The Research On The Synthesis And Performance Of Novel Polycarboxylic Superplasticizers

Polycarboxylic superplasticizer is a new type of concrete superplasticizer, it has become a hot research topic frontier because of its high water-reducing rate at low dosage and superior performance in keeping the concrete slump. In this thesis, on the basis of molecular characteristics of polycarboxylic superplasticizer, the relationship between structure and properties, the main mechanism of action and the domestic supply situation of raw materials, three kinds of comb comb-like polymers was synthesized and tested for properties.Maleic anhydride citric acid ester (MACA) was synthesized by using an esterification reaction technique; The methacrylic acid (MAA) reacts with the polyethylene glycol monomethyl ether (mPEG) to form macromonomer mPEGMAA. Then, the novel polycarboxylic superplasticizers marked PC-1,PC-2and PC-3were synthesized through free radical polymerization from mPEGMAA, MACA, acrylic acid (AA), methacrylic acid (MAA), allyl sulfonate (SAS), maleic anhydride (MA), etc; By performing a series of orthogonal and signal experiments individually, the crucial factors in the performances and optimum parameters of synthesizing various types of polycarboxylic superplasticizers have been attained; The optimal mixing proportion for synthesizing PC-1which had long side chains of PEO was n(AA):n(MAA):n(mPEG600MAA):n(MA):n(SAS)=10.5:3.5:7:2:7, the dosage of initiator was1.0%. At PC-1usage of0.25wt%and water-cement ratio of0.29, the fluidity of cement grout can attain345mm and there was no loss within120minutes; When the mixing proportion for synthesizing PC-2which had short side chains of multi-carboxyl was n(AA):n(SAS):n(MACA)=10:3:3, the cement grout with PC-2had higher fluidity, less fluidity loss and homogeneousness without bleeding. The optimal raw materials mixture ratio of synthesizing PC-3which had diversity of side chains was n(AA):n(MAA):n(SAS):n(MACA):n(mPEG600MA)=4.5:1.5:3:1:3. The original fluidity of cement grout without bleeding reached360mm, and the fluidity after120minutes increased slightly. And, PC-3exhibited excellent dispersing and flow retention ability when the water-cement ratio was low.The relationships between structure and properties of three types of superplasticizers were characterized by FTIR, intrinsic viscosity and surface tension. The effects of novel superplasticizers in cement paste were explored by testing the C, potential of cement particles, and the action mechanism of the novel superplasticizers with cement agreed with the thoery model of electrostatic repulsive force, steric hindrance, etc; In order to investigate the performances of novel superplasticizers, drying shrinkage of cement, N2adsorption and desorption measurement, the slump and strength of concrete were tested. The results showed that PC-1, PC-2and PC-3have excellent slump retention stability. In addition, they can reduce the shrinkage and influence the pore volume of the cement. And, PC-3can increase the mesoporous volume and make cement hardenite more compact to improve the concrete strength. So, the novel superplasticizers improved the strength of concrete significantly to reached the standard of the high performance polycarboxylic superplasticizer.