AbstractIn this study, the effect of process control parameters, including aggregate gradation, emulsion content, and water content, on the rutting and bleeding characteristics of the microsurfacing mix was determined. A total of 30 combinations were selected to account for the synergistic variation of process control parameters in the field. Rutting and bleeding were assessed using a loaded wheel test and sand adhesion test, respectively. Laboratory investigations results showed that rutting was predominantly influenced by the combination of aggregate gradation and emulsion content. On the other hand, the combination of coarser gradation, higher emulsion content, and relatively lower water content led to increased risk of bleeding. Multigene symbolic genetic programming was used to model the rutting and bleeding behavior to better understand the complex behavior. The developed model was able to capture the behavior of the microsurfacing mix. A sensitivity analysis was conducted on the developed model by varying the values of input parameters one-by-one from 0.85 to 1.15 at an increment of 0.005. The results showed that the lateral displacement increased up to 1.6, 1.5, and 1.2 times the control mix for coarser aggregate gradation, higher emulsion content, and higher water content, respectively. Moreover, at the optimal emulsion content value, the lateral displacement was minimal. Sand adhesion increased up to 1.4, 1.2, and 1.1 times the control mix for coarser aggregate gradation, higher emulsion content, and lower water content, respectively. Hence, this study outcome identifies the aggregate gradation tending toward the coarser side, higher emulsion content, and variation of water content, either the dry or wet side, during production lead to poor rutting or bleeding performance of the microsurfacing mix.

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