Recovery of tire rubber waste after UV treatment as a recycled aggregate in cementitious composites

Abstract

Rubber is an extremely important source of raw material for the world industry, being used for various purposes. This diversification of applications is due to the vulcanization process that rubber undergoes to acquire an increase in its mechanical properties. A large amount of tire rubber is incorrectly discarded due to a lack of recycling alternatives, thus increasing the risk to the environment and public health around the world. One of the alternatives for valuing rubber is its use in civil construction by inserting it in cement matrices. If the crushed rubber is treated by physicochemical methods before mixing in with cement, possible improvements in the mechanical, thermal and acoustic properties of the cementitious mixture can be achieved. This work has as main objective to prepare a coating mortar through volumetric replacements of 5, 10, 15 and 20% of the fine aggregate by crushed tire rubber and treated by ultraviolet irradiation. Rubber samples were submitted at different times of exposure to UV irradiation for 12 h. After treating the rubber samples, the compressive strength, flexure strength and dynamic elasticity modulus of the rubber-modified mortar were characterized. From the findings, it was observed that the greater the addition of rubber to the mixture, the lower its dynamic modulus and mechanical strengths, as well. The specimens with 20% of substitution registered the lowest modulus value, which indicates that the material produced from this composite has greater deformability compared to other mixtures. Analysing the mechanical tests, it was observed that with the addition of rubber to the mixture there was a decrease in compressive strength. This is due to the fact that rubber is hydrophobic, making it difficult for water to migrate into the mixture, and consequently, decreasing the resistance of the mixture. In addition to the ductile nature of rubber itself, which behaves as a void within the mixture and does not help in load transition from one point to another, causing greater cracking. Combining the beneficial and potential environmental impact of finding new destinations of GTR with its high deformability, highlight this type of material as promising recycled aggregate in many applications that require this property.