The effect of cow dung ash and banana peels ash as a filler on marshall and volumetric properties of hot mix asphalt

Abstract

Increased cost of construction materials for flexible pavements has urged researchers to opt for alternative filler materials instead of the conventional cement filler towards greener materials. In this work, cow dung ash (CDA) and banana peels ash (BPA) were investigated as potential substitutes at varied percentage filler contents. The first approach involved replacing the 4 % cement filler content with 25 %, 50 %, 75 % and 100 % with either BPA or CDA filler materials in the Hot Mix Asphalt (HMA). Secondly, the cement filler material within the prepared HMA was fully replaced with either BPA or CDA filler materials at varied amounts of 2 %, 4 %, 6 % and 8 % each. Marshal and volumetric properties including voids in the mix, flow, voids in the mineral aggregate, stability, and voids filled with bitumen in both scenarios were evaluated. Indirect tensile strength (ITS) was obtained for the full cement filler material replacement condition. For partially replacing the cement filler material, optimum parameters were revealed at 50 % CDA and 50 % BPA. For 50 % CDA, voids in the mix, voids in the mineral aggregate (VMA), voids filled with bitumen (VFB), stability and flow were 4.4 %, 16.2 %, 72 %, 16.7 kN, and 3.6 mm respectively. Meanwhile, for 50% BPA, voids in the mix, VMA, VFB, stability and flow were 4.4 %, 16.1 %,72.7 %, 10.63 kN and 3.37 mm. On the other hand, optimum parameters for fully replacing the cement filler material were obtained at 4 % CDA and 4 % BPA. For 4 % CDA, voids in the mix, VMA, VFB, stability and flow were 3.89 %, 16.9 %, 77 %, 13.9 kN, and 3.61 mm respectively. Meanwhile, for 4% BPA, voids in the mix, VMA, VFB, stability and flow were 4.06 %, 16.98 %,76.08 %, 10.7 kN and 3.31 mm. An ITS of 93 % and 98 % for 4 % CDA and 4 % BPA were noted respectively. From the test results, the developed CDA and BPA materials met the Uganda MoWT general specifications for roads and bridges for lighter traffic loading less than 1x106 Equivalent standard axle (ESAS). Thus, the green filler materials portrayed a viable potentiality to substitute the cement filler in the HMA which fosters reduction in the overall cost of road construction materials. This will have a positive impact on the Sustainable Development Goals, specifically targeting SDG 9 (pertaining to Industry, Innovation, and Infrastructure), SDG 11 (focusing on Sustainable Cities and Communities), and SDG 13 (centered around Climate Action).