Refining Particle Size Specification for Asphalt Emulsion

Pavements begin to deteriorate as soon as they are constructed, and traffic is released. The rate at which a pavement deteriorates depends on the material quality, the environment, and the loads carried. To properly preserve pavements and extend their life, various pavement preservation treatments are used. For flexible pavements, a considerable number of these treatments use asphalt emulsion (which are refer to simply emulsions from here on). Emulsions are classified based on their particle charge and reactivity. Emulsions used in chip seals are usually of rapid set reactivity and are classified based on tests over fifty years old. It has been shown that particle size has an influence in rheology and stability ofemulsions. Preliminary particle size specifications have been developed based on only Cationic Slow Set (CSS) and Cationic Medium Set (CMS) emulsions. Therefore, there is a need for a particle size standard specification for asphalt emulsions that encompass Cationic Rapid Set (CRS) with additives such as solid polymer and latex polymer. This research links particle size metrics such as mean, D10 (particle size at which 10% is smaller than), D50, D90 and span, to an existing performance test – the sweep test- for chip seals (CRS-2, CRS-2P and CRS-2L asphalt emulsions). In addition to this performance test, it has been shown that the particle size distribution correlates to viscosity, which is one of the few rheological tests currently run on asphalt emulsions. In this research, the moderate correlation between storage time, viscosity and particle size led to develop a specification for CRS-2, CRS-2L and CRS-2P. Based on this analysis, a mean particle size of 1.9 μm for CRS-2, 3.0 μm for CRS-2L and 10.7 μm for CRS-2P are recommended