Laboratory Investigation on the High Temperature Performance of SMA Mixes Using combinations of Chitin Modified Bitumen Binder and Treated RCA

Abstract

With the ever-increasing load and harsh climatic conditions, the major concern that has emerged is the rutting failure of flexible pavements, which often precedes the fatigue failure of flexible pavements. Stone Matrix Asphalt (SMA) is widely used to resist rutting. VG 40 bitumen is commonly preferred for its superior high-temperature performance. However, VG 40 is costlier and less available in many regions. This study evaluates chitin - a sustainable, bio-based polymer recovered from seafood waste-as a modifier to upgrade VG 30 bitumen mixes. Unmodified VG 40 and VG-30 bitumen was used to make conventional VG-40 SMA and VG-30 SMA mixes respectively. Further the VG-30 SMA mix is modified by replacing the 50% of Natural Coarse Aggregate (NCA) by Treated Recycled Concrete Aggregate (TRCA) to make VG-30 SMA+50%TRCA+5%C Mix. Consequently, the VG 30 was modified with chitin at 5%, 7.5%, and 10% by weight and used to prepare SMA mixtures incorporating 50% NCA and 50% TRCA. Both modified bitumen SMA mixes and unmodified bitumen SMA mixes were compared under laboratory conditions. Laboratory characterization included Marshall Stability, indirect tensile strength (ITS), tensile strength ratio (TSR), and wheel-tracking rutting tests. Chitin modification increased binder stiffness and high-temperature resistance in a dose-dependent manner. Among the dosages tested, VG 30 modified with 5% chitin provided the best balance of rutting resistance, moisture susceptibility. SMA mix with VG 30 SMA+50%TRCA+5% chitin exhibited comparable or superior rutting resistance to VG 40 SMA Mixes while maintaining acceptable Marshall Stability and TSR values. Higher chitin contents (7.5% and 10%) further reduced permanent deformation but yielded marginal additional benefits in moisture resistance and slightly affected workability during compaction. These findings indicate that chitin-modified VG 30, particularly at 5% chitin content, can serve as an eco-friendly and resource efficient alternative to VG 40 for high-performance TRCA SMA pavements, while simultaneously contributing to the sustainable use of biowaste and Construction Demolition Waste (CDW).