Semester of Graduation

5

Degree

Master of Science in Civil Engineering (MSCE)

Department

Civil and Environmental Engineering

Document Type

Thesis

Abstract

Asphalt binder is composed of four chemical fractions, namely, saturates, aromatics, resins, and asphaltenes (SARA). Binders with the same performance grade (PG) can exhibit different chemical compositions due to variability in crude oil sources and refining processes. The objective of this study was to evaluate how such chemical variations influence the mechanical performance of asphalt mixtures at high, intermediate and low temperatures.

Eighteen 12.5-mm nominal Maximum Aggregate Size mixtures were designed using two aggregate types (limestone and gravel), and three binder grades (PG 67-22, PG 70-22m and PG 76-22m), each from three different sources with varying chemical fractions. A suite of laboratory mechanical performance tests was performed; the Hamburg Wheel Tracking (HWT) test, Ideal Rutting Tolerance (IDEAL-RT) test, Semi-Circular Bending (SCB) test, Ideal Cracking Tolerance (IDEAL-CT) test, Cantabro test and Simplified Low-temperature SCB test. Analysis of Variance, Tukey's HSD, and Pearson correlation were used to study binder chemistry relation to mixture performance.

Results indicated that binder sources with different chemistries significantly influenced performance despite sharing the same PG classification. Evaluation of eighteen mixtures showed that 1% asphaltene increase enhanced rutting resistance by 6.0%, 6.9% and 8.1% reduction in HWT rut depths, but reduced the critical strain energy release rate (Jc) by 3.6%, 6.70%, and 8.1% for PG 67-22, PG 70-22m, and PG 76-22m binders, respectively. Durability declined likewise, with a 9.2% increase in Cantabro mass loss for PG 70-22m, while the PG 76-22m mixtures were most resilient overall. Similarly, LT-SCB showed 19.9%, 14.1%, and 9.0% decrease in cracking parameter (CP) for PG 67-22, PG 70-22m, and PG 76-22m, respectively. IDEAL-RT test supported the rutting trend, while IDEAL-CT test results were inconsistent and not sensitive to the studied chemical differences of  binders. Within the Louisiana Balanced Mix Design (BMD) framework, the SCB Jc criterion governed compliance and distinguished same-grade binders that PG grading treats as equivalent, demonstrating that BMD can detect chemistry-driven differences. Asphaltene fraction is therefore identified as a candidate supplementary screening parameter. Limited to the eighteen mixtures evaluated, these findings demonstrate the need to supplement Superpave PG grading with a binder chemical composition parameter to better predict pavement performance.

Date

7-17-2026

Committee Chair

Mohammad, Louay N.

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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