The effect of nano-silica material and alkali resistant glass fibre on the OGFC asphalt mixture

The main objective of this study is to improve the physical and mechanical properties of open-graded friction courses (OGFCs). Therefore, the combination of nano-silica (NS) material and alkali resistant (AR) glass fibre was used as additives. The effects of these materials were evaluated on the OGFC mixtures by laboratory tests including draindown, cantabro abrasion test, porosity, permeability, slip resistance, indirect tensile strength (ITS), moisture susceptibility (TSR) and dynamic creep tests. Draindown tests were conducted on different mixtures including 4% NS by weight of the asphalt binder, 0.1% and 0.2% AR-glass fibre by weight of the mix and 5.5% and 6.5% asphalt binders by weight of mix. The results showed that the combination of 4% NS material, 0.2% AR-glass fibre and 5.5% asphalt binder is suitable and reduces the draindown significantly. The test results showed that, while the use of this compound in OGFC led to a reduction of porosity by only about 12%, cohesion resistance, slip resistance, wet and dry ITS and rutting resistance of OGFC were increased by about 50%, 16%, 30% and 50%, respectively. Also, due to the relatively similar effects of this combination on the wet and dry ITS, the percentage of TSR increased by a very small amount (about 3%).