, 25g urease bacteria solution with urease activity of 55mmol / (L·min), 15g dopamine hydrochloride, 550g coarse aggregate, 250g fine aggregate, 40g chopped basalt fiber, 80g kaolin, 30g urea, 450g fly ash, 480g PO42.5 silicate cement, and 18g calcium lignosulfonate.

[0047] The ratio of viable Bacillus pasteurellii to viable Micrococcus urealyticum in the bacterial culture was 3:2.

[0048] The preparation method of the above-mentioned fiber-reinforced self-healing concrete includes the following steps:

[0049] S1. Ethylene-vinyl acetate copolymer, thermoplastic polyester elastomer, and sodium chloride are mixed evenly and fed into an extruder for melt spinning at a spinning temperature of 195℃. The resulting blended fibers are cut to a length of 10mm and a fineness of 12μm. The fibers are then immersed in water and ultrasonically vibrated for 15min at an ultrasonic frequency of 85kHz. After filtration, washing, and vacuum drying, porous fibers are obtained.

[0050] S2. Add the porous fiber to 400g of deionized water, add urease bacteria solution, stir at 250r / min for 80min, adjust the pH of the system to 7.5-8, add dopamine hydrochloride, continue stirring for 18h, filter, and vacuum dry to obtain organic porous fiber.

[0051] S3. Mix coarse aggregate, fine aggregate, and chopped basalt fiber evenly, then add fly ash, kaolin, cement, and urea and mix evenly to obtain a premix.

[0052] S4. Stir the silica sol and organic porous fiber evenly, sonicate for 80 minutes at a frequency of 65 kHz, add the premix, calcium lignosulfonate, calcium sulfate and 120 g of water and stir evenly. Pour into the mold, vibrate and dry, demold and cure at 25 ℃.

[0053] Example 4

[0054] A fiber-reinforced self-healing concrete comprises the following raw materials: 90g silica sol, 18g calcium sulfate, 180g ethylene-vinyl acetate copolymer, 80g thermoplastic polyester elastomer, 7g sodium chloride, 15g urease bacteria solution with urease activity of 55mmol / (L·min), 25g dopamine hydrochloride, 450g coarse aggregate, 350g fine aggregate, 20g chopped basalt fiber, 120g kaolin, 20g urea, 550g fly ash, 420g PO42.5 silicate cement, and 12g calcium lignosulfonate.

[0055] The ratio of viable Bacillus pasteurellii to viable Micrococcus urealyticum in the Ureaplasma urealyticum culture was 1:4.

[0056] The preparation method of the above-mentioned fiber-reinforced self-healing concrete includes the following steps:

[0057] S1. Ethylene-vinyl acetate copolymer, thermoplastic polyester elastomer, and sodium chloride are mixed evenly and fed into an extruder for melt spinning at a spinning temperature of 185℃. The resulting blended fibers are cut to a length of 18mm and a fineness of 8μm. The fibers are then soaked in water and ultrasonically vibrated for 25 minutes at a frequency of 75kHz. After filtration, washing, and vacuum drying, porous fibers are obtained.

[0058] S2. Add the porous fiber to 500g of deionized water, add urease bacteria solution, stir at 150r / min for 100min, adjust the pH of the system to 7.5-8, add dopamine hydrochloride, continue stirring for 12h, filter, and vacuum dry to obtain organic porous fiber.

[0059] S3. Mix coarse aggregate, fine aggregate, and chopped basalt fiber evenly, then add fly ash, kaolin, cement, and urea and mix evenly to obtain a premix.

[0060] S4. Stir the silica sol and organic porous fiber evenly, sonicate for 100 minutes at a frequency of 55 kHz, add the premix, calcium lignosulfonate, calcium sulfate and 180 g of water and stir evenly. Pour into the mold, vibrate and dry, demold and cure at 25 ℃.

[0061] Example 5

[0062] A fiber-reinforced self-healing concrete comprises the following raw materials: 80g silica sol, 15g calcium sulfate, 150g ethylene-vinyl acetate copolymer, 100g thermoplastic polyester elastomer, 5g sodium chloride, 20g urease bacteria solution with urease activity of 55mmol / (L·min), 20g dopamine hydrochloride, 500g coarse aggregate, 300g fine aggregate, 30g chopped basalt fiber, 100g kaolin, 25g urea, 500g fly ash, 450g PO42.5 silicate cement, and 15g calcium lignosulfonate.

[0063] The ratio of viable Bacillus pasteurellii to viable Micrococcus urealyticum in the Ureaplasma urealyticum culture was 1:1.

[0064] The preparation method of the above-mentioned fiber-reinforced self-healing concrete includes the following steps:

[0065] S1. Ethylene-vinyl acetate copolymer, thermoplastic polyester elastomer, and sodium chloride are mixed evenly and fed into an extruder for melt spinning at a spinning temperature of 190℃. The resulting blended fibers are cut to a length of 15mm and a fineness of 10μm. The fibers are then soaked in water and ultrasonically vibrated for 20min at an ultrasonic frequency of 80kHz. After filtration, washing, and vacuum drying, porous fibers are obtained.

[0066] S2. Add the porous fiber to 450g of deionized water, add urease bacteria solution, stir at 200r / min for 90min, adjust the pH of the system to 7.5-8, add dopamine hydrochloride, continue stirring for 15h, filter, and vacuum dry to obtain organic porous fiber.

[0067] S3. Mix coarse aggregate, fine aggregate, and chopped basalt fiber evenly, then add fly ash, kaolin, cement, and urea and mix evenly to obtain a premix.

[0068] S4. Stir the silica sol and organic porous fiber evenly, sonicate for 90 minutes at a frequency of 60 kHz, add the premix, calcium lignosulfonate, calcium sulfate and 150 g of water and stir evenly. Pour into the mold, vibrate and dry, demold and cure at 25 ℃.

[0069] Comparative Example 1

[0070] A fiber-reinforced self-healing concrete comprises the following raw materials: 80g silica sol, 15g calcium sulfate, 150g ethylene-vinyl acetate copolymer, 100g thermoplastic polyester elastomer, 20g urease bacteria solution with urease activity of 55mmol / (L·min), 20g dopamine hydrochloride, 500g coarse aggregate, 300g fine aggregate, 30g chopped basalt fiber, 100g kaolin, 25g urea, 500g fly ash, 450g PO42.5 silicate cement, and 15g calcium lignosulfonate.

[0071] The ratio of viable Bacillus pasteurellii to viable Micrococcus urealyticum in the Ureaplasma urealyticum culture was 1:1.

[0072] The preparation method of the above-mentioned fiber-reinforced self-healing concrete includes the following steps:

[0073] S1. Ethylene-vinyl acetate copolymer and thermoplastic polyester elastomer are mixed evenly and fed into an extruder for melt spinning at a spinning temperature of 190℃. The resulting blended fibers are cut to a length of 15mm and a fineness of 10μm. The fibers are then soaked in water and ultrasonically vibrated for 20min at an ultrasonic frequency of 80kHz. After filtration, washing, and vacuum drying, porous fibers are obtained.

[0074] S2. Add the porous fiber to 450g of deionized water, add urease bacteria solution, stir at 200r / min for 90min, adjust the pH of the system to 7.5-8, add dopamine hydrochloride, continue stirring for 15h, filter, and vacuum dry to obtain organic porous fiber.

[0075] S3. Mix coarse aggregate, fine aggregate, and chopped basalt fiber evenly, then add fly ash, kaolin, cement, and urea and mix evenly to obtain a premix.

[0076] S4. Stir the silica sol and organic porous fiber evenly, sonicate for 90 minutes at a frequency of 60 kHz, add the premix, calcium lignosulfonate, calcium sulfate and 150 g of water and stir evenly. Pour into the mold, vibrate and dry, demold and cure at 25 ℃.

[0077] Comparative Example 2

[0078] A fiber-reinforced self-healing concrete comprises the following raw materials: 80g silica sol, 15g calcium sulfate, 150g ethylene-vinyl acetate copolymer, 100g thermoplastic polyester elastomer, 5g sodium chloride, 20g urease bacteria solution with urease activity of 55mmol / (L·min), 500g coarse aggregate, 300g fine aggregate, 30g chopped basalt fiber, 100g kaolin, 25g urea, 500g fly ash, 450g PO42.5 silicate cement, and 15g calcium lignosulfonate.

[0079] The ratio of viable Bacillus pasteurellii to viable Micrococcus urealyticum in the Ureaplasma urealyticum culture was 1:1.

[0080] The preparation method of the above-mentioned fiber-reinforced self-healing concrete includes the following steps:

[0081] S1. Ethylene-vinyl acetate copolymer, thermoplastic polyester elastomer, and sodium chloride are mixed evenly and fed into an extruder for melt spinning at a spinning temperature of 190℃. The resulting blended fibers are cut to a length of 15mm and a fineness of 10μm. The fibers are then soaked in water and ultrasonically vibrated for 20min at an ultrasonic frequency of 80kHz. After filtration, washing, and vacuum drying, porous fibers are obtained.

[0082] S2. Add the porous fiber to 450g of deionized water, add urease bacteria solution, stir at 200r / min for 90min, filter, and vacuum dry to obtain organic porous fiber.

[0083] S3. Mix coarse aggregate, fine aggregate, and chopped basalt fiber evenly, then add fly ash, kaolin, cement, and urea and mix evenly to obtain a premix.

[0084] S4. Stir the silica sol and organic porous fiber evenly, sonicate for 90 minutes at a frequency of 60 kHz, add the premix, calcium lignosulfonate, calcium sulfate and 150 g of water and stir evenly. Pour into the mold, vibrate and dry, demold and cure at 25 ℃.

[0085] Comparative Example 3

[0086] A fiber-reinforced self-healing concrete comprises the following raw materials: 15g calcium sulfate, 150g ethylene-vinyl acetate copolymer, 100g thermoplastic polyester elastomer, 5g sodium chloride, 20g urease bacteria solution with urease activity of 55mmol / (L·min), 20g dopamine hydrochloride, 500g coarse aggregate, 300g fine aggregate, 30g chopped basalt fiber, 100g kaolin, 25g urea, 500g fly ash, 450g PO42.5 silicate cement, and 15g calcium lignosulfonate.

[0087] The ratio of viable Bacillus pasteurellii to viable Micrococcus urealyticum in the Ureaplasma urealyticum culture was 1:1.

[0088] The preparation method of the above-mentioned fiber-reinforced self-healing concrete includes the following steps:

[0089] S1. Ethylene-vinyl acetate copolymer, thermoplastic polyester elastomer, and sodium chloride are mixed evenly and fed into an extruder for melt spinning at a spinning temperature of 190℃. The resulting blended fibers are cut to a length of 15mm and a fineness of 10μm. The fibers are then soaked in water and ultrasonically vibrated for 20min at an ultrasonic frequency of 80kHz. After filtration, washing, and vacuum drying, porous fibers are obtained.

[0090] S2. Add the porous fiber to 450g of deionized water, add urease bacteria solution, stir at 200r / min for 90min, adjust the pH of the system to 7.5-8, add dopamine hydrochloride, continue stirring for 15h, filter, and vacuum dry to obtain organic porous fiber.

[0091] S3. Mix coarse aggregate, fine aggregate, and chopped basalt fiber evenly, then add fly ash, kaolin, cement, and urea and mix evenly to obtain a premix.

[0092] S4. Mix the organic porous fiber, premix, calcium lignosulfonate, calcium sulfate, and 150g of water evenly, pour into the mold, vibrate and dry, demold, and cure at 25℃.

[0093] Referring to GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", the concrete samples obtained in Example 5 and Comparative Examples 1-3 were subjected to freeze-thaw cycle tests using the rapid freezing method. The specific operation was as follows: the concrete samples were immersed in water at 24℃, with the water level 20mm above the sample. After 4 days, they were removed. At the end of the freezing and thawing periods, the center temperature of the specimens was controlled at [temperature range missing]. The freeze-thaw cycles were conducted at 17±2℃ and 8±2℃; each freeze-thaw cycle was completed within 4 hours, with the thawing time being no less than 1 / 4 of the entire freeze-thaw cycle. After each set of freeze-thaw cycles, the corresponding samples were removed, their surfaces were wiped dry with a damp cloth, and their compressive strength and splitting tensile strength were tested.

[0094] The compressive strength test is as follows: After removing the specimen from the freeze-thaw cycler, wipe the surface of the specimen dry with a damp cloth and observe its appearance. Draw the center line and measure the dimensions of the compression surface of the specimen. Place the specimen in the center of the press. When the upper pressure plate is 10-20 mm away from the compression surface of the specimen, jog the adjusting ball seat to ensure even contact. Referring to GB / T 50081-2019 "Test Methods for Mechanical Properties of Ordinary Concrete", load each group of specimens with an acceleration of 0.5 MPa / s until the specimen fails, and record the failure load. The splitting tensile strength test is as follows: Place an arc-shaped pad (75mm radius, steel pad) and a pad (120mm long, 20mm wide, and 4mm thick, three-layer plywood pad, which cannot be reused) between the upper and lower pressure plates and the test block. When placing the test block, ensure that the center line of the test block is aligned with the center of the steel pad. The loading speed is 0.05MPa / s (1 / 10 of the loading speed of the compressive strength test). The subsequent process is the same as the compressive strength test.

[0095] like Figure 1 and Figure 2 As shown, under the same number of freeze-thaw cycles, the compressive strength and splitting tensile strength of the concrete specimens obtained in Example 5 were always the highest, which were better than those of Comparative Examples 1-3 (P<0.05).

[0096] The concrete dog-bone specimens obtained in Example 5 and Comparative Examples 1-3 were subjected to pre-damage testing. The specimens were pre-loaded using a universal testing machine, with the load level controlled to not exceed 60% of their compressive strength. Damage was pre-induced through repeated longitudinal and transverse loading. Every 3-5 loading cycles, the wave velocity of the damaged specimens was measured using an ultrasonic testing instrument. The degree of damage to the concrete specimens was calculated using the following formula.

[0097] M = 1 — (v1 ÷ v2) 2 Where M represents the degree of concrete damage, V1 represents the wave velocity of the specimen before precast damage, and V2 represents the wave velocity of the specimen after precast damage.

[0098] By adjusting the load size and number of loading cycles, the damage distribution of the specimens was finally made to be between 0.2 and 0.3. Subsequently, 25 cracks of different widths were marked as crack observation points. The residual width of the 25 crack points of different widths was measured again at the repair curing age of 7 days, 14 days, and 28 days, and the overall repair rate was calculated.

[0099] Overall repair rate = (Initial unrepaired crack width - Residual crack width after repair) ÷ Initial unrepaired crack width × 100%.

[0100] like Figure 3 As shown, the overall repair rate of the concrete specimens obtained in Example 5 was consistently the highest, which was better than that of Comparative Examples 1-3 (P<0.05).

[0101] The reason for the above results is that the present invention uses a dissolution pore-forming process of EVA / TPE resin and sodium chloride to form a fiber carrier with controllable pore size; while the combination of polydopamine coating and silica sol can effectively achieve bacterial cell immobilization and form a protective shell, significantly improving the survival rate of urease-producing bacteria in concrete. Moreover, when cracks extend to the fiber area, the CO3 produced by urease catalyzing the hydrolysis of urea... 2- With Ca in concrete 2+ The directional deposition of calcium carbonate on the fiber surface results in high interfacial bonding strength between the repair body and the matrix, and excellent self-healing performance. Simultaneously, the porous fibers obtained in this invention increase the friction coefficient between the fiber and aggregate, forming a uniform multidirectional branched system in concrete. Combined with the action of chopped basalt fibers, a three-dimensional strengthening effect is produced in concrete, thereby improving the overall integrity of the concrete and enhancing its resistance to cracking and shrinkage deformation. In the organic porous fibers obtained in this invention, the surface deposition of polydopamine and its compounding with silica sol effectively enhances the interfacial bonding with fly ash, kaolin, and cement. Further compounding with chopped basalt fibers allows the concrete to dissipate energy through plastic deformation of the composite fibers in the early stages of crack development. As the crack width continues to expand, the microbial repair of the porous fibers is initiated, and the calcium carbonate deposits, combined with the fiber structure, achieve a dynamic balance between strength and self-healing function. Moreover, even after freeze-thaw cycles, its mass loss rate is low, and its self-healing effect is good.

[0102] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A fiber-reinforced self-healing concrete, characterized in that, The raw materials, by weight, include: 5-10 parts silica sol, 1-2 parts calcium sulfate, 10-20 parts ethylene-vinyl acetate copolymer, 5-15 parts TPE resin, 0.1-1 parts sodium chloride, 1-3 parts urease bacteria solution, 1-3 parts dopamine hydrochloride, 40-60 parts coarse aggregate, 20-40 parts fine aggregate, 1-5 parts chopped basalt fiber, 5-15 parts kaolin, 1-4 parts urea, 40-60 parts fly ash, 40-50 parts cement, and 1-2 parts water-reducing agent. The method for preparing the fiber-reinforced self-healing concrete includes the following steps: S1. Mix ethylene-vinyl acetate copolymer, TPE resin and sodium chloride evenly, melt spin at 180-200℃, cut to obtain blended fibers; soak in water and ultrasonically vibrate for 10-30 minutes, filter, wash and vacuum dry to obtain porous fibers. S2. Add the porous fiber to water, add urease bacteria solution and stir for 1-2 hours. Adjust the pH of the system to 7.5-8, add dopamine hydrochloride and continue stirring for 10-20 hours. Filter and vacuum dry to obtain organic porous fiber. S3. Mix coarse aggregate, fine aggregate, and chopped basalt fiber evenly, then add fly ash, kaolin, cement, and urea and mix evenly to obtain a premix. S4. Stir the silica sol and organic porous fibers evenly, sonicate for 1-2 hours, add premix, water-reducing agent, calcium sulfate and water, stir evenly, pour, dry and cure.

2. The fiber-reinforced self-healing concrete according to claim 1, characterized in that, Urease-producing bacteria include Bacillus pasteurellii and / or Micrococcus urealyticum.

3. The fiber-reinforced self-healing concrete according to claim 1, characterized in that, The urease activity in the bacterial culture of Urease-producing bacteria is 50-60 mmol / (L·min).

4. The fiber-reinforced self-healing concrete according to claim 1, characterized in that, The coarse aggregate is crushed stone with a diameter of 15-25 mm, a water absorption rate of 2.5-4.5%, and an apparent density of 2200-2450 kg / m³. 3 .

5. The fiber-reinforced self-healing concrete according to claim 1, characterized in that, The fine aggregate is natural river sand with a fineness modulus of 2-3 and an apparent density of 2.25-2.55 g / cm³. 3 .

6. The fiber-reinforced self-healing concrete according to claim 1, characterized in that, The length of the chopped basalt fiber is 20-25 mm, and the diameter of the single filament is 5-15 μm.

7. The fiber-reinforced self-healing concrete according to claim 1, characterized in that, The water-reducing agent is at least one of lignin sulfonate, sulfonated melamine-formaldehyde resin, and aromatic aminosulfonate polymer.

8. A method for preparing fiber-reinforced self-healing concrete as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Mix ethylene-vinyl acetate copolymer, TPE resin and sodium chloride evenly, melt spin at 180-200℃, cut to obtain blended fibers; soak in water and ultrasonically vibrate for 10-30 minutes, filter, wash and vacuum dry to obtain porous fibers. S2. Add the porous fiber to water, add urease bacteria solution and stir for 1-2 hours. Adjust the pH of the system to 7.5-8, add dopamine hydrochloride and continue stirring for 10-20 hours. Filter and vacuum dry to obtain organic porous fiber. S3. Mix coarse aggregate, fine aggregate, and chopped basalt fiber evenly, then add fly ash, kaolin, cement, and urea and mix evenly to obtain a premix. S4. Stir the silica sol and organic porous fibers evenly, sonicate for 1-2 hours, add premix, water-reducing agent, calcium sulfate and water, stir evenly, pour, dry and cure.

9. The method for preparing fiber-reinforced self-healing concrete according to claim 8, characterized in that, In S1, the ultrasonic oscillation frequency is 70-90kHz.

10. The method for preparing fiber-reinforced self-healing concrete according to claim 8, characterized in that, In S4, the ultrasonic processing frequency is 50-70kHz.

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