Influence of fibers partially coated with rubber from tire recycling as aggregate on the acoustical properties of rubberized concrete

The aim of this study is to analyze the main parameters that influence the acoustic properties of lightweight concrete containing high volume of recycled rubber aggregates. To that end, the sound absorption and the sound insulation on rubberized concrete are tested under different frequencies. Concrete specimens were designed with 0-100% substitution of its coarse aggregate by two different rubber aggregates from recycled tires, which is up to a 60% of the overall concrete volume fraction. Moreover, to evaluate the influence of the external texture and the direct contact of rubber, concrete panels with different surface finishes (rough and smooth face) were casted. Crumb rubber (CR) and fibers partially coated with crumb rubber (FCR) have been studied for sound barriers. FCR are composed of steel and plastic fibers mixed with small rubber particles from recycled tires and obtained during the granulation process, before the complete rubber separation. The results of this research indicate that the combination of steel and textile fibers contaminated with rubber powder increase sound absorption when compared to ordinary or rubberized concrete. The addition of CR or FCR reduces concrete density and increases its open porosity. However, concrete with large VF of FCR presents an even larger volume of open pores than concrete with CR admixtures, which increases the sound absorption. In addition, the results obtained for sound insulation in high frequencies are also improved with CR and FCR, even when the concrete becomes lighter, because damping of CR and FCR concrete is enhanced. As a consequence, high VF of FCR (80-100%) can be incorporated to concrete for non-structural uses to increase sound absorption.