Performance evaluation of waste septage ash as filler in bitumen mixtures

Abstract This study systematically investigates Waste Septage Ash (WSA) as a sustainable filler in bituminous mixtures, comparing its performance with Municipal Solid Waste Ash (MSWA) and Sewage Sludge Ash (SSA) through comprehensive mechanical, durability, and environmental assessments. Nine performance parameters were evaluated following ASTM/AASHTO standards with statistical validation ( n = 3, ANOVA, p < 0.05). Results demonstrated WSA superiority with statistically significant improvements: 8.7 % higher Marshall Stability (11.2 ± 0.4 kN vs. 10.3 ± 0.5 kN for SSA, p < 0.01), 9.2 % enhanced ITS (950 ± 28 kPa), 86 % TSR exceeding AASHTO minimum (80 %), 12.5 % lower creep rate, and 15 % superior fatigue life (98.7 ± 4.2 × 10 3 cycles). SEM-EDS analysis confirmed continuous bitumen film formation attributed to WSA’s optimal SiO 2 /CaO ratio (3.2:1) and fine particle morphology (<63 μm). Life cycle assessment revealed 47 % CO 2 reduction and 40 % energy savings compared to conventional limestone filler. The findings establish WSA as a technically viable and environmentally sustainable alternative filler, contributing to circular economy principles and UN Sustainable Development Goals 11 and 12.