Comparative Laboratory Study on Fly Ash and Wood Ash as Filler Material in Hot Mix Asphalt
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Date
2016-06
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Addis Ababa University
Abstract
Mineral fillers have crucial effect on the mechanical property of asphalt concrete pavements. Some of the newly constructed highway pavements in Ethiopia have shown failures with consequential negative impacts on roadway safety, performance and economy. Fillers materials suspected to be one of the major contributors to these failures. This research is focused on the investigation of two types of mineral fillers effects in hot-mix-asphalt performance. The mineral fillers that were used for the study are crushed basaltic rock, fly ash and wood ash with different percentage by total weight of the mixture. A detailed laboratory study was carried out by preparing asphalt mixtures specimens using aggregates and (85/100) grade bitumen collected from Akaki new asphalt plant, and two different types of fillers (wood ash and Fly ash) were tested in the laboratory. Marshall Mix design test was conducted using all types of fillers and different content to evaluate the Marshall properties of different types and filler quantities in the asphalt mixture. Three different trials had been prepared with three filler types at different content.
The results of this study indicate that the traditional filler material (Crushed Basaltic Rock) fulfills all the design requirements at 7.85% filler content. This implies that Crushed Basaltic rock which has being used as a filler material in hot mix asphalt has a good performance in the construction of bituminous pavements in Ethiopia. Similarly comparing of fly ash with Crushed Basaltic rock, it has relative and optimum Marshall Property that fulfills design requirements. Therefore overlooking of the test result of fly ash it has a good Marshall test result as the traditional filler material which indicates it can be used as a substitute filler material in Asphalt paving.
On the other hand wood ash shows inconsistent test results of Marshall Property comparing with other filler materials. Even if higher bitumen content is consumed in the specimens, the VFA value for the wood ash is less compared with the basaltic rock filler and fly ash. Similarly the VMA, Stability and Bulk Density are very low in comparison with the other mineral filler materials. The consistent Marshall Property result for wood ash is the flow which increases its value with the increment of bitumen content. But wood ash at 7.85% and 7% of filler content, it fulfills the design requirements of asphalt pavement construction even if the VFA value is at the lowest margin at 7%. Generally the test result for wood ash entails deep investigation shall be deemed to increase the Marshall Properties in advance to provide durable pavement construction. Considering their cost AC prepared by the Fly ash and Wood ash filler materials have less cost than the traditional filler. But comparing the two new filler types Wood Ash have a higher cost of construction than Fly Ash at 7.85% of filler content since its lesser cost than 7% filler content for both types of the new filler materials. Therefore this research work is hoped to be used as a basis for future studies about different types of mineral fillers in provision of strong durable bituminous pavements from industrial and household waste materials.
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Road and Transport Engineering