Performance Evaluation of High-Content Rubber Asphalt Mixtures Using Superpave and Balanced Mix Design via Dry and Semi-Wet Processes

Document Type

Article

Publication Date

5-20-2026

Department

Department of Civil, Environmental, and Geospatial Engineering

Abstract

Growing environmental concerns and the rising costs of raw materials have driven increased interest in using high crumb rubber content in asphalt pavements. This study investigates mixtures containing 20% and 24% crumb rubber, incorporated using dry and semi-wet methods, under two mix design approaches: the Superpave volumetric procedure and a balanced mix design (BMD) framework. Volumetric compliance was first evaluated through Superpave parameters, including voids in mineral aggregate, voids filled with asphalt, and dust proportion. Tensile strength ratio tests confirmed moisture damage resistance above 80% for all mixtures, indicating that high rubber content did not compromise moisture susceptibility. Subsequently, the BMD approach combined the Hamburg wheel-tracking test (HWTT) and disk-shaped compact tension (DCT) test to establish binder content ranges that satisfy simultaneous rutting and cracking thresholds. Findings revealed that the 24% crumb rubber mixtures frequently exhibited improved cracking resistance and rutting resistance but decreased when increasing binder content. The semi-wet incorporation method generally yielded broader acceptable binder ranges, attributable to enhanced interaction between the rubber and binder. In addition, compaction energy index and traffic densification index analyses suggested that higher rubber contents elevate compaction energy requirements but reduce in-service densification. Overall, high crumb rubber contents can be successfully employed within a balanced performance framework, and the optimal binder content determined through the BMD approach provides more flexibility for design adjustments, enabling improved performance in both the HWTT and the DCT test, while also offering potential economic benefits.

Publication Title

Journal of Materials in Civil Engineering

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