Performance evaluation of asphalt concrete mixture incorporating calcite powder as filler substitute for sustainable pavement construction

Abstract

The increasing cost and paucity of conventional pavement construction materials has in recent times become very worrisome and a serious challenge in the road construction industry. This has spurred the search for a less expensive and environmentally friendly material, readily available and suitable for the purpose of constructing sustainable pavements both in the rural and urban areas of developing countries. In this research, the suitability of calcite powder in asphalt as filler in substituted proportions was investigated through tests on the modified samples for enhanced engineering properties. This was achieved by partially replacing conventional filler with calcite in proportion of “10%, 20%, 30%, 40% and 50%” respectively. After the production of the modified bituminous concrete at the various proportions, the samples produced were placed in a water bath for 30 minutes at a temperature of 60°C before conducting the Marshall stability test and flow. Marshall stability values of 37.7 kN, 37.9 kN, 34.0 kN, 35.0 kN, 28.9 kN and corresponding flow values of 12.0 mm, 11.3 mm, 10.5 mm, 9.60 mm, 10.3 mm, were obtained for the modification proportions respectively. The stability values were observed to be higher than the control mix and likewise satisfy the minimum requirement of 3.33 kN or 340 kg according to the Marshal mix design specification for wearing course surfacing. Similarly, the flow values obtained where found to be within the specified range of 8 – 17 mm at 0.25mm units. Percentage air voids (Vv) values of 3.7%, 5.2%, 4.7%, 3.0%, and 5.9% obtained where also found to satisfy the required range of 3-5% according to the specification. Voids filled with bitumen (VFB) values of 78.58%, 69.56%, 69.73%, 76.63%, and 58.93% derived where also within specified range 75 – 85 % of the specification. The X-Ray diffraction (XRD) micrograph showed the distinct presence of calcium and oxygen in the hot mix asphalt modified with calcite, while the scanning electron microscope (SEM) provided an in-depth perspective of the concrete grains in the hot mix matrix and the improved bonding of the aggregates, bitumen and calcite due the presence of calcium. The results have shown the possibility of calcite utilization in bituminous mixes, towards reducing cost of construction and best suitable for medium trafficked roads, parking lots and walkways.