Waste tire rubber particles modified by gamma radiation and their use as modifiers of concrete

Nowadays the excessive amount of waste tire rubber generates serious environmental problems. One of the alternative ways for its recycling is as filler in cement concrete. Nevertheless, as it is known recycled materials added to cement concrete decrease certain mechanical properties due to the poor adhesion between fillers and cement matrix. For resolve this problem, ionizing radiation has been used. For these reasons, in this work, cement concrete specimens were produced with cement, water, rock crushed and sand; this last was partially substituted by particles of waste tire rubber. Then the compression properties of the specimens were evaluated following the experimental parameters: a) gamma irradiation dose (200, 250 and 300 kGy), b) particle size of tire rubber (0.85 and 2.8 mm), and c) particulate concentration of tire rubber (1, 3 and 5 wt. %). In addition, the mechanical compression results were related with the changes on the physicochemical properties of the irradiated tire particles, which were analyzed by Fourier Transform Infrared (FT-IR), Raman and UV-vis spectroscopies, as well as by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA) an Differential Scanning Calorimetry (DSC). The results show improvements on the: a) elasticity modulus, up to 161 %, for cement concrete with non-irradiated particles of tire rubber, and up to 108 % when adding irradiated ones, b) deformation, up to 21 %, when adding non-irradiated tire particles; and c) compressive strength up to 8 % when adding non-irradiated tire particles. Such improvements on the mechanical features were related with the physicochemical changes provoke by gamma rays on the waste tire particles. Such changes were evaluated by the mentioned analytic techniques.