Abstract:
A review of recent research on bottom ash seems to indicate it has the capability to improve asphalt pavement performance when used to replace a portion of the aggregate in asphalt mixes. Bottom ash can be used as an aggregate replacement, providing a substantial savings to both highway agencies and utility companies. Bottom ash has been used as fine aggregates in asphalt paving mixtures since the early 1970's. The American Coal Ash Association reported that, over 17,200 metric tons of bottom ash was used in asphalt paving during 2006.
The research is focused on investigation of properties of bottom ash, which is the byproduct of Norochcholai coal power plant and feasibility study of use of bottom ash in hot mix asphalt concrete in Sri Lankan roads. According to the results obtained, the best mixtures are produced by blending bottom ash with well-graded, angular, rough-textured aggregate and limiting the percentage of bottom ash to 25% for wearing and 16% for binder course. Marshall Stability and flow values have been found to decrease as the percentage of Wet bottom ash is increased in the mixture.
Further, high percentage of bottom ash replacement increases optimum bitumen content, which mainly affects to high production cost. Although the cost per 1 Mt of bottom ash blended mix is higher than the conventional mix for both surface courses, its low density increases overlay area. Because of that the cost per 1 m2 is lower than the conventional mix. The successful use of bottom ash in asphalt pavements in Sri Lanka would provide not only significant economic savings but also an environmental friendly solution for a waste material.
