Compaction behaviour of a sandy road base contaminated with microplastics from vehicle tires

Abstract Disintegrated tire particles can easily be transferred into the road bases because of the abrasion of vehicle tires on roads. The fragmented tire particles that have a grain size of smaller than 5 mm can be expressed as microplastics. In order to simulate the tire chip microplastic concentration in a sandy road base and assess the effect of microplastics on the compaction degree of the road base, standard Proctor compaction tests were performed on 0.05%, 0.1%, 0.2%, 0.4%, 1%, 2%, 4% and 8% tire chip microplastics‐amended sandy soil by dry mass. Results showed that maximum dry unit weight ( ɣ dmax ) of the sand increased from 16.04 to 16.99 kN/m 3 as the tire chip microplastic concentration increased up to 0.4%. Further increase in the microplastic concentration resulted in a decrease in ɣ dmax . Contrarily, optimum water content ( w opt ) decreased from 15.9 to 12.5% as a result of the tire chip microplastic addition up to a concentration of 0.4%. An additional increase in the microplastic concentration led to an increase in w opt . By considering these results, a concentration of 0.4% tire chip microplastics was found to be the optimum amount that enhanced the degree of compaction. Besides contributing to the stabilization of a sandy road base, tire chip microplastics can also be assessed in terms of environmental protection. These microplastics are forced to be stacked in the sand because of compaction. As a result, they cannot easily be transferred to water resources or agricultural products that may threaten human health and cause environmental contamination.