Assessing performance characteristics of Modified Asphalt containing coarse grains of Gravel for use in temporary pothole patching.

Abstract

This study was carried out to assess the performance characteristics of modified Asphalt Concrete containing coarse grains of gravel for use in temporary pothole patching, as a cheaper material than granite aggregates, prepared using penetration bitumen grades (60/70 grade) and coarse grains of gravel. The bitumen was obtained from Stirling Contractors in Uganda, granite aggregates were obtained from Stirling quarry in Mukono district, and gravel was obtained from Robert Mugabi road in Mbuya, an ongoing road project in Kampala district. The coarse grains were obtained by sieving gravel and collecting the material retained on sieves of sizes of 14mm, 10mm and 5mm. The characteristics and engineering properties of the two different kinds of aggregates were determined. Granite aggregates were used as a basis and were therefore used to compare the performance of coarse grains of gravel with that of granite aggregates. Marshall Mix design was used to obtain the optimum bitumen contents for the mixes; the mixture of bitumen and aggregates, and the modified mixture of bitumen and coarse grains of gravel. The optimum bitumen content for asphalt with aggregates was obtained at 4.9% and the optimum bitumen content for asphalt with coarse grains of gravel could not be obtained because the Marshall specimens ruptured into two halves. Finally, the study shows that Asphalt modified using coarse grains of gravel cannot be used for temporary pothole patching due to the low affinity of coarse grains of gravel to bitumen, a smooth surface texture of the coarse grains, poor gradation of the material which affected the interlocking of the particles.