Mechanical and durability behaviours of concrete made with recycled coarse and fine aggregates

The effects of RCA and RFA replacement ratio on the mechanical and durability behaviour of RAC are experimentally studied. A total of 36 concrete mixtures were considered with natural aggregate and three W/C ratio (i.e. .4, .5 and .6) as well as two replacement levels of RCA (i.e. 75, 100%) and three replacement levels of RFA (i.e. 30, 60, 100%). The mechanical performance, in terms of cube compressive strength, splitting tensile strength and axial compressive strength were studied as well as the durability behaviour in terms of drying shrinkage and freeze-thaw resistance. The experimental results indicate that the strength of RAC decreases with the increase of recycled aggregates replacement percentage. When the incorporation rate of both RCA and RFA are 100%, the cube compressive strength is decreased by 36 to 42%. However, no significant reduction was observed in compressive strength, for RFA replacement ratio up to 30%. The durability performances of concrete made with RCAs and RFAs were found to decline with the RFA replacement level increasing. Based on the data regression, an equation for calculating the compressive strength of concrete incorporating RCAs and RFAs is presented. Equations to calculate the relationship between different strength indexes are also proposed.