Moisture damage is one of the most common damages that appear in the asphalt mixtures. This damage happens
mainly due to the environmental condition that reduces the service life and the performance of the asphalt pavement. To
improve the water stability performance of asphalt mixtures, there are different materials such as fibers that could improve
the service life and quality of the pavement. In this study, 70# asphalt and AC-16 gradation were used; in addition, glass
fiber was used as a modifier in bituminous mixtures to improve the water stability performance. Glass fiber is an organic
fiber, which has high strength. Marshall Stability and Marshall Immersion tests are conducted, respectively, to calculate the
Optimum Asphalt Content (O.A.C), and the water stability, resistance of control asphalt mixture and asphalt mixture
modified with glass fiber. Results showed that the water stability resistance of a modified asphalt mixture with glass fiber is
better than an unmodified asphalt mixture after evaluating the optimum asphalt content.