Preparation method of capillary crystalline self-repairing concrete

Abstract

The invention discloses a preparation method of capillary crystalline self-repairing concrete, which comprises the following steps: adding zeolite powder into a urease solution for dipping treatment to obtain pretreated zeolite powder; adding the pretreated zeolite powder into a mixed solution A containing urea and sodium alginate, adding a calcium chloride solution A, and separating a solid phase to obtain coated zeolite powder; fumed silica is added into a magnesium chloride solution to be mixed, polyethylene glycol is added, ultrasonic dispersion is conducted, and dispersion liquid is obtained; mixing the coated zeolite powder with the dispersion liquid, adding a sodium alginate solution, mixing, adding a calcium chloride solution B, and separating a solid phase to obtain modified zeolite powder; mixing preparation raw materials including the modified zeolite powder, the cement, the fly ash, the polycarboxylic acid water reducing agent and the aggregate to obtain the concrete. The concrete prepared through the method is good in crack self-repairing effect and good in mechanical strength, and the durability and the service life of the concrete can be improved easily.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete materials, and in particular to a method for preparing permeable crystallization self-repairing concrete. Background Art

[0002] Concrete is a building material made from cement, aggregate, and water mixed in specific proportions. It boasts high strength, low cost, and excellent formability, making it widely used in various building structures. However, during the pouring, curing, and service life of concrete structures, microcracks often form within the material due to factors such as uneven settlement, temperature and humidity fluctuations, and uneven hydration reactions. These microcracks can serve as infiltration pathways for moisture and corrosive media, significantly weakening the concrete's impermeability, mechanical properties, and durability, posing safety risks and causing economic losses.

[0003] Existing concrete crack repair technologies mainly include surface spraying and grouting repair. Surface spraying is a simple process, but it is only suitable for surface cracks and cannot effectively seal internal defects. Grouting repair can fill deep cracks, but it has problems such as complex construction process, high equipment requirements, low repair efficiency, and high cost. In recent years, some studies have proposed incorporating functional self-healing materials into concrete to achieve autonomous repair and healing when cracks occur. However, such materials often have problems such as high process control requirements, poor environmental adaptability, limited repair effect, or adverse effects on concrete strength, making them difficult to promote and apply in actual projects.

[0004] Therefore, it is necessary to develop a self-healing material with stable performance, rapid response and simple process. Summary of the Invention

[0005] The present invention provides a method for preparing permeable crystallization self-repairing concrete. The prepared concrete has good mechanical properties and can achieve effective spontaneous repair after cracks are generated, thereby significantly improving the durability and service life of the concrete.

[0006] Specifically, an embodiment of the present invention relates to a method for preparing permeable crystallization self-repairing concrete, comprising the following steps:

[0007] S1, adding zeolite powder to urease solution for immersion treatment, and drying to obtain pretreated zeolite powder;

[0008] S2, adding the pretreated zeolite powder to a mixed solution A containing urea and sodium alginate, adding calcium chloride solution A under stirring, separating the solid phase, washing, and drying to obtain coated zeolite powder;

[0009] S3, adding fumed silica to the magnesium chloride solution, mixing, adding polyethylene glycol, and ultrasonically dispersing to obtain a dispersion;

[0010] S4, mixing the coated zeolite powder with the dispersion, adding the sodium alginate solution and mixing, adding the calcium chloride solution B under stirring, separating the solid phase, washing, and drying to obtain modified zeolite powder;

[0011] S5. Mixing the raw materials including the modified zeolite powder, cement, fly ash, polycarboxylate water reducer and aggregate to obtain permeable crystallization self-repairing concrete.

[0012] The method for preparing the infiltration crystallization self-repairing concrete according to the first embodiment of the present invention has at least the following beneficial effects:

[0013] The porous structure of zeolite powder effectively immobilizes urease; urea molecules easily penetrate the zeolite pores, forming a stable loading system with the urease. When cracks form, water seeps in, releasing urease to hydrolyze urea to form carbonate ions, which react with calcium ions to deposit calcium carbonate at the cracks, achieving self-healing. The calcium alginate gel layer formed by the reaction of sodium alginate and calcium chloride coats the surface of the zeolite powder, effectively blocking the effects of the concrete's alkaline environment on urease activity and improving its long-term stability.

[0014] Fumed silica adsorbs magnesium ions to form a silicon-magnesium composite carrier. Polyethylene glycol molecules are introduced to enhance particle dispersibility and inhibit agglomeration. A secondary coating with a calcium alginate gel layer immobilizes the magnesium-loaded fumed silica on the surface of the coated zeolite powder. Once cracks form, the magnesium ions and fumed silica act synergistically to rapidly induce the formation of a dense calcium carbonate precipitate, significantly enhancing the crack self-healing rate and effectiveness. The hypothesized mechanism is as follows: the fumed silica surface is rich in reactive groups, such as hydroxyl groups, which adsorb calcium ions, lowering the nucleation barrier for calcium carbonate at the interface and promoting heterogeneous nucleation. Magnesium ions, acting as a nucleation inducer, further promote multi-point nucleation of calcium carbonate, increasing deposition and leading to the formation of a dense structure with smaller grain size and lower porosity. Furthermore, the fumed silica particles themselves act as a hard core skeleton, providing support for the dense calcium carbonate deposition on their surface. This enhances the continuity and mechanical strength of the deposited layer, thus strengthening the crack self-healing effect.

[0015] In summary, the modified zeolite powder achieves stable loading and release of urease, synergistically inducing the formation of a dense calcium carbonate deposit with fumed silica and magnesium ions, enhancing self-repair efficiency. Furthermore, its surface coating possesses excellent water retention, enhancing interfacial strength and improving the concrete's workability and mechanical strength.

[0016] By incorporating fly ash and polycarboxylate superplasticizers, the alkaline environment within concrete can be effectively reduced, alleviating the problem of reduced urease activity caused by excessive alkalinity. By rationally combining the components, the self-healing properties of modified zeolite powder are fully utilized, improving the mechanical properties and long-term service reliability of concrete.

[0017] According to some embodiments of the present invention, the activity of the urease solution is 6 to 15 U / mL, for example, 6 U / mL, 9 U / mL, 12 U / mL or 15 U / mL.

[0018] The urease solution can be extracted using soybeans as raw material using methods known in the art, which has the advantages of simple process and low cost. Specifically, soybean powder can be dispersed in water at a mass concentration of 20 to 100 g / L, stirred at room temperature for 30 to 60 minutes, and then centrifuged to remove insoluble matter. The resulting supernatant is collected as the urease solution. The particle size of the soybean powder is controlled to be no coarser than 100 mesh to improve the extraction efficiency of urease. The present invention does not impose any particular restrictions on the stirring rate; there are no particular restrictions on the centrifugation conditions. For example, solid-liquid separation can be achieved by centrifugation at a speed of 4000 to 10000 rpm and 4 to 8°C for 8 to 15 minutes.

[0019] According to some embodiments of the present invention, the zeolite powder is clinoptilolite, which has low cost and good adsorption performance.

[0020] According to some embodiments of the present invention, the particle size of the zeolite powder is 300-800 mesh. For example, common commercial specifications include 325 mesh, 425 mesh, 600 mesh and 800 mesh. The appropriate particle size can be selected according to actual needs.

[0021] According to some embodiments of the present invention, the solid-liquid ratio of the zeolite powder to the urease solution is 1 kg / 2 to 5 L, for example, 1 kg / 2 L, 1 kg / 3 L, 1 kg / 4 L or 1 kg / 5 L.

[0022] According to some embodiments of the present invention, the immersion time is 60 to 120 hours, for example, 60 hours, 72 hours, 84 hours, 96 hours, 108 hours or 120 hours.

[0023] According to some embodiments of the present invention, stirring is performed during the immersion process, wherein the stirring rate is not particularly limited, and can be, for example, 200 to 300 rpm.

[0024] According to some embodiments of the present invention, the urea concentration in the mixed solution A is 0.8 to 2 mol / L, and the mass concentration of sodium alginate is 0.5% to 2%. Specifically, the urea concentration can be 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, or 2 mol / L; and the sodium alginate concentration can be 0.5%, 1%, 1.5%, or 2%.

[0025] According to some embodiments of the present invention, the solid-liquid ratio of the pretreated zeolite powder to the mixed solution A is 1kg / 5-10L, for example, 1kg / 5L, 1kg / 6L, 1kg / 7L, 1kg / 8L, 1kg / 9L or 1kg / 10L.

[0026] According to some embodiments of the present invention, the concentration of calcium chloride solution A is 0.05-0.15 mol / L, and the feeding rate is 5-15 mL / min. Specifically, the concentration of calcium chloride solution A can be 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.12 mol / L or 0.15 mol / L, and the feeding rate can be 5 mL / min, 8 mL / min, 10 mL / min, 12 mL / min or 15 mL / min.

[0027] By regulating the concentration of calcium chloride solution A and the solid-liquid ratio of the mixed liquid, rapid feeding can be achieved while ensuring the uniformity and stability of the coating process.

[0028] According to some embodiments of the present invention, the mass ratio of calcium chloride in the calcium chloride solution A to sodium alginate in the mixed solution A is 1 to 4:1, for example, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1.

[0029] According to some embodiments of the present invention, the specific surface area of ​​the fumed silica is 200 to 400 m 2 / g, for example 200m 2 / g、300m 2 / g or 400m 2 / g.

[0030] According to some embodiments of the present invention, in step S3, the mass ratio of the fumed silica to the zeolite powder is 1:4 to 6, for example, 1:4, 1:4.5, 1:5, 1:5.5 or 1:6.

[0031] According to some embodiments of the present invention, the concentration of the magnesium chloride solution is 0.05 to 0.1 mol / L, for example, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L or 0.1 mol / L.

[0032] According to some embodiments of the present invention, the solid-liquid ratio of the fumed silica to the magnesium chloride solution is 1 kg / 20 to 50 L, for example, 1 kg / 20 L, 1 kg / 25 L, 1 kg / 30 L, 1 kg / 35 L, 1 kg / 40 L, 1 kg / 45 L or 1 kg / 50 L.

[0033] According to some embodiments of the present invention, the number average molecular weight of the polyethylene glycol is 2000-6000, for example, PEG2000, PEG3000, PEG4000, PEG5000 or PEG6000 can be selected.

[0034] According to some embodiments of the present invention, the mass ratio of polyethylene glycol to fumed silica is 0.5 to 2:1, for example, 0.5:1, 1:1, 1.5:1 or 2:1.

[0035] According to some embodiments of the present invention, in step S3, the ultrasonic dispersion power is 200-600 W and the dispersion time is 10-30 min. The present invention does not strictly limit the ultrasonic dispersion conditions and parameters, which can be appropriately adjusted according to specific application requirements to achieve a good particle dispersion effect.

[0036] According to some embodiments of the present invention, in step S4, the mass concentration of the sodium alginate solution is 1% to 3%, for example, 1%, 1.5%, 2%, 2.5% or 3%.

[0037] According to some embodiments of the present invention, the solid-liquid ratio of the coated zeolite powder to the sodium alginate solution is 1 kg / 10-15 L, for example, 1 kg / 10 L, 1 kg / 12 L or 1 kg / 15 L.

[0038] According to some embodiments of the present invention, the concentration of the calcium chloride solution B is 0.05-0.15 mol / L, and the feeding rate is 5-15 mL / min. The specific values ​​can be selected with reference to the concentration and feeding rate of the calcium chloride solution A in step S2.

[0039] According to some embodiments of the present invention, the mass ratio of calcium chloride in the calcium chloride solution B to sodium alginate in the sodium alginate solution is 1 to 4:1, for example, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1.

[0040] According to some embodiments of the present invention, in steps S2 and S4, the stirring rate is independently selected from 500 to 650 rpm, such as 500 rpm, 550 rpm, 600 rpm or 650 rpm.

[0041] According to some embodiments of the present invention, in steps S2 and S4, the method for separating the solid phase is filtration.

[0042] According to some embodiments of the present invention, in steps S1, S2 and S4, the drying temperature is no higher than 40°C.

[0043] According to some embodiments of the invention, the aggregate includes coarse aggregate and fine aggregate.

[0044] According to some embodiments of the present invention, the raw materials for preparing the permeable crystallization self-repairing concrete include, by mass: 100 parts of cement, 35-40 parts of modified zeolite powder, 18-22 parts of fly ash, 2.8-3.5 parts of polycarboxylate water reducer, 450-500 parts of coarse aggregate, and 200-220 parts of fine aggregate.

[0045] According to some embodiments of the present invention, the raw materials further include water, and the water-cement ratio is 0.34 to 0.38, for example, 0.34, 0.35, 0.36, 0.37, or 0.38. By incorporating appropriate amounts of fly ash and polycarboxylate superplasticizer and optimizing aggregate gradation, the fluidity of the mixture can be effectively improved at a lower water-cement ratio, thereby achieving a balance between the mechanical strength, durability, and workability of the concrete.

[0046] In practical applications, all components (except water) can be pre-mixed to form dry-mix concrete, which can then be added with water and stirred on site before use; or all components can be directly mixed on site to prepare wet-mix concrete.

[0047] According to some embodiments of the present invention, the coarse aggregate is continuously graded in a range of 5 to 20 mm.

[0048] According to some embodiments of the present invention, the gradation ratio of the coarse aggregate is 20% to 30% for 5-10 mm, 30% to 40% for 10-16 mm, and 35% to 45% for 16-20 mm.

[0049] According to some embodiments of the present invention, the fine aggregate is medium sand, which complies with the provisions of GB / T 14684-2022 "Construction Sand" and has a fineness modulus of 2.3 to 3.0. Specifically, river sand can be selected as the raw material.

[0050] According to some embodiments of the present invention, the cement is ordinary Portland cement, for example, strength grades include PO42.5, PO42.5R, PO52.5, and PO52.5R. Ordinary Portland cement has a good cost-effectiveness and is suitable for large-scale engineering applications.

[0051] According to some embodiments of the present invention, the fly ash is Class F fly ash, preferably a Class I or Class II product that complies with the GB / T 1596-2017 standard, has a low calcium oxide content and a high pozzolanic activity, which helps to reduce the alkalinity of the system and improve the penetration and repair ability, mechanical strength and durability of the concrete.

[0052] According to some embodiments of the present invention, the polycarboxylate water-reducing agent is selected from HPEG type or TPEG type, with a molecular weight of 2400 to 3000, which can effectively reduce the water-cement ratio and alleviate the alkalinity fluctuation of the system. Its steric hindrance effect has a barrier protection effect on urease, reducing the impact of the alkaline environment on the enzyme activity.

[0053] As used herein, the term "water-cement ratio" refers to the mass ratio of water to cement, excluding the mass of other cementitious materials in concrete (such as fly ash).

[0054] The term "room temperature" refers to 23±2°C.

[0055] The term "not higher than" includes the value itself, for example, not higher than 40°C includes 40°C.

[0056] Herein, the numerical ranges mentioned include the endpoint values ​​and encompass any sub-ranges within the range, such as the range obtained by any combination of the specifically listed numerical values.

[0057] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. DETAILED DESCRIPTION

[0058] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0059] In the following examples, the fine aggregate is river sand with a fineness modulus of 2.4 to 2.8.

[0060] The zeolite powder has a particle size of 600 mesh and is of the type of clinoptilolite.

[0061] Fumed silica, specific surface area 300m 2 / g.

[0062] The fly ash is Class F fly ash, grade II, and complies with GB / T 1596-2017 standard.

[0063] The cement is ordinary Portland cement with strength grade PO42.5.

[0064] The polycarboxylate water reducer is selected from TPEG-2400.

[0065] The preparation method of urease solution is as follows:

[0066] The dried soybean powder was passed through a 100-mesh sieve, and the sieve material was dispersed in deionized water to prepare a dispersion with a concentration of 50 g / L. The dispersion was stirred at 200 rpm at room temperature for 40 minutes, allowed to stand for initial sedimentation, and then centrifuged at 8000 rpm at 5°C for 12 minutes. The supernatant was the urease solution.

[0067] The urease activity was determined by conductivity method, and the test result was 9.3U / mL. The specific test steps are as follows:

[0068] Draw a standard curve between urea concentration and conductivity change. Prepare urea solution (concentration is 1.11 mol / L), measure 9 mL and place it in a 25°C constant temperature water bath to fully preheat the system temperature to a constant, and then measure the initial conductivity. Then add 1 mL of the urease solution to be tested and mix it quickly and evenly, and calculate the rate of increase of conductivity within 5 minutes after the reaction starts. According to the established standard curve, the amount of urea decomposition per unit time R is converted. u The urease activity was calculated using the urease concentration (μmol / min) (unit: U / mL, where 1 μmol of urea is catalyzed by 1 mL of urease solution per minute, and the activity is 1 U).

[0069] Unless otherwise specified, all relevant raw materials are commercially available conventional products.

[0070] Example 1

[0071] Step S1: Urease immobilization treatment

[0072] 1 kg of 600-mesh clinoptilolite powder was added to 3 L of urease solution with an activity of 9.3 U / mL (solid-liquid ratio of 1 kg / 3 L), stirred evenly at 250 rpm at room temperature, and then allowed to stand and soak for 72 hours; then filtered and separated, the resulting solid was dried at 35°C to obtain pretreated zeolite powder.

[0073] Step S2: Primary coating treatment

[0074] The obtained pretreated zeolite powder was added to a mixed solution A containing 1.5 mol / L of urea and 1.5 wt% of sodium alginate at a solid-liquid ratio of 1 kg / 8 L; the stirring was started to 600 rpm, and 0.1 mol / L of calcium chloride solution A was added at a rate of 12 mL / min, and the mass ratio of calcium chloride to sodium alginate was controlled to be 2:1; after the reaction, the mixture was filtered and washed twice with deionized water. The obtained solid was dried at 40° C. to obtain the coated zeolite powder.

[0075] Step S3: Preparation of silicon-magnesium composite dispersion

[0076] 200g of specific surface area 300m 2 / g of fumed silica was added to 6L of 0.07mol / L magnesium chloride solution (solid-liquid ratio of 1kg / 30L), PEG4000 was added (the mass ratio of PEG4000 to fumed silica was 1:1), ultrasonic power was 400W, and dispersion was carried out for 20 minutes to obtain a uniform dispersion.

[0077] Step S4: Secondary coating to form modified zeolite powder

[0078] The obtained dispersion was mixed with the coated zeolite powder obtained in step S2, and a sodium alginate solution with a concentration of 2 wt% (based on the mass of the coated zeolite powder, the solid-liquid ratio was 1 kg / 12 L) was added and stirred evenly; the stirring was turned on to 600 rpm, and 0.1 mol / L calcium chloride solution B was added at a rate of 14 mL / min, controlling the mass ratio of calcium chloride to sodium alginate to be 2.5:1; after the reaction, the mixture was filtered, washed twice with deionized water, and the obtained solid was dried at 40° C. to obtain the modified zeolite powder.

[0079] Step S5: Concrete preparation

[0080] S5.1. Add cement, modified zeolite powder, fly ash and polycarboxylate water reducer into a mixer in proportion and premix evenly;

[0081] S5.2. Add mixing water and continue stirring to form a uniform slurry;

[0082] S5.3. While stirring, add fine aggregate and coarse aggregate and mix evenly to obtain a concrete mixture;

[0083] S5.4. Pour the concrete mixture into a mold and compact it by vibration. Curing it at 20±2℃ and relative humidity ≥95% for 28 days.

[0084] The proportion of raw materials for preparing concrete is as follows:

[0085] Cement (PO42.5): 100 parts

[0086] Modified zeolite powder: 38 parts

[0087] Fly ash (Class F, Grade II): 20 parts

[0088] Polycarboxylate water reducer (TPEG-2400): 3.2 parts

[0089] Coarse aggregate: 480 parts

[0090] Fine aggregate: 210 parts

[0091] Water: 36 parts.

[0092] The grading of coarse aggregate is: 5-10mm25%, 10-16mm35%, 16-20mm40%.

[0093] Example 2

[0094] Compared with Example 1, the difference is that, by mass, the raw material ratios for preparing the concrete are as follows:

[0095] Cement (PO42.5): 100 parts

[0096] Modified zeolite powder: 35 parts

[0097] Fly ash (Class F, Grade II): 18 parts

[0098] Polycarboxylate water reducer (TPEG-2400): 2.8 parts

[0099] Coarse aggregate: 460 parts

[0100] Fine aggregate: 200 parts

[0101] Water: 37 parts.

[0102] The grading of coarse aggregate is: 5-10mm28%, 10-16mm32%, 16-20mm40%.

[0103] Comparative Example 1

[0104] Compared with Example 1, the difference is that step S3 is as follows:

[0105] 200g of specific surface area 300m 2 / g of fumed silica was added to 6L of deionized water (solid-liquid ratio of 1kg / 30L), PEG4000 was added (the mass ratio of PEG4000 to fumed silica was 1:1), ultrasonic power was 400W, and dispersion was carried out for 20 minutes to obtain a uniform dispersion.

[0106] Comparative Example 2

[0107] Compared with Example 1, the difference is that step S3 is not included, and step S4 is as follows:

[0108] 6 L of 0.07 mol / L magnesium chloride solution was mixed with the coated zeolite powder obtained in step S2, and a 2 wt% sodium alginate solution (based on the mass of the coated zeolite powder, the solid-liquid ratio was 1 kg / 12 L) was added and stirred evenly; stirring was turned on to 600 rpm, and 0.1 mol / L calcium chloride solution B was added at a rate of 14 mL / min, controlling the mass ratio of calcium chloride to sodium alginate to be 2.5:1; after the reaction, the mixture was filtered, washed twice with deionized water, and the resulting solid was dried at 40° C. to obtain modified zeolite powder.

[0109] Test Case

[0110] 1. Compressive strength: tested according to GB / T 50081-2019. The specimen is a cube with a side length of 150 mm. Standard curing (temperature 20±2°C, relative humidity ≥95%) is carried out for 28 days. The loading rate is 0.5 MPa / s. The number of specimens in each group is 3.

[0111] 2. Self-repair performance: Prepare prismatic concrete specimens with a size of 40mm×40mm×160mm. After 28 days of standard curing, use a three-point bending loading method to create cracks with a width of 0.2 to 0.4mm in the middle of the axial direction. Place the cracked specimens in an environment with a temperature of 25±2°C and a relative humidity of ≥95% for spray curing for 28 days. Each group has 30 specimens. After the curing is completed, the number of specimens without visible cracks is counted, and the crack repair rate is calculated (number of repaired specimens / total number of initial specimens). Specimens with no visible cracks are considered repaired.

[0112] The test results are shown in Table 1.

[0113] Table 1

[0114]

[0115] From the above results, it can be seen that Example 1 and Example 2 achieve excellent crack self-repairing performance while maintaining good compressive strength by constructing a synergistic system of "urease fixation + silicon magnesium induction + double-layer coating". Porous zeolite is used to immobilize urease and urea, and a double-layer coating structure is used to encapsulate it to play a barrier and protective role; when cracks are generated, the coating layer ruptures and seeps water, releasing urease, prompting the hydrolysis of urea to generate carbonate, which reacts with calcium ions to form dense calcium carbonate deposits, thereby achieving rapid self-repair of cracks. Among them, the compressive strength of Example 1 is slightly higher than that of Example 2, which may be due to its higher aggregate usage and better grading, which improves the overall density and bearing capacity of the concrete.

[0116] Comparative Example 1 does not use magnesium chloride, that is, the surface of the fumed silica is not loaded with magnesium ions, lacking nucleation induction centers, resulting in low nucleation efficiency in the calcium carbonate deposition process, insufficient density and continuity of the deposited layer, and significantly affecting the crack repair effect.

[0117] Comparative Example 2, without the introduction of fumed silica and relying solely on magnesium ions to induce calcium carbonate formation, lacks a hard core skeleton for support, making it difficult for the sediment to form a continuous, dense structure at the interface. The repair rate is also significantly lower than that of Example 1. The compressive strength of Comparative Example 2 is slightly lower than that of Example 1, likely due to the lack of silica particles filling and reinforcing the interface, resulting in relatively insufficient interfacial compatibility and density.

[0118] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the relevant technical field without departing from the scope of the present invention.

Claims

1. A method for preparing permeable crystallization self-repairing concrete, characterized by: The following steps are involved: S1, adding zeolite powder to urease solution for immersion treatment, and drying to obtain pretreated zeolite powder; S2, adding the pretreated zeolite powder to a mixed solution A containing urea and sodium alginate, adding calcium chloride solution A under stirring, separating the solid phase, washing, and drying to obtain coated zeolite powder; S3, adding fumed silica to the magnesium chloride solution, mixing, adding polyethylene glycol, and ultrasonically dispersing to obtain a dispersion; S4, mixing the coated zeolite powder with the dispersion, adding the sodium alginate solution and mixing, adding the calcium chloride solution B under stirring, separating the solid phase, washing, and drying to obtain modified zeolite powder; S5. Mixing the raw materials including the modified zeolite powder, cement, fly ash, polycarboxylate water reducer and aggregate to obtain permeable crystallization self-repairing concrete.

2. The preparation method according to claim 1, wherein: In step S1, the activity of the urease solution is 6 to 15 U / mL; and / or the type of the zeolite powder is clinoptilolite; and / or the particle size of the zeolite powder is 300 to 800 mesh; and / or the solid-liquid ratio of the zeolite powder to the urease solution is 1 kg / 2 to 5 L; and / or the impregnation time is 60 to 120 h; and stirring is performed during the impregnation process.

3. The preparation method according to claim 1, wherein: In step S2, in the mixed solution A, the concentration of urea is 0.8-2 mol / L, and the mass concentration of sodium alginate is 0.5%-2%; and / or the concentration of the calcium chloride solution A is 0.05-0.15 mol / L, and the feeding rate is 5-15 mL / min; and / or the mass ratio of calcium chloride in the calcium chloride solution A to the sodium alginate in the mixed solution A is 1-4:1; and / or the solid-liquid ratio of the pretreated zeolite powder to the mixed solution A is 1 kg / 5-10 L.

4. The preparation method according to claim 1, wherein: In step S3, the specific surface area of ​​the fumed silica is 200 to 400 m 2 / g; and / or, the mass ratio of the fumed silica to the zeolite powder is 1:4-6; and / or, the concentration of the magnesium chloride solution is 0.05-0.1 mol / L; and / or, the solid-liquid ratio of the fumed silica to the magnesium chloride solution is 1 kg / 20-50 L; and / or, the number average molecular weight of the polyethylene glycol is 2000-6000; and / or, the mass ratio of the polyethylene glycol to the fumed silica is 0.5-2:

1.

5. The preparation method according to claim 1, wherein: In step S4, the mass concentration of the sodium alginate solution is 1% to 3%; and / or the solid-liquid ratio of the coated zeolite powder to the sodium alginate solution is 1 kg / 10 to 15 L; and / or the concentration of the calcium chloride solution B is 0.05 to 0.15 mol / L; and / or the feeding rate is 5 to 15 mL / min; and / or the mass ratio of calcium chloride in the calcium chloride solution B to sodium alginate in the sodium alginate solution is 1 to 4:

1.

6. The preparation method according to claim 1, wherein: In steps S2 and S4, the stirring rate is independently selected from 500 to 650 rpm; and / or, in steps S1, S2 and S4, the drying temperature is no higher than 40°C.

7. The preparation method according to claim 1, wherein: In step S5, the aggregate includes coarse aggregate and fine aggregate. The raw materials for preparing the permeable crystallization self-repairing concrete include, by mass, 100 parts of cement, 35-40 parts of modified zeolite powder, 18-22 parts of fly ash, 2.8-3.5 parts of polycarboxylate water reducer, 450-500 parts of coarse aggregate, and 200-220 parts of fine aggregate.

8. The preparation method according to claim 7, characterized in that: The preparation raw materials also include water, wherein the water-cement ratio is 0.34-0.

38.

9. The preparation method according to claim 7, characterized in that: The coarse aggregate is continuously graded in the range of 5 to 20 mm, and the grading ratio of the aggregate is 20% to 30% for 5 to 10 mm, 30% to 40% for 10 to 16 mm, and 35% to 45% for 16 to 20 mm; and / or, the fine aggregate is medium sand.

10. The preparation method according to claim 1, characterized in that: The cement is ordinary Portland cement; and / or the fly ash is Class F fly ash; and / or the polycarboxylate water reducer is selected from HPEG type or TPEG type, with a molecular weight of 2400 to 3000.

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