Introduction to the Technology and Characteristics of Polyacid Water-reducing Agent
The technical knowledge of the polyglycolic acid water reducing agent is as follows: the high water-reducing rate can reach 40%, and the performance of the water reducing agent is good. The high-strength growth, the early strength development is increased, and the later strength of the concrete is improved. Stronger plasticizing and dispersing of the cement particles. Can be used at very low water-cement ratios, such as the production of c100. And the shrinkage of the concrete is reduced. And the carbonization rate and the chloride ion erosion of the concrete are reduced. Lower base content. And the compactness of the concrete is increased, and the appearance quality of the concrete is improved. The concrete has good thixotropy and is easy to construct. Good air-entraining performance, and is beneficial to the improvement of the durability of the concrete. The preparation method has the following specific effects: (1) the poly-acid-based polymer has a relatively obvious retarding effect on the cement, and mainly due to the formation of the slow-setting component, the R-COO-and the Ca2 + ion, the Ca2 + ion concentration in the solution is reduced, the Ca (OH)2 is delayed to form a crystal, and the formation of the C-H-S gel is reduced, And the hydration of the cement is delayed. (2) the polar group with strong water affinity, such as the polar group (-COOH), the hydroxyl group (-OH), the amino group (-NH2), the polyoxyethylene (-O-R) n and the like, is mainly used for the surface-active action of adsorption, dispersion, wetting, lubrication and the like, so that the dispersion and the flow property of the cement particles can be provided, And the free energy of the cement particles and the water interface can be reduced, and the workability of the new mixed concrete can be increased by reducing the frictional resistance between the cement particles. at the same time, the polyphylactic acid substance is adsorbed on the surface of the cement particle, and the acid radical ion causes the cement particles to be negatively charged, so that the electrostatic repulsion effect is generated between the cement particles and the cement particles are dispersed, so that the aggregation tendency of the cement slurry body is restrained, the contact area of the cement particles and the water is increased, And the cement is fully hydrated. In the process of diffusing cement particles, the free water surrounded by the aggregate lock is released, the workability is improved, and the water mixing amount is reduced. And (3) the steric hindrance (i.e., the steric exclusion) of the polyalkanoic acid molecular chain. the surface of the cement particle is adsorbed on the surface of the cement particle to form a "comb", an adsorption layer is formed on the surface of the gel material, and when the polymer molecular adsorption layers are close to each other, a physical space blocking effect is generated between the polymer molecular chains, and the coagulation and aggregation of the cement particles are prevented, This is an important reason for the ability of the acid-reducing water-reducing agent to have a stronger dispersion than other systems. (4) The retention and dispersing mechanism of the high-efficiency water-reducing agent of the polyglycolic acid can be known from the relationship between the elapsed time and the zeta potential after the cement paste is mixed. In general, the loss of concrete after 60 minutes of concrete with high-performance water-reducing agent and melamine-based high-efficiency water-reducing agent is higher than that of high-performance water-reducing agent. It is mainly that the latter is different from the adsorption model of the cement particles, and the force of the polymer adsorption layer between the cement particles is the three-dimensional electrostatic repulsive force, and the Zeta potential change is small. It is only explained by these theories that the repulsion between the ions is often very different from the experimental results. The steric hindrance effect can be used to explain the mechanism of the dispersion of the water-reducing agent of the polyglycolic acid to the cement, that is, the polymer is adsorbed on the surface of the cement particle, and the branched chain of the stretched-in solution produces steric hindrance to make the particles not close to each other, thereby dispersing and stabilizing the cement particles. The mechanism is now generally accepted. It is pointed out that the polymer with long branch chain has low electric potential and high space repulsion, so it is very good to disperse the cement after the adsorption. The high-efficiency water-reducing agent of the high-efficiency water-reducing agent of the acid-based graft copolymer has a tooth profile on the surface of the cement particle. The water-reducing agent not only has excellent dispersibility to the cement particles but also can keep the falling degree of the cement small. There are three reasons: one is due to the presence of a large amount of the graft copolymer in the graft copolymer. The two-dimensional electrostatic repulsive force of the chain is an obstacle to the agglomeration of the particles, and the second is because the graft copolymerization chain is gradually broken and released to release the acid molecule in the strong alkaline medium such as the cement paste, so that the first effect is continuously valued; And thirdly, the absolute value of the Zeta potential of the graft copolymer is lower than that of the conventional water reducing agent, so that the total amount of the required charge is not as much as that of the conventional water reducing agent when the same dispersion state is to be achieved.