Optimizing Slurry Seal Mixtures with Different Aggregate Types: Performance, Durability, and Component Interaction Analysis

The primary objective of this study is to understand the aggregate–emulsion interaction in slurry seal coatings and to obtain cost-effective, improved performance characteristics by overcoming the restrictive effects of aggregate chemistry on workability through hybrid designs. In this study, the interactions of granite (GR), basalt (BA), and limestone (LS) aggregates with bitumen emulsion were examined; specifically, limestone-substituted designs were analyzed to overcome workability problems stemming from the high reactivity of basalt and to achieve optimum performance. Laboratory specimens were subjected to mixing time, cohesion, Wet Track Abrasion (WTAT), and Loaded Wheel (LWT) tests in accordance with the procedures specified by the International Slurry Surfacing Association (ISSA); and the effect of the determined optimum emulsion content on performance was analyzed with ±2% sensitivity. While experimental findings indicated that the predicted optimum emulsion contents for all selected aggregate types satisfied the specification limits, the mixture with 30% basalt substitution (LS70+BA30) among the hybrid designs achieved the highest design compatibility by providing an exact match between theoretical and experimental optimum points. Conversely, despite having lower design sensitivity (66.7% match), the mixture with 50% basalt substitution (LS50+BA50) offered a superior alternative for situations requiring quick opening to traffic by exhibiting 54% higher early cohesion strength (20 kg-cm) at 120 min compared to pure limestone. Statistical analyses confirmed that aggregate origin is the most determinant factor on mixing time and that the fluidity characteristic of the system is predominantly controlled by water content. Furthermore, correlation matrices demonstrated the need to optimize the liquid phase balance in hybrid designs according to aggregate mineralogy by revealing the rheological sensitivity developed by limestone towards water and granite towards emulsion. Through the study outputs, the restrictive effects of aggregate chemical content on workability—which have not been sufficiently detailed in the literature compared to the frequently discussed effects of particle size distribution and mineral filler in slurry seal mixtures—were identified, and solution strategies were developed.