Investigation of the rutting potential and moisture susceptibility for open graded frictional courses
Aboke, Derrick Okecho
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Open-graded asphalt friction course (OGFC) is an open-graded Hot Mix Asphalt (HMA) mixture with interconnecting voids that provides improved surface drainage during rainfall. The rainwater drains vertically through the OGFC to an impermeable underlying layer and then laterally to the day lighted edge of the OGFC. In addition to minimizing hydroplaning potential during rainfall and providing improved friction values on wet pavements, the OGFC offers the following advantages compared to other dense-graded surfaces: (a) reduced vehicle splash and spray behind vehicles, (b) enhanced visibility of pavement markings, (c) reduced nighttime surface glare in wet weather, and (d) reduced tire-pavement noise. The emphasis of this research was therefore based on its possible application in Uganda to improve on the performance of the HMA present. This research focused on mainly the rutting and moisture susceptibility of the different materials that can be used in road construction. To establish a correlation between the volumetric properties of the material to deduce rutting and also to see the materials that are more susceptible to moisture damage. This was executed using the Marshall mix design method. This was conducted using different aggregates (Limestone, Quartz and granite) obtained from Kasese, Mukono and Kakiri respectively. Different bitumen grades (60-70 and 80-100) obtained from Stirling construction company limited. The materials were then subjected to tests so as to deduce the aggregate and bitumen characteristics. Preliminary tests were then carried our according to Marshall procedures stipulated in standards ASTM D 1559 while varying the bitumen contents. The different aggregate mixes with different grades were subjected to Tensile strength ratio.