Effect of Process Control Parameters on the Workability and Strength Characteristics of Microsurfacing Mix

Abstract

This study investigates the effect of production process variation on the workability and strength evolution of microsurfacing mix. Overall, 35 different mixes were produced by varying aggregate gradation, emulsion content, and water content, within the allowable limits. Results showed that when aggregate gradation was coarser, and emulsion and water content higher than the optimum, the mix failed to meet the workability criteria. However, the variation of process control parameters within the allowable limits had minimal effect on strength (cohesion). It was interesting to note that the mix failed to meet the workability limits when the water content was 1% lower than the optimum, or emulsion content was at the lower limit with finer gradation, or both. Regression models were, therefore, developed to understand the individual and interaction effect of process control parameters. Sensitivity analysis of model parameters showed that emulsion and water content predominantly influenced workability, whereas aggregate gradation had the highest impact on strength. In particular, the mix would tend to prematurely break when the total surface area (TSA) increased to 1.1 times the optimum, and emulsion and water content reduced to 0.9 times the optimum. Alternatively, if TSA is 0.9 times and emulsion and water content is 1.1 times the optimum, the mix would be too workable and could potentially lead to segregation. Findings suggested that limiting the variation of water content within ±1% of the optimum ensures acceptable workability. Further, mix with finer gradation and emulsion content on the lower limit should be avoided during production.