Laboratory evaluation of seashells used as fine aggregate in hot mix asphalt

Oyster farming annually generates millions of empty hard seashells as by-product waste in municipal landfills worldwide. Using this waste as fine and coarse aggregates as construction materials offers a low energy consumption alternative to recycling and mining of virgin materials. This research explores the use of seashell as a cost-effective replacement of virgin fine aggregate in hot mix asphalt (HMA). The properties of HMA mixtures with seashells were investigated using indirect tensile strength, permanent deformation and moisture susceptibility tests; tests used in standard practice in Peru. The results indicate that seashells can be used as fine aggregate improving the indirect tensile strength and the permanent deformation of HMA. Seashells in the asphalt mixture reduced moisture susceptibility compared to conventional HMA, with an increase of tensile strength ratio (TSR) values of 22-262%, a very important finding since with areas of Peru recently experiencing severe flooding events where seashells have the potential to reduce stripping. The laboratory study also showed that seashell sizes of 300-2.36 mm yielded highest TSR values. Replacement of fine aggregate with seashells increases total HMA cost by about 2.9-4.6%.