Effect of Fillers on Hot-Mix Asphalt Concrete

Abstract

Different studies have shown that the properties of fillers have significant effect on the performance of HMA concrete pavements. This study was intended to investigate the effect of different types of fillers on Hot- Mix-Asphalt performance. The fillers, with different percentages (4% to 8%) by total weight of the mixture, used in the study where crushed stone dust, brick dust and fly ash passing 0.075mm sieve. Using the different types and quantity of the fillers, a number of trial mixes have been prepared using the Marshall mix design procedure to arrive at asphalt concrete mixture that fulfilled the Marshall criteria. The effects of each filler type on Marshall properties of the HMA mixtures at their individual optimum asphalt content were calculated and possible basis for difference in properties was discussed. Using the different fillers at their optimum asphalt content, sample were prepared to observe Marshall properties and moisture susceptibility of asphalt mixtures. The Marshall Immersion test method was adopted to determine the moisture effect of mixtures in the laboratory. The test results show that all types of fillers have an effect on various mixture properties. Mixtures prepared with brick dust require higher bitumen content to fulfill all the Marshall requirements. This makes these mixtures more costly practically. Higher stability values obtained by mixes with stone dust as compared to brick dust and fly ash. Higher retained stability was obtained by mixes prepared with brick dust and fly ash as compared to the widely used stone dust. From the study, similar trend of mixture properties, particularly Marshall properties were observed for mixes made with brick dust and stone dust as compared to that of fly ash. This indicates that brick dust can be used as an alternative for the widely used stone dust. Different characteristics of HMA mixtures were observed by varying the fillers in the mixture by type and quantity. This indicates that, Fillers are indicates as an important ingredient in the HMA mixture properties. From the results obtained, there is a common trend in obtaining different mixture properties with different filler content, which shows, there exists optimum filler content that based performance will be achieved. The results of this research work is hoped to be used as the basis for further investigation on the effects of fillers on HMA mixes and improve asphalt concrete mixtures as well as find alternative filler materials.