A green ultrafine high-performance composite admixture and its preparation method and application

Abstract

The present invention relates to the technical field of high-performance concrete, and specifically discloses a green ultra-fine high-performance composite admixture, a preparation method and an application. The raw materials of the above-mentioned green ultra-fine high-performance composite admixture include: fly ash, microsilica powder, silane coupling agent, mesoporous silica, waste building materials, nano calcium carbonate, nano bentonite, polyethylene wax, paraffin wax, fatty acid glyceride, calcium lactate, acrylamide, ammonium persulfate, alkaliphilic Bacillus agent, limestone powder, urea, light-burned magnesium oxide expansion agent, quartz powder, redispersible latex powder, and defoaming agent. The present invention is not only green and environmentally friendly, and effectively saves cost investment, but also has self-repairing characteristics. It can be applied to concrete projects in harsh environments and effectively improve the long-term durability of high-performance concrete.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, and in particular to a green ultrafine high-performance composite admixture, a preparation method and an application thereof. Background Art

[0002] Cement concrete, with its readily available, versatile, adaptable, relatively economical, and engineering properties suitable for a wide range of structural applications, has become the most widely used structural material worldwide. As the most widely used building material in engineering construction, concrete has diversified its structural forms with the advancement of engineering construction and science and technology, and high-strength and high-performance concrete is now a common pursuit.

[0003] Currently, the working environment of cement concrete is becoming increasingly demanding, and the requirements for its early and long-term durability are also increasing. Compared with ordinary concrete, high-performance concrete has superior properties such as high durability, high workability, and high volume stability. It can utilize various industrial waste and minerals, reducing pollution to the natural environment and energy consumption. It is also easy to construct and reduces labor input, making it the future development trend of green concrete.

[0004] The degradation process of cement-based materials occurs when existing micro-defects in concrete, under the influence of external factors, continuously expand and form macro-cracks. The interconnectedness of these micro-cracks within the concrete provides a rapid pathway for the intrusion of harmful media, severely impacting the durability and service life of concrete structures. Currently, high-performance concrete (HPC) exhibits poor durability due to the insufficient stability of cement hydrates.

[0005] The addition of ultrafine admixtures can improve the microstructure of cement-based materials, increase their hydration level, and extend the service life of reinforced concrete structures. However, reinforced concrete is prone to fine cracks due to structural stress, leading to structural cracking. Currently, concrete cracks are usually repaired manually, but the results are not ideal. Summary of the Invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a green ultrafine high-performance composite admixture and its preparation method and application.

[0007] A green ultrafine high-performance composite admixture comprises the following raw materials in parts by mass: 20-50 parts of fly ash, 15-25 parts of microsilica powder, 1.1-3 parts of silane coupling agent, 5-10 parts of mesoporous silica, 5-10 parts of waste building materials, 1-5 parts of nano-calcium carbonate, 1-2 parts of nano-bentonite, 1-3 parts of polyethylene wax, 10-20 parts of paraffin wax, 1-2 parts of fatty acid glyceride, 1-3 parts of calcium lactate, 1-4 parts of acrylamide, 0.01-0.1 parts of ammonium persulfate, 1-2 parts of alkaliphilic bacillus agent, 15-30 parts of limestone powder, 5-10 parts of urea, 1-6 parts of light-burned magnesium oxide expansion agent, 3-15 parts of quartz powder, 0.1-2 parts of redispersible latex powder, and 0.1-0.5 parts of defoaming agent.

[0008] Preferably, the density of microsilica powder is ≥550kg / m 3 , of which SiO2 and Al2O3 account for ≥95% by mass.

[0009] Preferably, the mesoporous silica particle size is 100-500 nm.

[0010] Preferably, the silane coupling agent is at least one of silane coupling agent KH570, silane coupling agent KH590, and silane coupling agent Si69.

[0011] Preferably, the redispersible latex powder is redispersible vinyl acetate / ethylene copolymer powder.

[0012] Preferably, the content of live alkaliphilic Bacillus in the alkaliphilic Bacillus agent is 1-5×10 9 cfu / g.

[0013] Preferably, the alkaliphilic Bacillus is at least one of Bacillus sphaericus, Bacillus pasteurianus, Bacillus cohnii, Bacillus cereus, and Bacillus licheniformis.

[0014] The preparation method of the green ultrafine high-performance composite admixture comprises the following steps:

[0015] S1. Mix fly ash and microsilica powder uniformly to obtain premix a;

[0016] S2, silane coupling agent, mesoporous silica, and waste building materials are mixed and ground for 10-20 minutes, nano calcium carbonate, nano bentonite, and polyethylene wax are added thereto, and grinding is continued for 5-15 minutes, paraffin wax, fatty acid glyceride, and calcium lactate are added, and stirred at 70-80° C. to obtain premix b;

[0017] S3, mixing and grinding the silane coupling agent and fly ash, adding deionized water and acrylamide, stirring for 1-2 hours, adding ammonium persulfate, stirring at 70-80°C for 1-2 hours, cooling to room temperature, adding the alkaliphilic Bacillus agent, ultrasonically dispersing for 1-4 hours, centrifuging, freeze-drying, crushing and sieving, feeding into a drum, spraying premix b on the surface, and freeze-drying to obtain premix c;

[0018] S4. Mix limestone powder, urea, light-burned magnesium oxide expansion agent, quartz powder, redispersible latex powder, and defoaming agent evenly, add premix a and premix c thereto and mix evenly.

[0019] Preferably, the mass ratio of the silane coupling agent used in S2 to the silane coupling agent used in S3 is 0.1-1:1-2.

[0020] Preferably, in S2, the mesh size of the material after adding nano calcium carbonate, nano bentonite and polyethylene wax and grinding is 700-1000 mesh.

[0021] Preferably, in S3, the ultrasonic frequency is 5-12 kHz.

[0022] The application of the above-mentioned green ultrafine high-performance composite admixture in the preparation of concrete.

[0023] The green ultrafine high-performance composite admixture can replace 3-15% of the mass of cement in concrete.

[0024] Beneficial effects:

[0025] The present invention adopts a silane coupling agent to compound and activate mesoporous silica and waste building materials. In combination with polyethylene wax, the compatibility and lubricity between the fly ash and nano calcium carbonate and nano bentonite are good, and the fly ash can be evenly dispersed in paraffin wax. The fly ash is then activated by the silane coupling agent and then grafted with polyacrylamide, which significantly enhances the adsorption and load strength of the fly ash on alkaliphilic bacillus, further coats the premix b, and the product is dispersed among the admixtures. It can not only effectively reduce the surface energy between particles and effectively reduce the agglomeration of particles, but also absorb water and expand after the wall is broken, can closely fit the cracks to achieve filling and plugging, react with water, calcium hydroxide and other substances at the crack interface to repair the cracks, and at the same time, the alkaliphilic bacillus further overflows after the wall is broken, further repairs the cracks, and comprehensively improves the strength and durability of concrete, with excellent repair effect.

[0026] The present invention adopts mesoporous silica and waste building materials for compound grinding, which not only forms a large number of fine pores and a large specific surface area, but also the high silica content can effectively promote the formation of hydration products and effectively improve the void structure of concrete materials; and the combination of fly ash and microsilica has good porosity, and when combined with prefabricated material C, it has excellent dispersion uniformity in the admixture, which not only effectively promotes the dispersion of structural stress, thereby producing an effective strengthening effect, but also can inhibit the generation and development of fine cracks, and has a significant structural stress compensation and anti-cracking effect.

[0027] The present invention is not only green and environmentally friendly, effectively saving cost investment, but also can alleviate the problem of tight supply of traditional mineral admixtures, reduce engineering costs, enhance internal maintenance, and reduce the cracking problem caused by stress in high-performance concrete structures. The concrete has good fluidity, water retention, and workability, and is extremely dense and uniform. It has excellent crack resistance and resistance to ion corrosion, good volume stability, and self-repairing characteristics. It can be used in concrete projects in harsh environments and effectively improve the long-term durability of high-performance concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a comparison chart of the flexural strength of the concrete specimens of Example 5 and Comparative Examples 1-3.

[0029] Figure 2 The figure is a comparison chart of the compressive strength of the concrete samples of Example 5 and Comparative Examples 1-3 after standard curing for different times.

[0030] Figure 3 It is a comparison chart of the early compressive strength ratio of the concrete specimens of Example 5 and Comparative Examples 1-3.

[0031] Figure 4 The figure is a comparison chart of the strength loss rate of the concrete samples of Example 5 and Comparative Examples 1-3 after 200 freeze-thaw cycles.

[0032] Figure 5 These are the self-repair rate curves of the concrete specimens of Example 5 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0033] The present invention will be further explained below with reference to specific embodiments.

[0034] The fly ash used in the following is a new type of ultra-fine volcanic ash powder microbeads produced by Beijing Mouyuan Yixinxin Material Technology Co., Ltd. The microsilica powder used in the following is purchased from Shijiazhuang Moujiang Mineral Products Co., Ltd. After random inspection upon storage, its density is 557.29kg / m 3The mass percentage of SiO2 and Al2O3 is 95.26%. The mesoporous silica used below was purchased from Qinghe County Moujiang Metal Materials Co., Ltd., and after random inspection upon arrival, its average particle size was 200nm. The waste building materials used below were purchased from Zhengzhou Yuanmoufa Environmental Protection Technology Co., Ltd., and after random inspection upon arrival, its screening results are shown in Table 1:

[0035] Table 1 Screening results of waste building materials

[0036]

[0037] The light-burned magnesium oxide expansion agent used below was purchased from Xu Magnesium Materials Factory in the Nanlou Economic Development Zone of Yingkou, with a particle size of 250 mesh. The redispersible latex powder used below (saponification-resistant redispersible vinyl acetate / ethylene copolymer powder) was sourced from Wacker Chemie, Hebei Xing Chemical Co., Ltd., with the product number 5134. The polyether-modified silicone defoamer used below was purchased from Qingdao Side Silicone Co., Ltd., with the model number MSD-916.

[0038] The strain of Bacillus sphaericus used below has a deposit number of CCTCC WB 20081587; the strain of Bacillus cohnii used below has a deposit number of CCTCC WB 20081136; and the strain of Bacillus cereus used below has a deposit number of CCTCC AB 93038. All three strains are from the China Center for Type Culture Collection.

[0039] Example 1

[0040] A green ultrafine high-performance composite admixture, the raw materials of which include: 200g fly ash, 150g microsilica, 1g silane coupling agent KH570, 10g silane coupling agent Si69, 50g mesoporous silica, 50g waste building materials, 10g nano calcium carbonate, 10g nano bentonite, 10g polyethylene wax, 100g paraffin, 10g fatty acid glyceride, 10g calcium lactate, 10g acrylamide, 0.1g ammonium persulfate, and a viable bacteria content of 1×10 9 10g of spherical Bacillus agent with a cfu / g content, 150g of limestone powder, 50g of urea, 10g of light-burned magnesium oxide expansion agent, 30g of quartz powder, 1g of redispersible latex powder, and 1g of polyether-modified silicone defoaming agent.

[0041] The preparation method of the green ultrafine high-performance composite admixture comprises the following steps:

[0042] S1. Mix 100g of fly ash and microsilica powder to obtain premix a. The specific surface area of ​​premix a is 812m 2 / kg;

[0043] S2, silane coupling agent KH570, mesoporous silica, and waste building materials were mixed and ground for 10 min at a grinding speed of 1000 r / min, nano calcium carbonate, nano bentonite, and polyethylene wax were added thereto and continued to grind for 5 min, and after passing through a 700 mesh sieve without sieve residue, paraffin wax, fatty acid glyceride, and calcium lactate were added, and stirred at a temperature of 70° C. to obtain premix b;

[0044] S3, silane coupling agent Si69 and 100g fly ash were mixed and ground at a grinding speed of 1000r / min, 400g deionized water and acrylamide were added and stirred for 1h, ammonium persulfate was added, stirred at a temperature of 70°C for 1h, cooled to room temperature, spherical Bacillus agent was added and ultrasonically dispersed for 1h at an ultrasonic frequency of 5kHz, centrifuged, freeze-dried, crushed through a 50-mesh sieve, and fed into a drum, premix b was sprayed on the surface, and freeze-dried to obtain premix c;

[0045] S4. Mix limestone powder, urea, light-burned magnesium oxide expansion agent, quartz powder, redispersible latex powder, and polyether-modified silicone defoamer evenly, and add premix a and premix c thereto and mix evenly.

[0046] Example 2

[0047] A green ultrafine high-performance composite admixture, the raw materials of which include: 500g fly ash, 250g microsilica, 10g silane coupling agent KH590, 20g silane coupling agent KH570, 100g mesoporous silica, 100g waste building materials, 50g nano calcium carbonate, 20g nano bentonite, 30g polyethylene wax, 200g paraffin, 20g fatty acid glyceride, 30g calcium lactate, 40g acrylamide, 1g ammonium persulfate, and a viable bacteria content of 5×10 9 20g of Bacillus coli agent with a cfu / g content, 300g of limestone powder, 100g of urea, 60g of light-burned magnesium oxide expansion agent, 150g of quartz powder, 20g of redispersible latex powder, and 5g of polyether-modified silicone defoaming agent.

[0048] The preparation method of the green ultrafine high-performance composite admixture comprises the following steps:

[0049] S1. 300g of fly ash and microsilica powder were mixed evenly to obtain premix a. The specific surface area of ​​premix a was 1076m 2 / kg;

[0050] S2, silane coupling agent KH590, mesoporous silica, and waste building materials were mixed and ground for 20 min at a grinding speed of 2000 r / min, nano calcium carbonate, nano bentonite, and polyethylene wax were added thereto, and grinding was continued for 15 min. After passing through a 1000 mesh sieve without sieve residue, paraffin wax, fatty acid glyceride, and calcium lactate were added, and stirred at a temperature of 80° C. to obtain premix b;

[0051] S3, silane coupling agent KH570 and 200g fly ash were mixed and ground at a grinding speed of 2000r / min, 600g deionized water and acrylamide were added and stirred for 2h, ammonium persulfate was added, and the temperature was stirred at 80°C for 2h, cooled to room temperature, and Bacillus coli agent was added and ultrasonically dispersed for 4h at an ultrasonic frequency of 12kHz, centrifuged, freeze-dried, crushed through an 80-mesh sieve, and fed into a drum, premix b was sprayed on the surface, and freeze-dried to obtain premix c;

[0052] S4. Mix limestone powder, urea, light-burned magnesium oxide expansion agent, quartz powder, redispersible latex powder, and polyether-modified silicone defoamer evenly, and add premix a and premix c thereto and mix evenly.

[0053] Example 3

[0054] A green ultrafine high-performance composite admixture, the raw materials of which include: 430g fly ash, 180g microsilica, 20g silane coupling agent KH570, 90g mesoporous silica, 70g waste building materials, 40g nano calcium carbonate, 13g nano bentonite, 25g polyethylene wax, 120g paraffin, 18g fatty acid glyceride, 15g calcium lactate, 30g acrylamide, 0.3g ammonium persulfate, and a viable bacteria content of 4×10 9 13g cfu / g Bacillus cereus agent, 240g limestone powder, 70g urea, 50g light-burned magnesium oxide expansion agent, 70g quartz powder, 14g redispersible latex powder, and 2g polyether modified silicone defoaming agent.

[0055] The preparation method of the green ultrafine high-performance composite admixture comprises the following steps:

[0056] S1. Mix 250g of fly ash and microsilica powder to obtain premix a. The specific surface area of ​​premix a is 893m 2 / kg;

[0057] S2, 7g of silane coupling agent KH570, mesoporous silica, and waste building materials were mixed and ground for 12min at a grinding speed of 1700r / min, nano calcium carbonate, nano bentonite, and polyethylene wax were added thereto and continued to grind for 8min, and after passing through an 800-mesh sieve without sieve residue, paraffin wax, fatty acid glyceride, and calcium lactate were added, and stirred at a temperature of 77°C to obtain a premix b;

[0058] S3, 13g silane coupling agent KH570 and 180g fly ash were mixed and ground at a grinding speed of 1200r / min, 550g deionized water and acrylamide were added and stirred for 80min, ammonium persulfate was added, and the mixture was stirred at 77°C for 80min, cooled to room temperature, and Bacillus cereus agent was added and ultrasonically dispersed for 3h at an ultrasonic frequency of 6kHz, centrifuged, freeze-dried, crushed through a 70-mesh sieve, and fed into a drum, premix b was sprayed on the surface, and freeze-dried to obtain premix c;

[0059] S4. Mix limestone powder, urea, light-burned magnesium oxide expansion agent, quartz powder, redispersible latex powder, and polyether-modified silicone defoamer evenly, and add premix a and premix c thereto and mix evenly.

[0060] Example 4

[0061] A green ultrafine high-performance composite admixture, the raw materials of which include: 270g fly ash, 220g microsilica powder, 20g silane coupling agent KH570, 70g mesoporous silica, 90g waste building materials, 20g nano calcium carbonate, 17g nano bentonite, 15g polyethylene wax, 180g paraffin, 12g fatty acid glyceride, 25g calcium lactate, 20g acrylamide, 0.7g ammonium persulfate, and a viable bacteria content of 2×10 9 17g of Bacillus cereus agent with a cfu / g content, 200g of limestone powder, 90g of urea, 20g of light-burned magnesium oxide expansion agent, 110g of quartz powder, 7g of redispersible latex powder, and 4g of polyether-modified silicone defoaming agent.

[0062] The preparation method of the green ultrafine high-performance composite admixture comprises the following steps:

[0063] S1. Mix 150g of fly ash and microsilica powder to obtain premix a. The specific surface area of ​​premix a is 969m 2 / kg;

[0064] S2, 3g of silane coupling agent KH570, mesoporous silica, and waste building materials were mixed and ground for 18min at a grinding speed of 1300r / min, nano calcium carbonate, nano bentonite, and polyethylene wax were added thereto and continued to grind for 12min, and after passing through a 900-mesh sieve without sieve residue, paraffin wax, fatty acid glyceride, and calcium lactate were added, and stirred at a temperature of 73°C to obtain a premix b;

[0065] S3, 17g of silane coupling agent KH570 and 120g of fly ash were mixed and ground at a grinding speed of 1800r / min, 450g of deionized water and acrylamide were added and stirred for 100min, ammonium persulfate was added, and the temperature was stirred at 73°C for 100min, cooled to room temperature, and Bacillus cereus agent was added and ultrasonically dispersed for 2h at an ultrasonic frequency of 9kHz, centrifuged, freeze-dried, crushed through a 60-mesh sieve, and fed into a drum, premix b was sprayed on the surface, and freeze-dried to obtain premix c;

[0066] S4. Mix limestone powder, urea, light-burned magnesium oxide expansion agent, quartz powder, redispersible latex powder, and polyether-modified silicone defoamer evenly, and add premix a and premix c thereto and mix evenly.

[0067] Example 5

[0068] A green ultrafine high-performance composite admixture, whose raw materials include: 350g fly ash, 200g microsilica, 20g silane coupling agent KH570, 80g mesoporous silica, 80g waste building materials, 30g nano calcium carbonate, 15g nano bentonite, 20g polyethylene wax, 150g paraffin, 15g fatty acid glyceride, 20g calcium lactate, 25g acrylamide, 0.5g ammonium persulfate, and a live bacteria content of 3×10 9 15g of Bacillus cereus agent with a cfu / g content, 220g of limestone powder, 80g of urea, 35g of light-burned magnesium oxide expansion agent, 90g of quartz powder, 10g of redispersible latex powder, and 3g of polyether-modified silicone defoaming agent.

[0069] The preparation method of the green ultrafine high-performance composite admixture comprises the following steps:

[0070] S1. Mix 200g of fly ash and microsilica powder to obtain premix a. The specific surface area of ​​premix a is 943m 2 / kg;

[0071] S2, 5g of silane coupling agent KH570, mesoporous silica, and waste building materials were mixed and ground for 15min at a grinding speed of 1500r / min, nano calcium carbonate, nano bentonite, and polyethylene wax were added thereto and continued to grind for 10min, and after passing through an 800-mesh sieve without sieve residue, paraffin wax, fatty acid glyceride, and calcium lactate were added, and stirred at a temperature of 75°C to obtain a premix b;

[0072] S3, 15g of silane coupling agent KH570 and 150g of fly ash were mixed and ground at a grinding speed of 1500r / min, 500g of deionized water and acrylamide were added and stirred for 90min, ammonium persulfate was added, and the mixture was stirred at 75°C for 90min, cooled to room temperature, and Bacillus cereus agent was added and ultrasonically dispersed for 2.5h at an ultrasonic frequency of 7.5kHz, centrifuged, freeze-dried, crushed through a 65-mesh sieve, and fed into a drum, premix b was sprayed on the surface, and freeze-dried to obtain premix c;

[0073] S4. Mix limestone powder, urea, light-burned magnesium oxide expansion agent, quartz powder, redispersible latex powder, and polyether-modified silicone defoamer evenly, and add premix a and premix c thereto and mix evenly.

[0074] Comparative Example 1

[0075] A green ultrafine high-performance composite admixture, whose raw materials include: fly ash 350g, microsilica 200g, silane coupling agent KH570 20g, mesoporous silica 80g, waste building materials 80g, nano calcium carbonate 30g, nano bentonite 15g, polyethylene wax 20g, paraffin 150g, fatty acid glyceride 15g, calcium lactate 20g, and viable bacteria content of 3×10 9 15g of Bacillus cereus agent with a cfu / g content, 220g of limestone powder, 80g of urea, 35g of light-burned magnesium oxide expansion agent, 90g of quartz powder, 10g of redispersible latex powder, and 3g of polyether-modified silicone defoaming agent.

[0076] The preparation method of the green ultrafine high-performance composite admixture comprises the following steps:

[0077] S1. Mix 200g of fly ash and microsilica powder to form premix a. The specific surface area of ​​premix a is 943m 2 / kg;

[0078] S2, 5g of silane coupling agent KH570, mesoporous silica, and waste building materials were mixed and ground for 15min at a grinding speed of 1500r / min, nano calcium carbonate, nano bentonite, and polyethylene wax were added thereto and continued to grind for 10min, and after passing through an 800-mesh sieve without sieve residue, paraffin wax, fatty acid glyceride, and calcium lactate were added, and stirred at a temperature of 75°C to obtain a premix b;

[0079] S3, 15g of silane coupling agent KH570 and 150g of fly ash were mixed and ground at a grinding speed of 1500r / min, 500g of deionized water and Bacillus cereus agent were added, and ultrasonic dispersion was carried out for 2.5h at an ultrasonic frequency of 7.5kHz. The mixture was centrifuged, freeze-dried, crushed through a 65-mesh sieve, and fed into a drum. Premix b was sprayed on the surface and freeze-dried to obtain premix c;

[0080] S4. Mix limestone powder, urea, light-burned magnesium oxide expansion agent, quartz powder, redispersible latex powder, and polyether-modified silicone defoamer evenly, and add premix a and premix c thereto and mix evenly.

[0081] Comparative Example 2

[0082] A green ultrafine high-performance composite admixture, whose raw materials include: 350g fly ash, 200g microsilica, 20g silane coupling agent KH570, 80g mesoporous silica, 80g waste building materials, 30g nano calcium carbonate, 15g nano bentonite, 20g polyethylene wax, 150g paraffin, 15g fatty acid glyceride, 20g calcium lactate, 25g acrylamide, 0.5g ammonium persulfate, and a live bacteria content of 3×10 9 15g of Bacillus cereus agent with a cfu / g content, 220g of limestone powder, 80g of urea, 35g of light-burned magnesium oxide expansion agent, 90g of quartz powder, 10g of redispersible latex powder, and 3g of polyether-modified silicone defoaming agent.

[0083] The preparation method of the green ultrafine high-performance composite admixture comprises the following steps:

[0084] S1. Mix 200g of fly ash and microsilica powder to obtain premix a. The specific surface area of ​​premix a is 943m 2 / kg;

[0085] S2, 5g of silane coupling agent KH570, mesoporous silica, and waste building materials were mixed and ground for 15min at a grinding speed of 1500r / min, and nano calcium carbonate, nano bentonite, and polyethylene wax were added thereto and continued to grind for 10min. After passing through an 800-mesh sieve without sieve residue, paraffin wax, fatty acid glyceride, and calcium lactate were added, stirred evenly at a temperature of 75°C, cooled to room temperature, crushed, and then 15g of silane coupling agent KH570, 150g of fly ash, acrylamide, ammonium persulfate, and Bacillus cereus agent were added and mixed evenly to obtain a premix c;

[0086] S3. Mix limestone powder, urea, light-burned magnesium oxide expansion agent, quartz powder, redispersible latex powder, and polyether-modified silicone defoamer evenly, add premix a and premix c thereto and mix evenly.

[0087] Comparative Example 3

[0088] A green ultrafine high-performance composite admixture, whose raw materials include: 350g fly ash, 200g microsilica powder, 80g waste building materials, 10g redispersible latex powder, and 3g polyether modified silicone defoamer.

[0089] The preparation method of the green ultrafine high-performance composite admixture comprises the following steps: uniformly mixing fly ash, microsilica powder, waste building materials, redispersible latex powder and polyether modified silicone defoamer.

[0090] The green ultrafine high-performance composite admixtures obtained in Example 5 and Comparative Examples 1-3 were added to cast-in-place concrete, and their performance after curing was compared, as shown below:

[0091] The raw materials for each group are: PO 52.5 Portland cement 780kg / m 3 , green ultra-fine high-performance composite admixture 120kg / m 3 , 5-31.5mm crushed stone 125kg / m 3 , fine aggregate (machine-made sand) 950kg / m 3 , water 200kg / m 3 , polycarboxylate water reducer 25kg / m 3 .

[0092] Each group mixed the corresponding raw materials according to the ratio for 120 seconds and poured them out immediately. Referring to GB / T17671-2021 "Test method for strength of cement mortar (ISO method)", each group of mortar was poured into 40mm×40mm×160mm specification specimens and cured for the corresponding standard time.

[0093] After curing is completed, a flexural strength test is first carried out, and a compressive test is carried out on the broken prism. The compressive surfaces are the two side surfaces of the specimen when it is formed, with an area of ​​40mm×40mm.

[0094] Flexural strength is tested on a compression-flexure testing machine. The side of the specimen is placed on the fixture, and the loading rate of the testing machine is 50±10N / s. The side of the broken specimen is then placed on the fixture, and the loading rate is set to 2400±200N / s, with constant loading until the specimen fails.

[0095] like Figure 1 As shown in the figure, after 28 days of curing, the flexural strength of the Example 5 group was the highest, which was better than that of the other groups (P < 0.05).

[0096] like Figure 2 As shown in the figure, the compressive strength of Example 5 group after curing for different time periods was always higher than that of the other groups (P < 0.05), but it was difficult to evaluate the early strength of each group. The applicant compared the 3d compressive strength and 7d compressive strength with the 28d compressive strength, and calculated the percentage of the early compressive strength of each group to the final compressive strength.

[0097] like Figure 3As shown, the early compressive strength ratio of the Example 5 group is always higher than that of the other groups (P < 0.05), which proves that the green ultrafine high-performance composite admixture obtained in Example 5 can effectively improve the early strength of concrete.

[0098] With reference to GB50164-2011 "Concrete Quality Control Standard", each group of samples was tested for impermeability after 28 days of standard curing. The impermeability grade of the samples in Example 5 reached P27, the impermeability grade of the samples in Comparative Example 1 was P18, the impermeability grade of the samples in Comparative Example 2 was P22, and the impermeability grade of the samples in Comparative Example 3 was P14.

[0099] After standard curing for 28 days, each group of specimens was immersed in 20±2℃ water for 4 days, with the water surface 25.0±5.0mm higher than the top surface of the specimens. After the immersion, the specimens were taken out and the moisture on the surface of the specimens was wiped off, and the external dimensions were measured and weighed. Each specimen was placed in a specimen box and then in a freeze-thaw chamber, with a 20mm gap between the specimens and the wall of the specimen box. In the quick freezing test, clean water should be injected into the specimen box, with the water surface 50mm higher than the specimens. When the temperature in the freeze-thaw chamber dropped to -18℃, the timing began. The freezing time in each freeze-thaw cycle was 4h. After the freezing was completed, water at a temperature of 19.0±1.0℃ was immediately added within 10min, with the water surface at least 20mm higher than the specimens. The thawing time was 4h. After the thawing was completed, the freeze-thaw cycle was considered to be over and the next freeze-thaw cycle could be carried out.

[0100] The freeze-thaw test was stopped after 200 freeze-thaw cycles, the compressive strength of the specimens was tested, and the strength loss rate was calculated.

[0101] Strength loss rate = 1-compressive strength of sample after 100 freeze-thaw cycles ÷ original compressive strength of sample × 100%

[0102] like Figure 4 As shown, the sample of Example 5 had the lowest strength loss rate after freeze-thaw and the best anti-freeze-thaw effect, which were better than those of Comparative Examples 1-3 (P < 0.05).

[0103] After 28 days of standard curing, the samples from Example 5, Comparative Example 1, and Comparative Example 2 were split using a three-point bending press, with crack widths controlled to approximately 300-400 μm. The sample surfaces, except for a 1 cm wide area on either side of the crack, were sealed with epoxy resin. The samples were then placed in an environment with a temperature of 25°C and a humidity of 75% for 8 weeks. The crack widths were measured on the 14th, 28th, and 56th day, and the self-healing rate was calculated.

[0104] Self-repair rate = (initial crack width - crack width after standing for a certain period of time) ÷ initial crack width × 100%

[0105] like Figure 5As shown, the self-repair rate of the samples in Example 5 is the highest, which is better than that of the samples in Comparative Examples 1-2.

[0106] The applicant believes that the reason for the above results is that: the present invention adopts silane coupling agent to compound and activate mesoporous silica and waste building materials, and has good compatibility and lubricity with nano calcium carbonate and nano bentonite in combination with polyethylene wax, and can be evenly dispersed in paraffin; the fly ash is then activated by silane coupling agent and then grafted with polyacrylamide, which significantly enhances the adsorption and loading strength of fly ash on alkaliphilic Bacillus, further coats the premix b, and the product is dispersed among the admixtures, which can not only effectively reduce the surface energy between particles and effectively reduce the agglomeration of particles, but also absorbs water and expands after breaking the wall, can closely fit the cracks to achieve filling and plugging, reacts with water, calcium hydroxide and other substances at the crack interface to repair the cracks, and at the same time, the alkaliphilic Bacillus further overflows after breaking the wall, further repairs the cracks, comprehensively improves the strength and durability of concrete, and has excellent repair effect. The present invention adopts mesoporous silica and waste building materials for compound grinding, which not only forms a large number of fine pores and a large specific surface area, but also the high silica content can effectively promote the formation of hydration products and effectively improve the void structure of concrete materials; and the combination of fly ash and microsilica has good porosity, and when combined with prefabricated material C, it has excellent dispersion uniformity in the admixture, which not only effectively promotes the dispersion of structural stress, thereby producing an effective strengthening effect, but also can inhibit the generation and development of fine cracks, and has a significant structural stress compensation and anti-cracking effect.

[0107] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A green ultra-fine high-performance composite admixture, characterized in that: The raw materials include, by mass, 20-50 parts of fly ash, 15-25 parts of microsilica powder, 1.1-3 parts of silane coupling agent, 5-10 parts of mesoporous silica, 5-10 parts of waste building materials, 1-5 parts of nano calcium carbonate, 1-2 parts of nano bentonite, 1-3 parts of polyethylene wax, 10-20 parts of paraffin wax, 1-2 parts of fatty acid glyceride, 1-3 parts of calcium lactate, 1-4 parts of acrylamide, 0.01-0.1 parts of ammonium persulfate, 1-2 parts of alkaliphilic bacillus agent, 15-30 parts of limestone powder, 5-10 parts of urea, 1-6 parts of light-burned magnesium oxide expansion agent, 3-15 parts of quartz powder, 0.1-2 parts of redispersible latex powder, and 0.1-0.5 parts of defoaming agent. The preparation method of the green ultrafine high-performance composite admixture comprises: S1. Mix fly ash and microsilica powder evenly to obtain a premix a ; S2. Mix and grind the silane coupling agent, mesoporous silica, and waste building materials for 10-20 minutes, add nano calcium carbonate, nano bentonite, and polyethylene wax, and continue grinding for 5-15 minutes. Add paraffin wax, fatty acid glyceride, and calcium lactate, and stir evenly at 70-80°C to obtain a premix. b ; S3. Grind the silane coupling agent and fly ash, add deionized water and acrylamide, and stir for 1-2 hours. Add ammonium persulfate, stir at 70-80℃ for 1-2 hours, cool to room temperature, add alkaliphilic Bacillus agent, and ultrasonically disperse for 1-4 hours. Centrifuge, freeze-dry, crush and sieve, and put into a drum. Spray the premix on the surface. b , freeze-dried to obtain premix c ; S4, mix limestone powder, urea, light-burned magnesium oxide expansion agent, quartz powder, redispersible latex powder, and defoaming agent evenly, and add premix a , premix c Mix well.

2. The green ultrafine high-performance composite admixture according to claim 1, characterized in that: Density of microsilica fume ≥550kg / m 3 , of which SiO2 and Al2O3 account for ≥95% by mass.

3. The green ultrafine high-performance composite admixture according to claim 1, characterized in that: The particle size of mesoporous silica is 100-500nm.

4. The green ultrafine high-performance composite admixture according to claim 1, characterized in that: The silane coupling agent is at least one of silane coupling agent KH570, silane coupling agent KH590, and silane coupling agent Si69.

5. The green ultrafine high-performance composite admixture according to claim 1, characterized in that: The content of live alkaliphilic Bacillus in the alkaliphilic Bacillus agent is 1×10 9 CFU / g-5×10 9 CFU / g.

6. The green ultrafine high-performance composite admixture according to claim 5, characterized in that: The alkaliphilic Bacillus is at least one of Bacillus sphaericus, Bacillus pasteurianus, Bacillus cohnii, Bacillus cereus, and Bacillus licheniformis.

7. A method for preparing the green ultrafine high-performance composite admixture according to any one of claims 1 to 6, characterized in that: The steps include: S1. Mix fly ash and microsilica powder evenly to obtain a premix a ; S2. Mix and grind the silane coupling agent, mesoporous silica, and waste building materials for 10-20 minutes, add nano calcium carbonate, nano bentonite, and polyethylene wax, and continue grinding for 5-15 minutes. Add paraffin wax, fatty acid glyceride, and calcium lactate, and stir evenly at 70-80°C to obtain a premix. b ; S3. Grind the silane coupling agent and fly ash, add deionized water and acrylamide, and stir for 1-2 hours. Add ammonium persulfate, stir at 70-80℃ for 1-2 hours, cool to room temperature, add alkaliphilic Bacillus agent, and ultrasonically disperse for 1-4 hours. Centrifuge, freeze-dry, crush and sieve, and put into a drum. Spray the premix on the surface. b , freeze-dried to obtain premix c ; S4, mix limestone powder, urea, light-burned magnesium oxide expansion agent, quartz powder, redispersible latex powder, and defoaming agent evenly, and add premix a , premix c Mix well.

8. The method for preparing the green ultrafine high-performance composite admixture according to claim 7, characterized in that: The mass ratio of the silane coupling agent used in S2 to the silane coupling agent used in S3 is 0.1-1:1-2.

9. The method for preparing the green ultrafine high-performance composite admixture according to claim 7, characterized in that: In S3, the ultrasound frequency is 5-12 kHz.

10. Use of the green ultrafine high-performance composite admixture according to any one of claims 1 to 6 in preparing concrete.

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