Effect of Electrical Surface Charge on Seal Coat Curing and Aggregate Loss Performance

Abstract This study presents quantifications of the electrical interactions between aggregates and emulsions using zeta potentials and evaluates the interaction influence on seal coat curing and aggregate loss performances. Three emulsions and seven aggregates consisting of CRS-2P, RS-2P, and AE-90S for emulsions and Trap Rock, Sandstone, Blast Furnace Slag, Steel Slag, Limestone, Dolomite, and Crushed Gravel were used for the zeta potential for electrostatic interaction, the water content test for the curing performance, and the sweep test for aggregate loss performance. All aggregates and emulsions showed positive zeta potentials at a low pH and negative zeta potentials at high pH with the exception of Blast Furnace Slag, which exhibited negative zeta potential values regardless of pH levels. This observation confirms that the zeta potential sensitively varies with the pH of solution. Conclusively, the electrical surface charge of an aggregate in emulsions varies with the type of emulsion. CRS-2P presented the fastest water evaporation among the three emulsions, which confirms that cationic emulsions show fast curing due to a negatively charged existing pavement surface, in general, like a felt disk used in this study. Another observation made from the water content test is that Limestone aggregate can slow down the water evaporation rate in CRS-2P. RS-2P and AE-90S show similar retardations, but they are statistically insignificant. It should be noted that there was no electrostatic attraction among the emulsions and Limestone based on the zeta potential test results. However, the electrostatic interaction between CRS-2P and Limestone has the smallest repulsion among Limestone with the emulsions. This study also showed that the electrostatic interaction and aggregate loss performance had a poor correlation (R2 = 0.3212), which may lead to a conclusion that repulsion and attraction between emulsion particle and aggregate particle does not significantly affect the aggregate loss performance of seal coat.