Performance evaluation of dense-graded asphalt mixture for high-strength application

Abstract

Sustaining an efficient transportation system in Singapore for a large population in a limited land area is a challenge. Cost-effective road construction is vital due to budget constraints. Road pavements typically comprise granite aggregates and pen 60/70 grade binders in Singapore. Hence, to optimize road construction, it is essential to understand how aggregate gradation affects mechanical performance in high-strength applications.

In this study, PG-76 binder and granite aggregates were utilized in the creation of specimens for dense-graded Hot Mix Asphalt (HMA), aligning with the Land Transport Authority's (LTA) design mixes of W3B, W3, and W1. PG 76 binder, a polymer-modified bitumen known for its higher viscosity and suitability in high-stress environments, was selected for its commendable performance in Singapore's variable climate. The study established the Optimum Binder Content (OBC) by evaluating various criteria through four laboratory test: Marshall test, Creep Resistance, Moisture susceptibility, and Indirect Tensile Strength test. Additionally, aggregates were classified according to the three gradations stipulated by LTA. Given the limited research on performance distinctions within the three design mixes for wearing courses, this research explores how aggregate gradation influences the mechanical properties of high-strength wearing courses.

Following laboratory testing, optimal binder content (OBC) values of 4.5%, 5.5%, and 5.5% were determined for W3B, W3, and W1, respectively. The findings indicate that W3B is the most promising design mix, meeting the required stability standards, displaying excellent resistance to moisture-induced damage, and exhibiting superior performance in resisting cracking and permanent deformation. In contrast, W3 and W1 mixes encountered challenges related to flow and stiffness. Overall, W3B stands out as the optimal choice for high-strength applications in road pavements among the three mixes.