Civil Engineering ETDs

Publication Date

Summer 7-25-2021

Abstract

During the last 20 years, asphalt pavements were built in New Mexico (NM) and around the country using mostly Superpave coarse graded mixes as opposed to fine graded mixes. This is because coarse mix uses larger aggregates with good interlocking and requires less asphalt binder than a fine mix, while both mixes fulfill the Superpave criteria. Recently, it was observed nationally that the Superpave coarse graded mixes have good field rutting performances but poor cracking performances. It is hypothesized that fine graded mix can help improve pavement cracking performances. The idea is, the fine mixes would have less air voids which would transmit less air and water, and thereby, fine mixes would have less aging/cracking and moisture damage, respectively. In an effort to examine fine and coarse mix performances, mixes were collected from NM 14 that was built using the coarse mix in the southbound lane and a fine mix in the northbound lane. Both fine and coarse mixes have used identical performance grade (PG) binders, reclaimed asphalt pavement (RAP) materials, and aggregate sources. Mixes were compacted in the laboratory, and samples were tested for dynamic modulus, Hamburg Wheel Tracking Device (HWTD) rutting, beam fatigue (BF), and Thermal Stress Restrained Specimen Test (TSRST). The coarse mix shows higher dynamic moduli and better rutting performances than the fine mix, which was expected. Surprisingly, the fine mix failed (more than 12.5 mm rutting for 10,000 passes) in HWTD rutting. The fatigue test data have been analyzed by employing the viscoelastic continuum damage model (VECD). The analysis results reveal that the coarse mix has better resistance to fatigue damage and higher fatigue life than the fine mix. TSRST test results demonstrate higher failure strength and lower failure temperature for coarse mix compared to fine mix. Based on these results, this study postulates that simply replacing coarse mix with a fine mix cannot be the way to address the Superpave pavements’ cracking issue, rather continue looking for other solutions, for example, a balanced mix or gradation.

Keywords

Coarse, Fine, Asphalt Mix, Modulus, Rutting, Fatigue

Sponsors

New Mexico Department of Transportation (NMDOT)

Document Type

Thesis

Language

English

Degree Name

Civil Engineering

Level of Degree

Masters

Department Name

Civil Engineering

First Committee Member (Chair)

Rafiqul A. Tarefder

Second Committee Member

Tang-Tat Ng

Third Committee Member

Fernando Moreu

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