LAUSR

Abstract The increasing accumulation of tire waste has become a social environmental and public health problem because rubber degradation is extremely difficult to achieve and time consuming. The incorporation of rubber waste in concrete has become a recourse to assist in the disposal of this solid waste. This investigation evaluated the influence of a chemical pretreatment with sodium hydroxide solution (NaOH) on the physical, mechanical, microstructural properties of concretes with two rubber residue contents (15% and 30%) as a natural fine aggregate replacement, and the addition of silica fume (7.5% and 15%) to replace Portland cement. X-ray microtomography and scanning electron microscopy were used to investigate the influence of treatment rubber and silica fume in the microstructure of concretes. The use of rubber in the cement matrix, regardless of the treatment (or lack thereof), decreases the concrete density (lower 10.5%) and compressive strength at 28 d (54%), besides the increase the porosity (18%) than reference concretes. The rubber pre-treatment did not significantly influence the concrete behavior. In contrast, the use of silica fume showed significant compressive strength gains, up to 80% for concretes with 30% of rubber replacement at 28 days. These gains were confirmed by the microstructural analysis and the densification of the interfacial transition zone.