Durability properties evaluation of self-compacting concrete prepared with waste fine and coarse recycled concrete aggregates
Construction and Building Materials
School of Engineering
Using recycled aggregates obtained from construction and demolition waste in concrete is a promising and appropriate solution to control the excessive consumption of natural resources in construction. In this study, the effect of fine and coarse recycled concrete aggregates (RCA) was evaluated by replacing 25%, 50%, 75% and 100% in self-compacting concretes (SCC) on mechanical properties such as compressive and tensile strength, ultrasonic pulse velocity in hardened concrete and durability properties including water absorption, volume of permeable voids, electrical resistivity and resistance to chloride ion penetration. The fresh properties of the SCC were determined using slump flow and J-ring tests. Three series of mixes were made; in the first series, coarse recycled aggregates were replaced by natural coarse aggregates. In the second series, fine recycled aggregates replaced fine natural ones. In the third series, the combination of the coarse and fine recycled aggregates was used in the mixes. In all mixes, the cement content and water-cement ratio were constant equal to 420 kg/m3 and 0.4, respectively. Replacement of recycled aggregates causes a decrease in compressive strength of all mixes and their effect on tensile strength was insignificant. The measured durability properties such as water absorption and volume of permeable voids of recycled aggregate concretes were also adversely affected by the incorporation of RCAs and these properties increase with an increase in RCAs contents. The results indicate that replacement of 25% coarse RCAs had no significant effect on the durability properties of self-compacting concrete including electrical resistivity and chloride ion resistance, while with the increasing fine and coarse RCAs the electrical resistivity and resistance to chloride ion penetration decreased. Results indicate that the resistance to chloride ion penetration was greatly reduced by increasing replacement of fine recycled aggregates. Very strong correlations of electrical resistivity with water absorption, and total charge passed with permeable voids of mixes containing RCA were also observed.