High-content crumb rubber modified asphalt mixture via wet process: Laboratory evaluation and field application

Document Type

Article

Publication Date

10-10-2025

Department

Department of Civil, Environmental, and Geospatial Engineering

Abstract

To promote the recycling of waste tires in the asphalt industry, high-content crumb rubber-modified asphalt (CRMA) has received growing attention. This study evaluates the performance of high-content CRMA mixtures through two phases: (1) laboratory evaluation using laboratory-produced CRMA at 15 %, 22 % and 28 % rubber content, and factory-produced CRMA at 22 %; and (2) field construction using plant-produced CRMA at 22 %. All CRMA binders were modified from a base binder graded PG 52–28. Performance evaluation included binder performance and mixture-level assessments of resistance to rutting, cracking, and moisture damage. The Dynamic Shear Rheometer (DSR) and Multiple Stress Creep Recovery (MSCR) tests confirmed enhanced rutting resistance, while the Bending Beam Rheometer indicated an improvement in low-temperature performance grade (PG) to −34 to −40 °C. CRMA enhanced fatigue resistance but reduced storage stability. In the laboratory evaluation, the rutting resistance of the 22 % and 28 % CRMA mixtures was between those of the control mixtures with PG 70–28 and PG 58–34 binders. The factory 22 % CRMA ranked second lowest, and the laboratory 15 % CRMA performed the worst. All CRMA mixtures exhibited excellent cracking resistance, although higher rubber content did not consistently outperform the conventional 15 % CRMA. Field results showed a similar trend: plant 22 % CRMA mixture had strong cracking resistance but weaker rutting resistance than the control. In laboratory tests, the Tensile Strength Ratio was near the failure threshold due to the high natural sand content; however, it improved to above 90 % in the field after adjusting the aggregate type. Notably, A better DSR or MSCR rutting index (G*/sinδ, Jnr and %Recovery) did not necessarily indicate better mixture-level rutting resistance for CRMA when compared with control asphalt. In contrast, a lower low-temperature PG generally correlated with improved cracking resistance. Overall, high-content CRMA mixtures offer significantly improved cracking resistance while maintaining acceptable rutting performance, supporting waste tire recycling, and advancing circular economy goals.

Publication Title

Construction and Building Materials

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