INVESTIGATION OF DIFFERENT TREATMENTS IN TIRE RUBBER WITH A VIEW TO CONCRETE APPLICATION

摘要

The inadequate disposal of used tires can result in serious consequences to the environment and human health, which calls for the need of more studies about the reuse of this material. This paper presents an initial part of an experimental program carried out with mortars, with a view to the application of tire rubber in concrete. In this research study the tire rubber was investigated, with maximum size of 1mm, in 4 different surface conditions: without surface treatment, treated with water, calcium hydroxide and sodium hydroxide. Mortar specimens were cast with cement sand relation of 1:2.5 and water cement ratio of 0.6, and the rubbers were used in the contents of 5% and 10%, in substitution to the sand volume. Thus, the study contemplated 11 mortar mixes, including the reference sample (without tire rubber). Mortar specimens were characterized both in the fresh state (incorporated air, workability and specific gravity) and in the hardened state (compressive strength, splitting tensile strength, direct tensile strength and modulus of elasticity). In addition to the aforementioned tests, scanning electron microscopy analyses were carried out with the tire rubbers as well as the sample mortars in order to characterize their microstructure and also verify the differences between the mortars. The main results of this study indicated a different behavior among the mortars, showing an increase of air incorporation in the presence of tire rubber when compared to the reference mortar (without rubber). This behavior was responsible for the reduction in the values of compressive strength. In addition, a decrease in both elasticity modulus and specific gravity were verified, although the tensile strength was not significantly affected in the presence of the rubbers. Based on these studies, a promising use of tire rubber was made evident, since this material influenced the characteristics of the mortars yielding properties that proved satisfactory.