A study on the effects of aggregate shape and percent embedment on chip seal performance via image-based finite element analysis

Chip seals are mostly designed on the basis of empirical methods, which fail to account for the effect of microstructural factors (i.e. percent embedment of aggregates and aggregate shape) on chip seal performance. Two-dimensional (2-D) viscoelastic Finite Element (FE) analyses coupled with laboratory-based sweep tests as per ASTM D7000 were performed to evaluate the impact of such factors on the performance of chip seals. The factors considered in this study were percent embedment, two different aggregate shapes (cubical and flaky), temperature, and aggregate application rates. The 2-D FE models were developed from actual images of the chip seal specimens with cubical and flaky aggregates. The analyses revealed that the maximum tensile strain at the aggregate-binder interface for the chip seals with cubical aggregates follows an asymptotic trend after the percent embedment level of 50%. The trend was not evident in the case of the chip seals with flaky aggregates. The FE simulations also indicated that the chip seals with cubical aggregates outperformed the chip seals with flaky aggregates, which was also observed through the laboratory tests. Furthermore, it was determined that excess aggregate application rates, i.e. higher than that of the optimum design rates, are detrimental to the chip seal performance.