Effects of latex modification on fresh state consistency, short term strength and long term transport properties of cement mortars

Abstract

In this study, two different types of latexes (Styrene Acrylate Rubber and Styrene Butadiene Rubber) at five different dosages by weight of cement have been employed in the preparation of latex modified mortars. Two sets of cement mortars have been designed at constant water/cement ratio and consistency, respectively. Densities at fresh state, flexural and compressive strengths at 28days were measured for each mortar. Capillary water absorption and carbonation depth values were determined from the cylindrical specimens after 7years. Also, the total porosities of selected specimens were measured with a mercury porosimeter in order to compare the effect of porosity on long term transportation properties of cement mortars.Results showed that it is possible to improve the fresh state and mechanical performances of cement mortars with SBR latex addition. SBR modified cement mortars also exhibited an improved impermeability in terms of both water and CO2 gas penetration at the long term. The most important advantage of SBR latex addition was the improvement in CO2 gas penetration resistance compared to SAR latex modified mortars. The mechanism behind this improvement is discussed with the aid of porosity analysis.