Polymer Modified Cement-based Repair Materials Research

For high strength and good durability, cement concrete pavement has been one of two main types high way pavements in China. As a result of the national economys rapid development and the sharp growth of traffic volume, the breakage of centmet concrete pavement is in-creasingly serious, especially for the crack. The crack not merely affects the appearance of the pavement, but also the security and the comfortableness of driving. As a result, the repairing on cement concrete pavement is so significant in practice.By Studying the crack filling material in concrete pavement at home and abroad, this paper takes polymer emulsion to modify cement, to repair the cracks in pavement and restore the pavement features. The main research contents and conclusions of this paper are as follows:1. As the viscosity in 5min and compressive strength in 7d of crack filling material for controlling indicators, through orthogonal experiment, the paper at first selected the optimum modified cement-based material by three-factor and four-level from four Polymer emulsions:SRB,VAE,CB,SD. The results showed that:the best one was when cement modified with carboxylated SBR latex by orthogonal test, the viscosity in 5min was minimum and compressive strength in 7d maximum, and gotten the initial mixture proportion, based on the text of workability of the repair material to optimize the mixture proportion. The results showed that:The W/C was from 0.42 to 0.45 and the polymer content from 5% to 20%, the modified paste viscosity increased and then decreased with P/C increasing and increased with development of time. polymer emulsion could improve groutlbliity but stagnate the the setting time of modified paste. 2. Based on optimized mixture proportion of repair materials, this paper systematically studied the factors affecting the properties of repair material from polymer content,W/C and so on. The results showed that: the compressive strength of polymer modified mortar decreased with P/C increasing, the flexural strength at first rised and then decreased; and polymer emulsion could improve flexibility and resistance to chloride ion permeability of mortar.3. Polymer emulsion can decrease the contraction of cement mortar, polymer modified mortar's shrinkage trends was similar to ordinary mortar, the pre-contraction was larger, and later steady, with increasing the polymer emulsion content, the contraction of modified mortar decreased first and then increased, when the P/C= 10%, the shrinkage of modified mortar was minimum.4. From the research of interfacial bond strength on repair materials, it reveals that:the interfacial bond strength of polymer modified cement paste and mortar were higher than ordinary cement paste and mortar, with the increasing of polymer content polymer modified cement and mortar's interfacial bond strength increased first and then decreased. When the W/C=0.42, P/C=10%; the bond strength of modified cement paste increased up to 52% in 28d comparing with in 7d, up to 28% for reference cement paste in 28d; for modified mortar, when P/C increased from 5% to 10%, the bond strength in 28d increases from 36% to 38% than in 7d. It indicated that the polymer emulsion can improve the bonded performance of cement substrate significantly.5. Researched five different curing system for polymer modified cement mortar's strength, the results showed that:the water-curing time of polymer modified mortar should not be too long, the best pre-conservation in water was 3d, the post-curing could be in dry conditions, so that it was best for the strength development of polymer modified mortar.