Study On Polymer Content Optimisation And Cracking Resistance Mechanism Of Polymer Modified Concrete

Among all cracks that develop in concrete structures,20% are caused by structural stresses and the remaining 80% are due to non-structural stresses.Moreover,cracking of ordinary Portland cement concrete(OPCC)is more pronounced at early age where it is highly vulnerable to endogenous and exogenous forces.Worldwide,polymer modified concrete(PMC)has been used in the construction industry because of its good mechanical and durability properties.Although substantial research efforts have been directed towards understanding the modifying mechanisms for mechanical properties(compression,flexure,abrasion and many others),little is known regarding the crack resistance mechanism of PMC.This research is supported by the National Natural Science Foundation of China(51108207),the Postdoctoral Science Foundation of China(2015M581403),and the Open Foundation for the State Key Laboratory of Permafrost Engineering(SKLFSE201514)and aims to study the polymer content optimization and crack resistance mechanism of PMC.The main work of this article is as follows:(1)Determine the best operating conditions for styrene-butadiene rubber latex(SBR)and Polyacrylate(PAE)based on ASTM C1579 by selecting polymer/cement ratio as the independent variable;and select crack width and crack length are as the dependent variables.Conduct the crack resistance experiment and calculate the corresponding crack reduction factor(CRR)for each formulation.Analyse the distribution pattern and governing law on the effect of polymer addition on crack resistance of concrete,then determine the optimum polymer content for both PMC formulations(SBR modified concrete and PAE modified concrete).(2)Use scanning electron microscopy(SEM)with higher magnification to observe the microstructural features in both SBR and PAE formulations.Observe,identify and characterise the nature of binding between aggregates and mortar in all concrete mixes.Process and analyze microcracks in the concrete matrix using Image J program.Explain the significance of the different observed microstructural features.(3)Combine the macroscopic phenomenon and microscopic connections;identify,and establish the possible synergy between polymer modification(using SBR and PAE)and the crack resistance mechanism of PMC,thereby providing a design basis for the engineering applications of PMC.