PERFORMANCE AND LIFE-CYCLE COST ANALYSIS OF HYBRID WASTE-MODIFIED ASPHALT CONCRETE

• Engr. Ayoade M. Ajani

• Prof. Olugbenga J. Oyedepo

• Prof. (Mrs.) Bamitale D. Oluyemi-Ayibiowuwu

• Dr. Oladunni. O. Alabi

  federal university of technology akure

• Engr. Oladapo J. Omomomi

  Federal University of Technology Akure

The increasing demand for sustainable pavement materials has necessitated incorporating waste-derived modifiers to improve performance while reducing environmental impact. This study investigates the mechanical performance and life-cycle cost implications of asphalt concrete modified with lignite, waste polythene (WPT), and worn-out tyre rubber (WOT). Asphalt mixtures were produced with varying proportions of modifiers, and their performance was evaluated using Marshall stability, flow, indirect tensile strength (ITS), rutting resistance, and fatigue tests. The results indicate that the best-performing mixture within the investigated range (7% bitumen, 2% lignite, 2% WPT, and 5% WOT) achieved a Marshall stability of 11.38 kN, representing a substantial improvement over the control mixture, while maintaining a balanced flow of approximately 3.73 mm. The mixture exhibited a 56.5% reduction in rut depth (from 6.2 mm to 2.7 mm) and a 121% increase in fatigue life (from 4.8 × 10? to 10.6 × 10? cycles), indicating enhanced resistance to permanent deformation and cracking. A 20-year deterministic life-cycle cost analysis (LCCA), conducted using a 10% discount rate, showed that although the hybrid mixture incurred a 1.68% higher initial construction cost (?90.10 million/km vs ?88.61 million/km), it resulted in a 22.2% reduction in maintenance cost. This led to a total life-cycle cost reduction from ?108.02 million/km to ?105.20 million/km, corresponding to a net saving of ?2.82 million/km (approximately 2.6%). The findings demonstrate that hybrid modification of asphalt concrete using locally available waste materials significantly enhances mechanical performance and provides measurable long-term economic benefits, making it a viable and sustainable option for road construction in Nigeria.

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