The Dow 890SL performed very well for five years. Unfortunately, because of a long curing time, Dow Corning decided to reformulate the product. Therefore, the product was not available for the remainder of the project, which resulted in two of the objectives not being met. The optimum shape factor and the actual water infiltration were not determined. Also, the sealant was not subjected to high moisture levels resulting in shear forces between the two pavements conditions present in much of the state. Other problems with test sections in the study included poor pavement with many cracks, which resulted in an unfair evaluation. The study recommended that the Office of Research should initiate a project to evaluate the performance and cost-effectiveness of the reformulated sealant in 0.5 and 0.75 channels on new or recently constructed asphalt shoulders in a wet climate. A sample of the reformulated Dow 890SL was obtained after the study. It did not meet the manufacturer's specifications, and required seven days to cure. Work must be done to determine whether the 890SL can be improved to meet the specification.
SDDOT has specifications for joint sealant on transverse joints. These same specifications are used for longitudinal joints. This may not be appropriate because the two types of joints may behave differently, requiring the use of different materials. Work must be done to determine whether specifications for joint sealants on PCC/AC joints are appropriate.
Findings: The SDDOT Materials Lab conducted in-house tests on both the Crafco Incorporated Roadsaver 903 SL Silicone and Dow Corning 890 SL Silicone sealants. The results of the tests were compared to the SDDOT 1998 Standard Specifications for Roads and Bridges, Section 870 Concrete Joint Sealer Specifications as well as to each manufacturer's silicone sealant specifications. Military Specification S-8802E and ASTM Designation 5893-96 Standard Specification for Cold Applied, Single Component, Chemically Curing Silicone Joint Sealant for Portland Cement Concrete Pavements were reviewed to determine appropriate curing and tack free times for the silicone samples.
Neighboring states were contacted to determine if they used silicone sealants to seal longitudinal joints between PCCP and AC pavements. The results of the survey, as well as recommendations from Crafco Incorporated are contained in the report. Based on this information, the researcher recommended that the SDDOT only allow the use of approved hot-pour sealants for PCCP/AC longitudinal joints.