Modeling the effect of environmental factors on evaporative water loss in asphalt emulsions for chip seal applications

This paper proposes a methodology to determine the total amount of evaporative water loss of an emulsion before the aggregates are placed. An algorithm is presented that can be used by field inspectors and practitioners for the optimal timing of chip placement.Evaporation of water from the emulsion was modeled as a two stage process. The first stage involves the emulsion losing water as it cools down from its application temperature until it is in a state of thermal equilibrium with the surrounding environment while the latter involves determining the amount of moisture loss due to the vapor pressure deficit in the ambient air and the turbulence in the surrounding environment. Finally, based on the observations from field construction programs, moisture loss thresholds were determined to calculate the optimal time to place the aggregates.

► The rate of evaporation varies as the square of the water in the emulsion.
► The VPD and wind speed has a significant effect on the rate of evaporation of water.
► The timing of aggregates for cationic emulsions corresponds to 20% removal of water.
► The timing of aggregates for anionic emulsions corresponds to 3% removal of water.