An evaluation of the usability of glass and polypropylene fibers in SMA mixtures

Abstract

The use of stone mastic asphalt (SMA) is generally preferred to combat the undulation problem of roads due to wheel rutting, which is considered to be the most serious deterioration of road superstructure under heavy vehicle loads and thermal conditions. This type of mixture has a high level of aggregate interaction and interlocking effect with a high bitumen ratio in order to increase the lifetime of pavements. Commonly, polymer modified bitumen or cellulosic fiber additives involving a bitumen modification process is favored during the application. In this study, the usability of mixture modification was investigated by adding glass and polypropylene fibers directly into the dry mixture, unlike bitumen modification process that is requiring two mixing stages. In total, 169 specimens were prepared using a gyratory compactor according to the superpave design method. Of these specimens, 120 were fiber added samples with a ratio from 0.1% to 0.8% by dry weight aggregate. The draindown resistance, resilient modulus and water susceptibility including indirect tensile strength values, were improved by the addition of glass and polypropylene fibers according to experimental results within a range of 0.6% to 0.8% generally. However, calculated strain results show that satisfactory creep values could not be obtained in terms of static and dynamic uniaxial tests. Despite the fact that higher displacement occurred, reflecting cracks were eliminated owing to ductile behavior.