| dc.description.abstract | With South Sudan embarking on the development of the road network to improve its growth and economy, the need to use asphalt pavements has been on the rise. However, various pavement failures have been observed throughout the country such as rutting, fatigue cracking, potholes, and thermal cracking. These pavement failures have been as a result of several factors such as the high temperatures, vehicular load variations, poor mix design and poor drainage. Therefore research is required to determine how best to improve the pavements across the country due to increasing load variations, and the ever changing climatic conditions with very extreme temperatures.
The use of conventional bitumen across the country hasn’t yet proved effective over the past few years. This has brought the need to have a bitumen type that can handle the conditions within the country. The use of a polymer modified bitumen binder to address the above problems has been the basis for this research. Polymer modification with ethylene vinyl acetate (EVA), and styrene-butadiene-styrene (SBS). The project focused on the use of EVA as the PMB used to compare results with the conventional bitumen used in South Sudan projects.
The tests done include the penetration test, the softening point test, the Marshall Stability and Flow test and the Indirect Tensile Strength Test. Other volumetric properties of the asphalt were carried out such as bulk density, theoretical maximum specific gravity (GMM), VIM, VMA, and VFB. These however have had various results that shall be discussed in this report.
Conventional bitumen and PMB were heated in the oven and the rheological properties of softening point (ASTM 36-70) and penetration at 25 tests (ASTM D5-86) were carried out accordingly. The results showed that the decrease in penetration (below 40mm for PMB and above 50mm for bitumen) and increase in softening point (above 700C for PMB and less than 500C for the bitumen) for the PMB over the conventional bitumen can be attributed to the elastomeric and elastomeric characteristics of EVA. The conventional bitumen was gotten to be 50/60 grade.
The Marshall Stability was found to be higher for PMB at a higher bitumen contents that is 4% to 5.5% and lower at the 3.5% PMB content. The values for the stability however are lower with an increase in the bitumen content for both the PMB and the conventional bitumen. Therefore, the cohesion which gives the asphalt more strength can best be achieved by the use of PMB. On the other hand, the Marshall Flow for PMB was found lower than that for conventional bitumen but there is a rise in the flow for the PMB at 5% and 5.5% as compared to the conventional bitumen used.
The Indirect Tensile Strength Test showed that PMB has a higher strength than the conventional bitumen both at dry and wet conditions. However there is a gradual decrease in the strength of the wet samples for both the PMB and the conventional bitumen. | en_US |
