Pavement Joint Sealant Specifications—Past, Present, and Future

Abstract

Portland cement concrete (PCC) began to be used as a surface or wearing course for pavements in the United States in the early 1900s. The joint sealant or filler materials used during this early construction period were typically sand, tar paper, coal-tar pitch, asphaltic compounds, or wooden blocks. Material specifications for these early joint filler materials were nonexistent. The main emphasis of pavement construction during this period was to "get the country out of the mud" [1], not to provide a long lasting flexible joint sealant material to protect the pavement structure. In the early 1940s, pavement engineers began to concentrate on the construction of the joints in rigid pavements and the materials used to seal those joints. It was during this time period that elastomeric materials (generally an asphalt-based material modified with crumb rubber) began to be developed for use in pavement joints and the first material specifications were developed to provide a means of quality control. As user requirements changed (i.e., materials resistant to fuel spill-age, etc.), new materials (typically polymer modified and/or extended coal-tar materials) were introduced and new material specifications were developed. New formulations have continued to be introduced with individual material specifications eventually being developed for each sealant. Typical base materials used today for pavement joint sealing include asphalt-rubber, modified coal-tar, polysulfide, polyurethane, silicone, and polychloroprene. Improvements have been made to the sealant formulations but the current material specifications have hindered innovation because they are typically material specific and generally do not directly correlate to sealant field performance. A review of the history of joint sealant material specifications, current specifications, and potential techniques that may be included in material specifications of the future to provide a more direct correlation between laboratory evaluation and field performance is presented.