Results From the Western States' SPS-4 Experiment

The recently completed Strategic Highway Research Program (SHRP) included two projects that evaluated joint sealants for Portland Cement Concrete Pavements (PCCP). The major effort consisted of the innovative materials research which, among other things, evaluated silicone and hot pout sealant performance in transverse PCCP joints. This experiment provided intensive evaluations at regularly scheduled intervals. These evaluations consisted of the more traditional performance indicators of joint sealant performance such as the extent and severity of adhesive and cohesive failure, incompressibles, etc. Although fault measurements were obtained, no direct measurement of pavement performance or user satisfaction, such as ride comfort, was obtained. Similarly, no deflection testing was performed in this equipment to evaluate load transfer or to detect voids beneath the slab. The second SHRP effort was the Joint Sealant experiment (Specific Pavement Study No. 4 or SPS-4) which consisted of 500 ft sections of sealed and unsealed transverse joints in PCCP. This experiment was designed to evaluate the effect or benefit of sealing joints on pavement performance. The evaluation factors included ride comfort using an inertial profilometer, deflection testing using a falling weight deflectometer (FWD), and distress evaluations. The experiment did not include the traditional joint seal evaluation factors such as adhesive and cohesive failures, the amount of incompressibles, etc.