Effects Of Curing Conditions On The Performances And Mechanisms Of Polymer Modified Cement-based Repair Mortar

With the large-scale construction of infrastructure in our country,infrastructure has been transferred from the construction period to the repair and reinforce period.Due to the rapid increase of traffic flow and demand of the public travel,the destruction of cement concrete pavement has been a serious problem.Therefore,it is of vital significance to research and develop a kind of cement concrete road repair material with low price,wide application range,good performance and simple construction method.Portland cement-aluminate cement-gypsum ternary system is often used as repair material because it has the advantages of fast setting early strength and stable strength in late stage at the appropriate ratio.However,as a cement concrete pavement repair material,it still has the shortcomings of fast loss of fluidity,high brittleness and low toughness.During the repair process,the maintenance environment has a significant effects.Therefore,different types of polymers were used to modify the repair mortar of ternary system,and the mechanical properties of the polymer modified repair mortar under different curing environments were investigated,then the repair mortar suitable for concrete engineering under different conditions were optimally selected.In this paper,the ternary repair mortar was modified by styrene butadiene rubber emulsion(SBR),styrene acrylate emulsion(SAE)and ethylene vinyl acetate emulsion(EVA).The effects ofdifferent polymer contents(4%,8%,12%,and 16%)on the construction performance and mechanical properties of ternary system repair mortar under standard curing conditions were studied.Then the effects of different curing conditions on the mechanical properties of polymer modified ternary mortar were also studied.Finally,the characteristics of hydration products,microstructure and film formation of polymer modified ternary mortar were tested and analyzed by X-ray diffraction(XRD)and scanning electron microscope(SEM).Results show that:(1)SBR and SAE can improve the fluidity and decrease the fluidity loss rate of ternary sysytem.And SBR,SAE and EVA can prolong the setting time of cement paste to a certain extent.(2)The mechanical properties of polymer modified ternary mortar were the best under different curing humidity were researched.Under natural curing(RH 50 ± 10% and temperature of 22 ± 2 ?),SBR,SAE and EVA emulsion greatly improved the flexural strength and toughness of the ternary system repair mortar,and reduced its water absorption rate.(3)Compared with different curing temperature,the best mechanical properties of polymer modified ternary system repair mortar are obtained at 40? and 60?.Under 40? and 60? curing,SBR,SAE and EVA emulsion greatly improved the flexural strength and toughness of the ternary system repair mortar,and reduced its water absorption rate.And three kinds of polymer emulsions can prevent the shrinkage phenomenon caused by the decomposition of ettringite at 40? and 60?.