Properties of steam cured recycled aggregate concrete

The effects of steam c uring on the hardened properties of r ecycled aggregate concrete were investigated. In this study, two series of concrete mixtures with water to cement ratios of 0.55 and 0.45 were prepared. Recycled aggregates were used as 20, 50, 80 and 100 % replacements of natural coarse aggregate in the concrete mixtures. The concrete specimens underwent standard water curing and steam curing regimes. The test results showed that the strength of concrete decreased as the recycled aggregate content increased. An initial steam curing regime increased the 1-day strength of the concrete but the corresponding 28 and 90-day strength decreased. Furthermore, steam curing reduced the static modulus of elasticity of the concrete compared to that of the water cured concrete. However, the negative effect of steam curing diminished as the recycled aggregate content increased. Moreover, steam curing decreased the drying shrinkage and increased the resistance against chloride ion penetration of the recycled aggregate concrete. The results demonstrate that one of the practical ways to utilize a higher percentage of recycled aggregates in concrete is "precasting" with an initial steam curing stage immediately a fter casting.