POTENTIAL USE OF 'ENSET' FIBER ASH AS PARTIAL REPLACEMENT OF CONVENTIONAL FILLER MATERIAL IN HOT MIX ASPHALT

Abstract

The main problems in road construction and maintance work in Ethiopia  availability of a large amount of appropriate quality materials in road construction sites, aggregates in different size fractions are not readily obtainable, 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 investigates 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 of ‘Enset’ fiber ash (EFA) of 15%, 25%, 35% and 45% filler replacement the total filler weight used in the control mix. Specimens were prepared and tests 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 satisfies the EN 13108 requirement. As a result, Enset fiber ash filler can replace traditional filler material up to 25% of the total filler weight used in this study. It was recommended to use ‘Enset' fiber ash (EFA) as a filler material as a partial replacement in a bituminous paving mixture up to the specificed percentage by weight replacement.