Assessment of The Rutting and Moisture Susceptibility of SBS-Sasobit-Modified Asphalt Mixtures

Authors

• Aqeel Y. Alkhafaji, State of roads and bridges, Babylon Governorate, Babylon, Iraq AND Highways and Geotechnical Engineering Department, College of Civil Engineering, University of Technology-Iraq, Alsina'a Street, 10066 Baghdad, IraqFollow
• Hasan H. Joni, Highways and Geotechnical Engineering Department, College of Civil Engineering, University of Technology-Iraq, Alsina'a Street, 10066 Baghdad, IraqFollow
• Basim H. Al-Humeidawi, Roads and Transportation Engineering Department, College of Engineering, University of Al-Qadisiyah, Al-Diwaniyah 58002, IraqFollow

Keywords

SBS, Sasobit, Rutting, Hamburg wheel tracking test, Moisture susceptibility

Document Type

Article

Abstract

High temperatures and heavy traffic loads are major factors causing rutting in asphalt pavements. In the presence of moisture, these conditions significantly contribute to pavement deterioration, leading to moisture-related deformations. The combined impact of high hot-season temperatures and heavy traffic axle loads, especially in Iraq, accelerates rutting and reduces pavement lifespan. This study aims to assess the balanced performance of asphaltic mixtures produced utilizing a selected modified bitumen containing 3.0% styrene-butadiene-styrene (SBS) and 2.0% Sasobit wax. The modified mixture was compared with the unmodified and 3% SBS-modified reference mixtures. All mixes were designed using the Superpave methodology. The indirect tensile strength (ITS) and tensile strength ratio (TSR) tests were used to evaluate moisture resistance. Rutting and moisture susceptibility were evaluated using the Hamburg Wheel Tracking Test under submerged conditions. All mixtures, modified and unmodified, were tested at a 60°C immersion temperature with a 700 N wheel load. The results show that the mixture of 3% SBS-2% Sasobit improved permanent deformation and moisture sensitivity compared to the unmodified mixture. The rut depth decreased by 71.80, 69.20, and 68.60% for specimen thicknesses of 60, 50, and 40 mm, respectively, compared to the unmodified mix. The TSR of the SBS–Sasobit-modified mixture was 89.80%, which was higher than the unmodified mixture (86%) but slightly lower than the SBS-modified mixture (92%). All mixtures were above the minimum specification limit of 80%. The results indicate that the 3% SBS-2 % Sasobit modification offers a practical compromise among rutting resistance, moisture sensitivity, and reduced mixing and rolling temperatures, providing economic and environmental benefits through reduced energy required for mixing and emissions.

Recommended Citation

Alkhafaji, Aqeel Y.; Joni, Hasan H.; and Al-Humeidawi, Basim H. (2026) "Assessment of The Rutting and Moisture Susceptibility of SBS-Sasobit-Modified Asphalt Mixtures," Engineering and Technology Journal: Vol. 44: Iss. 11, Article 7.
DOI: https://doi.org/10.30684/2412-0758.2418

DOI

10.30684/2412-0758.2418

First Page

128

Last Page

148