Performance evaluation of fog seals on chip seals and verification of fog seal field tests

With an increasing emphasis on pavement preservation treatments due to economic concerns over the high costs of paving materials, one of the most cost-effective pavement preservation treatments, chip seals, now constitutes a significant proportion of the pavement preservation treatments used in the North Carolina highway network. To mitigate a major problem with chip seals, i.e., the loose aggregate particles, fog seals, which are composed of an emulsified product placed on top of the chip seal, can be used to help control the loose aggregate. For this study, fog seals were applied on top of newly fabricated chip. The surface texture of the fog-sealed chip seals was analyzed using the British pendulum test and a three-dimensional laser. Also, fog seal field test methods that were developed to suggest appropriate traffic opening times after fog seal construction were verified. The main findings presented in this paper are that: (i) the use of polymer-modified emulsions improves fog seal performance in terms of better aggregate retention and bleeding resistance; (ii) the skid resistance problems are not evident once the fog seal is applied on the recommended chip seal type; (iii) the relationship between skid number and mean profile depth can be determined based on three trends that are dependent on traffic loadings, and (iv) although the fog seal field tests were unable to be completed due to safety concerns, it can nonetheless be recommended that approximately 60 min after fog seal construction is an appropriate traffic opening time.