A Study on Development in Engineering Properties of Dense Grade Bituminous Mixes with Coal Ash by Using Natural Fiber

Coal-based thermal power plants in India produce significant waste, primarily fly ash and bottom ash, which poses environmental and health risks when disposed of in large quantities. This research explores the effective use of these waste products in bituminous paving mixes, substituting natural aggregates to conserve resources. Dense-graded bituminous macadam (DBM) specimens were prepared using natural coarse aggregates, bottom ash as fine aggregate, and fly ash as filler, with sisal fiber as a reinforcing additive. Varying percentages (0–1%) and lengths (5–20 mm) of SS1 emulsion-coated sisal fiber were tested to optimize the mix’s engineering properties. VG30 bitumen, chosen for its superior Marshall characteristics, resulted in an optimum binder content of 5.57%, fiber content of 0.5%, and fiber length of 10 mm, achieving a Marshall stability of 15 kN. Additional performance tests, including moisture susceptibility, indirect tensile strength (ITS), creep, and tensile strength ratio assessments, confirmed that the coal ash and sisal fiber mix significantly enhances pavement durability. This approach offers an eco-friendly and economical solution for bituminous pavement construction, addressing coal ash disposal challenges and conserving natural aggregates.