Self-compacting bare concrete and preparation method thereof

Abstract

The invention relates to the field of fair-faced concrete, in particular to self-compacting fair-faced concrete and a preparation method thereof. The self-compacting bare concrete comprises the following substances in parts by weight: 35-50 parts of cement; 70 to 90 parts of basalt coarse aggregate; 65 to 75 parts of fine aggregate; 15 to 25 parts of water; 0.01 to 0.03 part of an additive; 8-10 parts of a self-compacting modified material; the self-compacting modified material comprises a mineral admixture, and the mineral admixture comprises one or a mixture of more of silica fume, fly ash or metakaolin. Particle composition and volcanic ash activity are optimized by combining the basic formula with the mineral admixture, the concrete is endowed with high flowability and self-compaction performance while the cement consumption is reduced by optimizing the proportion of the added materials, and the compactness is improved by the micro-filling effect of the mineral admixture, so that the concrete has the advantages of high flowability and high self-compaction performance. The self-compacting performance of the self-compacting bare concrete is further improved.

Description

Technical Field

[0001] The present application relates to the field of fair-faced concrete, and particularly to a self-compacting fair-faced concrete and a preparation method thereof. Background Art

[0002] Self-compacting fair-faced concrete is a high-performance building material with high fluidity, self-compacting property and decorative property. Its core feature is that it can fill complex formworks by its own weight without mechanical vibration, forming a fair-faced finish without honeycombing and pockmarks and with uniform color, and is widely used in engineering scenarios such as high-rise buildings, bridges, subway stations, etc. where strict requirements are imposed on structural accuracy and aesthetics. Traditional fair-faced concrete relies on vibration compaction, and it is easy to cause defects such as surface color difference and air holes due to uneven vibration. While the self-compacting technology realizes high-fluidity characteristics with a slump flow ≥ 650 mm and a T50 flow time ≤ 15 s by optimizing the cementitious material system and aggregate gradation, significantly improving the construction efficiency and appearance quality.

[0003] Currently, the mainstream technical route of self-compacting fair-faced concrete replaces part of the cement with mineral admixtures to improve the late strength and impermeability through the pozzolanic effect. However, this solution has significant defects: firstly, the secondary reaction of admixtures such as fly ash lags behind, resulting in a 3-day compressive strength of only 15 - 20 MPa, which is difficult to meet the requirement of rapid formwork removal; secondly, high dosages of mineral admixtures rely on large dosages of water reducers, and the existing system has insufficient ability to inhibit chloride ion penetration and freeze-thaw damage; finally, traditional self-compacting concrete lacks a crack self-healing mechanism, and the propagation of microcracks is prone to cause steel bar corrosion, shortening the service life. Summary of the Invention

[0004] In order to improve the above technical problems, the present application provides a self-compacting fair-faced concrete and a preparation method thereof.

[0005] In the first aspect, the present application provides a self-compacting fair-faced concrete, adopting the following technical solution: A self-compacting fair-faced concrete comprises the following substances in parts by weight: 35 - 50 parts of cement; 70 - 90 parts of basalt coarse aggregate; 65 - 75 parts of fine aggregate; 15 - 25 parts of water; 0.01 - 0.03 parts of admixture; 8 - 10 parts of self-compacting modifier; the self-compacting modifier comprises mineral admixtures, and the mineral admixtures comprise one or a mixture of more of silica fume, fly ash or metakaolin.

[0006] Through the above technical solution, the present application optimizes the particle gradation and pozzolanic activity by combining the basic formula with mineral admixtures. By optimizing the proportion of the added materials, while reducing the cement dosage, it endows the concrete with high fluidity and self-compacting property, and the micro-filling effect of the mineral admixtures improves the density, further improving the self-compacting performance of the self-compacting fair-faced concrete.

[0007] Furthermore, the self-compacting modified material further includes silica particles with a particle size of 80 - 150 μm.

[0008] Through the above technical solution, 80 - 150 μm silica particles are introduced into the mineral admixture in this application. Utilizing their high specific surface area and nano-nucleation effect, it accelerates cement hydration and refines the pore structure, significantly improving the early strength and chloride ion permeability resistance. At the same time, the synergistic effect between the nano-particles and the mineral admixture reduces the risk of shrinkage cracks.

[0009] Furthermore, the self-compacting modified material further includes microbial self-compacting modified particles, and the microbial self-compacting modified particles include fly ash hollow microspheres and microbial modified gel liquid filled inside the fly ash hollow microspheres.

[0010] Through the above technical solution, this application adds microbial self-compacting modified particles, encapsulates the microbial gel liquid with fly ash hollow microspheres as the carrier to achieve the function of self-healing cracks; the light weight property of the fly ash hollow microspheres avoids aggregate settlement and maintains the uniformity of the concrete, while the CaCO3 generated by microbial metabolism and nano-silica jointly fill the pores, further enhancing the durability.

[0011] Furthermore, the fly ash hollow microspheres are prepared by the following technical solution: Mix the as-received fly ash with water, then add sodium hexametaphosphate and stir to mix, and collect the mixed slurry; Take the mixed slurry and introduce compressed air to float and separate the foam layer on the surface of the mixed slurry; Centrifuge the foam layer and collect the fly ash hollow microspheres in the center of the drum, and perform drying treatment to prepare the fly ash hollow microspheres.

[0012] Through the above technical solution, this application uses the air flotation - centrifugation combined selection process to purify the hollow microspheres from fly ash, and realizes industrialized high-efficiency separation through the sodium hexametaphosphate dispersant and vacuum adsorption technology, solves the problem of low recovery rate of the traditional flotation method, and the purified microspheres have high activity.

[0013] Furthermore, the microbial self-compacting modified particles are prepared by the following technical solution: Put the fly ash hollow microspheres into hydrochloric acid, perform ultrasonic-assisted treatment to remove the surface metal oxides, wash and dry them, and then perform calcination treatment in a muffle furnace; Take the calcined fly ash hollow microspheres and stir and mix them with the microbial modified gel liquid, perform vacuum treatment, then centrifuge, separate, wash and dry to prepare the microbial self-compacting modified particles.

[0014] Through the above technical solution, the present application activates the surface of the microspheres by pickling and calcination to enhance their loading capacity, combines vacuum adsorption and centrifugation processes to ensure the stable encapsulation of the microbially modified gel solution, and the compressive strength of the microspheres is effectively improved after calcination, further improving the performance of withstanding the impact of concrete mixing.

[0015] Furthermore, the microbially modified gel solution comprises the following substances in parts by weight: Sporulation suspension: 8 - 15 parts; Nanocalcium lactate particles: 10 - 20 parts; Starch particles: 3 - 5 parts; Deionized water: 30 - 50 parts.

[0016] Through the above technical solution, the present application optimizes the formula of the microbially modified gel solution. The rapid release of calcium ions by nanocalcium lactate, the slow release of carbon source by starch to maintain the long-term metabolism of microorganisms, and the adjustment of viscosity by deionized water to ensure uniform perfusion achieve the balance between the self-healing function and the construction performance of concrete.

[0017] Furthermore, the spores in the sporulation suspension include at least one of Bacillus sphaericus spores and Bacillus pasteurii spores.

[0018] Through the above technical solution, the present application optimizes the spore type to alkali-tolerant bacillus (Bacillus sphaericus / Bacillus pasteurii). Its spores can remain dormant in a concrete environment with pH > 12 for more than 5 years, generate CaCO3 within 48 hours after being activated by water, and the genetically modified strains have strong stress resistance, further extending the self-healing life of concrete materials.

[0019] In the second aspect, the present application provides a preparation method of self-compacting fair-faced concrete, adopting the following technical solution: A preparation method of self-compacting fair-faced concrete comprises the following preparation steps: First, take cement, coarse aggregate, fine aggregate and self-compacting modification material, stir and mix them for dry material premixing treatment; Take the dry material premixing treatment material and add water and admixture, stir and mix them and adjust the slump; Take the mixed material, pour it into the mold, after vibrating and exhausting, carry out standard curing for 7 days, and then carry out wet curing with the self-healing hydrogel until 28 days, then the self-compacting fair-faced concrete can be prepared.

[0020] Through the above technical solution, the present application ensures uniform dispersion through dry material premixing, precisely controls the slump in the wet mixing stage, combines standard curing and self-healing hydrogel curing to form gradient hardening, the strength reaches the standard after 28 days and there are no cracks on the surface, which is suitable for pouring complex structures.

[0021] Further, the self-healing hydrogel wet curing is carried out by spraying a microbial modified gel solution with a mass fraction of 1% onto the concrete surface using a high-pressure airless spraying machine, controlling the spraying amount to be 0.5 - 1.0 kg / m2, spraying once every 8 hours, and curing for 28 days.

[0022] Through the above technical solution, the self-healing hydrogel wet curing of this application uses a 1% microbial gel solution, continuously supplies moisture through surface penetration and activates surface microorganisms, and at the same time, the nano-SiO2 in the gel solution strengthens the surface hardness, making the prepared self-compacting fair-faced concrete have good mechanical properties and self-compacting repair properties.

[0023] In summary, this application has the following beneficial effects: First, this application optimizes the particle size distribution and pozzolanic activity through the basic formula combined with mineral admixtures. By optimizing the proportion of the added materials, while reducing the cement consumption, it endows the concrete with high fluidity and self-compactability, and the micro-filling effect of the mineral admixtures improves the density, further improving the self-compacting performance of the self-compacting fair-faced concrete.

[0024] Second, this application adds microbial self-compacting modified particles, encapsulates the microbial gel solution with fly ash hollow microspheres to achieve the function of crack self-healing; the light weight characteristics of the fly ash hollow microspheres avoid aggregate settlement and maintain the uniformity of the concrete, and the CaCO3 generated by microbial metabolism and nano-silica jointly fill the pores, further improving the durability.

[0025] Third, the self-healing hydrogel wet curing of this application uses a 1% microbial gel solution, continuously supplies moisture through surface penetration and activates surface microorganisms, and at the same time, the nano-SiO2 in the gel solution strengthens the surface hardness, making the prepared self-compacting fair-faced concrete have good mechanical properties and self-compacting repair properties. Specific embodiments

[0026] The following further elaborates on this application with reference to examples.

[0027] Preparation Example 1 Fly ash hollow microspheres First, take the original fly ash and mix it with water at a ratio of 1:4, add sodium hexametaphosphate with a mass of 0.2% of the water, stir at a stirring speed of 800 rpm for 30 minutes, collect the mixed solution, pass 0.3 MPa compressed air into the mixed solution, collect the upper foam layer and dilute it to a solid content of 15%, then separate it at 3000 rpm in a scroll centrifuge for 10 minutes. After collecting the light-phase microspheres, dry them at 80 °C until the moisture content is <5%, and the fly ash hollow microspheres can be prepared.

[0028] Preparation Example 2 Microbial modified gel solution 1 Take 80 g of Bacillus pasteurii spores, 100 g of nano calcium lactate, 30 g of starch and 300 g of deionized water, stir and mix them to prepare Microbial Modified Gel Liquid 1.

[0029] Preparation Example 3 Microbial Modified Gel Liquid 2 Take 100 g of Bacillus sphaericus spores, 150 g of nano calcium lactate, 40 g of starch and 400 g of deionized water, stir and mix them to prepare Microbial Modified Gel Liquid 2.

[0030] Preparation Example 4 Microbial Modified Gel Liquid 3 Take 60 g of Bacillus sphaericus spores, 90 g of Bacillus pasteurii spores, 200 g of nano calcium lactate, 50 g of starch and 500 g of deionized water, stir and mix them to prepare Microbial Modified Gel Liquid 3.

[0031] Preparation Example 5 Microbial Self-Compacting Modified Particle 1 Take 200 g of fly ash cenospheres and soak them in 2000 g of 5% mass fraction HCl solution, ultrasonically treat them at 200 W for 30 min, wash them with deionized water until neutral, then calcine them in a muffle furnace at 600 °C for 1 h. Take the calcined fly ash cenospheres and stir and mix them with Microbial Modified Gel Liquid 1 at a mass ratio of 1:3, evacuate to -0.1 MPa, keep the pressure for 30 min, then centrifuge to remove the surface residue, and perform surface treatment: spray nano-SiO2 sol, and spray dry at an inlet temperature of 180 °C and an outlet temperature of 80 °C to prepare Microbial Self-Compacting Modified Particle 1.

[0032] Preparation Example 6 Microbial Self-Compacting Modified Particle 2 Take 200 g of fly ash cenospheres and soak them in 2000 g of 5% mass fraction HCl solution, ultrasonically treat them at 200 W for 30 min, wash them with deionized water until neutral, then calcine them in a muffle furnace at 600 °C for 1 h. Take the calcined fly ash cenospheres and stir and mix them with Microbial Modified Gel Liquid 1 at a mass ratio of 1:3, evacuate to -0.1 MPa, keep the pressure for 30 min, then centrifuge to remove the surface residue, and perform surface treatment: spray nano-SiO2 sol, and spray dry at an inlet temperature of 180 °C and an outlet temperature of 80 °C to prepare Microbial Self-Compacting Modified Particle 2.

[0033] Preparation Example 7 Microbial Self-Compacting Modified Particle 3 Take 200 g of fly ash hollow microspheres and soak them in 2000 g of 5% HCl solution by mass. Ultrasonically treat them for 30 min at 200 W. After washing with deionized water until neutral, then calcine them in a muffle furnace at 600 °C for 1 h. Take the calcined fly ash hollow microspheres and stir and mix them with the microorganism-modified gel solution 1 at a mass ratio of 1:3, and evacuate to -0.1 MPa. After maintaining the pressure for 30 min, centrifuge to remove the surface residues, and perform surface treatment: spray nano-SiO2 sol, and spray-dry at an inlet temperature of 180 °C and an outlet temperature of 80 °C to obtain the microorganism self-compacting modified particles 3.

[0034] Example Example 1 A self-compacting fair-faced concrete comprises the following substances by weight: 35 kg of cement, 70 kg of basalt coarse aggregate, 65 kg of fine aggregate sand, 15 kg of water, 0.01 kg of water reducer, and 8 kg of silica fume.

[0035] A preparation method of a self-compacting fair-faced concrete comprises the following steps: First, take cement, coarse aggregate, fine aggregate, and self-compacting modified material, stir and mix them, and perform dry material premixing treatment; Take the dry material premixing treatment material and add water and additives, stir and mix them, and adjust the slump; Take the mixed material and pour it into a mold. After vibrating and exhausting, after standard curing for 7 days, spray the microorganism-modified gel solution 1 with a mass fraction of 1% onto the concrete surface, and control the spraying amount to be 0.5 kg / m 2 , spray once every 8 h, and cure until 28 days to obtain the self-compacting fair-faced concrete.

[0036] Example 2 A self-compacting fair-faced concrete comprises the following substances by weight: 42 kg of cement, 80 kg of basalt coarse aggregate, 70 kg of fine aggregate sand, 20 kg of water, 0.02 kg of water reducer, and 9 kg of fly ash.

[0037] A preparation method of a self-compacting fair-faced concrete comprises the following steps: First, take cement, coarse aggregate, fine aggregate, and self-compacting modified material, stir and mix them, and perform dry material premixing treatment; Take the dry material premixing treatment material and add water and additives, stir and mix them, and adjust the slump; Take the mixed material and pour it into a mold. After vibrating and exhausting, after standard curing for 7 days, spray the microorganism-modified gel solution 1 with a mass fraction of 1% onto the concrete surface, and control the spraying amount to be 0.7 kg / m 2 , spray once every 8 h, and cure until 28 days to obtain the self-compacting fair-faced concrete.

[0038] Example 3 A self-compacting fair-faced concrete comprises the following substances by weight: 50 kg of cement, 90 kg of basalt coarse aggregate, 75 kg of fine aggregate sand, 25 kg of water, 0.03 kg of water reducer, and 10 kg of metakaolin.

[0039] A preparation method of a self-compacting fair-faced concrete comprises the following steps: First, take cement, coarse aggregate, fine aggregate and self-compacting modification materials, stir and mix them, and perform dry material premixing treatment; Take the premixed dry material and add water and admixtures, stir and mix them, and adjust the slump; Take the mixed material and pour it into a mold. After vibrating and exhausting, after standard curing for 7 days, spray 1% by mass of microbial modified gel liquid 1 onto the concrete surface, and control the spraying amount to be 1.0 kg / m 2 , spray once every 8 h, and cure until 28 days, then the self-compacting fair-faced concrete can be prepared.

[0040] Example 4 A self-compacting fair-faced concrete comprises the following substances by weight: 42 kg of cement, 80 kg of basalt coarse aggregate, 70 kg of fine aggregate sand, 20 kg of water, 0.02 kg of water reducer, 2 kg of fly ash, 3 kg of silica fume, and 3 kg of microbial self-compacting modification particles 1.

[0041] A preparation method of a self-compacting fair-faced concrete comprises the following steps: First, take cement, coarse aggregate, fine aggregate and self-compacting modification materials, stir and mix them, and perform dry material premixing treatment; Take the premixed dry material and add water and admixtures, stir and mix them, and adjust the slump; Take the mixed material and pour it into a mold. After vibrating and exhausting, after standard curing for 7 days, spray 1% by mass of microbial modified gel liquid 1 onto the concrete surface, and control the spraying amount to be 0.7 kg / m 2 , spray once every 8 h, and cure until 28 days, then the self-compacting fair-faced concrete can be prepared.

[0042] Example 5 A self-compacting fair-faced concrete comprises the following substances by weight: 42 kg of cement, 80 kg of basalt coarse aggregate, 70 kg of fine aggregate sand, 20 kg of water, 0.02 kg of water reducer, 2 kg of fly ash, 3 kg of silica fume, and 3 kg of microbial self-compacting modification particles 2.

[0043] A preparation method of a self-compacting fair-faced concrete comprises the following steps: First, take cement, coarse aggregate, fine aggregate and self-compacting modification materials, stir and mix them, and perform dry material premixing treatment; Take the premixed dry material and add water and admixtures, stir and mix them, and adjust the slump; Mix the materials and pour them into the mold. After vibrating to exhaust air, cure them under standard conditions for 7 days, then spray 1% by mass of microbial modified gel liquid 1 onto the concrete surface, with the spraying amount controlled at 0.7 kg / m 2 , and spray once every 8 hours. Cure until 28 days, then self-compacting fair-faced concrete can be prepared.

[0044] Example 6 A kind of self-compacting fair-faced concrete comprises the following substances by weight: 42 kg of cement, 80 kg of basalt coarse aggregate, 70 kg of fine aggregate sand, 20 kg of water, 0.02 kg of water reducer, 2 kg of fly ash, 3 kg of silica fume, and 3 kg of microbial self-compacting modified particles 3.

[0045] A preparation method of self-compacting fair-faced concrete comprises the following steps: First, take cement, coarse aggregate, fine aggregate and self-compacting modified material, stir and mix them, and perform dry material premixing treatment; Take the premixed dry material and add water and admixture, stir and mix them, and adjust the slump; Mix the materials and pour them into the mold. After vibrating to exhaust air, cure them under standard conditions for 7 days, then spray 1% by mass of microbial modified gel liquid 1 onto the concrete surface, with the spraying amount controlled at 0.7 kg / m 2 , and spray once every 8 hours. Cure until 28 days, then self-compacting fair-faced concrete can be prepared.

[0046] Comparative example Comparative example 1 A kind of self-compacting fair-faced concrete, compared with Example 1, adjusts the mass of silica fume to 15 kg, and the other components and steps are the same as those in Example 1.

[0047] Comparative example 2 A kind of self-compacting fair-faced concrete, compared with Example 1, uses traditional wet curing (only sprinkling water without adding microbial modified gel liquid) to replace the self-healing hydrogel wet curing in Example 1, and the other components and steps are the same as those in Example 1.

[0048] Performance detection Self-healing performance test: Make cracks with a width of 0.3 mm, cure in an environment with a humidity of 60% for 7 days, and observe the reduction ratio of the crack area through a microscope.

[0049] Mechanical properties: According to ASTM C666, test the mass loss rate after 300 freeze-thaw cycles.

[0050] Self-compacting performance test: According to ASTM C1611, test the flow diameter of the concrete.

[0051] The test results are shown in Table 1 below: Table 1 Performance detection table It can be found from the comparison between Examples 1-3 and Comparative Examples 1-2 that: In Examples 1-3, as the content of mineral admixtures (silica fume, fly ash, metakaolin) increases, the slump flow value increases, indicating the optimization of fluidity. Combining with the solution of Comparative Example 1, due to the excessive silica fume in Comparative Example 1, the viscosity increases and the fluidity decreases significantly. It shows that the technical solution of this application optimizes the particle gradation and pozzolanic activity through the basic formula combined with mineral admixtures. By optimizing the proportion of the added materials, while reducing the cement consumption, it endows the concrete with high fluidity and self-compacting property, and the micro-filling effect of the mineral admixtures improves the density, further improving the self-compacting performance of the self-compacting fair-faced concrete.

[0052] After introducing the microbial self-compacting modified particles by combining Examples 1-3 with Examples 4-6, the crack healing rate reaches 90-96%, proving that the microbial metabolism of calcium carbonate effectively fills the pores; Combined with Comparative Example 2 using traditional wet curing, it can be seen that its repair efficiency is lower than that of Examples 4-5. It further shows that this application adds microbial self-compacting modified particles, encapsulates the microbial gel liquid with fly ash hollow microspheres, and realizes the function of crack self-repair; the light weight property of the fly ash hollow microspheres avoids the settlement of aggregates and maintains the uniformity of the concrete, while the CaCO3 generated by the microbial metabolism and nano-silica jointly fill the pores, further improving the durability.

[0053] This specific embodiment is only an explanation of this application, and it is not a limitation of this application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of this application, it is protected by the patent law.

Claims

1. A self-compacting fair-faced concrete, characterized in that, It comprises the following substances in parts by weight: Cement: 35 - 50 parts; Basalt coarse aggregate: 70 - 90 parts; Fine aggregate: 65 - 75 parts; Water: 15 - 25 parts; Admixture: 0.01 - 0.03 parts; Self - compacting modification material: 8 - 10 parts; The self - compacting modification material includes mineral admixtures, and the mineral admixtures include one or a mixture of silica fume, fly ash or metakaolin.

2. The self-compacting fair-faced concrete according to claim 1, wherein, The self - compacting modification material further includes silica particles with a particle size of 80 - 150 μm.

3. A self-compacting fair-faced concrete according to claim 2, characterized in that, The self - compacting modification material further includes microbial self - compacting modification particles, and the microbial self - compacting modification particles include fly ash hollow microspheres and microbial modified gel liquid filled inside the fly ash hollow microspheres.

4. A self-compacting fair-faced concrete according to claim 3, characterized in that, The fly ash hollow microspheres are prepared by the following technical scheme: Mix the original fly ash with water, then add sodium hexametaphosphate and stir to mix, and collect the mixed slurry; Take the mixed slurry and introduce compressed air to float and separate the foam layer on the surface of the mixed slurry; Centrifugally separate the foam layer and collect the fly ash hollow microspheres at the center of the drum, and perform drying treatment to prepare the fly ash hollow microspheres.

5. A self-compacting fair-faced concrete according to claim 3, characterized in that, The microbial self - compacting modification particles are prepared by the following technical scheme: Put the fly ash hollow microspheres into hydrochloric acid, perform ultrasonic - assisted treatment to remove the surface metal oxides, wash and dry them, and then perform calcination treatment in a muffle furnace; Take the fly ash hollow microspheres after calcination treatment and stir - mix them with the microbial modified gel liquid, perform vacuum treatment, then centrifugally separate, wash and dry to prepare the microbial self - compacting modification particles.

6. The self-compacting fair-faced concrete according to claim 3, characterized in that, The microbial modified gel liquid includes the following substances in parts by weight: Sporulation suspension: 8 - 15 parts; Nano calcium lactate particles: 10 - 20 parts; Starch particles: 3 - 5 parts; Deionized water: 30 - 50 parts.

7. A self-compacting fair-faced concrete according to claim 6, characterized in that, The spores in the sporulation suspension include at least one of spores of Bacillus sphaericus and Bacillus pasteurii.

8. A method for preparing self-compacting fair-faced concrete according to any one of claims 1-7, characterized in that, It includes the following preparation steps: First, take cement, coarse aggregate, fine aggregate and self - compacting modification material and stir - mix them for dry - material premixing treatment; Take the dry - material premixed treatment material and add water and admixture, stir - mix and adjust the slump; Pour the mixed material into a mold, vibrate and exhaust, then perform standard curing for 7 days, and perform wet curing with self - repairing hydrogel until 28 days to prepare the self - compacting fair - faced concrete.

9. The preparation method of a self-compacting fair-faced concrete according to claim 8, characterized in that, The self-healing hydrogel wet curing is to spray the microbial modified gel solution with a mass fraction of 1% onto the concrete surface by using a high-pressure airless spraying machine, and control the spraying amount to be 0.5-1.0 kg / m 2 , and spray once every 8 hours until the curing reaches 28 days.

Images