Concrete made with recycled tire rubber: Effect of alkaline activation and silica fume addition

The present work deals with the investigation of the potential use of recycled tire rubbers in cement matrices. This facilitates the development of concrete with a lesser environmental impact. Thus, it contributes to developing construction in a sustainable way. Concrete formulations were produced with the replacement of 10% sand aggregate by recycled tire rubber using conventional rubber and rubber modified with alkaline activation and silica fume addition to improve the mechanical properties. The water/cement ratio (or composition) and the testing age were used as additional variables. The concrete characterization was performed by testing the compressive strength, elastic modulus, density and microstructure (SEM). The recycled tire rubber proved to be an excellent aggregate to use in the concrete. It was observed that its compressive strength was reduced by only 14% (28 days), in comparison to the conventional concrete, reaching 48 MPa for the mixture with higher resistance. The concrete compositions were found to be lighter and a reduced interface was observed between the rubber and cement matrix after the chemical treatment. The rubberized concrete can support construction sustainability, minimize the consumption of natural resources by using an industrial residue and produce a material with special features.