Enhancing mechanical properties of hot mix asphalt with olive kernel ash: A sustainable modifier

Abstract

The use of agricultural waste as a sustainable modifier with functional and environmental advantages has grown appealing. While conventional modifiers offer several benefits, utilizing biological modifiers generated from agricultural resources like ash can be more effective in both technical and economic aspects. This study examines the performance of hot mix asphalt (HMA) containing modified bitumen with olive kernel ash (OKA) collected from an olive canning factory. To accomplish this goal, the modified bitumen was subjected to kinematic viscosity testing and Fourier-transforms infrared spectroscopy (FTIR) analysis to assess its chemical characteristics. Additionally, the following tests were performed on HMA: Marshall, resilient modulus, indirect tensile strength, repeated load axial creep, and semicircular bending test. Research findings reveal that the addition of 20 % OKA increases the resistance to rutting by more than 1.3 times. This is attributed to the stiffening capabilities and high density of OKA within the bitumen mixture. Reducing the moisture sensitivity of the modified mixtures, especially in the samples containing 10 % OKA, is attributed to the reduction of air voids and the improved bonding between the bitumen and aggregate. This is due to the OKA's more absorbent and reactive surface. Furthermore, fatigue analysis at intermediate temperatures showed that limiting the OKA dosage to 5–10 % can increase resistance to fatigue cracking by 11 %. Additionally, incorporating OKA at 5 % and 10 % doses into modified asphalt mixtures significantly improves fracture energy and stress intensity factors by up to 24 %. However, when the OKA dosage exceeds 10 %, a decline in performance is observed at low temperatures. In summary, according to the desired performance and workability, OKA is considered a viable alternative for bitumen modification with technical, economic, and environmental goals.