Potential use of ‘Enset’ Fiber Ash as Partial Replacement of Conventional Filler Material in Hot Mix Asphalt

Abstract

A large amount of appropriate quality materials is required for road construction and maintenance work in Ethiopia. The main constituent of the bituminous paving mixes are aggregates in coarse, fine and filler fractions. In many construction sites, aggregates in different size fractions are not readily available, necessitating their procurement from long distances, thereby causing an exorbitant increase in construction costs. One of the main problems in constructing the asphalt paving mixture is obtaining a sufficient amount of filler material from crushing fine rock material and low percent using ordinary Portland cement (OPC), hydrated lime (HL) and marble dust. To overcome this problem, it is important to come across alternative filler material to address this gap using naturally available material. Currently, renewed attention has been given to the use of ‘waste’ materials instead of conventional aggregates in pavement construction. This research study was to investigate the potential use of ‘Enset’ fiber ash as a partial replacement of conventional filler material in hot mix asphalt supported by experimental laboratory investigation. In order to achieve this study, purposive sampling techniques were adopted to select the sample size and location. The study evaluated the potential of ‘Enset’ fiber ash as filler for the design of dense-graded hot mix asphalt by referencing traditional filler control mix procedures based on standard specifications, and a crush rock filler was utilized as a conventional filler material as a control for comparison. The Marshal Stability and Rutting Test (RT) was conducted to determine the HMA specimen's performance. Several HMA specimens were prepared using aggregate blend according to ASTM D 1559 with four different percentages ‘Enset’ fiber ash (EFA) of 15%, 25%, 35% and 45% filler replacement by the total filler weight used in the control mix. Specimens were prepared and test performed according to EN 12697-22 procedure-B for rutting test. All HMA properties were taken at 4% air void and determined their optimum bitumen content (OBC). Almost the same result with the control mix was observed in the study at 15% and 25% of the ‘Enset’ fiber ash (EFA) replacement. However, higher Marshall Stability, a lower void filled with asphalt, better flow, a good void in mineral were observed at 25% ‘Enset’ fiber ash (EFA) replacement. At this rate, the rutting performance is less than that of the control mix but is within the specifications of 2.78mm and 2.9 mm of rutting depth less than 6mm that is satisfy EN 13108 requirement. As a result, Enset fiber ash filler can replace traditional filler material 25% of the total filler weight used in this study. It is advised to use ‘Enset' fiber ash (EFA) as a filler material as a partial replacements in a bituminous paving mixture