Calprene-Modified Asphalt Mixtures: A Comprehensive Investigation of Performance Enhancement

Abstract

The deterioration of flexible pavements under increasing traffic loads and extreme thermal conditions demands advanced binder modification strategies. This study presents a comprehensive experimental investigation of Calprene-modified asphalt mixtures, where Calprene a radial styrene-butadiene-styrene (SBS) block copolymer manufactured by Dynasol Elastomers was incorporated into a base Pen 60/70 bitumen at dosages of 3%, 4.5%, and 6% by weight of binder. A Superpave 12.5-mm nominal maximum aggregate size (NMAS) gradation was employed for all hot-mix asphalt (HMA) formulations. Binder characterisation encompassed penetration, softening point, ductility, rotational viscosity, dynamic shear rheometer (DSR), bending beam rheometer (BBR), and multiple stress creep-recovery (MSCR) tests. Mixture-level performance was evaluated through Marshall stability and flow, dynamic modulus (|E*|) testing, Hamburg Wheel Tracking Device (HWTD), four-point beam fatigue, semi-circular bending (SCB) fracture energy, and indirect tensile strength ratio (TSR). One-way analysis of variance (ANOVA) with post-hoc Tukey–Kramer comparison and Pearson correlation analysis were applied for statistical discrimination. Results demonstrate that 4.5% Calprene content constitutes the optimal dosage: performance grade advanced from PG 64-22 to PG 76-22, Marshall stability increased by 39.7%, rut depth under HWTD decreased by 58.9%, fatigue life at 800 µε extended by 163%, and SCB fracture energy improved by 81.6% compared to the control mixture. These findings confirm that Calprene is a technically superior modifier for asphalt binders in hot-climate, high-traffic pavement applications and provide calibrated benchmarks for practitioners.