Geocell-Reinforced Unpaved and Paved Roads with Recycled Asphalt Pavement (RAP) Bases: Experimental Study and Damage Model Development

Abstract

Recycled Asphalt Pavement (RAP) is a removed and reprocessed pavement material from deteriorated asphalt pavements containing asphalt binder and aggregates. The use of RAP can reduce the cost of construction materials, reduce the amount of waste to be land-filled, and conserve natural resources by requiring less virgin aggregate and asphalt in road construction projects. Literature showed that RAP bases had more permanent deformation under static and dynamic loading compared to conventional aggregate base. Geocell is one type of geosynthetic products manufactured in a form of three-dimensional interconnected honeycomb shape polymeric cells. Geocell was used in this study to reinforce RAP bases in unpaved and paved roads. The objective of this study is to understand the behavior of unpaved and paved roads with unreinforced and geocell-reinforced RAP bases. Fifteen large-scale laboratory cyclic plate loading tests were conducted on unpaved and paved road sections with unreinforced or geocell-reinforced RAP bases. The unpaved road sections consisted of unreinforced or geocell-reinforced RAP bases over weak or moderate (target CBR = 2% or 5%) subgrade, whereas paved road sections consisted of hot mix asphalt (HMA) surface over unreinforced or geocell-reinforced RAP bases over moderate (target CBR = 5%) subgrade to investigate their performance and shake down responses under cyclic loading. The test results showed that geocell improved the performance of RAP bases as compared with the unreinforced bases by increasing the percentage of resilient deformation and reducing the permanent deformations and the vertical stresses transferred to the subgrade. A thin (about 50 mm) HMA surface significantly improved the performance of RAP bases. The thicker geocell-reinforced RAP base behaved as a slab with bending resistance and the thinner base behaved as a slab initially at a smaller deformation and then as a tensioned membrane at a larger deformation. The geocell-reinforced RAP bases showed a stable shakedown response whereas the unreinforced RAP base showed an unstable shakedown response. Based on cyclic plate loading test results, damage models for the empirical correlation between the permanent strain and/or the resilient strain with the number of loading cycles were developed for unpaved and paved roads including unreinforced and geocell-reinforced RAP bases. The mechanistic empirical model can be incorporated in the AASHTO Mechanistic Empirical Pavement Design Guide (MEPDG), which will promote the sustainable use of RAP with geocell for roadway construction.