Systematic approach to address challenges in microsurfacing mix design

Abstract

This paper presents a systematic laboratory approach for microsurfacing mix design to address the challenges faced due to multiple components and associated chemical complexity. A comprehensive laboratory study was undertaken to understand the variation in microsurfacing mix performance with respect to filler characteristics, mineral filler and emulsion components including emulsifier dosage, asphalt binder type and solvent. First, replacement of filler was done to address the issue of pre-mature breaking which was related to very high reactivity of aggregates. Next, the type and dosage of mineral filler was selected using cohesion test. Interestingly, the combination of cement (2%) and fly ash (1%) imparted highest cohesion highlighting the benefits associated with incorporation of waste materials having pozzolanic characteristics in the mix. In terms of emulsion components, use of higher emulsifier dosage showed a delay in the curing process which in turn, resulted in inferior cohesion, raveling and rutting resistance. Further, incorporation of harder asphalt binder and the use of solvent during emulsion production resulted in reduction in rutting by>61%. Raveling resistance was also found to be dependent on the use of solvent indicating the importance of maintaining equiviscous temperature during emulsion production. From the results, a narrow range diagram illustrating the acceptable range of emulsion content considering all design parameters was recommended to determine optimum emulsion content (OEC). The mid-point of acceptable emulsion content range was termed as OEC which, in the present study, was found to be 14% by dry weight of aggregates.