Effects of Excessive Pavement Joint Opening and Freezing on Sealants

Abstract

The primary purposes of joint sealing in jointed concrete pavements are to minimize moisture infiltration through the joints, to reduce moisture-related distress (such as pumping), and to prevent the intrusion of incompressible material into joints to minimize pressure-related distress (such as spalling). However, the dilemma of whether “to seal or not to seal” has frequently arisen since the benefit of improvement in pavement performance with joint sealing could not be clearly demonstrated in a number of previous studies. Premature failure of sealant has been considered as a major cause of the ineffectiveness of joint seal. Poor construction quality and material properties of sealant have been considered as problems that induce the premature failure of joint seal. In this study, other causes, which are related to the shortcomings of the AASHTO joint seal design method, which may induce premature failure of joint seal, are addressed. The first cause is in situ joint openings larger than AASHTO predictions. Variability of joint openings in a given pavement section, including erratic large openings at a considerable portion of joints, has been discussed. High chances of adhesion-type failure are plausibly related with such erratic large openings. The relationship between sealant damage and the ratio of in situ maximum joint opening to permissible sealant elongation was demonstrated in this study based on the observations from 90 joints in 16 jointed concrete long term performance pavement special pavement studies (LTPP SMP) sites. The second cause is joint freezing (defined as joints showing no movement). At frozen joints, joint seals are likely to be redundant, and a waste of money. A method for joint seal design with survival criteria is suggested in this study. In this model, joint openings are estimated based on the Lee-Stoffels model. The Lee-Stoffels model is a probabilistic model that can predict the magnitudes of joint opening with its probabilities. The joint seal designs for 16 LTPP SMP sites, based on this survival model, indicated that some sections should have sealant-type changed, to permit more elongation with the given joint reservoir, whereas other sections do not need joint seal.