Durability and microstructural properties of concrete with recycled brick as fine aggregates

Abstract

To tackle the shortage of natural sand and to reduce the construction waste from clay bricks, the use of recycled bricks to replace sand as fine aggregates to produce more sustainable concrete is explored. This paper studied the effect of replacement levels of sand aggregates (SA) by recycled brick aggregates (rBA) at 0%, 50%, and 100%, and the additional water included in the mix proportion to represent the different moisture states of rBA (oven-dry, partial-dry, saturated-surface-dry) on the microstructure and durability of the concrete. The results show that the replacement of SA by rBA reduces the chloride migration but increases the water absorption, water sorptivity, drying shrinkage and carbonation. The water absorption, water sorptivity and carbonation can be minimized by reducing the additional water content. The microscopy results show that the pore structure of concrete deteriorate with the increase in the replacement because of the porous structure of rBA. Due to the pozzolanic reactivity of the rBA, the Ca(OH)2 crystals in concrete were consumed to generate hydration products, resulting in denser interfacial transition zone and enhanced adhesion between the rBA and the cement matrix.