Case study evaluation of selected binder course asphalt concrete used in road construction in Nigeria

This study evaluates asphalt concrete (binder course) being one of the components of flexible pavement to determine the quality grade of asphalt used in construction in line with the Nigeria General specification (NGS). Compacted binder course samples were collected from three selected asphalt plants in Akwa Ibom State and subjected to bitumen extraction, Marshall Stability and flow test. Characterization of materials was carried out in line with requisite standard and specification for binder course. Statistical data analysis tool (minitab and Microsoft excel 2013) was used to validate the relationship between bitumen content and other related variables. The results indicate that more than 95 % samples satisfied the requirement of Marshall Stability, flow and bitumen content, based on the NGS for roads. The results of multiple regression models and analysis of variance as well as the relationship between the experimental and predicted outcome of bitumen content indicate that stability and flow cannot be used in predicting the optimum bitumen content yields. Also, the relationship between bitumen content and other related Marshall variables show that these variables should be carefully monitored during Marshall Stability for optimum design. The scan electron microscopy results revealed voids in compacted specimen. This study has shown that microanalysis through SEM is significant and should be incorporated into pavement evaluations in addition to conventional material characterization and various physical and mechanical quality control tests.