Mechanical characterization of high performance concrete prepared with recycled aggregates and silica fume from precast industry

Abstract

The growth of the precast industry has led to the emergence of waste with enormous potential for recycling, given the strict quality control of these companies and the need of construction/demolition of structures with increasing strength capacities. In this investigation, an analysis of the mechanical behaviour of high-performance concrete (HPC) incorporating fine and coarse recycled aggregates (FRA and CRA) was made. The recycled aggregates (RA) originated from rejected precast elements with compressive strengths of 75 MPa and were used to replace natural aggregates (NA) in concrete mixes. The experimental campaign also included three families of concrete with proportions of densified silica fume (SF) of 0%, 5% and 10% (relative and in addition to cement). Each family comprised a reference concrete (RC) and three recycled aggregate concretes (RAC) with replacement ratios (FRA/CRA%) of 50/50, 0/100 and 100/100. The results obtained in the compressive strength, splitting tensile strength, modulus of elasticity, ultrasonic pulse velocity and bond strength tests showed that it is possible to produce high-performance concrete without NA. The silica fume led to a performance increase in the properties analysed with the creation of a new concrete mixing method that considered the specificities of RA and the difficulties of dispersing SF particles.