EVALUATION OF PERFORMANCE OF JOINT SEALANTS IN COLD CLIMATE AREAS

This paper describes how today, almost all agencies building and maintaining concrete airport pavements require joint sealing for new pavements. The provision of joints is an integral part of the construction. Their role is to provide relief from tensile and warping stresses and to accommodate movements caused by thermal expansion and contraction. The purpose of a joint sealant is also to seal a joint or a crack against certain environmental factors like infiltration of surface water and incompressible material into the joint system. Secondarily, sealants are also purported to reduce the potential for dowel bar corrosion by reducing entrance of de-icing chemicals. It is known that water can contribute to subgrade or subbase softening and lead to pumping of subgrade or subbase fines under heavy traffic. This degradation usually results in loss of structural support, pavement settlement, and/or joint faulting. In the cold climate areas, the infiltrating water can cause frost heaving that leads to break of concrete slabs and thus risk for accidents in traffic. The other function of modern joint sealants is to prevent incompressible material from entering the joint reservoir. In some circumstances, incompressible materials may contribute to spalling, and in extreme cases, may induce pavement migration and blow-ups. These problems are caused when incompressible materials obstruct pavement expansion in hot weather and create compressive pressure along the joint faces. Sealants may be poured or preformed. The poured sealants may be applied hot or cold and are required to meet performance specifications related to the environmental conditions rather than compositional recipes. In the cold climate areas the width of joints and cracks is changing widely with temperature. The joint sealant must thus be flexible enough to compensate for the relatively large dimensional changes within a broad temperature range, sometimes down to - 30 degrees C. In this context, particular attention must be paid to the cyclic mechanical stresses of the sealant. Re-sealing joints is costly and the remedial work can cause considerable traffic disruption.