The Synthesis And Performance Research Of Shrinkage Reducing Agent Of Poly-Acrylate

Because concrete can be made diversified form and dimension, and have favorable wearing, and it's cost is very low, concrete is the used very widely and generous, but the shrinkage of concrete is puzzling all the engineers, With wide using of the high strength concrete and high performance concrete in recent years, it is more possibility to further increasing of concrete shrinkage-cracking. the shrinkage reducing rate is a relatively steady value when raw material and the mixture ratio are certain, and has the good compatibility with other admixtures. Therefore, doing researches on the shrinkage reducing agent is a vital and significant task.According to the chemical structure and effective mechanism of high-efficiency water-reducing agent, Shrinkage Reducing Agent of Poly-Acrylate with comb like molecular which contained"methyl groups—ester groups—sulphonic groups"was synthesized, the synthesized product's performance was tested. The shrinkage reducing agent was synthesized by two step reaction: (1) Esterification, a intermediate macromonomer(PEA) was made through the reaction of crylic acid and methyl polyethylene glycol-1200 under the effect of catalyzer; (2) Polymerization, methyl methacrylate (MMA) and intermediate macromonomer(PEA) by using ammonium persulfate as initiator.Furthermore, the experiment conditions and mixing proportion of intermediate macromonomer(PEA) were found by esterified reaction: in the condition of decompressing distillation, the dosage of P-toluene sulfonic acid used as catalyzer was 5% of methyl polyethylene glycol-1200's weight, and hydroquinone used as antipolymerizer was 0.3% of crylic acid's weight. The reaction temperature was about 100℃, the mol ratio of crylic acid and methyl polyethylene glycol-1200 was 3:1; The influence for mol ratio of methyl methacrylate (MMA), intermediate macromonomer (PEA) and the dosage of initiator to the performance of Shrinkage Reducing Agent of Poly-Acrylate was found by experiments. The optimal mixing proportion for synthesizing the superplasticizer was MMA:PEA=2:3, the dosage of initiator was 2.5% of gross weight of monomer. It proved that the shrinkage reducing agent was co-polymerized by unsaturated monomer with methyl groups,ester groups and polyoxyethylene groups as side chain through infrared spectral analysis for the favorable product of Shrinkage Reducing Agent of Poly-Acrylate. The Shrinkage Reducing Agent of Poly-Acrylate. prepared by ourselves was carried out performance testing according to correlative standard. The result showed that the water reducer possessed a lot of characteristics such as low dosage (solide dosage was 0.2～0.3% of the cement's weight), high-efficiency water-reducing ratio, wide adaptability, improved the strength of concrete remarkably and definite retarding effect.The performance test showed that the shrinkage reducing agent possessed a lot of characteristics such as low dosage (dosage was 0.5% of the water),low alkali,control the concrete shrinkage cracking effectively and greatly reduces the surface tension of water solvent. When the mix content of shrinkage reducing agent is 1.0 %,the shrinkage reducing rate of mortar can reach to 62% at 3d and 41% at 28d,the shrinkage reducing rate of concrete can reach to 50% at 3d and 30% at 28d,and without decrease in strength of mortar and concerte.