Evaluation of coal ash use as an adhesion improver in asphalt mixtures

ABSTRACT The presence of moisture in asphalt mixtures interferes in the adhesion between the asphalt binder and the aggregates, as well as interferes into the asphalt binder film itself causing cohesive failure. This work evaluated the use of coal ashes as a bonding improver in asphalt mixtures, comparing this material with hydrated lime and stone powder. A total of 36 ash samples were collected at the UTE Energia Pecém/São Gonçalo do Amarante-CE, and a chemical characterization was performed using the X-ray fluorescence. It was found that about 68% of the ashes belong to class C, the remainder of the ashes being framed in class F. In the evaluation of the moisture damage resistance, through the Lottman test, it was verified that the use of 4 % of ash in the asphalt mixtures generated results similar to those found for the asphalt mixture containing natural filler. The use of the ashes combined with lime led to an increase in resistance to moisture damage. It is emphasized that the fact that some ashes belong to class C or F, or even that some ashes are more alkaline than others, did not necessarily lead to significant gains in the moisture damage resistance.