To evaluate the impact of using Peruvian scallop crushed seashell (CSS) as fine aggregate a range of 0.75, 0.55, 0.45 and 0.41 w/c ratio concretes were tested. The hardened and fresh properties of concrete at 7, 28 and 90 day periods were investigated. The experimental results show that the effects of CSS replacement on concrete properties depend on the size particle distribution of the global aggregate after replacement, and that the angular shape of CSS particles can contribute to a better arrangement. The maximum level of CSS replacement is variable and limited to a maximum for a given size of CSS particles and a w/c ratio. A maximum of 40% replacement can be suggested in a range of 1.19–4.75 mm CSS particle size, but 5% can be considered optimal for all cases. It means that cleaned CSS can be used as fine aggregate replacement in conventional concretes. © 2017 Elsevier Ltd