Porosity and pore size distribution in recycled concrete

Abstract

The reuse of construction and demolition wastes as replacement for natural coarse aggregate in the production of recycled concrete has been spreading worldwide as a method for recycling waste materials. However, recycled aggregates are of higher porosity than natural aggregates, which can decrease the mechanical properties and durability of recycled concrete. The study reported in this paper compared the porosity and pore size distributions of a control concrete and concretes made with different replacement levels of natural coarse aggregates. The research intended to relate the influence of the aforementioned aspects on mechanical and durability characteristics by assessing the compressive strength and the capillary water absorption of each concrete mix. Although there was a decline in compressive strength, the recycled concretes exceeded the design strength grade of 25 MPa. It was also found that recycled concrete possessed a higher capillary water absorption, which was more pronounced in the short term due to the presence of capillary pores but was less significant in the long term as the presence of macropores in both concrete mixes was very similar.