A method for preparing a high crack-resistant concrete waterproofing and densifying agent

Abstract

This invention discloses a method for preparing a high-crack-resistant, waterproof, and densifying agent for concrete, belonging to the field of concrete admixtures. The preparation method includes preparing a silica fume composite, preparing silicon carbide whisker-modified silica, grading, and mixing to prepare the densifying agent. The densifying agent prepared by this invention can effectively improve the performance of concrete in saline environments. The compressive strength after 180 days of burial in saline soil is 43.3-44.1 MPa, and the compressive strength after 360 days of burial in saline soil is 38.9-41.1 MPa; the electrical flux after 180 days of burial in saline soil is 46-51 C, and the electrical flux after 360 days of burial in saline soil is 76-82 C.

Description

Technical Field

[0001] This invention relates to a method for preparing a high crack-resistant waterproof and dense concrete agent, belonging to the field of concrete admixtures. Background Technology

[0002] Due to the relatively extensive production and construction methods in the concrete industry, coupled with the segmentation and certain deficiencies in design, construction, and supervision, numerous problems persist, such as poor raw material quality, low strength grades, widespread quality defects, and premature deterioration of many buildings and structures. For example, in recent years, phenomena such as basement leaks, subway leaks and corrosion, underground pipe gallery leaks, premature corrosion and damage to sewage treatment plants, and premature deterioration of reinforced concrete in coastal areas have become increasingly common. Therefore, there is an urgent need for admixtures that can improve concrete durability to address these problems.

[0003] Silica-based densifiers are a type of concrete admixture with siliceous materials as the main component. They are high-performance, green, and novel admixtures designed to improve the density, impermeability, and durability of concrete through chemical reactions and physical filling. Their core characteristic is the interaction between the activity of siliceous materials and cement hydration products, forming a denser microstructure that effectively blocks the penetration of harmful substances such as chloride ions and sulfates, significantly extending the service life of concrete in corrosive environments.

[0004] The main components of silica-based densifiers are ultrafine silica fume and nano silica. Ultrafine silica fume can fill the capillary pores and microcracks in concrete, reducing the porosity of concrete through physical filling. Nano silica reacts with cement hydration products to produce more CSH gel, forming a dense structure. Silica fume is relatively expensive, costing around 3,000 yuan per ton, while nano silica is even more expensive, costing 10,000 to 20,000 yuan per ton. This results in the high cost of silica-based densifiers containing ultrafine silica fume and nano silica.

[0005] To reduce costs, the particle size of silica fume and nano silica can be increased. However, increasing the 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 cause coarse particles to form "weak interface zones" in cement paste, which become stress concentration points, leading to a decrease in flexural strength.

[0006] To reduce costs while ensuring that concrete performance is not affected, larger particles can be blended with nano-sized particles. The "gradation filling effect" can be used to optimize the pore structure, thereby ensuring the performance of the concrete. At the same time, alkaline activators (such as NaOH and water glass) can be added to accelerate the pozzolanic reaction of large particles, which can also compensate for the performance degradation caused by the use of large-particle siliceous materials, such as crack resistance and compressive strength. However, the impermeability of the concrete will deteriorate significantly, especially in saline environments, where the lifespan 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 of the existing technology. By specially treating the silica fume with a larger particle size and then grading it with ultrafine silica fume, and by specially treating the silica with a larger particle size and then grading it with nano silica, a densifying agent is finally prepared. This agent can improve the service life of concrete in saline environment while ensuring its crack resistance and compressive strength.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A method for preparing a high crack-resistant concrete waterproof densifier, the method comprising preparing a silica fume composite, preparing silicon carbide whisker modified silica, grading, and mixing to prepare the densifier.

[0010] The following are further improvements to the above technical solution:

[0011] The method for preparing the silica fume composite is as follows: silica fume is mixed with aluminum sol and stirred for 30-40 minutes. After stirring, it is allowed to stand for 18-25 minutes, then filtered, washed, and dried to obtain aluminum sol-impregnated silica fume. Then, aluminum sol-impregnated silica fume, talc, bis(dioctyloxypyrophosphate) ethylene titanate, and cyclohexanone are mixed and stirred at a controlled temperature of 85-91°C for 100-130 minutes. After stirring, it is filtered, washed, and dried to obtain the silica fume composite.

[0012] The mass ratio of silica fume to aluminum sol is 1:2.75-3.25;

[0013] The silica fume is micron-sized silica fume with a particle size of 25-35μm;

[0014] The aluminum sol has a solid content of 17 wt% and a pH of 2.2.

[0015] The mass ratio of silica fume, talc, bis(dioctyloxypyrophosphate) ethylene titanate, and cyclohexanone impregnated in the aluminum sol is 175-225:9-11:6.5-7.5:750-1250.

[0016] The talc powder has a particle size of 10-20 μm.

[0017] The method for preparing silicon carbide whisker-modified silica is as follows: silicon carbide whiskers are mixed with deionized water, and the pH is adjusted to 4.7-4.9 using acetic acid. Then, chitosan and sodium dodecylbenzenesulfonate are added and stirred evenly to obtain a silicon carbide whisker mixture for later use. Then, micron-sized silica is activated at 475-525℃ for 40-50 minutes. The activated micron-sized silica is mixed with the silicon carbide whisker mixture and stirred at a speed of 250-350 r / min for 50-70 minutes. After stirring, the mixture is filtered, washed, and dried to obtain silicon carbide whisker-modified silica.

[0018] 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.

[0019] The silicon carbide whiskers are 8 μm long and 1.5 μm in diameter;

[0020] The mass ratio of the micron-sized silica to silicon carbide whisker mixture is 1:2.75-3.25;

[0021] The micron-sized silica has a particle size of 40-55 μm.

[0022] The gradation method is as follows: the silica ash composite and ultrafine silica ash are mixed evenly to obtain silica ash gradation material, and silicon carbide whisker modified silica and nano silica are mixed evenly to obtain silica gradation material.

[0023] The mass ratio of the silica fume composite to ultrafine silica fume is 2.75-3.25:1;

[0024] The particle size of the ultrafine silica fume is 5-10 μm;

[0025] The mass ratio of silicon carbide whisker-modified silica to nano-silica is 3.5-4.5:1;

[0026] The particle size of the nano-silica is 10-15 nm.

[0027] The method for preparing the densifying agent by mixing silica fume grade ingredients, silica grade ingredients, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol evenly to obtain a high crack-resistant concrete waterproof densifying agent.

[0028] The mass ratio of the silica fume grade, silica grade, 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.

[0029] The particle size of the heavy calcium carbonate is 20-30 μm.

[0030] Compared with the prior art, the present invention achieves the following beneficial effects:

[0031] The compactor prepared by this invention can effectively guarantee the strength of concrete. According to the method in GB / T50081-2019, the compressive strength and flexural strength of the concrete were tested. The compressive strength was 44.9-46.0 MPa and the flexural strength was 12.17-12.34 MPa.

[0032] The densifying agent prepared by this invention can effectively improve the crack resistance of concrete. According to the method in GB / T50082-2024, the early crack resistance of concrete was tested, and the average crack opening area was 0.24-0.51 mm. 2 The number of cracks per unit area is 3.4; the shrinkage ratio of concrete is tested according to the method in GB / T8076-2008, and the shrinkage ratio is 100.7-101.5%; the splitting tensile strength of concrete is tested according to the method in GB / T50081-2019, and the splitting tensile strength is 5.50-5.61 MPa.

[0033] The densifier prepared by this invention can effectively improve the impermeability of concrete. According to the electric flux method in GB / T50082-2024, the impermeability of concrete was tested. The electric flux was 29-34C at 56 days, 18-19C at 90 days, and 12-14C at 180 days.

[0034] The compacting agent prepared by this invention can effectively improve the performance of concrete in saline environments. The compressive strength after 180 days of burial in saline soil is 43.3-44.1 MPa, and the compressive strength after 360 days of burial in saline soil is 38.9-41.1 MPa. The electrical flux after 180 days of burial in saline soil is 46-51 C, and the electrical flux after 360 days of burial in saline soil is 76-82 C.

[0035] The densifying agent prepared by this invention can effectively improve the waterproof performance of concrete. According to the method in GB / T50082-2024, the water seepage height of the concrete is tested. The water seepage height at 1.2MPa is 2.2-2.5mm, at 1.5MPa is 2.7-3.1mm, and at 2.0MPa is 3.5-4.0mm. Detailed Implementation

[0036] Example 1

[0037] (1) Preparation of silica fume composite

[0038] After mixing silica fume and aluminum sol, the mixture was stirred for 35 minutes. After stirring, it was allowed to stand for 20 minutes, then filtered, washed, and dried to obtain silica fume impregnated with aluminum sol. Then, silica fume impregnated with aluminum sol, talc, bis(dioctyloxypyrophosphate) ethylene titanate, and cyclohexanone were mixed and stirred at a controlled temperature of 87°C for 120 minutes. After stirring, the mixture was filtered, washed, and dried to obtain silica fume composite.

[0039] The mass ratio of silica fume to alumina sol is 1:3.

[0040] The silica fume is micron-sized silica fume with a particle size of 30μm;

[0041] The aluminum sol has a solid content of 17 wt% and a pH of 2.2.

[0042] The mass ratio of silica fume, talc, bis(dioctyloxypyrophosphate) ethylene titanate, and cyclohexanone impregnated in the aluminum sol is 200:10:7:1000.

[0043] The talc powder has a particle size of 15 μm.

[0044] (2) Preparation of silicon carbide whisker modified silicon dioxide

[0045] Silicon carbide whiskers were mixed with deionized water, and the pH was adjusted to 4.8 using acetic acid. Then, chitosan and sodium dodecylbenzenesulfonate were added and stirred until homogeneous to obtain a silicon carbide whisker mixture for later use. Micron-sized silica was then activated at 500°C for 45 minutes. The activated micron-sized silica was then mixed with the silicon carbide whisker mixture and stirred at 300 r / min for 60 minutes. After stirring, the mixture was filtered, washed, and dried to obtain silicon carbide whisker-modified silica.

[0046] The mass ratio of silicon carbide whiskers, deionized water, chitosan, and sodium dodecylbenzenesulfonate is 100:750:7:1.

[0047] The silicon carbide whiskers are 8 μm long and 1.5 μm in diameter;

[0048] The mass ratio of the micron-sized silica to silicon carbide whisker mixture is 1:3;

[0049] The micron-sized silica has a particle size of 50 μm.

[0050] (3) Grading

[0051] The silica ash composite and ultrafine silica ash are mixed evenly to obtain silica ash graded feedstock. The silicon carbide whisker modified silica and nano silica are mixed evenly to obtain silica graded feedstock.

[0052] The mass ratio of the silica fume composite to the ultrafine silica fume is 3:1;

[0053] The particle size of the ultrafine silica fume is 8 μm;

[0054] The mass ratio of silicon carbide whisker-modified silica to nano-silica is 4:1.

[0055] The particle size of the nano-silica is 12 nm.

[0056] (4) Mixing to prepare a densifying agent

[0057] A high crack-resistant concrete waterproofing and densifying agent is obtained by uniformly mixing silica fume grade ingredients, silica grade ingredients, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol.

[0058] The mass ratio of the silica fume grade material, silica grade material, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol is 25:35:5:2:5:12:4.

[0059] The particle size of the heavy calcium carbonate is 25 μm.

[0060] Example 2

[0061] (1) Preparation of silica fume composite

[0062] After mixing silica fume and aluminum sol, the mixture was stirred for 30 minutes. After stirring, it was allowed to stand for 25 minutes, then filtered, washed, and dried to obtain silica fume impregnated with aluminum sol. Then, silica fume impregnated with aluminum sol, talc, bis(dioctyloxypyrophosphate) ethylene titanate, and cyclohexanone were mixed and stirred at a controlled temperature of 85°C for 130 minutes. After stirring, the mixture was filtered, washed, and dried to obtain silica fume composite.

[0063] The mass ratio of silica fume to aluminum sol is 1:2.75.

[0064] The silica fume is micron-sized silica fume with a particle size of 25μm;

[0065] The aluminum sol has a solid content of 17 wt% and a pH of 2.2.

[0066] The mass ratio of silica fume, talc, bis(dioctyloxypyrophosphate) ethylene titanate, and cyclohexanone impregnated in the aluminum sol is 175:9:6.5:750.

[0067] The talc powder has a particle size of 10 μm.

[0068] (2) Preparation of silicon carbide whisker modified silicon dioxide

[0069] Silicon carbide whiskers were mixed with deionized water, and the pH was adjusted to 4.7 with acetic acid. Then chitosan and sodium dodecylbenzenesulfonate were added and stirred evenly to obtain a silicon carbide whisker mixture for later use. Micron-sized silica was then activated at 475°C for 50 minutes. The activated micron-sized silica was then mixed with the silicon carbide whisker mixture and stirred at 250 r / min for 70 minutes. After stirring, the mixture was filtered, washed, and dried to obtain silicon carbide whisker-modified silica.

[0070] The mass ratio of silicon carbide whiskers, deionized water, chitosan, and sodium dodecylbenzenesulfonate is 85:700:6.5:0.9.

[0071] The silicon carbide whiskers are 8 μm long and 1.5 μm in diameter;

[0072] The mass ratio of the micron-sized silica to silicon carbide whisker mixture is 1:2.75;

[0073] The micron-sized silica has a particle size of 40 μm.

[0074] (3) Grading

[0075] The silica ash composite and ultrafine silica ash are mixed evenly to obtain silica ash graded feedstock. The silicon carbide whisker modified silica and nano silica are mixed evenly to obtain silica graded feedstock.

[0076] The mass ratio of the silica fume composite to the ultrafine silica fume is 2.75:1;

[0077] The particle size of the ultrafine silica fume is 5 μm;

[0078] The mass ratio of silicon carbide whisker-modified silica to nano-silica is 3.5:1;

[0079] The particle size of the nano-silica is 10 nm.

[0080] (4) Mixing to prepare a densifying agent

[0081] A high crack-resistant concrete waterproofing and densifying agent is obtained by uniformly mixing silica fume grade ingredients, silica grade ingredients, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol.

[0082] The mass ratio of the silica fume grade, silica grade, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol is 23:30:4.5:1.8:4.5:11:3.5.

[0083] The particle size of the heavy calcium carbonate is 20 μm.

[0084] Example 3

[0085] (1) Preparation of silica fume composite

[0086] After mixing silica fume and aluminum sol, the mixture was stirred for 40 minutes. After stirring, it was allowed to stand for 18 minutes, then filtered, washed, and dried to obtain silica fume impregnated with aluminum sol. Then, silica fume impregnated with aluminum sol, talc, bis(dioctyloxypyrophosphate) ethylene titanate, and cyclohexanone were mixed and stirred at a controlled temperature of 91°C for 100 minutes. After stirring, the mixture was filtered, washed, and dried to obtain silica fume composite.

[0087] The mass ratio of silica fume to aluminum sol is 1:3.25.

[0088] The silica fume is micron-sized silica fume with a particle size of 35μm;

[0089] The aluminum sol has a solid content of 17 wt% and a pH of 2.2.

[0090] The mass ratio of silica fume, talc, bis(dioctyloxypyrophosphate) ethylene titanate, and cyclohexanone impregnated in the aluminum sol is 225:11:7.5:1250.

[0091] The talc powder has a particle size of 20 μm.

[0092] (2) Preparation of silicon carbide whisker modified silicon dioxide

[0093] Silicon carbide whiskers were mixed with deionized water, and the pH was adjusted to 4.9 using acetic acid. Then, chitosan and sodium dodecylbenzenesulfonate were added and stirred until homogeneous to obtain a silicon carbide whisker mixture. Micron-sized silica was then activated at 525°C for 40 minutes. The activated micron-sized silica was then mixed with the silicon carbide whisker mixture and stirred at 350 r / min for 50 minutes. After stirring, the mixture was filtered, washed, and dried to obtain silicon carbide whisker-modified silica.

[0094] The mass ratio of silicon carbide whiskers, deionized water, chitosan, and sodium dodecylbenzenesulfonate is 115:800:7.5:1.1.

[0095] The silicon carbide whiskers are 8 μm long and 1.5 μm in diameter;

[0096] The mass ratio of the micron-sized silica to silicon carbide whisker mixture is 1:3.25;

[0097] The micron-sized silica has a particle size of 55 μm.

[0098] (3) Grading

[0099] The silica ash composite and ultrafine silica ash are mixed evenly to obtain silica ash graded feedstock. The silicon carbide whisker modified silica and nano silica are mixed evenly to obtain silica graded feedstock.

[0100] The mass ratio of the silica fume composite to the ultrafine silica fume is 3.25:1;

[0101] The particle size of the ultrafine silica fume is 10 μm;

[0102] The mass ratio of silicon carbide whisker-modified silica to nano-silica is 4.5:1.

[0103] The particle size of the nano-silica is 15 nm.

[0104] (4) Mixing to prepare a densifying agent

[0105] A high crack-resistant concrete waterproofing and densifying agent is obtained by uniformly mixing silica fume grade ingredients, silica grade ingredients, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol.

[0106] The mass ratio of the silica fume grade, silica grade, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol is 27:40:5.5:2.2:5.5:13:4.5.

[0107] The particle size of the heavy calcium carbonate is 30 μm.

[0108] Comparative Example 1

[0109] Unlike Example 1, the step of preparing silica fume composite is omitted, and in the grading step, untreated micron-sized silica fume and ultrafine silica fume are used for gradation. The remaining steps are the same to prepare the densifying agent.

[0110] The mass ratio of the untreated micron-sized silica fume to the ultrafine silica fume is 3:1;

[0111] The particle size of the ultrafine silica fume is 8 μm;

[0112] The untreated micron-sized silica fume has a particle size of 30 μm.

[0113] Comparative Example 2

[0114] Unlike Example 1, the step of preparing silicon carbide whisker modified silica is omitted, and in the gradation step, micron-sized silica and nano-sized silica are used for gradation. The remaining steps are the same to prepare the compacting agent.

[0115] The mass ratio of the micron-sized silica to the nano-sized silica is 4:1;

[0116] The particle size of the nano-silica is 12 nm;

[0117] The micron-sized silica has a particle size of 50 μm.

[0118] Test Example 1: Effect of Densifier on Concrete Strength

[0119] The densifying agents prepared in Examples 1-2 and Comparative Examples 1-2 were added at a ratio of 3.5 wt% of the gel material;

[0120] The test used C40 ready-mixed concrete as the inspection standard, with the following mix proportions:

[0121] 250kg / m³ of cement 3 75kg / m³ of mineral powder 3 70kg / m³ of fly ash 3 , sand 810kg / m 3 1070 kg / m³ of gravel 3 160kg / m³ of water 3 ;

[0122] The cement is P·O 42.5R silicate cement;

[0123] The specific surface area of ​​the mineral powder is 370 m². 2 / kg;

[0124] The sand is medium sand from Zone II with a fineness modulus of 2.5;

[0125] The gravel is a 5-25mm continuous gradation;

[0126] The compressive strength and flexural strength of concrete were tested according to the method in GB / T50081-2019, and the results are shown in Table 1.

[0127] Table 1

[0128]

[0129] Examples 1-3 involve special treatment of silica fume with larger particle size, followed by gradation with ultrafine silica fume; and special treatment of silica with larger particle size, followed by gradation with nano silica. Finally, a densifying agent is prepared, resulting in concrete with high compressive strength and flexural strength.

[0130] Comparative Example 1 omits the step of preparing silica fume composite and uses untreated micron-sized silica fume and ultrafine silica fume for gradation and preparation of a densifying agent in the gradation step, which leads to a decrease in the compressive strength and flexural strength of concrete, with the decrease in flexural strength being particularly severe.

[0131] Comparative Example 2 omits the step of preparing silicon carbide whisker modified silica, and in the gradation step, uses micron-sized silica and nano-sized silica for gradation and prepares a densifying agent, which leads to a decrease in the compressive strength and flexural strength of concrete, with the decrease in compressive strength being particularly severe.

[0132] Test Example 2: Effect of Densifier on Crack Resistance of Concrete

[0133] The densifying agents prepared in Examples 1-2 and Comparative Examples 1-2 were added at a ratio of 3.5 wt% of the gel material;

[0134] The test used C40 ready-mixed concrete as the inspection standard, with the following mix proportions:

[0135] 250kg / m³ of cement 3 75kg / m³ of mineral powder 3 70kg / m³ of fly ash 3 , sand 810kg / m 3 1070 kg / m³ of gravel 3 160kg / m³ of water 3 ;

[0136] The cement is P·O 42.5R silicate cement;

[0137] The specific surface area of ​​the mineral powder is 370 m². 2 / kg;

[0138] The sand is medium sand from Zone II with a fineness modulus of 2.5;

[0139] The gravel is a 5-25mm continuous gradation;

[0140] According to the method in GB / T50082-2024, the early crack resistance of concrete is tested, and the average crack area and the number of cracks per unit area are used as evaluation indicators.

[0141] The shrinkage rate of concrete was tested according to the method in GB / T8076-2008;

[0142] The splitting tensile strength of concrete was tested according to the method in GB / T50081-2019.

[0143] The results are shown in Table 2.

[0144] Table 2

[0145]

[0146] Examples 1-3 involve special treatment of silica fume with larger particle size, followed by gradation with ultrafine silica fume; and special treatment of silica with larger particle size, followed by gradation with nano silica. Finally, a densifying agent is prepared, resulting in concrete with good crack resistance, small crack area, few cracks, low shrinkage, and high splitting tensile strength.

[0147] Comparative Example 1 omits the step of preparing silica fume composite and uses untreated micron-sized silica fume and ultrafine silica fume for gradation and preparation of densifier in the gradation step, which leads to a decrease in the crack resistance of concrete. Although the number of cracks per unit area increases significantly, the increase in crack opening area is moderate. At the same time, the shrinkage ratio also increases to a certain extent, and the splitting tensile strength decreases significantly.

[0148] Comparative Example 2 omits the step of preparing silicon carbide whisker modified silica and uses micron-sized silica and nano-sized silica for gradation and prepares a densifier in the gradation step, which leads to a decrease in the crack resistance of concrete. Although the crack opening area increases significantly, the increase in the number of cracks per unit area is moderate. At the same time, the shrinkage rate increases significantly, and the splitting tensile strength decreases to a certain extent.

[0149] Test Example 3: Effect of Densifier on the Impermeability of Concrete

[0150] The densifying agents prepared in Examples 1-2 and Comparative Examples 1-2 were added at a ratio of 3.5 wt% of the gel material;

[0151] The test used C40 ready-mixed concrete as the inspection standard, with the following mix proportions:

[0152] 250kg / m³ of cement 3 75kg / m³ of mineral powder 3 70kg / m³ of fly ash 3 , sand 810kg / m 3 1070 kg / m³ of gravel 3 160kg / m³ of water 3 ;

[0153] The cement is P·O 42.5R silicate cement;

[0154] The specific surface area of ​​the mineral powder is 370 m². 2 / kg;

[0155] The sand is medium sand from Zone II with a fineness modulus of 2.5;

[0156] The gravel is a 5-25mm continuous gradation;

[0157] The permeability of concrete was tested according to the electrical flux method in GB / T50082-2024, including the electrical flux at 56d, 90d and 180d. The results are shown in Table 3.

[0158] Table 3

[0159]

[0160] Examples 1-3 involve special treatment of silica fume with larger particle size, followed by gradation with ultrafine silica fume; and special treatment of silica with larger particle size, followed by gradation with nano silica. Finally, a densifying agent is prepared, resulting in concrete with relatively low electrical flux. Moreover, the electrical flux will gradually decrease over time.

[0161] Comparative Example 1 omits the step of preparing silica fume composite and uses untreated micron-sized silica fume and ultrafine silica fume for gradation and preparation of a densifier in the gradation step, which leads to a decrease in the impermeability of concrete. The initial electrical flux is high, but the electrical flux will decrease to a low level over time.

[0162] Comparative Example 2 omits the step of preparing silicon carbide whisker modified silica and uses micron-sized silica and nano-sized silica for gradation and preparation of a densifier in the gradation step, which leads to a decrease in the impermeability of concrete. Although the initial electrical flux is low, the decrease in electrical flux is small over time.

[0163] Test Example 4: Effect of Densifier on the Performance of Concrete in Saline Environments

[0164] The densifying agents prepared in Examples 1-2 and Comparative Examples 1-2 were added at a ratio of 3.5 wt% of the gel material;

[0165] The test used C40 ready-mixed concrete as the inspection standard, with the following mix proportions:

[0166] 250kg / m³ of cement 3 75kg / m³ of mineral powder 3 70kg / m³ of fly ash 3 , sand 810kg / m 3 1070 kg / m³ of gravel 3 160kg / m³ of water 3 ;

[0167] The cement is P·O 42.5R silicate cement;

[0168] The specific surface area of ​​the mineral powder is 370 m². 2 / kg;

[0169] The sand is medium sand from Zone II with a fineness modulus of 2.5;

[0170] The gravel is a 5-25mm continuous gradation;

[0171] After the concrete was cured normally for 28 days, it was buried in saline soil with a chloride ion content of 5325 mg / kg and a sulfate ion content of 13571 mg / kg. The compressive strength and electrical flux were tested after 180 days and 360 days of burial, and the results are shown in Table 4.

[0172] Table 4

[0173]

[0174] Examples 1-3 involve special treatment of silica fume with larger particle size, followed by gradation with ultrafine silica fume; and special treatment of silica with larger particle size, followed by gradation with nano silica. Finally, a densifying agent is prepared, and the concrete can maintain high strength and low electrical flux in saline soil environment.

[0175] Comparative Example 1 omits the step of preparing silica fume composite and uses untreated micron-sized silica fume and ultrafine silica fume for gradation and preparation of a densifying agent in the gradation step. In the saline soil environment, the compressive strength of the concrete decreases significantly, while the electrical flux increases to a certain extent.

[0176] Comparative Example 2 omits the step of preparing silicon carbide whisker modified silica, and in the grading step, uses micron-sized silica and nano-sized silica to grade and prepare a densifying agent. In a saline soil environment, the compressive strength of the concrete decreases to a certain extent, while the electrical flux increases significantly.

[0177] Test Example 5: Effect of Densifier on Waterproofing Performance of Concrete

[0178] The densifying agents prepared in Examples 1-2 and Comparative Examples 1-2 were added at a ratio of 3.5 wt% of the gel material;

[0179] The test used C40 ready-mixed concrete as the inspection standard, with the following mix proportions:

[0180] 250kg / m³ of cement 3 75kg / m³ of mineral powder 3 70kg / m³ of fly ash 3 , sand 810kg / m 3 1070 kg / m³ of gravel 3 160kg / m³ of water 3 ;

[0181] The cement is P·O 42.5R silicate cement;

[0182] The specific surface area of ​​the mineral powder is 370 m². 2 / kg;

[0183] The sand is medium sand from Zone II with a fineness modulus of 2.5;

[0184] The gravel is a 5-25mm continuous gradation;

[0185] The water seepage height of concrete was tested according to the method in GB / T50082-2024, and the test pressures were 1.2MPa, 1.5MPa and 2.0MPa. The results are shown in Table 5.

[0186] Table 5

[0187]

[0188] Examples 1-3 involve special treatment of silica fume with larger particle size, followed by gradation with ultrafine silica fume; and special treatment of silica with larger particle size, followed by gradation with nano silica. Finally, a densifying agent is prepared, resulting in concrete with good waterproof performance and low water seepage height.

[0189] Comparative Example 1 omits the step of preparing silica fume composite and uses untreated micron-sized silica fume and ultrafine silica fume for gradation and preparation of a densifying agent in the gradation step, which leads to a certain degree of increase in the water seepage height of the concrete.

[0190] Comparative Example 2 omits the step of preparing silicon carbide whisker modified silica and uses micron-sized silica and nano-sized silica for gradation and prepares a densifying agent in the gradation step, which leads to a serious increase in the water seepage height of concrete, especially under high water pressure.

Claims

1. A method for preparing a high crack-resistant concrete waterproofing and densifying agent, characterized in that, The preparation method includes preparing silica fume composite, preparing silicon carbide whisker modified silica, grading, and mixing to prepare a densifying agent. The method for preparing the silica fume composite is as follows: silica fume is mixed with aluminum sol, stirred and allowed to stand, then filtered, washed and dried to obtain aluminum sol-impregnated silica fume. Then, aluminum sol-impregnated silica fume, talc, bis(dioctyloxypyrophosphate) ethylene titanate and cyclohexanone are mixed and stirred, then filtered, washed and dried to obtain the silica fume composite. The mass ratio of silica fume to aluminum sol is 1:2.75-3.25; The mass ratio of silica fume, talc, bis(dioctyloxypyrophosphate) ethylene titanate, and cyclohexanone impregnated in the aluminum sol is 175-225:9-11:6.5-7.5:750-1250. The method for preparing silicon carbide whisker-modified silica is as follows: silicon carbide whiskers are mixed with deionized water, the pH is adjusted to 4.7-4.9 with acetic acid, chitosan and sodium dodecylbenzenesulfonate are added, and the mixture is stirred evenly to obtain a silicon carbide whisker mixture for later use. The activated micron-sized silica is mixed and stirred with the silicon carbide whisker mixture. After stirring, the mixture is filtered, washed, and dried to obtain 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 mass ratio of the micron-sized silica to silicon carbide whisker mixture is 1:2.75-3.25; The gradation method is as follows: the silica ash composite and ultrafine silica ash are mixed evenly to obtain silica ash gradation material, and silicon carbide whisker modified silica and nano silica are mixed evenly to obtain silica gradation material. The method for preparing the densifying agent by mixing silica fume grade ingredients, silica grade ingredients, sodium silicate, aluminum nitrate, hydroxypropyl methylcellulose, heavy calcium carbonate, and polyvinyl alcohol evenly to obtain a high crack-resistant concrete waterproof densifying agent.

2. The preparation method of a high crack-resistant concrete waterproofing and densifying agent according to claim 1, characterized in that: In the method for preparing silica fume composite, the method of mixing silica fume and aluminum sol, stirring and letting stand is as follows: the stirring time is 30-40 minutes, and the stand time is 18-25 minutes after stirring is completed. After mixing silica fume, talc, bis(dioctyloxypyrophosphate) ethylene titanate and cyclohexanone impregnated with aluminum sol, the mixture is stirred at a temperature of 85-91℃ for 100-130 minutes.

3. The preparation method of a high crack-resistant concrete waterproofing and densifying agent according to claim 1, characterized in that: In the method for preparing silica fume composite, the silica fume is micron-sized silica fume with a particle size of 25-35 μm; The aluminum sol has a solid content of 17 wt% and a pH of 2.

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4. The preparation method of a high crack-resistant concrete waterproofing and densifying agent according to claim 1, characterized in that: In the method for preparing silicon carbide whisker modified silicon dioxide, the method for activating the micron-sized silicon dioxide is to activate it at 475-525℃ for 40-50 min. The method for mixing the activated micron-sized silica and silicon carbide whisker mixture is to stir at a speed of 250-350 r / min for 50-70 min.

5. The preparation method of a high crack-resistant concrete waterproofing and densifying agent according to claim 1, characterized in that: In the method for preparing silicon carbide whisker-modified silicon dioxide, the length of the silicon carbide whisker is 8 μm and the diameter is 1.5 μm. The micron-sized silica has a particle size of 40-55 μm.

6. The preparation method of a high crack-resistant concrete waterproofing and densifying agent according to claim 1, characterized in that: In the gradation method, the mass ratio of silica fume composite to 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 silicon carbide whisker-modified silica to 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 high crack-resistant concrete waterproofing and densifying agent according to claim 1, characterized in that: In the method for preparing the compacting agent by mixing, the mass ratio of silica fume grade material, silica grade 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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