Preparation method of high-crack-resistance concrete waterproof compacting agent

Abstract

The invention discloses a preparation method of a high-crack-resistance concrete waterproof compacting agent, and belongs to the field of concrete admixtures. The preparation method comprises the following steps: preparing a silica fume compound, preparing silicon carbide whisker modified silicon dioxide, grading, and mixing to prepare the compacting agent. The prepared compacting agent can effectively improve the performance of concrete in a salinized environment, the compressive strength of the concrete is 43.3-44.1 MPa after the concrete is buried in salinized soil for 180 days, and the compressive strength of the concrete is 38.9-41.1 MPa after the concrete is buried in the salinized soil for 360 days; and the electric flux after being buried in salinized soil for 180 days is 46-51 C, and the electric flux after being buried in salinized soil for 360 days is 76-82 C.

Description

Technical Field

[0001] The present invention relates to a preparation method of a high crack-resistant concrete waterproofing and densifying agent, belonging to the field of concrete admixtures. Background Art

[0002] Due to the relatively extensive production and construction in the concrete industry, combined with the industry segmentation and a certain degree of absence in design, construction, and supervision, there are still many problems in the concrete industry, such as poor raw material quality, low strength grade, many quality common problems, and premature deterioration of many buildings and structures. For example, in recent years, phenomena such as basement leakage, subway leakage and corrosion, underground pipe gallery leakage, premature corrosion and damage of sewage treatment ponds, and premature deterioration of coastal reinforced concrete have emerged in an endless stream. Therefore, there is an urgent need for admixtures that can improve the durability of concrete to solve these problems.

[0003] Siliceous densifying agents are a type of concrete admixture mainly composed of siliceous materials, which are a high-performance green new type of admixture designed to enhance the density, impermeability, and durability of concrete through chemical reactions and physical filling effects. Its core feature is to utilize the interaction between the activity of siliceous materials and the hydration products of cement to form a denser microstructure, effectively blocking the penetration of harmful substances such as chloride ions and sulfates, and significantly extending the service life of concrete in corrosive environments.

[0004] The main components of siliceous densifying agents are ultra-fine silica fume and nano-silica dioxide. Among them, ultra-fine silica fume can fill the capillary pores and micro-cracks of concrete, reducing the porosity of concrete through physical filling. Nano-silica dioxide undergoes a pozzolanic reaction with the hydration products of cement to generate more C-S-H gels, forming a dense structure. The cost of silica fume is relatively high, about 3000 yuan per ton, and the price of nano-silica dioxide is even higher, 10,000 - 20,000 yuan per ton, which leads to a relatively high cost of siliceous densifying agents containing ultra-fine silica fume and nano-silica dioxide.

[0005] In order to reduce the cost, the particle size of silica fume and nano-silica dioxide can be increased. However, the increase in particle size will cause a huge change in the specific surface area of the particles. For every 10-fold increase in particle size, the specific surface area decreases by about 90%. Moreover, larger particle sizes will form a "weak interface zone" of coarse particles in the cement paste, becoming stress concentration points and leading to a reduction in flexural strength.

[0006] In order to ensure the performance of concrete is not affected while reducing costs, larger particles can be compounded with nanoscale particles, and the pore structure can be optimized using the "grading filling effect" to ensure the performance of concrete. At the same time, alkaline activators (such as NaOH and water glass) can be added to accelerate the pozzolanic reaction of the larger particles, which can also make up for the performance degradation caused by using large-sized siliceous materials, such as crack resistance and compressive strength. However, the impermeability of the concrete will deteriorate significantly, especially in a saline environment, and the service life of the impermeability will be significantly reduced. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the defects existing in the prior art. By specially treating silica fume with a larger particle size and then grading it with ultrafine silica fume, and specially treating silicon dioxide with a larger particle size and then grading it with nano-silicon dioxide, a densifier is finally prepared to improve the service life in a saline environment while ensuring the crack resistance and compressive strength of the concrete.

[0008] To solve the above technical problems, the present invention adopts the following technical solutions: A preparation method of a high crack-resistant concrete waterproof densifier, the preparation method including preparing a silica fume composite, preparing silicon carbide whisker-modified silicon dioxide, grading, and mixing to prepare the densifier.

[0009] The following is a further improvement of the above technical solution: The method for preparing the silica fume composite is as follows: Mix silica fume with aluminum sol and then stir for 30 - 40 min. After stirring, let it stand for 18 - 25 min, then filter, wash, and dry to obtain silica fume impregnated with aluminum sol. Then mix the silica fume impregnated with aluminum sol, talc powder, bis(dioctyloxyphosphate) ethylene titanate, and cyclohexanone, control the temperature at 85 - 91 °C, and stir for 100 - 130 min. After stirring, filter, wash, and dry to obtain the silica fume composite; The mass ratio of the silica fume to the aluminum sol is 1:2.75 - 3.25; The silica fume is micron-sized silica fume with a particle size of 25 - 35 μm; The solid content of the aluminum sol is 17 wt% and the pH is 2.2; The mass ratio of the silica fume impregnated with aluminum sol, talc powder, bis(dioctyloxyphosphate) ethylene titanate, and cyclohexanone is 175 - 225:9 - 11:6.5 - 7.5:750 - 1250; The particle size of the talc powder is 10 - 20 μm.

[0010] The method for preparing silicon carbide whisker-modified silica is as follows: Mix silicon carbide whiskers with deionized water, adjust the pH to 4.7 - 4.9 using acetic acid, then add chitosan and sodium dodecylbenzenesulfonate, stir evenly to obtain a silicon carbide whisker mixture for standby. Then activate micro-scale silica at 475 - 525 °C for 40 - 50 min. Mix the activated micro-scale silica with the silicon carbide whisker mixture, stir at a speed of 250 - 350 r / min for 50 - 70 min. After stirring, filter, wash, and dry to obtain silicon carbide whisker-modified silica; The mass ratio of the silicon carbide whiskers, deionized water, chitosan, and sodium dodecylbenzenesulfonate is 85 - 115:700 - 800:6.5 - 7.5:0.9 - 1.1; The length of the silicon carbide whiskers is 8 μm and the diameter is 1.5 μm; The mass ratio of the micro-scale silica to the silicon carbide whisker mixture is 1:2.75 - 3.25; The particle size of the micro-scale silica is 40 - 55 μm.

[0011] The method for gradation is as follows: Mix the silica fume composite and ultra-fine silica fume evenly to obtain a silica fume gradation material, and mix the silicon carbide whisker-modified silica and nano-silica evenly to obtain a silica gradation material; The mass ratio of the silica fume composite to the ultra-fine silica fume is 2.75 - 3.25:1; The particle size of the ultra-fine silica fume is 5 - 10 μm; The mass ratio of the silicon carbide whisker-modified silica to the nano-silica is 3.5 - 4.5:1; The particle size of the nano-silica is 10 - 15 nm.

[0012] The method for mixing and preparing the densifier is as follows: Mix the silica fume gradation material, silica gradation material, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol evenly to obtain a high crack-resistant concrete waterproof densifier; The mass ratio of the silica fume gradation material, silica gradation material, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol is 23 - 27:30 - 40:4.5 - 5.5:1.8 - 2.2:4.5 - 5.5:11 - 13:3.5 - 4.5; The particle size of the heavy calcium carbonate is 20 - 30 μm.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The densifier prepared by the present invention can effectively ensure the strength of concrete. According to the method in GB / T50081-2019, the compressive strength and flexural strength of concrete are detected. The compressive strength is 44.9 - 46.0 MPa, and the flexural strength is 12.17 - 12.34 MPa; The densifier prepared by the present invention can effectively improve the crack resistance of concrete. According to the method in GB / T50082-2024, the early crack resistance of concrete is detected. The average cracking area of the cracks is 0.24 - 0.51 mm 2 , and the number of cracks per unit area is 3.4; According to the method in GB / T8076-2008, the shrinkage ratio of concrete is detected, and the shrinkage ratio is 100.7 - 101.5%; According to the method in GB / T50081-2019, the splitting tensile strength of concrete is detected, and the splitting tensile strength is 5.50 - 5.61 MPa; The densifier prepared by the present invention can effectively improve the impermeability of concrete. According to the electric flux method in GB / T50082-2024, the impermeability of concrete is detected. The electric flux at 56 d is 29 - 34 C, the electric flux at 90 d is 18 - 19 C, and the electric flux at 180 d is 12 - 14 C; The densifier prepared by the present invention can effectively improve the performance of concrete in a saline environment. The compressive strength after being buried in saline soil for 180 d is 43.3 - 44.1 MPa, and the compressive strength after being buried in saline soil for 360 d is 38.9 - 41.1 MPa; The electric flux after being buried in saline soil for 180 d is 46 - 51 C, and the electric flux after being buried in saline soil for 360 d is 76 - 82 C; The densifier prepared by the present invention can effectively improve the waterproof performance of concrete. According to the method in GB / T50082-2024, the water penetration height of concrete is detected. The water penetration height at 1.2 MPa is 2.2 - 2.5 mm, the water penetration height at 1.5 MPa is 2.7 - 3.1 mm, and the water penetration height at 2.0 MPa is 3.5 - 4.0 mm. Detailed implementation methods

[0014] Example 1 (1)Prepare silica fume composite Mix silica fume and aluminum sol, and stir for 35 min. After stirring, let it stand for 20 min, then filter, wash, and dry to obtain silica fume impregnated with aluminum sol. Then mix the silica fume impregnated with aluminum sol, talc powder, bis(dioctyloxyphosphate) ethylene titanate, and cyclohexanone, control the temperature at 87 °C, and stir for 120 min. After stirring, filter, wash, and dry to obtain the silica fume composite; The mass ratio of the silica fume to the aluminum sol is 1:3 The silica fume is micron-sized silica fume with a particle size of 30 μm; The solid content of the aluminum sol is 17 wt% and the pH is 2.2; The mass ratio of the silica fume, talcum powder, bis(dioctyloxyphosphate) ethylene titanate, and cyclohexanone impregnated with the aluminum sol is 200:10:7:1000; The particle size of the talcum powder is 15 μm.

[0015] (2) Preparation of silicon carbide whisker-modified silica Mix the silicon carbide whiskers with deionized water, adjust the pH to 4.8 using acetic acid, then add chitosan and sodium dodecylbenzenesulfonate, stir evenly to obtain a silicon carbide whisker mixture for standby. Then activate the micron-sized silica at 500 °C for 45 minutes. Mix the activated micron-sized silica with the silicon carbide whisker mixture, stir at a speed of 300 r / min for 60 minutes. After stirring, filter, wash, and dry to obtain silicon carbide whisker-modified silica; The mass ratio of the silicon carbide whiskers, deionized water, chitosan, and sodium dodecylbenzenesulfonate is 100:750:7:1; The length of the silicon carbide whiskers is 8 μm and the diameter is 1.5 μm; The mass ratio of the micron-sized silica to the silicon carbide whisker mixture is 1:3; The particle size of the micron-sized silica is 50 μm.

[0016] (3) Gradation Mix the silica fume composite and ultrafine silica fume evenly to obtain a silica fume gradation material, and mix the silicon carbide whisker-modified silica and nano-silica evenly to obtain a silica gradation material; The mass ratio of the silica fume composite to the ultrafine silica fume is 3:1; The particle size of the ultrafine silica fume is 8 μm; The mass ratio of the silicon carbide whisker-modified silica to the nano-silica is 4:1; The particle size of the nano-silica is 12 nm.

[0017] (4) Mixing to prepare a densifier Mix the silica fume gradation material, silica gradation material, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol evenly to obtain a high crack-resistant concrete waterproof densifier; The mass ratio of the silica fume gradation material, silica gradation material, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol is 25:35:5:2:5:12:4; The particle size of the heavy calcium carbonate is 25 μm.

[0018] Example 2 (1)Preparation of silica fume composite Mix silica fume and aluminum sol, stir for 30 min, let stand for 25 min after stirring, then filter, wash, and dry to obtain silica fume impregnated with aluminum sol. Then mix the silica fume impregnated with aluminum sol, talc powder, bis(dioctyloxyphosphate) ethylene titanate, and cyclohexanone, control the temperature at 85 °C, stir for 130 min, and after stirring, filter, wash, and dry to obtain the silica fume composite; The mass ratio of the silica fume to the aluminum sol is 1:2.75 The silica fume is micron-sized silica fume with a particle size of 25 μm; The solid content of the aluminum sol is 17 wt% and the pH is 2.2; The mass ratio of the silica fume impregnated with aluminum sol, talc powder, bis(dioctyloxyphosphate) ethylene titanate, and cyclohexanone is 175:9:6.5:750; The particle size of the talc powder is 10 μm.

[0019] (2)Preparation of silicon carbide whisker modified silica Mix silicon carbide whiskers and deionized water, adjust the pH to 4.7 with acetic acid, then add chitosan and sodium dodecylbenzenesulfonate, stir evenly to obtain a silicon carbide whisker mixed solution for standby. Then activate the micron-sized silica at 475 °C for 50 min, mix the activated micron-sized silica with the silicon carbide whisker mixed solution, stir at a speed of 250 r / min for 70 min, and after stirring, filter, wash, and dry to obtain the silicon carbide whisker modified silica; The mass ratio of the silicon carbide whiskers, deionized water, chitosan, and sodium dodecylbenzenesulfonate is 85:700:6.5:0.9; The length of the silicon carbide whiskers is 8 μm and the diameter is 1.5 μm; The mass ratio of the micron-sized silica to the silicon carbide whisker mixed solution is 1:2.75; The particle size of the micron-sized silica is 40 μm.

[0020] (3)Gradation Mix the silica fume composite and ultrafine silica fume evenly to obtain a silica fume graded mixture, and mix the silicon carbide whisker modified silica and nano-silica evenly to obtain a silica graded mixture; The mass ratio of the silica fume composite to the ultrafine silica fume is 2.75:1; The particle size of the ultrafine silica fume is 5 μm; The mass ratio of the silicon carbide whisker-modified silica to the nano-silica is 3.5:1; The particle size of the nano-silica is 10 nm.

[0021] (4) Mixing to prepare a densifier Mix the silica fume batching, silica batching, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol evenly to obtain a high crack-resistant concrete waterproof densifier; The mass ratio of the silica fume batching, silica batching, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol is 23:30:4.5:1.8:4.5:11:3.5; The particle size of the heavy calcium carbonate is 20 μm.

[0022] Example 3 (1) Preparation of silica fume composite Mix silica fume and aluminum sol, stir for 40 min, let stand for 18 min after stirring, then filter, wash, and dry to obtain silica fume impregnated with aluminum sol. Then mix the silica fume impregnated with aluminum sol, talc powder, bis(dioctyloxyphosphate) ethylene titanate, and cyclohexanone, control the temperature at 91 °C, stir for 100 min, and after stirring, filter, wash, and dry to obtain a silica fume composite; The mass ratio of the silica fume to the aluminum sol is 1:3.25 The silica fume is micron-sized silica fume with a particle size of 35 μm; The solid content of the aluminum sol is 17 wt% and the pH is 2.2; The mass ratio of the silica fume impregnated with aluminum sol, talc powder, bis(dioctyloxyphosphate) ethylene titanate, and cyclohexanone is 225:11:7.5:1250; The particle size of the talc powder is 20 μm.

[0023] (2) Preparation of silicon carbide whisker-modified silica Mix silicon carbide whiskers with deionized water, adjust the pH to 4.9 with acetic acid, then add chitosan and sodium dodecylbenzenesulfonate, stir evenly to obtain a silicon carbide whisker mixture for standby. Then activate the micron-sized silica at 525 °C for 40 min, mix the activated micron-sized silica with the silicon carbide whisker mixture, stir at a speed of 350 r / min for 50 min, and after stirring, filter, wash, and dry to obtain silicon carbide whisker-modified silica; The mass ratio of the silicon carbide whiskers, deionized water, chitosan, and sodium dodecylbenzenesulfonate is 115:800:7.5:1.1; The length of the silicon carbide whiskers is 8 μm and the diameter is 1.5 μm; The mass ratio of the micro-scale silica and the silicon carbide whisker mixture is 1:3.25; The particle size of the micro-scale silica is 55 μm.

[0024] (3) Gradation Mix the silica fume composite and the ultrafine silica fume evenly to obtain a silica fume gradation material, and mix the silicon carbide whisker-modified silica and the nano-silica evenly to obtain a silica gradation material; The mass ratio of the silica fume composite to the ultrafine silica fume is 3.25:1; The particle size of the ultrafine silica fume is 10 μm; The mass ratio of the silicon carbide whisker-modified silica to the nano-silica is 4.5:1; The particle size of the nano-silica is 15 nm.

[0025] (4) Mixing to prepare a densifier Mix the silica fume gradation material, the silica gradation material, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol evenly to obtain a high crack-resistant concrete waterproof densifier; The mass ratio of the silica fume gradation material, the silica gradation material, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol is 27:40:5.5:2.2:5.5:13:4.5; The particle size of the heavy calcium carbonate is 30 μm.

[0026] Comparative Example 1 Different from Example 1, the step of preparing the silica fume composite is omitted, and in the gradation step, untreated micro-scale silica fume and ultrafine silica fume are used for gradation, and the other steps are the same to prepare a densifier; The mass ratio of the untreated micro-scale silica fume to the ultrafine silica fume is 3:1; The particle size of the ultrafine silica fume is 8 μm; The particle size of the untreated micro-scale silica fume is 30 μm.

[0027] Comparative Example 2 Different from Example 1, the step of preparing the silicon carbide whisker-modified silica is omitted, and in the gradation step, micro-scale silica and nano-silica are used for gradation, and the other steps are the same to prepare a densifier; The mass ratio of the micro-scale silica to the nano-silica is 4:1; The particle size of the nano-silica is 12 nm; The particle size of the micro-scale silica is 50 μm.

[0028] Test Example 1 Influence of the densifier on the strength of concrete Add the densifiers prepared in Examples 1-2 and Comparative Examples 1-2 in a proportion of 3.5 wt% of the gel material; The test uses the C40 commercial concrete mix ratio as the inspection standard, and the mix ratio is as follows: Cement 250 kg / m 3 , Mineral powder 75 kg / m 3 , Fly ash 70 kg / m 3 , Sand 810 kg / m 3 , Gravel 1070 kg / m 3 , Water 160 kg / m 3 ; The cement is P·O 42.5R Portland cement; The specific surface area of the mineral powder is 370 m 2 / kg; The sand is medium sand in Zone II, and the fineness modulus is 2.5; The gravel is a continuous grading of 5-25 mm; According to the method in GB / T50081-2019, detect the compressive strength and flexural strength of the concrete, and the results are shown in Table 1.

[0029] Table 1

[0030] In Examples 1-3, the larger particle size silica fume was specially treated and then graded with ultrafine silica fume, and the larger particle size silicon dioxide was specially treated and then graded with nano-silicon dioxide. Finally, a densifier was prepared, and the compressive strength and flexural strength of the final concrete were both relatively high; In Comparative Example 1, the step of preparing the silica fume composite was omitted, and in the grading step, untreated micron-sized silica fume was graded with ultrafine silica fume to prepare the densifier, which would cause the compressive strength and flexural strength of the concrete to decrease, and the flexural strength decreased particularly severely; In Comparative Example 2, the step of preparing the silicon carbide whisker modified silicon dioxide was omitted, and in the grading step, micron-sized silicon dioxide was graded with nano-silicon dioxide to prepare the densifier, which would cause the compressive strength and flexural strength of the concrete to decrease, and the compressive strength decreased particularly severely.

[0031] Test Example 2 Influence of the densifier on the crack resistance of concrete Add the densifiers prepared in Examples 1-2 and Comparative Examples 1-2 in a proportion of 3.5 wt% of the gel material; The test uses the C40 commercial concrete mix ratio as the inspection standard, and the mix ratio is as follows: Cement 250 kg / m 3 、Mineral powder 75 kg / m 3 、Fly ash 70 kg / m 3 、Sand 810 kg / m 3 、Gravel 1070 kg / m 3 、Water 160 kg / m 3 ; The cement is P·O 42.5R Portland cement; The specific surface area of the mineral powder is 370 m 2 / kg; The sand is medium sand in Zone II with a fineness modulus of 2.5; The gravel has a continuous gradation of 5 - 25 mm; According to the method in GB / T50082 - 2024, the early anti - cracking performance of the concrete is detected, and the average cracking area of the cracks and the number of cracks per unit area are used as evaluation indicators; According to the method in GB / T8076 - 2008, the shrinkage ratio of the concrete is detected; According to the method in GB / T50081 - 2019, the splitting tensile strength of the concrete is detected; The results are shown in Table 2.

[0032] Table 2

[0033] In Examples 1 - 3, the larger - sized silica fume is specially treated and then graded with ultrafine silica fume, and the larger - sized silicon dioxide is specially treated and then graded with nano - silicon dioxide to finally prepare the densifier. The anti - cracking performance of the final concrete is good, with a small crack area, few crack numbers, a low shrinkage rate, and a high splitting tensile strength; In Comparative Example 1, the step of preparing the silica fume composite is omitted, and in the grading step, untreated micron - sized silica fume is graded with ultrafine silica fume to prepare the densifier, which will lead to a decline in the anti - cracking performance of the concrete. Although the number of cracks per unit area increases severely, the increase in the crack opening area is average. At the same time, there is also a certain increase in the shrinkage ratio, and the splitting tensile strength decreases severely; In Comparative Example 2, the step of preparing the silicon carbide whisker - modified silicon dioxide is omitted, and in the grading step, micron - sized silicon dioxide is graded with nano - silicon dioxide to prepare the densifier, which will lead to a decline in the anti - cracking performance of the concrete. Although the crack opening area increases severely, the increase in the number of cracks per unit area is average. At the same time, the shrinkage ratio increases severely, and the splitting tensile strength decreases to a certain extent.

[0034] Effect of the densifier on the impermeability performance of concrete in Test Example 3 The compacting agents prepared in Examples 1-2 and Comparative Examples 1-2 were added at a ratio of 3.5 wt% of the gel material; The test was based on the mix ratio of C40 commercial concrete as the inspection standard, and the mix ratio was as follows: Cement 250 kg / m 3 、Mineral powder 75 kg / m 3 、Fly ash 70 kg / m 3 、Sand 810 kg / m 3 、Gravel 1070 kg / m 3 、Water 160 kg / m 3 ; The cement is P·O 42.5R Portland cement; The specific surface area of the mineral powder is 370 m 2 / kg; The sand is medium sand in Zone II, and the fineness modulus is 2.5; The gravel is continuously graded from 5 to 25 mm; According to the electric flux method in GB / T50082-2024, the impermeability of the concrete was detected, including the electric flux at 56 d, 90 d, and 180 d respectively. The results are shown in Table 3.

[0035] Table 3

[0036] In Examples 1-3, the larger-sized silica fume was specially treated and then graded with ultrafine silica fume, and the larger-sized silicon dioxide was specially treated and then graded with nano-silicon dioxide to finally prepare the compacting agent. The electric flux of the final concrete was small, and with the passage of time, the electric flux would gradually decrease; In Comparative Example 1, the step of preparing the silica fume composite was omitted, and in the grading step, untreated micron-sized silica fume was graded with ultrafine silica fume to prepare the compacting agent, which would lead to a decrease in the impermeability of the concrete. The initial electric flux was high, but with the passage of time, the electric flux would drop to a lower level; In Comparative Example 2, the step of preparing the silicon carbide whisker-modified silicon dioxide was omitted, and in the grading step, micron-sized silicon dioxide was graded with nano-silicon dioxide to prepare the compacting agent, which would lead to a decrease in the impermeability of the concrete. Although the initial electric flux was low, with the passage of time, the degree of decrease in the electric flux was small.

[0037] Test Example 4 Effect of the compacting agent on the performance of concrete in a saline environment The compacting agents prepared in Examples 1-2 and Comparative Examples 1-2 were added at a ratio of 3.5 wt% of the gel material; The test was based on the mix ratio of C40 commercial concrete as the inspection standard, and the mix ratio was as follows: Cement 250 kg / m 3 and mineral powder 75 kg / m 3 and fly ash 70 kg / m 3 and sand 810 kg / m 3 and gravel 1070 kg / m 3 and water 160 kg / m 3 ; The cement is P·O 42.5R portland cement; The specific surface area of the mineral powder is 370 m 2 / kg; The sand is medium sand in Zone II with a fineness modulus of 2.5; The gravel has a continuous gradation of 5 - 25 mm; After the concrete is normally cured for 28 d, it is buried in saline soil with a chloride ion content of 5325 mg / kg and a sulfate content of 13571 mg / kg. The compressive strength and electric flux after being buried for 180 d and 360 d are respectively detected, and the results are shown in Table 4.

[0038] Table 4

[0039] In Examples 1 - 3, by specially treating silica fume with larger particle size and then grading it with ultrafine silica fume, and specially treating silicon dioxide with larger particle size and then grading it with nano - silicon dioxide, a densifier is finally prepared. The final concrete can maintain relatively high strength and low electric flux in the saline - soil environment; In Comparative Example 1, the step of preparing the silica fume composite is omitted, and in the grading step, untreated micron - sized silica fume and ultrafine silica fume are used for grading to prepare the densifier. In the saline - soil environment, the compressive strength of the concrete decreases severely, and at the same time, the electric flux increases to a certain extent; In Comparative Example 2, the step of preparing silicon carbide whisker - modified silicon dioxide is omitted, and in the grading step, micron - sized silicon dioxide and nano - silicon dioxide are used for grading to prepare the densifier. In the saline - soil environment, the compressive strength of the concrete decreases to a certain extent, and at the same time, the electric flux increases severely.

[0040] Test Example 5 Influence of the densifier on the waterproof performance of concrete The densifiers prepared in Examples 1 - 2 and Comparative Examples 1 - 2 are added according to the proportion of 3.5 wt% of the gel material; Testing is carried out with the C40 commercial concrete mix ratio as the inspection standard, and the mix ratio is as follows: Cement 250 kg / m 3 and mineral powder 75 kg / m 3 and fly ash 70 kg / m3 , sand: 810 kg / m 3 , gravel: 1070 kg / m 3 , water: 160 kg / m 3 ; The cement is P·O 42.5R Portland cement; The specific surface area of the mineral powder is 370 m 2 / kg; The sand is medium sand in Zone II with a fineness modulus of 2.5; The gravel has a continuous grading of 5 - 25 mm; According to the method in GB / T50082 - 2024, the water penetration height of the concrete was detected, and the test pressures were 1.2 MPa, 1.5 MPa, and 2.0 MPa respectively. The results are shown in Table 5.

[0041] Table 5

[0042] In Examples 1 - 3, the larger - sized silica fume was specially treated and then graded with ultrafine silica fume, and the larger - sized silicon dioxide was specially treated and then graded with nano - silicon dioxide to finally prepare the densifier. The waterproof performance of the final concrete is good and the water penetration height is low; In Comparative Example 1, the step of preparing the silica fume composite was omitted, and in the grading step, untreated micron - sized silica fume was graded with ultrafine silica fume to prepare the densifier, which led to a certain increase in the water penetration height of the concrete; In Comparative Example 2, the step of preparing the silicon carbide whisker - modified silicon dioxide was omitted, and in the grading step, micron - sized silicon dioxide was graded with nano - silicon dioxide to prepare the densifier, which led to a serious increase in the water penetration height of the concrete, especially in a high - water - pressure environment, where the increase was particularly severe.

Claims

1. A preparation method of a high crack-resistant concrete waterproofing and densifying agent, characterized in that, The preparation method includes preparing a silica fume composite, preparing silicon carbide whisker-modified silica, grading, and mixing to prepare a densifier; The method for preparing the silica fume composite is as follows: Mix silica fume with aluminum sol, stir and let stand, then filter, wash, and dry to obtain aluminum sol-impregnated silica fume. Then, mix and stir the aluminum sol-impregnated silica fume, talcum powder, bis(dioctyloxyphosphate) ethylene titanate, and cyclohexanone, and then filter, wash, and dry to obtain the silica fume composite; The method for preparing silicon carbide whisker-modified silica is as follows: Mix silicon carbide whiskers with deionized water, adjust the pH to 4.7 - 4.9 using acetic acid, then add chitosan and sodium dodecylbenzenesulfonate, stir evenly to obtain a silicon carbide whisker mixture for standby. Mix and stir the activated micron-sized silica with the silicon carbide whisker mixture. After stirring is completed, filter, wash, and dry to obtain silicon carbide whisker-modified silica; The method for grading is as follows: Mix the silica fume composite and ultrafine silica fume evenly to obtain a silica fume graded mixture, and mix the silicon carbide whisker-modified silica and nano-silica evenly to obtain a silica graded mixture; The method for mixing and preparing the densifier is as follows: Mix the silica fume graded mixture, the silica graded mixture, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol evenly to obtain a high crack-resistant concrete waterproof densifier.

2. The preparation method of a high crack-resistant concrete waterproof densifier according to claim 1, wherein: In the method for preparing the silica fume composite, the method of mixing silica fume with aluminum sol and then stirring and letting stand is as follows: The stirring time is 30 - 40 min, and after stirring is completed, let stand for 18 - 25 min; After mixing the aluminum sol-impregnated silica fume, talcum powder, bis(dioctyloxyphosphate) ethylene titanate, and cyclohexanone, the method of stirring is as follows: Control the temperature at 85 - 91 °C and stir for 100 - 130 min.

3. The preparation method of a high crack-resistant concrete waterproof densifier according to claim 1, wherein: In the method for preparing the silica fume composite, the mass ratio of silica fume to aluminum sol is 1:2.75 - 3.25; The silica fume is micron-sized silica fume with a particle size of 25 - 35 μm; The solid content of the aluminum sol is 17 wt% and the pH is 2.2; The mass ratio of the aluminum sol-impregnated silica fume, talcum powder, bis(dioctyloxyphosphate) ethylene titanate, and cyclohexanone is 175 - 225:9 - 11:6.5 - 7.5:750 - 1250.

4. The preparation method of a high crack-resistant concrete waterproof densifier according to claim 1, wherein: In the method for preparing silicon carbide whisker-modified silica, the method of activating the micron-sized silica is as follows: Activate at 475 - 525 °C for 40 - 50 min; The method of mixing and stirring the activated micron-sized silica with the silicon carbide whisker mixture is as follows: Stir at a speed of 250 - 350 r / min for 50 - 70 min.

5. The preparation method of a highly crack-resistant concrete waterproofing and densifying agent according to claim 1, characterized in that: In the method for preparing silicon carbide whisker-modified silica, the mass ratio of silicon carbide whiskers, deionized water, chitosan, and sodium dodecylbenzenesulfonate is 85-115:700-800:6.5-7.5:0.9-1.1; The length of the silicon carbide whiskers is 8 μm, and the diameter is 1.5 μm; The mass ratio of the micron-sized silica and silicon carbide whisker mixture is 1:2.75-3.25; The particle size of the micron-sized silica is 40-55 μm.

6. The preparation method of a highly crack-resistant concrete waterproofing and densifying agent according to claim 1, characterized in that: In the grading method, the mass ratio of the silica fume complex and ultrafine silica fume is 2.75-3.25:1; The particle size of the ultrafine silica fume is 5-10 μm; The mass ratio of the silicon carbide whisker-modified silica and nano-silica is 3.5-4.5:1; The particle size of the nano-silica is 10-15 nm.

7. The preparation method of a highly crack-resistant concrete waterproofing and densifying agent according to claim 1, characterized in that: In the method for mixing and preparing the densifying agent, the mass ratio of the silica fume gradation material, the silica gradation material, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol is 23-27:30-40:4.5-5.5:1.8-2.2:4.5-5.5:11-13:3.5-4.5; The particle size of the heavy calcium carbonate is 20-30 μm.

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