Evaluation of the Use of Seashell in Open-Graded Asphalt Mixtures

Over the past few decades, due to the depletion of many good aggregate sources and increased negative environmental impact from excavation and processing of virgin aggregates, we should consider other alternatives to replace natural aggregates. This study investigates the substitution of conventional aggregate with a seashell in open-graded asphalt mixtures and evaluates the optimal substitution percentage in aggregate gradations of various nominal maximum aggregate sizes (NMASs) (i.e., 4.75, 9.5, and 12.5 mm). Natural aggregate is the largest source of pavement construction, thus the use seashell as coarse and fine aggregate in asphalt mixtures would be beneficial from both economic and environmental perspectives in road construction. Laboratory experiments were performed on open-graded asphalt mixture specimens with the coarse aggregate of sizes between 2.36 and 12.5 mm being replaced by the seashell at various percentages (0, 15, 30, 45, and 100%). Specimen properties relevant to the performance of open-graded asphalt mixtures in the field were tested, evaluated, and compared. Specifically, a Marshall stability test, Cantabro test, indirect tensile strength test, air void content test, permeability test and impedance tube test were conducted to evaluate the strength, resistance to raveling, cracking resistance, void content, permeability and sound absorption coefficient of open graded asphalt mixtures. The results show that there is no significant difference in the Marshall stability and indirect tensile strength when the coarse aggregates are replaced with seashell. This study also found that the optimum percentages of seashell in open-graded asphalt mixture were 15, 30, and 45% for 12.5, 9.5, and 4.75 mm NMAS gradations, respectively.