Influence of fine inclusions in recycled fine aggregates from clay bricks on water transport and pore structure of concrete

To curtail the waste clay bricks stockpile and alleviate the non-renewable resources shortage, recycled fine aggregates from clay bricks (RFCB) were used as an alternative to natural fine aggregates (NAF) in the preparation of low-carbon concrete. The pore structure and water absorptivity capacity of RFCB with and without fine inclusions and its effect together with initial water saturation degree on the water transport behaviour and pore structure of concrete at 365 days were explored. The porous structure of RFCB aggravated without addition of fine inclusions, leading to elevate the water absorption capacity. Furthermore, the pore structure deteriorated with the incorporation of RFCB, resulting in the increase in water absorption, porosity and water sorptivity of concrete. However, thanks to the pozzolanic activity together with micro-aggregate effect of fine inclusions, the presence of RFCB with 50 % replacement and partial saturation degree was beneficial for decreasing the open pores, increasing the closed pores and improving the pore shape, thus better improving the water transport behaviour of concrete. Based on the grey correlation analysis, both the water absorption and water sorptivity were proportionally influenced by the average pore volume and average pore area. Overall, the fine inclusions in RFCB were crucial to its own characteristics, water transport behaviour and pore structure of recycled concrete.