Phosphate Waste in Mixtures to Improve Their Deformation

Abstract

The objective of this research is to investigate the deformation behavior of asphalt concrete mixtures containing four phosphate waste fillers (12.7-mm reject, 4.5-mm reject, slime, and phosphogypsum) as compared to the behavior of a standard mixture containing limestone filler. The Marshall test results revealed that, generally, there was improved Marshall characteristics for the mixtures containing these wastes when compared to the standard mixture. The immersion wheel tracking machine results revealed that the 12.7- and 4.5-mm reject fillers increased resistance to deformation by 2.2 and 1.5 times, respectively, as compared to the standard mixture. As measured by the immersion wheel tracking machine, the effect of water on the slime and phosphogypsum indicated poor behavior of the mixtures containing both fillers. It is recommended that the slime and phosphogypsum fillers should not be used in wearing course mixtures. It was further concluded that the Marshall test method provided misleading conclusions with respect to the effects of water on the mixtures containing slime and phosphogypsum fillers and in terms of ranking mixtures in the order of their ability to resist deformation.