INVESTIGATION AND COMPARISON OF THE PROPERTIES OF CEMENT-BACED MIXTURES CONTAINING DIFFERENT TYPE OF POLYMERS

In this research the effects of three types of commercial polymers including Styrene-butadiene-rubber, Ethylene- vinyl acetate and Styrene-acrylic on the properties of cement mixtures have been investigated. Polymer contents in the test mortar mixtures were 5, 10, 15 and 20% by weight of cement and the water-cement ratio was kept constant at 0.33. In order to investigate and compare the influences of polymer materials on the mortar specifications the mechanical properties including compressive strength, flexural toughness and durability properties including rapid chloride migration coefficient and the amount of capillary and volumetric absorption, resistance to sulfuric acid were evaluated. The specimens were cured under wet conditions at early ages (7 days) and air cured at later ages (After 7 days until the test). The results indicate an improvement in several mechanical characteristics such as flexural toughness and significant influence on reducing the adsorption rates of cement mixtures in the rapid chloride migration coefficient, water absorption and resistance to sulfuric acid. Comparing the results at different ages showed that dry curing period has had a significant effect on the strength growth process and mechanical properties of polymer modified mortars. According to the results of mechanical tests, the Styrene-acrylic and Ethylene-vinyl acetate provided significant improvements in the flexural toughness and this improvement was enhanced by increasing the polymer-cement ratio. Concerning the penetration and adsorption of water in the mortars by same polymer-cement ratio, Styrene-acrylic modified mortars have obtained higher enhancements than other compounds. Also, in the ratio of 15% polymer to cement, the lowest amount of water absorption and penetration was observed in the Styrene- acrylic modified mortars which showed the optimal ratio. According to the results of the sulfuric acid test, the best practice was for the Ethylene-vinyl acetate modified mortars. The results of this study indicate that modified polymeric cementitious base mixtures can be widely used in construction industry applications.