Effect of natural and recycled aggregate packing on properties of concrete blocks

Recycled aggregate (RA) could be re-utilized in concrete paving blocks. However, the use of RA in concrete might lead to inferior performance, which constitutes a major barrier in the wider application of recycled aggregate concrete (RAC). To tackle this issue, one promising solution might be the tailoring of aggregate packing without increasing the cement content, carbon footprint and cost. In this study, an experimental program was carried out to systematically investigate the effect of packing density on the properties of concrete blocks. Tests results showed that appropriate proportioning of RA increased the packing density and thus the compressive strength to approach that of natural aggregate (NA) mixtures. Such increased packing density was conducive to the performance of concrete blocks. After packing optimization, RAC exhibited comparable strength to that of NA concrete. Lastly, prediction equations were derived for various performance attributes of concrete paving blocks based on particle packing.