Weather effect on the quality of a seal coat
Cool air or pavement temperatures (under 55°-60° F) can affect the binding characteristics of the asphalt by making it less tacky (sticky) and/or increasing its viscosity. This can result in a poorer bond between the existing pavement, the asphalt, and the rock. Further, it can reduce the embedment of the rock into the asphalt. In either case, it can result in extensive rock loss. A moderate increase of the asphalt application rate in cooler conditions seems to improve the rock retention. An asphalt with some petroleum solvent (cutter) remains tackier in these cooler conditions. However, with the higher shot rate and the cutter, there is the possibility of fl ushing or bleeding when the weather warms.
Sealing in hot weather (air temperatures of 90° F and higher) can also create some construction problems with a seal coat. Pavement temperature can be 150° F or higher. At these elevated temperatures, the asphalt is less viscous (more fl uid) and does not have its full strength (adhesiveness). This is particularly true with the cutbacks. The cutbacks contain a petroleum solvent (cutter). While the cutter remains, the cutback is more fl uid and has less strength at these elevated temperatures. A better choice may be a paving grade asphalt or an emulsion. The asphalt in these forms can be less susceptible to hot weather. Traffi c control and a dry choke also help protect the new seal in hot weather.