by Scott Eilken
A concrete pavement’s longevity can be affected by several factors, including the design and construction of the transverse joint. Research was recently conducted to determine what conditions will influence the performance and life cycle cost of a sealed pavement joint, and to understand how the initial conditions affect the joint and sealant.
This research involved evaluating and developing the best practices related to joint sealing with the intent of extending the life of concrete pavement. To accomplish this, the Seal/No Seal Group (an industry-formed coalition committed to the long-term effectiveness of sealants used in concrete pavement) began working with Dan Zollinger at the Texas Transportation Institute (TTI) to study the various factors over an extended period.
Zollinger’s research focused on sealant effectiveness on jointed concrete pavement performance. The newly released outcome will likely be useful to pavement designers, contractors, state departments of transportation (DOTs), and maintenance agencies making critical design-related decisions on using sealants with respect to long-term performances. (To learn more about this research and its results, read a complete version of Zollinger’s report, Qualification of Joint Sealant Effectiveness Regarding Jointed Concrete Pavement Performance, visit sealnoseal.org/PDF/TechBrief/Tech_Brief_SNS_TTI_Report.pdf.) Such decisions include striking a balance between traffic, climate, and base erodibility to minimize costs, streamline maintenance, and improve performance and pavement serviceability.
Why is this important?
As cost pressures continue to increase, there has been an increased interest in eliminating joint sealants as a means of lowering the initial cost of concrete pavements. However, there has also been a lack of data in the industry to instruct owners on sealant effectiveness and the long-term impact of using or forgoing them.
The primary purpose of sealing joints in rigid pavement is to reduce the amount of water and incompressible infiltration in the structure. Both issues contribute to various distress types that eventually deteriorate the structure and result in decreased service life. For instance, an inevitable consequence of water infiltration through joints in concrete pavement is the erosion at the slab/subbase interface. Subbase erosion directly contributes to joint faulting.
Faulting is a major distress type in seen jointed concrete pavements, and a key feature in designing them, as its effects have structural and serviceability implications. The effectiveness of joint sealants in protecting jointed concrete pavement against water-related distresses has been a focus of interest.
For more than a decade, both formal and informal studies on the effects of joint sealing—funded by state agencies, Federal Highway Administration (FHWA), and National Cooperative Highway Research Program (NCHRP)—have focused on the question of ‘to seal or not to seal’ joints in concrete pavements. These studies variously involved performance data, field cores, field observations, personal opinions, drainage modeling, and statistical analysis. Their results have largely lacked evidence supporting the idea using sealed joints in concrete pavements is beneficial.
Out of concern this lack of compelling beneficial evidence has caused several agencies to elect not to seal pavements, the Seal/No Seal Group joined Zollinger in conducting a study on sealing effectiveness. However, this was not an attempt to research sealant effectiveness through traditional approaches (such as characterizing sealant performance in terms of joint seal properties). Instead, a more rigorous and fundamental approach was implemented, focusing on the amount of water infiltration through the joint and its consequential impacts on subbase erosion and pavement distress.
A field-testing program was carried out at the Riverside Campus of Texas A&M University on SR-59 near Joliet, Illinois, and on the site of the Specific Pavement Studies-2 (SPS-2) experiment, Strategic Study of Structural Factors for Rigid Pavements, on I-10 in Goodyear, Arizona. The goal was to study the effectiveness of different sealant types several years beyond installation—after failure conditions begin to manifest and limit surface drainage-related infiltration of the joint—under different degrees of failure, as represented by various joint-openings and bonding conditions.