Abstract: The principle and method of synthesis of superplasticizer discussed the water reducing mechanism and its advantages and disadvantages are compared, and finally discusses the status and prospects of development Polycarboxylate.

Polylactic acid-based organic material is currently widespread concern, it is mainly used for concrete water reducer, detergent additives, paint and ink pigment dispersing agent field. This class of surfactants with excellent washing, penetration, dispersion, emulsification, demulsification properties, especially low temperature washing effect and good resistance to hard water, biodegradable good performance, strong coordination performance advantages. Therefore, a wide range of applications, the polycarboxylic acid-type polymer used as concrete water reducer is not long history, Japan is the primary research and development and user countries. In recent years, Polycarboxylate is widely accepted in the concrete industry, and has been increasingly concerned about domestic and foreign researchers and users of concrete admixtures. The reason, as compared with conventional superplasticizer naphthalene sulfonic acid and sulfonated melamine condensates, they can give concrete high dispersion at low dosage, fluidity and high dispersion stability to prevent slump loss. Meanwhile, prices of industrial naphthalene, naphthalene superplasticizer long production cycle, serious environmental pollution problems have become increasingly prominent also superplasticizer applications imperative. Currently, Japan's highly efficient air-entraining water-reducing agent commonly used in the main component being added from naphthalene sulfonate highly reactive molecule transition to the polycarboxylic acid, closely followed by Europe and the United States also.

Research progress of the Polycarboxylate superplasticizer especially less preparation principle, mechanism, and other aspects of the development prospects of the class Summary report. Research progress in preparation principle of this kind of water reducing agent, mechanism of action, the development prospects of the author intends to do a review.

Principle 1 Preparation

Polycarboxylate superplasticizer is a sulfonic acid group, a carboxyl group, an amino group and a macromolecular compound having a side chain containing a polyoxyethylene like, in an aqueous solution, synthesized by radical copolymerization principle comb-type structure having a high molecular surfactant. Synthesis of salts of polycarboxylate Superplasticizer needed for the main raw material are: methacrylic acid, acrylic acid, ethyl acrylate, hydroxyethyl acrylate, allyl sulfonate, methyl methacrylate, 2-acrylamido- methyl acrylate, methoxy polyoxyethylene methacrylate, ethoxy-polyethylene glycol acrylate, allyl ether and the like, may be employed during the polymerization initiators are: persulfates aqueous initiator agents, benzoyl peroxide, azobisisobutyronitrile; chain transfer agent: 3- mercaptopropionic acid, thioglycolic acid, mercaptoethanol and isopropanol.

2 Mechanism

Polycarboxylate superplasticizer is a new water-reducing agent, has many outstanding advantages, but the mechanism is not fully understood, the following are some of the views:

(1) polycarboxylic acid polymer cement have a more significant retarding effect, mainly due to the carboxyl group acts as a retarding component, R-COO ~ and Ca2 + ions form a complex solution to reduce the Ca2 + ion concentration, slow Ca (OH) 2 to form crystals, reducing the formation of CHS gel, delaying the cement.

(2) carboxy (-COOH), hydroxyl (-OH), amino (-NH2 in), a polyoxyethylene alkyl (-OR) n strong affinity with water, such polar group adsorbingmechanism, dispersing, wetting, lubricating, etc. surface-active effect on the cement particles provide dispersion and flow properties, and by reducing the frictional resistance between the particles of cement, cement particles and reduce the free water interface can be used to increase the workability of fresh concrete. Meanwhile poly carboxylic acids adsorbed on the surface of cement particles, carboxylate ion cement particles with a negative charge, so that between the cement particles and produce the electrostatic repulsion of cement particles are dispersed, leading to inhibition of cement paste agglomeration tendency (DLVO theory ), cement particles and water to increase the contact area, so that the cement fully hydrated. In the process of diffusion of cement particles, aggregates lock release surrounded by free water, improved workability, reduced water mix.