Mechanical property of cement mortar is closely related to polymer modifier type. Four kinds of polymer latex including Chloroprene Rubber (CR), Styrene Butadiene (SBR), Styrene Acrylic (SA) and Polyvinyl Acetate (PVAc) were selected to prepare the modified cement mortar in this study. Mechanical behavior of modified cement mortar was evaluated by flexural strength, Compressive Strength and Tensile Strength, respectively. The micro-morphology of modified cement mortar was observed by scanning electron microscope (SEM), which was useful to analyze the modification mechanism. The results show that the SBR and PVAc latex can effectively improve the flexural strength of cement mortar, while the compressive strength is reduced slightly. Tensile strength of modified cement mortar was increased, especially the PVAc latex modified cement mortar.
lectron micrographs of ordinary cement mortar in 28 days It can be seen that there are both more gel pores and capillary pores in the ordinary cement stones, so it performs worse compactness FIG.9 shows micrographs of PVAc modified cement mortar in 28 days As a kind of high molecular material, PVAc almost combines with cement paste by physical function, while enrichment area of PVAc are appearance during the polymer content being added and overtaking the level It may be caused by the different density of polymer, cement and sand, and it also can be explained through the assumption of Grosskurth that the polymer is pushed and concentrated by cement stone during hydration process With water evaporating and observed by other base materials, the polymer particles interweaves with cement and hydration products through a condensation reaction This conclusion can be proved by the result of FIG It can be seen that the presence of PVAc can reduce pores and increase the compactness of mortar Crosslinking network structure of polymer with other materials can improve adhesion property of cement with sand, and toughness also can be increased Figure Scanning electron micrographs of ordinary cement mortar Figure Scanning electron micrographs of PVAC modified cement mortar CONCLUSIONS Based on the laboratory test results and analysis of the modified mechanism, the following conclusions were drawn a Four types of polymer emulsion can improve mechanical properties of cement mortar in a degree 969 b The SBR and PVAc latex can effectively increase the flexural strength of cement mortar c The PVAc latex modified cement mortar The tensile strength of all modified cement mortar were increased d PVAc can interweave with cement and hydration products, and form crosslinking network structure, which is useful to improve toughness of mortar ACKNOWLEDGEMENTS The corresponding author of this paper is Huaxin Chen The authors gratefully acknowledge the Special Fund for Excellent Doctoral 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