Mechanical Properties of Concrete with Recycled Tires and Silica Fume

Sustainability helps the environment by reducing the consumption of non-renewable natural resources. Concrete uses a significant amount of non-renewable resources. Efforts aimed at producing environmentally friendly concrete can play a major role in securing sustainable construction. Candidate technologies for sustainable concrete materials include the incorporation of supplementary cementitious materials (SCMs) such as fly ash, silica fume and granulated blast furnace slag as a partial replacement for portland cement; the incorporation of recycled materials in concrete production. As a result, an experimental investigation was conducted to study the hardened properties of concrete constructed with 10% and 15% recycled tires (coarse and fine) as well as 6% silica fume. This experimental program consisted of ten mix designs. The hardened properties (compressive strength and tensile splitting strength) of concrete were compared with the provisions of the international design codes (U.S., Australia, Canada, Europe, and Japan). Results of this study show that using coarse recycled tires in the mix designs decreases compressive strengths between 35% and 45% and splitting tensile strength up to 20%. To overcome inferior hardened properties of recycled tire concrete mixes, silica fume (6%) has been added to the recycled tire concrete mixes. Results of the mixes including both recycled tire concrete and silica fume show better hardened properties compared with the mixes without silica fume, but still the hardened properties of the mixes with recycled tire and silica fume are less than the conventional concrete.