Investigation on material quality of asphalt layer in jimma town road project

Abstract

Roads contribute to regional cohesion by playing a prominent role in the geographic distribution of economic growth and wealth. Generally, zones with high job densities are located near major road arteries because of the businesses' need for easy access to suppliers, customers and employees. Those roads may construct either in Flexible pavement or rigid pavement. Flexible pavement is one of the most important infrastructures that involve multiple layers of different materials subjected to non-uniform traffic loadings and varying environmental conditions. The repetitive traffic loadings that the road experiences during its service life, combined with temperature fluctuations, cause rutting, fatigue and other forms of deteriorations, which ultimately degrade the performance and durability of pavement structures. Both traffic volume and loads are increasing from year to year with rapid rate. This study emphasizes on the material quality of asphalt layer which is constructed in Jimma town, either the failure due to material quality or due to construction management which is workmanship, leadership problem. From this point of view the main objective of the research is to investigate the material quality of asphalt layer. According to test procedure specified by ASTM D1559 several hot asphalt mixture were prepared, the aggregate blend made by Job mix formula to obtain the percentage of mix material is give Hot-bin one is 26%, Hot-bin two is 23%, and Hot-bin three 51% where hot-bin one is (20-13.2mm), hot-bin two (13.2-5.0mm) and hot-bin three (5.0-0.00mm). The result of Marshall Test on mix design for hot asphalt mixture, for wearing coarse were conclude that the material used for mix design is good, which gives Marshall stability, 12.57 KN with optimum bitumen content of 5.2% (by weight of total aggregate). Hence the quality of aggregate is good but the influence of other factors such us poor drainage courses, level of ground water table, Varity of geological materials along the road rout and poor construction methodology caused the defect. The flow result of the Marshall mix design gives as 3.6 % which is approach of upper limit of specification 4%, So when flow become high in the mix it result long term deterioration of asphalt performance, hence the pavement condition along the study area has been affected by different failure types such as cracks, surface defect and disintegrating from site observation may result of this. Finally a possible remedial measure is recommended for every observed result is to minimize the value of the flow in the Marshall mix design either by minimizing the bitumen content or adding additional filler to the hot-bin material and failures or distress on the pavement condition of the study area in order to sustain the design life of the pavement.