Investigation of Hot In-Place Recycling Effects on Hot Mix Asphalt Pavement
Abstract In March 2006, a hot in-place recycling (HIR) technique was employed for the first time on Lahore-Islamabad Motorway (M-2) to rehabilitate sections where the rut depth was about 40 mm. Since HIR technology was new to Pakistan, research was carried out to study the effects of recycled wearing course on overall pavement performance. This was accomplished by comparing structural adequacy of pavement and material characterization before and after recycling. Laboratory investigations included hot mix asphalt (HMA) volumeteric analysis, aggregate gradation analysis, extracted asphalt properties (penetration test and dynamic shear rheometer (DSR)) and resilient modulus. Analysis of recycled HMA wearing course indicated a reduction in modulus for a mix which was stiff and aged prior to recycling. Relative degradation of the aggregates in HMA wearing course, before and after recycling, was observed; however, it remained close to National Highway Authority (NHA) standard specifications. The research enhanced awareness of HIR among local engineers and contractors.