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CN-121974596-A - Preparation method of special additive for reservoir rock-fill self-compacting concrete

CN121974596ACN 121974596 ACN121974596 ACN 121974596ACN-121974596-A

Abstract

The invention relates to the technical field of concrete additives, in particular to a preparation method of a special additive for reservoir rock-fill self-compacting concrete, which comprises the following steps of S1, taking N-vinylformamide, itaconic acid and stearyl methacrylate as reaction monomers, adding an initiator, and preparing a terpolymer through copolymerization, and S2, compounding and mixing the terpolymer with a slump retaining agent, a shrinkage reducing agent, an air entraining agent, a defoaming agent and water to obtain the special additive. The special additive prepared by the invention can ensure that the concrete mixture has good initial fluidity and high diffusion speed, keeps good time-lapse fluidity for a long time, has good clearance passing property and water retention property, and can effectively control the drying shrinkage of concrete.

Inventors

  • WU LINSEN
  • CHEN JING

Assignees

  • 福建兴纳科技有限公司

Dates

Publication Date
20260505
Application Date
20260210

Claims (9)

  1. 1. The preparation method of the special additive for the reservoir rock-fill self-compacting concrete is characterized by comprising the following steps of: s1, taking N-vinylformamide, itaconic acid and stearyl methacrylate as reaction monomers, adding an initiator, and preparing a terpolymer through copolymerization; S2, compounding and mixing the terpolymer with a slump retaining agent, a shrinkage reducing agent, an air entraining agent, a defoaming agent and water to obtain the special additive for the reservoir rock-fill self-compacting concrete.
  2. 2. The preparation method according to claim 1, wherein the mass ratio of N-vinylformamide, itaconic acid and stearyl methacrylate in the step S1 is (2.5-4.5): (1-3): (0.5-2), the initiator is at least one selected from azodiisobutyronitrile, ammonium persulfate and potassium persulfate, and the addition amount of the initiator is 0.3-0.8% of the total mass of the three reaction monomers.
  3. 3. The preparation method according to claim 1, wherein the step S1 specifically comprises the steps of: adding stearyl methacrylate and an emulsifier into deionized water, performing pre-emulsification treatment to obtain a pre-emulsion, adding itaconic acid and N-vinylformamide into the pre-emulsion, regulating the pH value of the system, heating the reaction system, adding an initiator, stirring for reaction for 2-6h, and filtering and purifying after the reaction is finished to obtain the terpolymer.
  4. 4. The method according to claim 3, wherein the pre-emulsification is shearing emulsification at a temperature of 30-40 ℃ and a shearing speed of 300-6000rpm.
  5. 5. A method according to claim 3, wherein the pH of the system is adjusted to 4.0-5.0, the target temperature for heating is 65-75 ℃, and the stirring speed is 100-200rpm.
  6. 6. The preparation method of claim 1, wherein in the step S2, the total mass of the special additive is taken as a reference, and the mass percentages of the components are 40-60% of terpolymer, 15-25% of slump retaining agent, 2.0-5.0% of shrinkage reducing agent, 0.3-1.0% of air entraining agent, 0.05-0.15% of defoaming agent and the balance of water.
  7. 7. The method according to claim 1, wherein the slump retaining agent in step S2 is selected from polycarboxylic acid slump retaining agents obtained by copolymerizing allyl polyoxyethylene ether with an unsaturated carboxylic acid monomer, and the shrinkage reducing agent is selected from at least one of polyoxyethylene alkyl ether, polyoxyethylene aryl ether or polyethylene glycol.
  8. 8. The method of claim 1, wherein the air entraining agent in step S2 is selected from at least one of a rosin thermopolymer, sodium dodecylbenzenesulfonate or sodium alpha-olefin sulfonate, and the defoamer is selected from a polyether modified silicone defoamer or a mineral oil based defoamer.
  9. 9. A special admixture for reservoir rock-fill self-compacting concrete prepared by the method of any one of claims 1-8, characterized by a pH of 6.0-7.5.

Description

Preparation method of special additive for reservoir rock-fill self-compacting concrete Technical Field The invention relates to the technical field of concrete additives, in particular to a preparation method of a special additive for reservoir rock-fill self-compacting concrete. Background The basic principle of the rock-fill concrete is that the rock-fill concrete is formed by pre-stacking large-grain-size rock blocks into a body, and then pouring special self-compacting concrete into the gaps of the rock-fill, so that all complex holes can be filled in a flowing manner by means of self-gravity, and the rock-fill concrete can be coagulated with the rock blocks into a compact integral structure without manual vibration, thereby effectively reducing the common temperature control risk of the traditional large-volume concrete and improving the construction efficiency. The invention patent with the publication number of CN108640610A discloses an underwater self-compacting concrete and a construction method thereof, wherein the concrete comprises, by weight, 400-610 parts of stone, 124-211 parts of sand, 200-220 parts of cement, 46-70 parts of fly ash, 110-180 parts of water and 2-3.1 parts of an additive. During construction, the retaining wall skeleton is built around the pouring position by adopting piled stones, a template is supported on the bin surface, and then the underwater self-compacting concrete is directly poured. The self-weight flow of the concrete is relied on, the gap between the rockfill can be completely filled, the rockfill is not easy to be dispersed by water, and the rockfill concrete which has complete structure, high compactness and good bonding and meets the requirements of strength and impermeability is finally formed. In the prior art, when the conventional polycarboxylate water reducer is applied to reservoir rock-fill self-compacting concrete, it is often difficult to provide enough plastic viscosity and cohesion while endowing the concrete with extremely low yield stress so as to ensure ultrahigh fluidity, so that aggregate separation and slurry bleeding are easy to occur when the concrete passes through complex and narrow rock-fill gaps, and structural uniformity is affected. Meanwhile, the additive has limited wetting and bonding wrapping capability on the surface of the rough rockfill, and the dispersibility and slump retention performance of the additive decay rapidly under severe conditions such as common temperature difference fluctuation and long-distance transportation in field construction, so that the workability is difficult to maintain stably. In addition, most of the prior art schemes focus on optimizing the rheological property of fresh concrete, but solve the problem of long-term crack resistance of large-volume concrete structures such as reservoir dams, and particularly aim at the shrinkage reducing property of self-shrinkage and drying shrinkage, thereby being a hidden danger for engineering long-term safe burying. Disclosure of Invention In order to solve the problems mentioned in the background art, the invention provides a preparation method of a special additive for reservoir rock-fill self-compacting concrete. In order to achieve the above purpose, the present invention adopts the following technical scheme: the preparation method of the special additive for the reservoir rock-fill self-compacting concrete comprises the following steps: s1, taking N-vinylformamide, itaconic acid and stearyl methacrylate as reaction monomers, adding an initiator, and preparing a terpolymer through copolymerization; S2, compounding and mixing the terpolymer with a slump retaining agent, a shrinkage reducing agent, an air entraining agent, a defoaming agent and water to obtain the special additive for the reservoir rock-fill self-compacting concrete. Further, in the step S1, the mass ratio of the N-vinylformamide, the itaconic acid and the stearyl methacrylate is (2.5-4.5), 1-3, 0.5-2, preferably (3.0-4.0), 1.5-2.5 and 0.8-1.5, the initiator is at least one of azodiisobutyronitrile, ammonium persulfate or potassium persulfate, and the addition amount of the initiator is 0.3-0.8 percent, preferably 0.4-0.6 percent of the total mass of the three reaction monomers. Further, the step S1 specifically includes the following steps: adding stearyl methacrylate and an emulsifier into deionized water, performing pre-emulsification treatment to obtain a pre-emulsion, adding itaconic acid and N-vinylformamide into the pre-emulsion, regulating the pH value of the system, heating the reaction system, adding an initiator, stirring for reaction for 2-6h, and filtering and purifying after the reaction is finished to obtain the terpolymer. Wherein the emulsifier is at least one selected from alkylphenol ethoxylates, fatty alcohol ethoxylates or sulfosuccinate, the dosage of the emulsifier is 1-5% of the weight of the stearyl methacrylate, and the dosage of deionized water is 2-4 times of the to