Improving Highway Surface Course Properties of Asphalt Concrete for Heavy Traffic Loading using Mineral Fillers

Abstract

Failure signs seen on both rigid and  flexible pavement as distresses is most often instigated by mix properties of the surface due to many factors. Traffic loading, Stripping or raveling is another possible cause of such effects. Stripping occurs when poor adhesion between asphalt cement and aggregate allows the aggregate at the surface to dislodge. As a result, mineral fillers in hot-mix asphalt concrete to obtain certain desirable properties has been practiced and they have improved mix design properties- particularly Density and stability. It is on this basis that this research attempts to show the impact of Fly Ash (FA) and Portland cement (PC) on the Mix Design properties of asphalt concrete, which will serve as basis for the use of such materials in pavement construction. An experimental approach was adopted to achieve this goal using the Marshal Mix design method to prepare representative samples. Stability was obtained using the Marshal apparatus, while the Asphalt Institute Model was used to obtain mix design properties, such as stability, density, flow, air voids, obtained from the modified HMA concrete was better than that of the conventional (unmodified) HMA concrete due to the addition of Fly Ash and Portland cement. However, 3.0% Portland Cement and 1.5% Fly Ash content by weight of aggregates is the threshold content to attain maximum values of stability and Density as part of the Mix Design properties considered; obtained from the modified HMA concrete significantly improved upon addition of PC and FA respectively. However, while the stability increases linearly with increasing PC content, the filler must not exceed 3.0% by weight of aggregates in order to achieve maximum strength and improved density that this study considered.

Keywords: Portland Cement, filler, Asphalt Concrete, Stability, Density, Modified and Mix Design Properties