Influence of glass fibre grid and its placement on the fatigue damage of asphalt mixture

Glass fibre grids is one of the maintenance and rehabilitation strategy used to mitigate reflection cracking in asphalt mixture overlay. Many challenges exist when quantifying the beneficial effects of glass fibre grids in laboratory investigations. Such challenges include sample preparation, spatial positioning of the grids, appropriate loading waveform, and post-processing methods to accurately characterize the beneficial effects of providing grids. Of the test methods available, four-point beam bending (4PB) comes in handy considering these factors. In the current study, a strain-controlled 4PB test is carried out with two different loading waveforms—sinusoidal and haversine, and at three different strain levels. Firstly, a new compaction procedure is developed to integrate glass fibre grids in asphalt mixtures using shear box compactor. Using such a procedure, it is shown that uniform air voids across the depth of the beam can be achieved for such grid inlaid samples. Secondly, a new fatigue failure criterion is proposed to capture the reinforcement effect of the glass fibre grid in 4PB fatigue tests. Instead of total energy dissipation corresponding to each loading cycle, the energy dissipated due to fatigue damage is used in the energy ratio expression to compute the fatigue life of asphalt mixtures. Finally, an evident influence of grids placed away from the loading axis is seen with the help of Lissajous plots, specifically at higher strain levels. The fatigue life of asphalt mixtures with grids placed away from the loading axis is found to be higher when the new fatigue failure criterion is used.