Construction process of waterproof mortar for backfilling

Abstract

The invention discloses waterproof mortar for backfilling and a construction process thereof, and relates to the field of building materials. The waterproof mortar comprises the following components in parts by weight: 100-120 parts of Portland cement, 5-8 parts of polypropylene fiber, 10-12 parts of dispersible latex powder, 1-2 parts of a water reducing agent, 25-30 parts of modified fly ash, 1-2 parts of a defoaming agent, 30-35 parts of water and 100-150 parts of natural river sand. The method has the beneficial effects that by synthesizing the water reducing agent with a specific structure, the fluidity and workability of mortar are effectively improved, so that the fly ash can be used as a substitute of part of cement, the cost is reduced, the durability and impermeability of concrete are effectively improved, and the concrete has a good application prospect. And the method can be better applied to reinforcement treatment of backfill soil on the side wall.

Description

Technical Field

[0002] The invention relates to the field of building materials, in particular to a construction process of waterproof mortar for backfilling. Background Art

[0004] With the acceleration of urbanization, the development demand for high-rise buildings and underground space is growing. As an important part of construction, the reinforcement technology of the side wall backfill of foundation pit engineering is particularly important. Traditional backfill methods (such as plain soil backfill, gray soil backfill, etc.) have many limitations, such as low construction efficiency, high requirements for soil quality, easy damage to the waterproof layer, poor durability, etc., which limit the quality and safety of foundation pit engineering. In contrast, the compaction grouting reinforcement method has obvious advantages: low requirements for the original soil quality, fast construction, no need for layered compaction, and can significantly shorten the construction period; grouting can make up for waterproof defects, and the strength is adjustable to meet different needs; the cost is relatively low and it is suitable for a variety of soil conditions. These advantages make compaction grouting more effective and economical in the reinforcement of the side wall backfill of foundation pit.

[0005] At the same time, the waterproof mortar used for backfill has limited anti-cracking performance and is prone to cracks that lead to leakage. During the improvement process, additives are often added, but compatibility problems arise, affecting the workability of the concrete.

[0006] Therefore, in order to solve the above problems, a construction process of waterproof mortar for backfilling is obtained. Summary of the invention

[0008] The purpose of the present invention is to provide a construction process of waterproof mortar for backfilling to solve the problems raised in the prior art.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A waterproof mortar for backfilling comprises the following components: by weight, 100-120 parts of silicate cement, 5-8 parts of polypropylene fiber, 10-12 parts of dispersible latex powder, 1-2 parts of water reducing agent, 25-30 parts of modified fly ash, 1-2 parts of defoaming agent, 30-35 parts of water and 100-150 parts of natural river sand.

[0011] More optimally: the preparation process of the water reducing agent is:

[0012] S1: Add 2-hydroxy-6-naphthylacetic acid to diethyl ether, stir ultrasonically for 20-30 min, add thionyl chloride, heat to 70-80°C, reflux for 4-6 h, cool in cold water overnight, filter, wash, dry, and recrystallize from diethyl ether to obtain intermediate A;

[0013] S2: Add intermediate product A and methoxypolyethylene glycol amine to ether, stir ultrasonically for 40-50 min, heat to 70-75°C, reflux for 5-6 h, cool to room temperature, filter, dry, pour the obtained solid into dilute hydrochloric acid, stir, filter, wash the solid with water, and then recrystallize with ethanol to obtain intermediate product B;

[0014] S3: Mix the intermediate product B, maleic acid glycoside and carbon disulfide, add anhydrous aluminum chloride under ultrasonic stirring, heat to 90-100°C, reflux for 1-2h, cool to room temperature, slowly add ice water and concentrated hydrochloric acid, stir for 30-40min, let stand for stratification, remove the aqueous phase, and dry in vacuo to obtain the intermediate product C;

[0015] S4: Add the intermediate product C, 2-acrylamide-2-methylpropanesulfonic acid and maleic anhydride into water, stir ultrasonically for 20-30 min, raise the temperature to 60-70°C, add aqueous ammonium persulfate solution dropwise for 2-3 h, keep the temperature constant for 6-8 h, and obtain a water reducing agent.

[0016] More optimally: the intermediate product A comprises the following components: by weight, 20-25 parts of 2-hydroxy-6-naphthylacetic acid, 100-150 parts of ether, and 10-12 parts of thionyl chloride;

[0017] The intermediate product B comprises the following components: by weight, 15-20 parts of the intermediate product A, 8-10 parts of methoxy polyethylene glycol amine, and 120-150 parts of ether;

[0018] The intermediate product C comprises the following components: by weight, 2.5-5 parts of the intermediate product B, 1.2-1.5 parts of maleic acid glycoside, 50-80 parts of carbon disulfide, and 0.02-0.05 parts of anhydrous aluminum chloride;

[0019] The water reducing agent comprises the following components: by weight, 20-22 parts of intermediate product C, 1.6-2 parts of 2-acrylamide-2-methylpropanesulfonic acid, 0.98-2 parts of maleic anhydride, and 0.01-0.02 parts of ammonium persulfate aqueous solution.

[0020] More optimally: the preparation process of the modified fly ash is: (1) adding anhydrous ethanol and 3-aminopropyltriethoxysilane to pure water by stirring, and then adding 10% by volume acetic acid solution thereto by stirring to obtain a treatment liquid; (2) after the fly ash is ground, the treatment liquid is sprayed on the surface of the fly ash, and after drying, the modified fly ash is obtained.

[0021] More optimally, the modified fly ash comprises the following components: by weight, 100-120 parts of pure water, 10-12 parts of anhydrous ethanol, 7-8 parts of 3-aminopropyltriethoxysilane, 3-4 parts of acetic acid solution, and 300-350 parts of fly ash.

[0022] More optimally, the dispersible latex powder includes one or more of redispersible vinyl acetate / ethylene copolymer latex powder, redispersible butadiene / styrene copolymer latex powder, and redispersible vinyl acetate / versatate copolymer latex powder.

[0023] More optimally: the defoamer is a powdered organosilicon defoamer; the particle size of the natural river sand is 0.1-0.2 mm.

[0024] In the scheme, a construction process of waterproof mortar for backfilling includes the following steps:

[0025] Step 1: Laying the pile position line: Use the theodolite and steel tape to locate the pile position according to the control point, and mark it with red paint to draw the pile position line;

[0026] Step 2: Drilling: Use a vibrating drill to vertically press the grouting pipe into the soil to the designed depth;

[0027] Step 3: Slurry mixing: Mix the slurry according to the mix ratio of waterproof mortar;

[0028] Step 4: Grouting: Use the jump hole grouting method to inject the slurry into the grouting pipe, in which the grouting volume and pressure are dual controlled, with the grouting volume as the main control. When the design requirements are met or the pressure exceeds the standard, the grouting is stopped;

[0029] Step 5: Cleaning: After stopping grouting, clean the pipeline and proceed to the next hole construction.

[0030] More optimally: the process parameters of the grouting are: pressure of 0.2-0.4MPa, slurry flow rate of 0-45L / min.

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

[0032] The present invention effectively improves the fluidity and workability of mortar by synthesizing a water reducing agent with a specific structure, thereby enabling fly ash to be used as a substitute for part of cement, reducing costs while effectively improving the durability and impermeability of concrete, making it better applicable to the reinforcement treatment of side wall backfill soil. The details are as follows:

[0033] First, the present invention firstly carries out acyl chlorination reaction on the carboxyl group of 2-hydroxy-6-naphthylacetic acid, and then carries out acylation reaction with the amino group of methoxypolyethylene glycol amine, thereby introducing polyethylene glycol segments; then, it reacts with maleic anhydride to introduce double bonds; finally, it carries out copolymerization reaction with 2-acrylamide-2-methylpropanesulfonic acid and maleic anhydride in the presence of initiator ammonium persulfate, thereby obtaining a water reducer with a specific structure.

[0034] Among them, the introduction of naphthalene groups can increase the hydrophilicity of water reducer molecules and improve their dispersibility in cement paste, thereby more effectively dispersing cement particles and reducing the amount of water used; and can enhance the plasticizing effect of the water reducer, so that the concrete can maintain its strength while reducing the amount of cement used, so that fly ash can be used as a substitute for part of cement and reduce the cost of concrete; the introduction of polyethylene glycol chain segments can also increase the steric hindrance effect between water reducer molecules and cement particles, thereby reducing the contact and aggregation between cement particles and improving the water reduction effect;

[0035] Secondly, the present invention uses 3-aminopropyltriethoxysilane to modify the fly ash, which effectively improves the bonding force between the fly ash and the cement paste. At the same time, the amino group on its surface can react with the carboxyl group in the water reducer, thereby enhancing the adsorption capacity of the fly ash to the water reducer, thereby improving the dispersion effect of the water reducer, thereby improving the mechanical properties of the concrete. DETAILED DESCRIPTION

[0037] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0038] It should be noted that the following parts are parts by weight, and the purchase manufacturers of all raw materials involved in the present invention are exemplified without any special restrictions: in the following embodiments, 2-hydroxy-6-naphthylacetic acid CAS is 10441-46-0, methoxypolyethylene glycol amine CAS is 80506-64-5, 2-acrylamide-2-methylpropanesulfonic acid CAS is 15214-89-8, the dispersible latex powder is German Wacker 5010N redispersible vinyl acetate / ethylene copolymer latex powder, and the defoamer is P803 powdered silicone defoamer produced by German Mingling Chemical.

[0039] In the experiment, the water reducing agent was obtained by the following preparation process:

[0040] S1: Add 20 parts of 2-hydroxy-6-naphthylacetic acid to 100 parts of diethyl ether, stir ultrasonically for 30 minutes, add 10 parts of thionyl chloride, heat to 80°C, reflux for 5 hours, cool in cold water overnight, filter, wash, dry, and recrystallize with diethyl ether to obtain intermediate product A;

[0041] S2: Add 15 parts of the intermediate product A prepared in step S1 and 8 parts of methoxypolyethylene glycolamine to 150 parts of ether, stir ultrasonically for 40 minutes, heat to 75°C, reflux for 5 hours, cool to room temperature, filter, and dry. Pour the obtained solid into dilute hydrochloric acid, stir, filter, wash the solid with water, and then recrystallize with ethanol to obtain intermediate product B;

[0042] S3: 2.5 parts of the intermediate product B prepared in step S2 were mixed with 1.5 parts of maleic acid glycoside and 60 parts of carbon disulfide, and 0.02 parts of anhydrous aluminum chloride were added under ultrasonic stirring, and the temperature was raised to 100°C, and the reaction was refluxed for 1.5 hours. The mixture was cooled to room temperature, and ice water and concentrated hydrochloric acid were slowly added, and the mixture was stirred for 30 minutes. The mixture was allowed to stand for stratification, and the aqueous phase was removed and then dried in vacuo to obtain the intermediate product C;

[0043] S4: Take 20 parts of the intermediate product C prepared in step S3, 2 parts of 2-acrylamide-2-methylpropanesulfonic acid, and 1 part of maleic anhydride, add them to 100 parts of pure water, stir ultrasonically for 30 minutes, raise the temperature to 70°C, add 0.02 parts of ammonium persulfate aqueous solution dropwise, and complete the addition within 2 hours. Keep the temperature constant for 8 hours to obtain a water reducing agent.

[0044] The preparation process of modified fly ash is as follows: add 10 parts of anhydrous ethanol and 8 parts of 3-aminopropyltriethoxysilane to 100 parts of pure water by stirring, and then add 3 parts of 10% by volume acetic acid solution by stirring to obtain a treatment liquid; grind 300 parts of fly ash, spray the treatment liquid on the surface of the fly ash, and obtain modified fly ash after drying.

[0045] Embodiment 1: A waterproof mortar for backfilling, the specific raw material formula is as follows:

[0046] Formula: by weight, including 100 parts of Portland cement, 5 parts of polypropylene fiber, 10 parts of dispersible latex powder, 1 part of water reducing agent, 25 parts of modified fly ash, 2 parts of defoaming agent, 30 parts of water, and 100 parts of natural river sand;

[0047] The preparation method of the waterproof mortar comprises the following steps:

[0048] Step 1: Weigh the raw materials according to the weight of the above formula;

[0049] Step 2: Add 2 / 3 of the weight of natural river sand, silicate cement and modified fly ash into a mortar mixer, then add all the water, and stir at 500r / min for 5 minutes; while the mortar mixer is in operation, stir and mix the remaining 1 / 3 weight of natural river sand, silicate cement and modified fly ash; after the mortar mixer stops, pour the remaining mixture into it, continue stirring at 400r / min, add water reducing agent continuously during this period, stir for 3 minutes until the mixture is uniform, then add dispersible latex powder, polypropylene fiber and defoaming agent, and stir at 200r / min for 4 minutes until the mixture is uniform.

[0050] Embodiment 2: A waterproof mortar for backfilling, the specific raw material formula is as follows:

[0051] In terms of weight, it includes 100 parts of Portland cement, 6 parts of polypropylene fiber, 10 parts of dispersible latex powder, 1 part of water reducing agent, 30 parts of modified fly ash, 2 parts of defoaming agent, 30 parts of water, and 100 parts of natural river sand;

[0052] The preparation method of the waterproof mortar comprises the following steps:

[0053] Step 1: Weigh the raw materials according to the weight of the above formula;

[0054] Step 2: Add 2 / 3 of the weight of natural river sand, silicate cement and modified fly ash into a mortar mixer, then add all the water, and stir at 500r / min for 5 minutes; while the mortar mixer is in operation, stir and mix the remaining 1 / 3 weight of natural river sand, silicate cement and modified fly ash; after the mortar mixer stops, pour the remaining mixture into it, continue stirring at 400r / min, add water reducing agent continuously during this period, stir for 3 minutes until the mixture is uniform, then add dispersible latex powder, polypropylene fiber and defoaming agent, and stir at 200r / min for 4 minutes until the mixture is uniform.

[0055] Embodiment 3: A waterproof mortar for backfilling, the specific raw material formula is as follows:

[0056] In parts by weight, it includes 100 parts of Portland cement, 8 parts of polypropylene fiber, 10 parts of dispersible latex powder, 2 parts of water reducing agent, 30 parts of modified fly ash, 2 parts of defoaming agent, 30 parts of water, and 100 parts of natural river sand;

[0057] The preparation method of the waterproof mortar comprises the following steps:

[0058] Step 1: Weigh the raw materials according to the weight of the above formula;

[0059] Step 2: Add 2 / 3 of the weight of natural river sand, silicate cement and modified fly ash into a mortar mixer, then add all the water, and stir at 500r / min for 5 minutes; while the mortar mixer is in operation, stir and mix the remaining 1 / 3 weight of natural river sand, silicate cement and modified fly ash; after the mortar mixer stops, pour the remaining mixture into it, continue stirring at 400r / min, add water reducing agent continuously during this period, stir for 3 minutes until the mixture is uniform, then add dispersible latex powder, polypropylene fiber and defoaming agent, and stir at 200r / min for 4 minutes until the mixture is uniform.

[0060] Comparative Example 1: Referring to Example 2, the difference is that a polycarboxylate water-reducing agent is added, and the specific formula is as follows:

[0061] In parts by weight, it includes 100 parts of Portland cement, 8 parts of polypropylene fiber, 10 parts of dispersible latex powder, 2 parts of polycarboxylic acid water reducer, 30 parts of modified fly ash, 2 parts of defoaming agent, 30 parts of water, and 100 parts of natural river sand;

[0062] The preparation method of the waterproof mortar comprises the following steps:

[0063] Step 1: Weigh the raw materials according to the weight of the above formula;

[0064] Step 2: Add 2 / 3 of the weight of natural river sand, silicate cement and modified fly ash into a mortar mixer, then add all the water, and stir at a speed of 500r / min for 5 minutes; while the mortar mixer is in operation, stir and mix the remaining 1 / 3 weight of natural river sand, silicate cement and modified fly ash; when the mortar mixer stops, pour the remaining mixture into it, continue stirring at 400r / min, during which time continuously add polycarboxylate water reducer, stir for 3 minutes until the mixture is uniform, then add dispersible latex powder, polypropylene fiber and defoaming agent, and stir at 200r / min for 4 minutes until the mixture is uniform.

[0065] Comparative Example 2: Referring to Example 2, the difference is that the fly ash is not modified, and the specific formula is as follows:

[0066] In parts by weight, it includes 100 parts of Portland cement, 8 parts of polypropylene fiber, 10 parts of dispersible latex powder, 2 parts of water reducing agent, 30 parts of fly ash, 2 parts of defoaming agent, 30 parts of water, and 100 parts of natural river sand;

[0067] The preparation method of the waterproof mortar comprises the following steps:

[0068] Step 1: Weigh the raw materials according to the weight of the above formula;

[0069] Step 2: Add 2 / 3 of the weight of natural river sand, silicate cement and fly ash into a mortar mixer, then add all the water, and stir at a speed of 500r / min for 5 minutes; while the mortar mixer is in operation, stir and mix the remaining 1 / 3 weight of natural river sand, silicate cement and fly ash; after the mortar mixer stops, pour the remaining mixture into it, continue stirring at 400r / min, add water reducing agent continuously during this period, stir for 3 minutes until the mixture is uniform, then add dispersible latex powder, polypropylene fiber and defoaming agent, and stir at 200r / min for 4 minutes until the mixture is uniform.

[0070] Comparative Example 3: Referring to Example 2, the difference is that an excessive amount of modified fly ash is added, and the specific formula is as follows:

[0071] In terms of weight, it includes 100 parts of Portland cement, 8 parts of polypropylene fiber, 10 parts of dispersible latex powder, 2 parts of water reducing agent, 50 parts of modified fly ash, 2 parts of defoaming agent, 30 parts of water, and 100 parts of natural river sand;

[0072] The preparation method of the waterproof mortar comprises the following steps:

[0073] Step 1: Weigh the raw materials according to the weight of the above formula;

[0074] Step 2: Add 2 / 3 of the weight of natural river sand, silicate cement and modified fly ash into a mortar mixer, then add all the water, and stir at 500r / min for 5 minutes; while the mortar mixer is in operation, stir and mix the remaining 1 / 3 weight of natural river sand, silicate cement and modified fly ash; after the mortar mixer stops, pour the remaining mixture into it, continue stirring at 400r / min, add water reducing agent continuously during this period, stir for 3 minutes until the mixture is uniform, then add dispersible latex powder, polypropylene fiber and defoaming agent, and stir at 200r / min for 4 minutes until the mixture is uniform.

[0075] Application example: The waterproof mortar obtained in the embodiment and the comparative example is used for construction, and the process is as follows:

[0076] Step 1: Laying out the pile position line: Based on the control points provided by the owner, use theodolite and steel tape to locate and lay out the pile position, and ask the supervisor to review it. Use red paint to make a triangular mark at the center of the pile position, and use the mark as the center of the circle to draw the pile position line from each axis, with an allowable deviation of 2cm;

[0077] Step 2: Drilling: According to the measured points, the vibrating drilling machine is in place, and the grouting head is added before the first section of the grouting pipe enters the soil. A 2.2kw vibration motor is used to press the Φ25mm special black iron grouting pipe into the soil, leaving 100mm on the top, and the second drill rod is connected. It is pressed into the formation to the designed depth in turn. When the grouting pipe is lowered, it should be kept vertical with a deviation of no more than 1%;

[0078] Step 3: Slurry mixing: obtaining slurry according to the preparation process of waterproof mortar;

[0079] Step 4: Grouting: Before grouting, the grouting equipment and materials should be fully checked, including the grouting pump, slurry mixing and storage system, high-pressure grouting pipe, pressure gauge, etc. Pay attention to not to interrupt the formal grouting at will, and strive to operate continuously to ensure the quality of pile formation; the grouting adopts the bottom-up construction requirement of more points and less amount, the grouting pressure is controlled at 0.2MPa, the slurry flow rate is 45L / min, and the SYB50 type squeeze grouting pump is used for grouting. According to the designed grouting pressure and grouting amount, the grouting is carried out from bottom to top. The upper grouting is lifted, and the grouting pipe pulling height is 0.33m. First, holes 1, 3, 5, 7, and 9 are constructed, and then holes 2, 4, 6, 8, and 10 are constructed. The skip hole grouting construction is carried out in this way. The compaction grouting adopts the principle of dual control of grouting volume and grouting pressure, with grouting volume as the main control and pressure as the auxiliary control. When the grouting volume reaches the design requirement, the grouting is terminated; when the pressure on the pressure gauge rises suddenly and exceeds the design pressure, the grouting is terminated. If the grouting pressure does not reach 80%, the drilling and grouting should be repeated.

[0080] Step 5: Cleaning: Raise the grouting to the designed elevation, end the grouting, lift the grouting pipe out of the ground, clean the pipe, and proceed to the next hole construction.

[0081] Performance test: (1) The prepared waterproof mortar is subjected to fluidity test according to GB / T2419-2005;

[0082] (2) The prepared waterproof mortar is filled into a test mold of 40 mm × 40 mm × 160 mm, and three test blocks are made for each test. The compressive strength and flexural strength are tested in accordance with GB / T17671-2021;

[0083] (3) The test mold prepared in experiment (2) was used to test the anti-permeability performance of the mortar according to JGJ / T70-2009 "Standard for Test Methods for Basic Properties of Building Mortar";

[0084] (4) The test molds prepared in experiment (2) were cured for 24 hours and then removed from the molds. They were first placed in water for curing for 48 hours, then taken out and the surface moisture of the test pieces and nail heads was wiped off with a wet cloth. The initial length L1 of the test pieces was then measured using a comparator. The same batch of test pieces removed from the water were dry-cured for 25 days and then their drying shrinkage length L2 was measured. Each measurement required that the test pieces be kept in the same position above and below the comparator. The drying shrinkage rate was then calculated. The results are shown in the following table:

[0085] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Flowability (mm) 290 292 285 272 269 258 Compressive strength (Mpa) 51.4 53.6 49.8 45.5 44.9 43.9 Flexural strength (Mpa) 15.1 15.5 14.9 13.9 13.7 13.5 Impermeability (Mpa) 2.5 2.8 2.6 2.3 2.2 1.8 Drying shrinkage (%) 0.05 0.04 0.06 0.07 0.06 0.1

[0086] Table 1

[0087] Conclusion: Examples 1-3 effectively improve the fluidity and workability of mortar by synthesizing a water-reducing agent with a specific structure, so that fly ash can be used as a substitute for part of cement, reducing costs while effectively improving the mechanical properties and impermeability of concrete, and can be used for the reinforcement of sidewall backfill soil. Comparative Example 1 uses a polycarboxylate water-reducing agent, and the performance is reduced; Comparative Example 2 does not modify the fly ash, and the performance is reduced; Comparative Example 3 adds an excessive amount of modified fly ash, and the performance is reduced.

[0088] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A waterproof mortar for backfilling, characterized in that: The waterproof mortar comprises the following components: by weight, 100-120 parts of silicate cement, 5-8 parts of polypropylene fiber, 10-12 parts of dispersible latex powder, 1-2 parts of water reducing agent, 25-30 parts of modified fly ash, 1-2 parts of defoaming agent, 30-35 parts of water, and 100-150 parts of natural river sand.

2. The waterproof mortar for backfilling according to claim 1, characterized in that: The preparation process of the water reducing agent is: S1: Add 2-hydroxy-6-naphthylacetic acid to diethyl ether, stir ultrasonically for 20-30 min, add thionyl chloride, heat to 70-80°C, reflux for 4-6 h, cool in cold water overnight, filter, wash, dry, and recrystallize from diethyl ether to obtain intermediate A; S2: Add intermediate product A and methoxypolyethylene glycol amine to ether, stir ultrasonically for 40-50 min, heat to 70-75°C, reflux for 5-6 h, cool to room temperature, filter, dry, pour the obtained solid into dilute hydrochloric acid, stir, filter, wash the solid with water, and then recrystallize with ethanol to obtain intermediate product B; S3: Mix the intermediate product B, maleic acid glycoside and carbon disulfide, add anhydrous aluminum chloride under ultrasonic stirring, heat to 90-100°C, reflux for 1-2h, cool to room temperature, slowly add ice water and concentrated hydrochloric acid, stir for 30-40min, let stand for stratification, remove the aqueous phase, and dry in vacuo to obtain the intermediate product C; S4: Add the intermediate product C, 2-acrylamide-2-methylpropanesulfonic acid and maleic anhydride into water, stir ultrasonically for 20-30 min, raise the temperature to 60-70°C, add aqueous ammonium persulfate solution dropwise for 2-3 h, keep the temperature constant for 6-8 h, and obtain a water reducing agent.

3. The waterproof mortar for backfilling according to claim 2, characterized in that: The intermediate product A comprises the following components: by weight, 20-25 parts of 2-hydroxy-6-naphthylacetic acid, 100-150 parts of ether, and 10-12 parts of thionyl chloride; The intermediate product B comprises the following components: by weight, 15-20 parts of the intermediate product A, 8-10 parts of methoxy polyethylene glycol amine, and 120-150 parts of ether; The intermediate product C comprises the following components: by weight, 2.5-5 parts of the intermediate product B, 1.2-1.5 parts of maleic acid glycoside, 50-80 parts of carbon disulfide, and 0.02-0.05 parts of anhydrous aluminum chloride; The water reducing agent comprises the following components: by weight, 20-22 parts of intermediate product C, 1.6-2 parts of 2-acrylamide-2-methylpropanesulfonic acid, 0.98-2 parts of maleic anhydride, and 0.01-0.02 parts of ammonium persulfate aqueous solution.

4. The waterproof mortar for backfilling according to claim 1, characterized in that: The preparation process of the modified fly ash is as follows: (1) adding anhydrous ethanol and 3-aminopropyltriethoxysilane to pure water by stirring, and then adding acetic acid solution with a volume fraction of 10% by stirring to obtain a treatment liquid; (2) after the fly ash is ground, the treatment liquid is sprayed on the surface of the fly ash, and after drying, the modified fly ash is obtained.

5. The waterproof mortar for backfilling according to claim 4, characterized in that: The modified fly ash comprises the following components: by weight, 100-120 parts of pure water, 10-12 parts of anhydrous ethanol, 7-8 parts of 3-aminopropyltriethoxysilane, 3-4 parts of acetic acid solution, and 300-350 parts of fly ash.

6. The waterproof mortar for backfilling according to claim 1, characterized in that: The dispersible latex powder includes one or more of redispersible vinyl acetate / ethylene copolymer latex powder, redispersible butadiene / styrene copolymer latex powder, and redispersible vinyl acetate / versatate copolymer latex powder.

7. The waterproof mortar for backfilling according to claim 1, characterized in that: The defoamer is a powdered organosilicon defoamer; the particle size of the natural river sand is 0.1-0.2 mm.

8. A construction process for backfill waterproof mortar according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Laying the pile position line: Use the theodolite and steel tape to locate the pile position according to the control point, and mark it with red paint to draw the pile position line; Step 2: Drilling: Use a vibrating drill to vertically press the grouting pipe into the soil to the designed depth; Step 3: Slurry mixing: Mix the slurry according to the mix ratio of waterproof mortar; Step 4: Grouting: Use the jump hole grouting method to inject the slurry into the grouting pipe, in which the grouting volume and pressure are dual controlled, with the grouting volume as the main control. When the design requirements are met or the pressure exceeds the standard, the grouting is stopped; Step 5: Cleaning: After stopping grouting, clean the pipeline and proceed to the next hole construction.

9. The construction process of the waterproof mortar for backfilling according to claim 8, characterized in that: The process parameters of the grouting are: pressure of 0.2-0.4 MPa, slurry flow rate of 0-45 L / min.