Mechanical properties of 5-year-old concrete prepared with recycled aggregates obtained from three different sources

The current paper presents the findings of a long-term study on the mechanical properties of concrete prepared with recycled aggregate obtained from three different sources. The concrete mixtures were prepared with a cement content of 355 kg/m(3) and water-to-cement (w/c) ratio of 0.55. The recycled aggregate was used as 0, 20, 50 and 100% replacements of natural aggregate. It was found that after 5 years of curing, the compressive strength and modulus of elasticity of the concrete made with recycled aggregates decreased with an increase in recycled aggregate content. Starting from the curing age of 1 year, however, the splitting tensile strengths of the concrete prepared with 100% recycled aggregate were higher than that of the natural aggregate concrete. The gain in strength and elastic modulus over time of the concrete prepared with recycled aggregates derived from pure crushed concrete was higher than the corresponding natural aggregate and recycled aggregates derived from other construction and demolition wastes. This is attributed to the improvement in bonding between the new cement matrix and the old recycled aggregates.