Anti-crack waterproof concrete admixture and preparation method thereof

Abstract

The application relates to the technical field of concrete processing, in particular to an anti-cracking waterproof concrete admixture and a preparation method thereof. The concrete admixture comprises the following components in parts by weight: 40-60 parts of a composite solid water reducing agent, 30-50 parts of a retarder, 5-10 parts of an anti-freezing agent, 2-7 parts of an air entraining agent and 5-10 parts of a stabilizer. In the application, the modified water reducing agent is loaded in the composite diatomite through vacuum impregnation to obtain the composite solid water reducing agent, so that the defects of the existing water reducing agent, such as difficulty in storage and high packaging and transportation cost, can be effectively solved, and the performance of the concrete can be better improved, and the concrete has good durability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete processing, in particular to an anti-cracking waterproof concrete admixture and a preparation method thereof. BACKGROUND

[0002] The concrete admixture has an important influence on the performance of concrete. In the production process of concrete, the concrete admixture is mixed with other raw materials and water. Although the hydration reaction of cement can improve the strength of concrete, the large amount of hydration heat generated by the hydration reaction will inevitably cause the cracking of concrete. Especially when the concrete is applied to coastal construction projects, the chloride ions in high-salt seawater will cause erosion to the concrete, and the cracking of the concrete will directly affect the effect of the concrete on resisting chloride ion erosion.

[0003] The concrete admixture lays the foundation for modern concrete technology and becomes an indispensable important component of concrete. The admixture includes water reducing agent, retarder, antifreeze agent, air entraining agent and rust inhibitor, etc. At present, the wide application of various admixtures with different functions effectively improves the workability, mechanical properties and durability of concrete. For example, the patent for invention with the announcement number CN114920492A discloses a composite concrete admixture and a preparation method thereof, which is composed of the following components in weight parts: 50-70 parts of melamine high-efficiency water reducing agent, 40-60 parts of retarder, 20-40 parts of stabilizer, and 30-50 parts of heat insulator. By using aminosulfonic acid as a sulfonating agent instead of traditional sodium bisulfite or sodium pyrosulfite, the solid content of the high-efficiency water reducing agent can be increased, the concentration can be increased, and the stability during storage can be higher, so that the storage period can be longer, about 1 year and 6 months, and the service life of the water reducing agent is improved. In the patent, although the water reducing agent is modified, the melamine high-efficiency water reducing agent is a liquid water reducing agent, which has the disadvantages of high packaging and transportation cost and is not conducive to storage, thereby affecting the use performance of the concrete admixture. SUMMARY

[0004] In view of the problems in the prior art, the present application aims to provide an anti-cracking waterproof concrete admixture and a preparation method thereof.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions.

[0006] An anti-cracking waterproof concrete admixture, which comprises the following components in weight parts: 40-60 parts of composite solid water reducing agent, 30-50 parts of retarder, 5-10 parts of antifreeze agent, 2-7 parts of air entraining agent, and 5-10 parts of stabilizer.

[0007] As a further preferred scheme of the present application, the retarder is composed of calcium formate, calcium sucrose and limestone according to a mass ratio of (3-5):2:(2-4);

[0008] The antifreezing agent is composed of sodium nitrite, calcium chloride, calcium nitrite, urea and ethylene glycol according to a mass ratio of 1:(2-5):(1-3):(1-3):(15-30);

[0009] The air entraining agent is at least one of a rosin air entraining agent, an alkyl benzene sulfonate air entraining agent and a fatty alcohol sulfonate air entraining agent.

[0010] The stabilizer is at least one of cocamide propyl betaine, dodecyl hydroxypropyl phosphate betaine and tetradecyl hydroxypropyl phosphate betaine.

[0011] As a further preferred scheme of the present application, the preparation method of the composite solid water reducing agent is as follows:

[0012] 1) Sodium silicate is added into deionized water, and after being fully stirred and dissolved, it is put into a water bath pot, and is heated to 50-60℃ while being stirred, hydrochloric acid is added to adjust the pH value to 5.0-5.5, and the stirring and heat preservation is continued for 3-5h, and after being filtered, it is repeatedly washed with deionized water, dried and ground to obtain a silica sol;

[0013] 2) After the diatomite is dried and ground, it is passed through a 200-300 mesh sieve, and then is poured into a container, and then the silica sol is added into the container, and then a sufficient amount of deionized water is added, and the water bath is heated to 80-85℃, and the constant temperature stirring is continued for 4-7h, and after being filtered and dried, it is moved into a muffle furnace, and is calcined at 500-560℃ for 3-7h, and is naturally cooled to room temperature to obtain modified diatomite;

[0014] 3) Molybdenum trioxide, thioacetamide and urea are dissolved in a mixed solution composed of deionized water and anhydrous ethanol, and after being fully stirred, a dispersion liquid is obtained, and then the modified diatomite is added, and after being mixed, it is moved into a reaction kettle, and after being sealed, it is heat preserved at 200-230℃ for 18-23h, and after the reaction is completed, it is cooled to room temperature, and after being repeatedly washed with deionized water and anhydrous ethanol, it is dried to obtain a composite diatomite;

[0015] 4) The composite diatomite is placed in a tube furnace, and under an argon atmosphere, it is heated to 600-650℃ at a rate of 3-8℃ / min, and is heat preserved for 2-5h, and is naturally cooled to room temperature to obtain pretreated composite diatomite, and then the pretreated composite diatomite is added into a vacuum impregnation tank, and is vacuumized to 20-80Pa, and is maintained for 20-40min, and then the modified water reducing agent is injected, and is continuously maintained for 1-2h, and then it is slowly depressurized to normal pressure, and after the product is drained of water, it is dried to obtain the required composite solid water reducing agent.

[0016] As a further preferred scheme of the present application, the adding amount of the silica sol is 35-50% of the mass of the diatomite.

[0017] As a further preferred scheme of the present application, the adding amount of the silica sol is 35-50% of the mass of the diatomite.

[0018] As a further preferred scheme of the present application, the adding amount of the silica sol is 35-50% of the mass of the diatomite.

[0019] As a further preferred scheme of the present application, the adding amount of the silica sol is 35-50% of the mass of the diatomite.

[0020] As a further preferred scheme of the present application, the adding amount of the silica sol is 35-50% of the mass of the diatomite.

[0021] 1) The isobutylene alcohol polyoxyethylene ether and the saturated solution of β-cyclodextrin are fully stirred at 65-68℃ for 60-100min to obtain an inclusion compound, and the inclusion compound, isobutylene alcohol polyoxyethylene ether and hydrogen peroxide are dissolved in distilled water, and after fully stirring at room temperature, an aqueous solution containing acrylic acid, vitamin C and mercaptoethanol is added dropwise, and after the dropwise addition is completed, the stirring is continued for 40-70min to obtain a standby product;

[0022] 2) The standby product and acrylic acid are added to distilled water, and after fully stirring and mixing, heating is performed to 30-36℃, then ammonium persulfate is added to obtain solution A, and then 2-acrylamide-2-methylpropenesulfonic acid and acrylic acid are added dropwise to solution A, and after the dropwise addition is completed, the stirring is continued for 3-5h, and the pH is adjusted to neutral with sodium hydroxide solution to obtain the modified water reducing agent.

[0023] As a further preferred scheme of the present application, the isobutylene alcohol polyoxyethylene ether and the saturated solution of β-cyclodextrin are mixed and stirred according to a molar ratio of (2.0-2.6):1.

[0024] The adding amount of the silica sol is 35-50% of the mass of the diatomite.

[0025] The mass ratio of acrylic acid, vitamin C and mercaptoethanol in the aqueous solution is (3-6):1:(8-13).

[0026] As a further preferred scheme of the present application, in the solution A, the proportions of the use amount of the standby product, the acrylic acid, the distilled water and the ammonium persulfate are (30-36) g : (1.2-2.0) g : (50-60) mL : (1-2) g;

[0027] The 2-acrylamide-2-methyl acrylate and the acrylic acid respectively account for 0.3-0.5% and 2.0-2.8% of the total mass of the solution A;

[0028] The concentration of the sodium hydroxide solution is 5-10 wt%.

[0029] A preparation method of a crack-resistant waterproof concrete admixture comprises the following steps:

[0030] According to weight parts, the composite solid water reducing agent, the retarder, the anti-freezing agent, the air entraining agent and the stabilizer are mixed, so that the required concrete admixture is obtained.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] In the present application, the beta-cyclodextrin and isobutylene alcohol polyoxyethylene ether form inclusion compounds, and the beta-cyclodextrin is introduced into the side chain of the polycarboxylic acid water reducing agent to synthesize the beta-cyclodextrin modified polycarboxylic acid water reducing agent, the molecular movement of the HPEG side chain is limited by the beta-cyclodextrin, so that the intercalation adsorption of the HPEG side chain with cement particles is not easy, and thus the cement particles can be more effectively dispersed, so as to help improve the anti-mud performance and the slump retention performance of the concrete; meanwhile, the 2-acrylamide-2-methyl propylene sulfonic acid is introduced to synthesize a sulfonate functional group, the sulfonate functional group is a polar functional group, a large number of negatively charged sulfonate functional groups are grafted onto the main chain, the charge density of the water reducing agent is increased, the adsorption capacity of the water reducing agent is significantly improved, so that the interaction between the water reducing agent and the cement or clay particles can be increased, a strong steric hindrance effect can be maintained in the cement slurry, and thus the slump retention performance is further improved.

[0033] Meanwhile, in order to improve the storage performance of the water reducing agent, in the application, the silicon sol and the diatomite both contain hydroxyl groups, and the two are combined to easily form hydrogen bonds or to generate chemical forces through dehydration reaction, so that the silicon sol is easily attached to the diatomite to coat the diatomite, thereby closing the micropores of the diatomite, and through calcination, the organic matter and other impurities in the diatomite can be decomposed to have the effect of expanding the volume, so that the modified diatomite with high porosity and high adsorption is obtained, then the modified diatomite is used as a base material, and through a simple hydrothermal method, a nanosheet array is synthesized and deposited on the modified diatomite to obtain a composite diatomite, through vacuum impregnation, the water reducing agent is loaded in the interstices of the composite diatomite, and the deposited nanosheet array is stacked to form a sheet structure through mutual intercalation, so that the water reducing agent can be well fixed, and the flow of the water reducing agent is inhibited, so that the composite solid water reducing agent is obtained, the composite solid water reducing agent is easy to store, and the packaging and transportation costs are also low, and when the composite solid water reducing agent is applied to concrete, the comprehensive performance of the concrete can be better improved.

[0034] In the application, through vacuum impregnation, the configured modified water reducing agent is loaded in the composite diatomite to obtain a composite solid water reducing agent, so that the defects that the existing water reducing agent is not easy to store and has high packaging and transportation costs can be effectively solved, so that the performance of the concrete can be better improved, and the durability of the concrete is good. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the application will be clearly and completely described below, obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0036] In the embodiments of the application, the retarder is composed of calcium formate, calcium sucrose and limestone according to a mass ratio of 5:2:3;

[0037] The antifreeze agent is composed of sodium nitrite, calcium chloride, calcium nitrite, urea and ethylene glycol according to a mass ratio of 1:2:3:2:25;

[0038] The air entraining agent is sodium abietate;

[0039] The stabilizer is cocamide propyl betaine.

[0040] Embodiment 1

[0041] The concrete admixture includes the following components in parts by weight: 40 parts of the composite solid water reducing agent, 30 parts of the retarder, 5 parts of the antifreeze agent, 2 parts of the air entraining agent and 5 parts of the stabilizer.

[0042] The preparation method of the concrete admixture is as follows:

[0043] According to the weight parts, the composite solid water reducing agent, the retarder, the anti-freezing agent, the air entraining agent and the stabilizer are mixed to obtain the required concrete admixture.

[0044] The preparation method of the composite solid water reducing agent is as follows:

[0045] 1) 5g of sodium silicate is added to 80mL of deionized water, and after being fully stirred and dissolved, it is placed in a water bath and heated to 50℃ while stirring, and hydrochloric acid is added to adjust the pH to 5.0, and then stirring and incubation is continued for 3h, after which it is filtered and washed repeatedly with deionized water, dried and ground to obtain a silica sol;

[0046] 2) The dried diatomite is ground and passed through a 200-mesh sieve, then poured into a container, and the silica sol is added to the container, with the amount of silica sol being controlled at 35% of the mass of the diatomite, then a sufficient amount of deionized water is added, and the water bath is heated to 80℃, and constant temperature stirring is continued for 4h, after which it is filtered and dried, then moved to a muffle furnace and calcined at 500℃ for 3h, and then naturally cooled to room temperature to obtain modified diatomite;

[0047] 3) 0.5g of molybdenum trioxide, 1g of thioacetamide and 10g of urea are dissolved in a mixed solution composed of 300mL of deionized water and 300mL of anhydrous ethanol, and after being fully stirred, a dispersion is obtained, then 5g of modified diatomite is added, mixed and then transferred to a reaction kettle, sealed and incubated at 200℃ for 18h, after which it is cooled to room temperature, washed repeatedly with deionized water and anhydrous ethanol and then dried to obtain a composite diatomite;

[0048] 4) The isobutenyl polyoxyethylene ether and the β-cyclodextrin saturated solution are fully stirred at 65℃ for 60min to obtain an inclusion compound, then 0.2g of the inclusion compound, 5g of isobutenyl polyoxyethylene ether and 2g of hydrogen peroxide solution are dissolved in 80mL of distilled water, and after being fully stirred at room temperature, 30mL of an aqueous solution containing acrylic acid, vitamin C and mercaptoethanol is added dropwise, with the mass ratio of acrylic acid, vitamin C and mercaptoethanol in the aqueous solution being 3:1:8, and after the dropwise addition is completed, stirring is continued for 40min to obtain a standby product;

[0049] 5) 30g of the standby product and 1.2g of acrylic acid are added to 50mL of distilled water, mixed and then heated to 30℃, then 1g of ammonium persulfate is added to obtain solution A, and then 2-acrylamide-2-methylpropenesulfonic acid and acrylic acid are added dropwise to solution A, with the amount of 2-acrylamide-2-methylpropenesulfonic acid and acrylic acid being 0.3% and 2% of the total mass of solution A respectively, and after the dropwise addition is completed, incubation and stirring are continued for 3h, and then a 5wt% sodium hydroxide solution is used to adjust the pH to neutral to obtain a modified water reducing agent.

[0050] 6) Put the composite diatomite into a tube furnace, and heat to 600℃ at a rate of 3℃ / min under argon atmosphere, and keep for 2h, and cool to room temperature naturally, to obtain pretreated composite diatomite, then put 10g pretreated composite diatomite into a vacuum impregnation tank, and vacuumize to 20Pa, keep for 20min, then inject 100mL modified water reducing agent, keep for 1h, then slowly release to normal pressure, and dry the product after draining water, to obtain the required composite solid water reducing agent.

[0051] Example 2

[0052] A kind of anti-crack waterproof concrete admixture, the concrete admixture includes the following weight parts components: composite solid water reducing agent 50 parts, retarder 40 parts, anti-freezing agent 7 parts, air entraining agent 5 parts, stabilizer 7 parts;

[0053] The preparation method of the concrete admixture is as follows:

[0054] According to weight fraction, composite solid water reducing agent, retarder, anti-freezing agent, air entraining agent and stabilizer are mixed, to obtain the required concrete admixture.

[0055] The preparation method of the composite solid water reducing agent is as follows:

[0056] 1) Put 8g sodium silicate into 100mL deionized water, dissolve after stirring sufficiently, put into a water bath, and heat to 55℃ while stirring, adjust pH to 5.2 by adding hydrochloric acid, keep for 4h while stirring, and then filter and wash repeatedly with deionized water, dry and grind, to obtain silica sol;

[0057] 2) Dry and grind diatomite, pass through a 300 mesh sieve, then pour into a container, add silica sol to the container, control the amount of silica sol to be 40% of the mass of diatomite, then add enough deionized water, heat to 82℃ in a water bath, and keep stirring for 5h, then filter and dry, and then move to a muffle furnace, and calcine at 540℃ for 5h, and then cool to room temperature naturally, to obtain modified diatomite;

[0058] 3) Dissolve 1g molybdenum trioxide, 2g thioacetamide and 15g urea in a mixed solution composed of 400mL deionized water and 400mL anhydrous ethanol, stir sufficiently to obtain a dispersion, then add 7g modified diatomite, mix uniformly, then transfer to a reaction kettle, seal, and keep at 210℃ for 20h, then cool to room temperature after the reaction is completed, wash repeatedly with deionized water and anhydrous ethanol, and then dry, to obtain composite diatomite;

[0059] 4) according to the molar ratio of 2.3:1, isobutylene alcohol polyoxyethylene ether and β-cyclodextrin saturated solution is fully stirred at 67℃ for 80min, to obtain the inclusion compound, 0.3g inclusion compound, 7g isobutylene alcohol polyoxyethylene ether and 3g hydrogen peroxide solution are dissolved in 90mL distilled water, after fully stirring at room temperature, 35mL aqueous solution containing acrylic acid, vitamin C and mercaptoethanol is added dropwise, the mass ratio of acrylic acid, vitamin C and mercaptoethanol in the aqueous solution is 5:1:10, after the dropwise addition is completed, continue to stir for 50min, to obtain the standby product;

[0060] 5) 35g standby product, 1.8g acrylic acid are added to 55mL distilled water, after fully stirring and mixing, heated to 32℃, then 1.5g ammonium persulfate is added to obtain solution A, 2-acrylamide-2-methyl methacrylate and acrylic acid are added dropwise to solution A, and the mass fraction of 2-acrylamide-2-methyl methacrylate and acrylic acid in solution A is 0.4% and 2.3% respectively, after the dropwise addition is completed, continue to heat and stir for 4h, and adjust the pH to neutral with 8wt% sodium hydroxide solution to obtain the modified water reducing agent.

[0061] 6) The composite diatomite is placed in a tube furnace, heated to 630℃ at 5℃ / min under argon atmosphere, and kept for 3h, and naturally cooled to room temperature to obtain the pretreated composite diatomite, then 15g pretreated composite diatomite is added to a vacuum impregnation tank, vacuumed to 50Pa, kept for 30min, then 130mL modified water reducing agent is injected, kept for 1.5h, then slowly released to normal pressure, the product is drained and dried to obtain the required composite solid water reducing agent.

[0062] Example 3

[0063] A kind of anti-crack waterproof concrete admixture, the concrete admixture includes the following weight components: composite solid water reducing agent 60 parts, retarder 50 parts, anti-freezing agent 10 parts, air entraining agent 7 parts, stabilizer 10 parts;

[0064] The preparation method of the concrete admixture is as follows:

[0065] According to weight fraction, the composite solid water reducing agent, retarder, anti-freezing agent, air entraining agent and stabilizer are mixed to obtain the required concrete admixture.

[0066] The preparation method of the composite solid water reducing agent is as follows:

[0067] 1) 10g sodium silicate is added to 120mL deionized water, fully stirred and dissolved, then placed in a water bath, stirred and heated to 60℃, hydrochloric acid is added to adjust the pH value to 5.5, continue to stir and keep for 5h, after filtration, repeatedly washed with deionized water, dried and ground to obtain silica sol;

[0068] 2) After drying the diatomite, grind it and pass it through a 300-mesh sieve, then pour it into a container, add silica sol to the container, control the amount of silica sol added to be 50% of the mass of the diatomite, then add enough deionized water, heat to 85°C in a water bath, constant temperature stirring for 7h, after filtration and drying, move to a muffle furnace, calcine at 560°C for 7h, naturally cool to room temperature, to obtain modified diatomite;

[0069] 3) Dissolve 1.5g of molybdenum trioxide, 3g of thioacetamide and 18g of urea in a mixed solution composed of 500mL of deionized water and 500mL of anhydrous ethanol, obtain a dispersion after sufficient stirring, then add 10g of modified diatomite, mix well and then transfer to a reaction kettle, seal and heat at 230°C for 23h after the reaction is completed, cool to room temperature, rinse the product repeatedly with deionized water and anhydrous ethanol and dry to obtain a composite diatomite;

[0070] 4) According to the molar ratio of 2.6:1, fully stir the inclusion complex of isobutenyl polyoxyethylene ether and β-cyclodextrin saturated solution at 68°C for 100min, dissolve 0.5g of the inclusion complex, 10g of isobutenyl polyoxyethylene ether and 5g of hydrogen peroxide in 100mL of distilled water, stir well at room temperature, then drop 40mL of an aqueous solution containing acrylic acid, vitamin C and mercaptoethanol, the mass ratio of acrylic acid, vitamin C and mercaptoethanol in the aqueous solution is 6:1:13, continue to stir for 70min after the dropwise addition is completed to obtain a standby product;

[0071] 5) Add 36g of the standby product and 2g of acrylic acid to 60mL of distilled water, mix well after stirring, then heat to 36°C, then add 2g of ammonium persulfate to obtain solution A, then drop 2-acrylamide-2-methyl methacrylate and acrylic acid into solution A, and control the mass fraction of 2-acrylamide-2-methyl methacrylate and acrylic acid in solution A to be 0.5% and 2.8% respectively, continue to heat and stir for 5h after the dropwise addition is completed, and adjust the pH to neutral with 10wt% sodium hydroxide solution to obtain a modified water reducing agent.

[0072] 6) Put the composite diatomite into a tube furnace, heat to 650°C at 8°C / min under argon atmosphere, and keep for 5h, then naturally cool to room temperature to obtain pretreated composite diatomite, then add 20g of pretreated composite diatomite to a vacuum impregnation tank, vacuum to 80Pa, keep for 40min, then inject 150mL of modified water reducing agent, continue to keep for 2h, then slowly release the pressure to normal pressure, drain the water from the product and air dry to obtain the desired composite solid water reducing agent.

[0073] Comparative Example 1: This comparative example is basically the same as Example 1, except that a polycarboxylic acid water reducing agent is used instead of a composite solid water reducing agent.

[0074] Comparative Example 2: This comparative example is substantially the same as Example 1, except that a modified water reducing agent is used instead of the composite solid water reducing agent.

[0075] Comparative Example 3: This comparative example is substantially the same as Example 1, except that in the preparation of the composite solid water reducing agent, steps 1) - 2) are omitted.

[0076] Comparative Example 4: This comparative example is substantially the same as Example 1, except that in the preparation of the composite solid water reducing agent, step 3) is omitted.

[0077] Comparative Example 5: This comparative example is substantially the same as Example 1, except that in the preparation of the composite solid water reducing agent, in step 6), the composite diatomite is not pretreated.

[0078] Test Experiment:

[0079] The concrete raw materials are composed of cement, aggregate, sand and fly ash, and the concrete slurry is obtained by mixing cement 300 kg, aggregate 620 kg, sand 480 kg, fly ash 70 kg, additive 14 kg and water 110 kg, wherein the additive is provided by Examples 1-3 and Comparative Examples 1-5, respectively.

[0080] After the concrete slurry is cured for 28 days, the concrete sample block is prepared, and the compressive strength thereof is tested. The concrete sample block is placed in a high-salt service environment for 6 months, and then the compressive strength thereof is tested again. By testing the compressive strength of the concrete sample block after 6 months and 28 days, respectively, the durability of the concrete is embodied. If the compressive strength of the concrete sample block after 6 months is significantly reduced compared with the compressive strength after 28 days, it indicates that the durability of the concrete is poor.

[0081] The compressive strength test is carried out according to the method specified in GB / T50081-2019 "Standard for Testing Methods of Physical and Mechanical Properties of Concrete", and the test results are shown in Table 1.

[0082] Table 1

[0083]

[0084] As shown in Table 1, the concrete additive in the present application can significantly improve the performance of the concrete when applied to the concrete, and the concrete has good durability.

[0085] The preferred embodiments of the application disclosed above are only to facilitate the elucidation of the application. The preferred embodiments do not describe all the details of the application and limit the application to the specific embodiments described. Obviously, many modifications and variations can be made in light of the teachings above. The description is chosen and described in order to best explain the principles of the application and its practical application to thereby enable others skilled in the art to best utilize the application and get the best results from the application. The application is only limited by the claims and their full scope and equivalents.

Claims

1. An anti-cracking waterproofing concrete admixture, characterized by, The concrete admixture comprises the following components in parts by weight: 40-60 parts of a composite solid water reducing agent, 30-50 parts of a retarder, 5-10 parts of an anti-freezing agent, 2-7 parts of an air entraining agent, and 5-10 parts of a stabilizer; The preparation method of the composite solid water reducing agent is as follows: 1) Sodium silicate is added to deionized water, and after being fully stirred and dissolved, it is placed in a water bath, and stirred and heated to 50-60℃, hydrochloric acid is added to adjust the pH value to 5.0-5.5, and the stirring and heating is continued for 3-5h, then after filtration, repeated washing with deionized water, drying and grinding, a silica sol is obtained; 2) After the diatomite is dried and ground, it is passed through a 200-300 mesh sieve, then poured into a container, silica sol is added to the container, and then a sufficient amount of deionized water is added, heated to 80-85℃ in a water bath, and stirred for 4-7h, then after filtration and drying, it is moved to a muffle furnace, calcined at 500-560℃ for 3-7h, and naturally cooled to room temperature to obtain modified diatomite; 3) Molybdenum trioxide, thioacetamide and urea are dissolved in a mixed solution composed of deionized water and anhydrous ethanol, fully stirred to obtain a dispersion, then the modified diatomite is added, mixed, transferred to a reaction kettle, sealed, and heated to 200-230℃ for 18-23h, then after the reaction is completed, the product is washed repeatedly with deionized water and anhydrous ethanol, and dried to obtain a composite diatomite; 4) The composite diatomite is placed in a tube furnace, heated to 600-650℃ at a rate of 3-8℃ / min under an argon atmosphere, and kept at this temperature for 2-5h, then naturally cooled to room temperature to obtain pretreated composite diatomite, which is then added to a vacuum impregnation tank, vacuumed to 20-80Pa, kept for 20-40min, then modified water reducing agent is injected, kept for 1-2h, then slowly released to normal pressure, the product is drained of water, and dried to obtain the required composite solid water reducing agent; The preparation method of the modified water reducing agent is as follows: 1) Isobutylene alcohol polyoxyethylene ether and a saturated solution of β-cyclodextrin are fully stirred at 65-68℃ for 60-100min to obtain an inclusion compound, the inclusion compound, isobutylene alcohol polyoxyethylene ether and hydrogen peroxide are dissolved in distilled water, fully stirred at room temperature, then an aqueous solution containing acrylic acid, vitamin C and mercaptoethanol is added dropwise, after the dropwise addition is completed, stirring is continued for 40-70min to obtain a standby product; 2) The standby product and acrylic acid are added to distilled water, fully stirred and mixed, then heated to 30-36℃, then ammonium persulfate is added to obtain solution A, then 2-acrylamide-2-methylpropenesulfonic acid and acrylic acid are added dropwise to solution A, after the dropwise addition is completed, the temperature is kept constant and stirring is continued for 3-5h, and the pH value is adjusted to neutral with sodium hydroxide solution to obtain a modified water reducing agent.

2. The anti-cracking waterproof concrete admixture according to claim 1, characterized in that, The retarder is composed of calcium formate, calcium sucrose and limestone in a mass ratio of (3-5):2:(2-4); The anti-freezing agent is composed of sodium nitrite, calcium chloride, calcium nitrite, urea and ethylene glycol in a mass ratio of 1:(2-5):(1-3):(1-3):(15-30); The air entraining agent is at least one of rosin air entraining agent, alkyl benzene sulfonate air entraining agent, fatty alcohol sulfonate air entraining agent. The stabilizer is at least one of cocamide propyl betaine, dodecyl hydroxypropyl phosphate betaine, and tetradecyl hydroxypropyl phosphate betaine.

3. The anti-cracking waterproof concrete admixture according to claim 1, characterized in that, The ratio of the amount of sodium silicate to the amount of deionized water is (5-10) g:(80-120) mL. The amount of the silica sol added accounts for 35-50% of the mass of diatomite.

4. The anti-cracking waterproof concrete admixture according to claim 1, characterized in that, The ratio of the amount of molybdenum trioxide, thioacetamide, urea, deionized water, anhydrous ethanol, and modified diatomite is (0.5-1.5) g:(1-3) g:(10-18) g:(300-500) mL:(300-500) mL:(5-10) g.

5. The anti-cracking waterproof concrete admixture according to claim 1, characterized in that, The ratio of the amount of pretreated composite diatomite to the amount of modified water reducing agent is (10-20) g:(100-150) mL.

6. The anti-cracking waterproof concrete admixture according to claim 1, characterized in that, The isobutenol polyoxyethylene ether and the β-cyclodextrin saturated solution are mixed and stirred according to a molar ratio of (2.0-2.6):

1. The ratio of the amount of the inclusion compound, isobutenol polyoxyethylene ether, hydrogen peroxide, distilled water, and aqueous solution is (0.2-0.5) g:(5-10) g:(2-5) g:(80-100) mL:(30-40) mL. In the aqueous solution, the mass ratio of acrylic acid, vitamin C, and mercaptoethanol is (3-6):1:(8-13).

7. The anti-cracking waterproof concrete admixture according to claim 1, characterized in that, In the solution A, the ratio of the amount of standby product, acrylic acid, distilled water, and ammonium persulfate is (30-36) g:(1.2-2.0) g:(50-60) mL:(1-2) g. The 2-acrylamide-2-methyl acrylate sulfonic acid and the acrylic acid respectively account for 0.3-0.5% and 2.0-2.8% of the total mass of the solution A. The concentration of the sodium hydroxide solution is 5-10 wt%.

8. The method for preparing the anti-cracking waterproof concrete admixture according to any one of claims 1-7, characterized in that, The method comprises the following steps: According to weight parts, the composite solid water reducing agent, the retarder, the antifreeze agent, the air entraining agent, and the stabilizer are mixed to obtain the required concrete admixture.

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