The Research Of Durability Properties Of Polymer Modified Rapid Harding Cement Mortars Based On The Freeze-thaw Cycle And Chlorine Salt Erosion Coupling Conditions

As a new type of rapid repair materials,the polymer modified rapid hardening cement mortar has good working performance,mechanical properties, short setting time,and meet the requirement of quick traffic, which has brought great convenience to the public.But as a kind of new material, the durability is the key to large-scale used,especially in the complicated actual service environments, whether the material can still maintain good performance become the focus of attention.In this paper, the durability of the polymer modified rapid hardening cement mortar in this special environmental conditions was studied.In this paper,we statisticed the meteorological data and harmful temperature of freezing and thawing damage of the last three years,and brought the experimental conditions closer to the actual service environment.By comparing the asic properties of the cement mortar with different ratio(such as setting time, fluidity, flexural strength,compressive strength, bond strength), we chose the optimum proportion of sulphoaluminate cement + ordinary Portland cement + polymer composite system.The durability of the polymer rapid hardening cement mortar in the freeze-thaw cycle and the chlorine salt erosion coupling conditions are researched.The internal relations between microstructure and durability was discussed by analyzing the pore structure and infrared spectrum,and further studied the modified mechanism of polymers.The experimental results show that:(1) the addition of redispersible polymer powder can improve the be workability,bonding strength and development of intensity of rapid hardening cement mortar,when the polymer content is 4%, the polymer rapid hardening cement mortar has the best comprehensive performance.(2) the addition of redispersible polymer powder obviously improved the frost resistance,impermeability and durability under the coupling conditions of the rapid hardening cement mortar.When the polymer content is 4%,the polymer rapid hardening cement mortar has the best frost resistance, after 150 times of freeze-thaw cycle,compared the comperative compress strength loss, flexural strength loss and weight loss of polymer cement mortar with 4% polymer and the specimens without adding polymer,declined by 27.03%, 56.55%, 45.68%. The resistance against chlorine penetration of the rapid hardening cement mortar is also improved,with the increase of the dosage of polymer, the chloride ion migration coefficientreduced in turn.(3) Through the study of the pore structure of polymer rapid hardening cement mortar and the infrared spectrum analysis, we found that thr reason of the addition of polymers improve the durability of cement mortar, on the one hand is due to its physical filling effect, on the other hand, polymer and cement hydration products can also occur chemical reaction, so as to improve its performance.