Laboratory design and investigation of the properties of continuously graded Asphaltic concrete containing recycled plastics aggregate replacement (Plastiphalt)

Abstract This paper discusses the laboratory design of continuously graded Asphaltic concrete (AC) mixtures containing recycled plastics aggregate replacement (Plastiphalt). Recycled waste plastics, predominantly composed of low density polyethylene (LDPE) in pellet form, were used in dense graded bituminous mixes to replace (by volume) a portion of the mineral aggregates of an equal size, i.e., 5.00-2.36 mm. The results obtained in this investigation indicate that at the same air-void content, the compacted Plastiphalt mix has lower bulk density than that of the conventional control mix. A 30% aggregate replacement by volume with the LDPE, results in a reduction in bulk compacted mix density of 16%. This reduction in density is advantageous in terms of haulage costs. LDPE partial aggregate replacement also results in a 250% times increase in the Marshall stability (strength) value and an improved Marshall quotient value (resistance to deformation). The value of creep stiffness of the Plastiphalt mix after 1 h loading of 60°C is found to be slightly lower than the control mix; however, the Plastiphalt gives 14% recovery after 1 h unloading time compared to 0.6% for the control mix. The indirect tensile stiffness modulus (ITSM) values of the Plastiphalt compacted mix were found to be lower than that of the control mix, whereas the static indirect tensile strength (ITS) values were found to be much higher. In this study, the future recyclability of the Plastiphalt was also investigated. The mechanical properties of the recycled mix were found to be equal to that of the original Plastiphalt and better than the control mixes.