Mechanistic Analysis and Durability of Thiophene Paving Mixtures

When compared to conventional bitumen, thiophene bitumen produced in northern Iraq is abundant and inexpensive (on the order of $125\mathrm{USD}/\mathrm{t}\mathrm{on}$). This type of bitumen contains higher sulfur content in terms of the heterocyclic compound (not elemental sulfur); furthermore, long-term aging (LTA) effects are not considered in research on this type of bitumen for use in paving mixtures. In this research, the influence of LTA at $85\pm 3°\mathrm{C}$ for $120\pm 0.5\mathrm{h}$ on thiophene mix asphalt (TMA) properties in terms of stability, indirect tensile strength at 25 and 60°C, rigidity, resilient modulus, and tensile strength ratio were determined and compared with hot-mix asphalt (HMA) containing conventional bitumen. Under a 40-kN dual load with a 105 mm wheel radius, pavement responses in terms of fatigue strain ($\epsilon {\mathrm{t}}^{\max }$), rutting strain ($\epsilon {\mathrm{c}}^{\max }$), and surface deflection ($\mathrm{\Delta }{\mathrm{z}}^{\max }$) were analyzed using multilayer elastic analysis software (BISAR). The test results of TMA showed slightly higher stability, indirect tensile strength, and resistance to moisture damage (higher durability) with a slightly lower resilient modulus than HMA. Generally, results showed that the performance of TMA at a mixing temperature of 130°C is considered similar to that of HMA under the effect of LTA. Furthermore, using thiophene bitumen can reduce the mixing temperature of paving mixes above about 20°C in a manner comparable to HMA. In addition, the results also indicated that LTA-TMA showed 10% higher fatigue life than LTA-HMA. In addition, it was found that the granular base layer in the LTA-TMA pavement system can be reduced by 55%.