Abstract
Increase in urbanization necessitate infrastructural facilities among which is road development. However, the use of limited and non-renewable constituents’ materials such as bitumen, aggregate and filler leads to increasing cost of road construction, maintenance and rehabilitation. Thus, exploitation of alternative material (waste or by-products) that can improve the properties of pavement is important. The physical properties of steel slag (SS), aggregate and bitumen was analyzed, while the chemical composition of SS was determined with the aid of X-ray diffraction and X-ray fluorescence. A cylindrical sample of the composite mixture of asphalt concrete was produced using varying proportion of steel slag (SS) at 2%, 4%, 6% and 8% to partially replace the conventional aggregates. Marshall Stability and flow test was performed on the sample produced, while the microstructural analysis of the sample was done using Scanning Electron Microscope (SEM). The marshal stability values obtained were 7.45 KN, 7.75 KN, 8.63 KN, 9.82KN and 11.0 KN for 2%, 4%, 6% and 8% replacement with SS. Comparing with criteria for the Marshal mix design method provided by Asphalt Institute (1997); 4%, 6%, and 8% of SS can be used as coarse and fine aggregate in heavy traffic roads while 2% is appropriate for medium traffic road. Hence SS can be used as partial replacement of aggregate (coarse and fine) in asphalt concrete to improve the performance of the mix and reduces the cost of road construction.

Key words: Asphalt concrete, Conventional aggregates, Marshal Stability, Pollution control and Steel slag.