Performance of Silicone Sealants in Sawn Joints

Concrete pavement joints are required to be sealed to prevent the ingress of debris, mainly incompressible and water. In the year of 2012, there are a number of reports of pavement joint sealants losing adhesion within the first 5 years of service and eventually being mostly depressed under the wheel paths at the contraction joints. The early distress of the sealants is of concern as the repair task requires lane closures and associated disruption to traffic.

To address this issue, Roads and Maritime issued a Quality Alert in October 2012 which set out interim approaches to a joint sealant application procedure. In the meantime, the Roads and Maritime undertook an investigation to identify the causes of premature failure of silicone sealants in sawn joint. The literature research and available investigation reports indicated insufficient cleaning effort and lack of quality control of the joint cleanliness prior to sealing as the main causes, along with the introduction of early-entry sawing resulting in dry powder remaining on the edges of the concrete. In addition, a possible cause was early sealing when high levels of moisture were presented in the concrete.

The Roads and Maritime research team developed two test methods titled “T379 Cleanliness of sawn concrete pavement joints” and “T380 Field adhesion of joint sealant to concrete”. The new version of concrete pavement specification R83 included these test methods for use on sealing sawn joints for new concrete pavements. Site inspections have been conducted on several projects and no significant failures have been reported to date. Roads and Maritime will continue to review the performance of sealants in sawn joints and gradually report the outcomes of this monitoring to project engineers and industry practitioners.