Fracture energy and mechanical characteristics of self-compacting concretes including waste bladder tyre

Management of solid wastes is one of the most important environmental problems in the world. Waste tyres are also one of these solid wastes. The growing number of waste tyres that are stocked every year brings problems in respect of human health, environmental pollution, and also causes esthetical problems. The main purpose of this study is to investigate the effect of waste tyre addition on self-compacting concretes' mechanical characteristics and fracture properties under bending. In this study, waste bladder tyres (RA) mechanically cut in 25, 50 and 75 mm lengths were used by volumetric replacement of coarse aggregates in self-compacting concretes (SCC). Unit weight, flow, J-ring, column segregation, water absorption, 28 days of compressive strength, ultrasound pulse velocity and fracture energy tests were applied on concretes obtained by replacement of coarse aggregates in 5%, 10% and 15% ratios by volume. Also, Scanning Electronic Microscope (SEM) and Energy Distribution Spectroscopy (EDS) analyses of the samples were examined. In the study, it was determined that RA replacement decreases unit weight of fresh concrete; when RA length ratio increases, it becomes difficult for the concrete to pass through reinforcement openings; in hardened concrete samples dry unit weight decreases; 10% fibre addition increases compressive strength values; after the ultrasonic pulse velocity measurement, the concretes are included in “good” quality concrete classifications. As a conclusion, it was determined that 25 mm long 10% rubber aggregate replacement to self-compacting concretes can give optimum results.