CN-122010453-A - Preparation method of multifunctional additive for concrete

CN122010453ACN 122010453 ACN122010453 ACN 122010453ACN-122010453-A

Abstract

The invention discloses a preparation method of a multifunctional additive for concrete. The preparation method of the multifunctional concrete additive comprises the steps of firstly mixing an oil phase system A, span-80 formed by PVC and an organic solvent, ettringite and calcium carbonate to obtain a solution B, then emulsifying the solution B with a sodium thiosulfate solution to obtain an emulsion D, secondly dripping the emulsion D into a double emulsion E formed by stirring in a PVA emulsion, stirring, centrifuging, washing, precipitating and drying to obtain microspheres F, finally mixing the microspheres F with the sodium sulfate solution, PVA and nano ferroferric oxide to obtain a suspension I, mixing the PVC with a plasticizer, the solvent and Span-80 to obtain an oil phase system G, and dripping the emulsion J emulsified by the I and the G into the PVA emulsion to obtain the multifunctional concrete additive. The admixture prepared by the method is a microsphere sleeve microsphere structure body, so that the integration of the early strength and crack repairing functions of concrete is realized, and the problem of generation of shrinkage cracks of the concrete caused by the early strength can be rapidly solved.

Inventors

GONG JIE
GAO GUIBO
Ji Henan
QIAN ZHENYU
XING CHEN
CHEN QIAO
JI REN
SHI RUN
FENG WEIFENG
XU LEI

Assignees

中交路桥建设有限公司
中交路桥北方工程有限公司

Dates

Publication Date: 20260512
Application Date: 20260212

Claims (10)

1. The preparation method of the multifunctional additive for the concrete is characterized by comprising the following steps of: (1) Adding PVC into an organic solvent in a stirrer, stirring until the PVC is completely dissolved to form an oil phase system A, adding an oil-soluble emulsifier Span-80, ettringite and calcium carbonate into the oil phase system A, performing ultrasonic dispersion, stirring until the mixture is completely uniform, and placing the stirrer in a constant-temperature water bath at 65-70 ℃ to obtain a solution B; (2) Adding excessive sodium thiosulfate into water at 65-70 ℃ to enable the water to be in a supersaturated state, dropwise adding sodium hydroxide solution to control the pH value to be 12-13, filtering to obtain supernatant C, then placing the supernatant C into a constant-temperature water bath at 65-70 ℃ in a stirrer, slowly mixing the supernatant C with the solution B obtained in the step (1), slowly dropwise adding the supernatant C into the solution B in the mixing process, uniformly dropwise adding, starting a high-shear emulsifying machine before dropwise adding, continuously emulsifying for 20-30 min after dropwise adding, and carrying out ultrasonic treatment by using an ultrasonic crusher to obtain W/O emulsion D with micron-sized sodium thiosulfate liquid drops dispersed; (3) Slowly dripping the emulsion D obtained in the step (2) into the PVA emulsion in a stirrer under the condition of constant-temperature water bath at 65-70 ℃ after adding PVA into water, starting a low-speed stirrer before dripping, and continuously stirring after finishing dripping to form stable W/O/W double emulsion E; (4) Placing the double emulsion E prepared in the step (3) in a constant-temperature water bath at 65-70 ℃, regulating the rotating speed of a stirrer and continuously stirring to form microspheres with a core-shell structure, after the reaction is finished, pouring all the products into a centrifugal machine to centrifuge and discard supernatant, repeatedly washing the centrifuged products with deionized water to precipitate, and transferring the washed microspheres into a vacuum drying box to be dried to constant weight to obtain dried micron-sized core-shell microspheres F; (5) Placing a stirrer in a constant-temperature water bath at 32-35 ℃, adding excessive sodium sulfate into water at 32-35 ℃ in the stirrer to enable the water to be in a supersaturated state, dropwise adding sodium hydroxide to control the pH value to be 12-13, filtering to obtain supernatant H, mixing the micron-sized core-shell microspheres F prepared in the step (4) with the supernatant H, adding PVA and nano ferroferric oxide, performing ultrasonic dispersion to form stable suspension I, controlling the temperature to be 32-35 ℃, mixing PVC and plasticizer, adding the mixture into a solvent, stirring until the mixture is completely dissolved, adding Span-80, mixing to form an oil phase system G, slowly and uniformly dropwise adding the suspension I into the oil phase system G, starting a high-shear emulsifying machine before dropwise adding, continuously emulsifying for 20-30 min, and performing ultrasonic treatment by using an ultrasonic breaker to obtain dispersed W/O emulsion J; (6) Preparing PVA emulsion, slowly dripping the emulsion J prepared in the step (5) into the PVA emulsion in a constant-temperature water bath at the temperature of 32-35 ℃ in a stirrer, starting a low-speed stirrer before dripping, adjusting the rotating speed to 180-300 r/min, continuously stirring for 60-120 s after dripping, wherein the stirring time in the whole stirring process is 25-30 min, the emulsion J is wrapped by a PVC oil phase film to form suspension K, continuously stirring the suspension K in the constant-temperature water bath at the temperature of 32-35 ℃ at the rotating speed of 100-120 r/min for 8-10 h every 1m 3 of suspension K to form microspheres with a core-shell structure, after the reaction is finished, pouring all the products into a centrifugal machine, centrifuging, discarding supernatant, repeatedly washing and precipitating the centrifuged products by deionized water, and finally transferring the washed microspheres to a vacuum drying box to constant weight to obtain dry core-shell microspheres L, namely the multifunctional concrete additive.
2. The preparation method of claim 1, wherein the mass ratio of the PVC to the organic solvent in the step (1) is 12-15:100; the organic solvent is formed by mixing cyclohexanone and tetrahydrofuran according to a mass ratio of 1:0.8-1.2; the addition amount of the Span-80 of the oil-soluble emulsifier is 2% -3% of the mass of the oil phase system A; the maximum particle size of the ettringite is not more than 1 mu m, and the addition amount of the ettringite is 3-5% of the mass of the oil phase system A; The maximum particle size of the calcium carbonate is not more than 0.5 mu m, and the addition amount of the calcium carbonate is 1-2% of the mass of the oil phase system A; The ultrasonic dispersion parameter is that the ultrasonic frequency is 20-25 kHZ, and the ultrasonic dispersion time is 3-5 min.
3. The preparation method of claim 1, wherein in the step (2), the volume ratio of the supernatant C to the solution B is 1:8-10, and the dripping time of the supernatant C to the solution B is controlled to be 8-10 min; the rotating speed of the high-shear emulsifying machine is regulated to 6000-10000 r/min; the ultrasonic treatment parameters of the ultrasonic crusher are that the power is 200-300W, and the treatment time is 3-5 min.
4. The preparation method of claim 1, wherein the mass ratio of PVA to water in the PVA emulsion in the step (3) is 3-5:100; The ultrasonic dispersion parameters are that the ultrasonic frequency is 20-25 kHZ, and the ultrasonic dispersion time is 20-30 min; The volume ratio of the emulsion D to the PVA emulsion is 1:8-10; the rotating speed of the stirrer is adjusted to be 180-300 r/min, stirring is continued for 60-120 s after dripping is completed, and the stirring time in the whole stirring process is 25-30 min.
5. The preparation method according to claim 1, wherein in the step (4), the rotation speed of the stirrer is adjusted to be 100-120 r/min, and the stirring time is kept for 8-10 h every 1m 3 of emulsion E; the centrifugal speed is 4000-6000 r/min, and the centrifugal time is 8-10 min; the washing and precipitating times are 3-5 times; The set temperature of the vacuum drying oven is not higher than 60 ℃.
6. The preparation method of claim 1, wherein in the step (5), the mass ratio of the micron-sized core-shell microspheres F to the supernatant H is 1:20-30; the PVA addition amount is 1-2% of the total mass of the micron-sized core-shell microspheres F and the supernatant H; the particle size of the nano ferroferric oxide is 10-20 nm, and the addition amount of the nano ferroferric oxide is 0.01-0.03% of the total mass of the micron-sized core-shell microsphere F and the supernatant H; The mass ratio of the mixture of the PVC and the plasticizer to the solvent is 12-15:100, the mass ratio of the PVC to the plasticizer is 100:32-38, the solvent is formed by mixing cyclohexanone and tetrahydrofuran according to the mass ratio of 1:0.8-1.2, and the Span-80 addition amount is 2-3% of the total mass of the PVC; the volume ratio of the suspension I to the oil phase system G is 1:8-10; The ultrasonic dispersion parameters are that the ultrasonic frequency is 20-25 kHZ, and the ultrasonic dispersion time is 20-30 min; slowly dripping the suspension I into an oil phase system G, wherein the dripping time is controlled to be 8-10 min, and the rotating speed of the high-shear emulsifier is regulated to be 6000-10000 r/min; the ultrasonic treatment parameters of the ultrasonic crusher are that the power is 200-300W, and the ultrasonic treatment time is 3-5 min.
7. The preparation method according to claim 1, wherein the mass concentration of the PVA emulsion in the step (6) is 3% -5%, and the PVA emulsion is obtained by adding PVA into water and performing ultrasonic dispersion for 20% -30 min; the volume ratio of the emulsion J to the PVA emulsion is 1:8-10; The centrifugal speed is 1000-1500 r/min, and the centrifugal time is 10-15 min; the washing and precipitating times are 3-5 times; The vacuum drying oven is set at a temperature not higher than 50 ℃.
8. The preparation method according to claim 1, wherein the polymerization degree of the PVC is 900-1000, and the basic softening temperature is 75-80 ℃, and the softening temperature of the formed PVC is controlled to be 55-62 ℃ by controlling the amount of the plasticizer; The plasticizer is dioctyl phthalate or acetyl tributyl citrate. The alcoholysis degree of the polyvinyl alcohol PVA is 88%, and the polyvinyl alcohol PVA is water-soluble.
9. The multifunctional concrete additive prepared by the preparation method of any one of claims 1 to 8 is characterized in that the multifunctional concrete additive is a core-shell structure of microsphere sleeve microspheres, the inner core of the structure is micron-sized core-shell microspheres F, the outer shell is PVC, the middle is saturated sodium sulfate solution at 32-35 ℃ and nano ferroferric oxide particles, and the inner part of the micron-sized core-shell microspheres F is saturated sodium thiosulfate, calcium carbonate and ettringite mixed solution at 60-70 ℃.
10. The application method of the multifunctional concrete additive of claim 9, wherein the mixing amount of the multifunctional concrete additive is 0.5% -5% of the mass of a cementing material when the multifunctional concrete additive is used in concrete, and after the concrete mixed with the multifunctional concrete additive is poured, the multifunctional concrete additive needs to be rapidly moved from the surface of the concrete by using a magnet, and the moving speed is 0.5-2 m/s.

Description

Preparation method of multifunctional additive for concrete Technical Field The invention belongs to the technical field of additives, and particularly relates to a preparation method of a multifunctional concrete additive. Background With the rapid development of modern civil engineering, mass concrete is widely applied to large-scale engineering structures such as high-rise building foundations, bridge piers, hydraulic junction dams and the like. The concrete has the characteristics of large casting volume, large consumption of cementing materials, concentrated hydration heat release and the like, and faces two major core technical problems in construction and service processes, namely the contradiction between early strength improvement and hydration temperature rise control, and the defect of self-repairing capability after crack generation in service stage, wherein the two major problems directly affect the safety, durability and service life of an engineering structure. In the aspect of early strength improvement, if early strength is slowly increased after pouring of large-volume concrete, plastic cracks are easily generated due to factors such as construction load, environmental disturbance and the like, so that a mode of adding an early strength agent is often adopted in engineering to accelerate the cement hydration process, and the maintenance period is shortened. The existing common early strength agents mainly comprise chlorides, sulfates, organic amines and the like, wherein the sulfate early strength agents (such as sodium sulfate) are widely applied due to obvious effect and low cost. On the one hand, the rapid reaction of sulfate can lead to concentrated release of hydration heat of cement, so that the internal temperature rise rate of concrete is accelerated, the temperature rise peak value is increased, temperature stress cracks are initiated, and the structural integrity is weakened, on the other hand, the traditional early strength agent has single function, only the early strength can be improved, the controllability of hydration temperature rise cannot be considered, and the crack in the service stage of the concrete has no repairing effect. In the aspect of self-repairing cracks, micro-cracks are extremely easy to generate in the service process of the mass concrete due to factors such as hydration heat shrinkage, drying shrinkage, temperature stress and the like, if the cracks cannot be repaired in time, external moisture and aggressive media can infiltrate into the inside through the cracks, corrode reinforcing steel bars and degrade cementing materials, so that the structural performance is gradually reduced. The existing concrete self-repairing technology mainly comprises microorganism repairing, crystal repairing, capsule repairing and the like. The microbial repair technology is greatly influenced by the pH value and the temperature of the environment, the stability is insufficient, the repair effect of the crystalline repair material depends on the long-term existence of water at a crack, the repair strength is limited, the capsule type repair material is mostly of a single core material packaging structure, only single repair can be realized, the cooperative function with the early strength function can not be realized, and the integrated requirement of 'early strength-temperature control-self repair' of the mass concrete is difficult to meet. In order to solve the problems, attempts are made in the industry to develop multifunctional composite additives, and compatibility of early strength, temperature control and self-repairing functions is expected to be achieved. However, most of the existing compound technologies are simply compounded, antagonism is easy to generate among different functional components, and the function superposition effect is poor. For example, when the early strength agent and the retarder are compounded to control the temperature rise, partial early strength effect is often sacrificed, and when the self-repairing component and the early strength component are mixed and added, the self-repairing component is easy to fail in advance in the early hydration process and cannot play a role in crack generation. In addition, the traditional additive lacks targeting property in the action mode, the release rate of the early strength component is difficult to match with the cement hydration process, the self-repairing component cannot precisely act on crack parts, and the comprehensive performance is difficult to meet the severe requirements of mass concrete. Meanwhile, the structural design of the existing capsule or microsphere additive has limitations, most of the existing capsule or microsphere additive has a single-layer wrapping structure, and multi-component and staged release cannot be realized. The single-layer structure is easily damaged by shearing force in the concrete stirring process, so that the core material leaks in advance, and the ordered re