Properties of HPC with recycled aggregates

The utilization of recycled aggregates can minimize environmental impact and slow the huge consumption of natural resources used for concrete applications. However, recycled aggregates are not suitable for use in the production of High Performance Concrete (HPC) due to their relatively high absorption capacity, unstable properties and recycled aggregates' weaker strength. Such inadequacies can be overcome through carefully examining the characteristics of recycled aggregates and then adopting proper mixture proportions. In this paper, recycled aggregates generated from demolished-construction wastes were examined and the Densified Mixture Design Algorithm (DMDA) was applied in the design of HPC. Results show that HPC specimens containing recycled aggregates can be designed to have a slump of more than 180 turn and a slump-flow larger than 550 mm. However, HPC specimens with high amounts of recycled aggregates and cement added lose their high-flowing and self-consolidating characteristics after 1 h due to their greater water absorption. Local standards of durability were satisfied at the age of 91 days both by concrete resistivity and chloride ion penetration. (C) 2005 Elsevier Ltd. All rights reserved.