An investigation into the adhesion of fiber-reinforced bitumen to aggregates by using pull-out test

Using fibers to reinforce bitumen is a new method to improve mechanical properties of asphalt-concrete. Economical competitive advantages, easy to work and improvement of physical and mechanical properties are the benefits of reinforcing asphalt-concrete by using fibers in comparison with other modifiers, e.g. polymers. This paper investigates the adhesion of aggregates to fiber-reinforced bitumen. This concept has been described in two parts including theoretical and experimental sections. In the former section, pull-out force of aggregate through a fiber-reinforced bitumen has been modeled by using "force-equilibrium method" and "slippage theory of short fiber composite theory". In the later section, polypropylene and polyester fibers of 12 mm length at 0.1%, 0.2% and 0.4% were used to reinforce 60-70 bitumen. Both of lime and quartz aggregates were considered in experimental design. Consequently, the instron tensile tester was modified to perform pull-out tests. Pull-out test measured the force required to pull-out the aggregate through the bitumen and/or fiber-reinforced bitumen. The experimental results showed that the proposed model can predict the pull-out force of fiber-reinforced samples.