Reclaimed Asphalt Pavement–soil Blends for Subgrade Construction

Reclaimed Asphalt pavement (RAP) - soil blends were examined as alternative material to use in constructing the subgrade sustainably. The growing need to use recycled geomaterials in transportation infrastructure needs performance-based assessment platforms, other than standard compaction reporting. The characteristics of natural soil and RAP used in this study were described using index testing and gradation and mixtures of 0–80% RAP were made. Proctor compaction tests were conducted on standard basis and a performance-based model involving normalized density, moisture efficiency, and relative cost ratio was established to assist the engineering decision making. The outcomes showed that the higher RAP incorporation the higher the maximum dry density and then reduced at higher contents but reached a maximum at around 40 % RAP incorporation. The optimum moisture content was found to decrease uniformly with the percentage of RAP and declining the total moisture content by 25–30 % in relation to natural soil. Compaction response exhibited clear dependence on the content of RAP, illustrating the shift of the behaviour of the cohesion-controlled behaviour to the friction-controlled behaviour. According to combined performance and cost evaluation, a range of 30–50 % of optimum RAP replacement is suggested to be used in the applications at the subgrade level. The results encourage the practical approaches toward RAP-soil blends as efficient and cost-effective substitutes of developing road structures.