Effect of shredded vehicle tyres as microplastics on stabilization of a sandy soil

One of the primary sources that contributes to the microplastic contamination in soil is the abrasion of vehicle wheel tyres on roads. On the other hand, the stability of a road is maintained by compacting the subbase soil beneath the road. In this study, standard Proctor compaction tests were performed on 0.025, 0.05, 0.1, 0.2, 0.5, 1, and 2% tyre microplastics-added well-graded sand (SW) that represented a subbase soil contaminated with shredded vehicle tyre microplastics. Test results indicated that a microplastic concentration of up to 0.1% caused the maximum dry unit weight (Ɣ_dmax) to increase from 16.58 to 17.03 kN/m³ and the optimum water content (w_opt) to decrease from 15.4 to 13.8%. As a result, 0.1% tyre microplastic addition caused an increase of 0.45% in the Ɣ_dmax and a decrease of 1.6% in the w_opt. Further increase in the microplastic concentration resulted in a decrease in the Ɣ_dmax and increase in the w_opt. In conclusion, by compacting a well-graded sandy subbase soil beneath a road that was contaminated with tyre microplastics not only prevented the scattering of the microplastics to the environment but also provided enhancement in stability. As a practical implication, a sandy subbase soil contaminated with tyre microplastics can be compacted with smooth wheel rollers in the field in order to enhance the compaction degree of the soil beneath a road and prevent the scattering of the microplastics to a certain extent.