Effect of carbon fiber additive on properties of open-graded asphalt concrete mixtures

Open graded asphalt mixes have become widespread in some countries because of its property on the drainage of runoff water, especially that one of the most important problems facing impermeable paving is how to control runoff water. In addition to its other advantages such as traffic safety (high resistance to skidding), reducing the ambient temperature in the city, in addition to controlling noise pollution. However, it has some disadvantages, of which low stability, high stripping, and moisture susceptibility. The research specifically aims to study the effect of carbon fiber addition on the volumetric and mechanical properties of open graded mixture and make a comparison between modified and control mixtures. One type of (12.5 mm NMAS) aggregate gradation, (40/50) penetration grade, and Portland cement filler are used for preparation the open-graded asphalt mixes. The carbon fiber is added by three percentages (0.2, 0.3, and 0.4%) by the weight of asphalt. The design of the asphaltic mixture is conducted based on the main criteria of the open graded mixes as air voids, permeability, draindown of asphalt in addition to Cantabro abrasion resistance. The optimum asphalt content was determined as 5.2%. Other properties of open-graded mixtures, such as indirect tensile strength (ITS), moisture susceptibility, Marshall stability, and flow were evaluated. Overall, the addition of carbon fiber leads to an enhancement in the characteristics of the open-graded asphalt mixes. Nevertheless, when the carbon fibers with (0.2, 0.3, and 0.4) % is added, there is an improvement in Marshall parameters means stability increasing and a decrease of flow. Also, a slight decreasing is noticed for permeability and air voids. For Cantabro abrasion loss (aging and un-aging condition), the abrasion resistance is increased by addition of carbon fiber, the drain down of asphalt is decreased from original mixture. Finally, the moisture sensitivity is improved with adding carbon indicating that modified mixes becomes more resistant to water damage.