Effect of using sewage sludge ash on the fatigue performance of mastic and asphalt mixture

The sewage sludge ash (SSA) produced from incineration of this waste can be used as a recycled material within various industries, including construction sector, enabling the mitigation of numerous environmental and economic issues. Nowadays, despite progressive adoption of SSA in pavement industry, lack of technical data mandates further investigation to capture its overarching properties. This study evaluates the effect of replacing fine aggregates (passing sieve No. 50) with SSA at four weight percentages (25 %, 50 %, 75 %, and 100 %) on the fatigue performance of mastic and hot-mix asphalts (HMAs). Also, granite and bitumen with PG 58–22 were used to prepare mastic and mixture samples containing varying SSA percentages. Dynamic shear rheometer (DSR), linear amplitude sweep (LAS), and indirect tensile fatigue (ITF) tests were conducted to determine the rheological properties of the mastic (fatigue parameter) and the fatigue life of HMAs and mastics at 10°C and 20°C. The results demonstrate that incorporating SSA and increasing its weight percentage enhances the fatigue life of both mastic and HMA samples. It has been observed that replacing 100 % SSA on average doubles the fatigue life of mastic and increases the fatigue life of the mixture by up to 90 %. Additionally, SSA reduced the fatigue parameter of the bituminous mastic, indicating improved fatigue resistance. Mastic samples containing 100 % SSA exhibited 22 % lower ( G * × sin δ ) compared to the control samples, attributed to a significant reduction in δ . Furthermore, Statistical analysis revealed that 100 % SSA replacement with fine aggregates yielded the best performance in enhancing mastic fatigue life, mixture fatigue life and mastic fatigue parameter ( p -value<0.05). Moreover, increasing the test temperature from 10°C to 20°C did not significantly alter the fatigue performance of the mastic and the mixture containing 100 % SSA, indicating that SSA plays a key role in reducing the bitumen's temperature sensitivity. In addition, correlation analysis of test results showed that the results of the LAS test exhibited better alignment with ITF test outcomes compared to the DSR test, confirming the LAS method’s stronger relevance to field performance (R 2 =98 %). Overall, this approach highlights SSA’s potential as a sustainable and practical material in pavement engineering.