International Concrete Abstracts Portal

Precast, prestressed concrete is widely used for parking structure construction. Because these structures are segmental and may be exposed to harsh environments, jointing practice is critical. The weld connections between double tees are especially vulnerable locations, requiring careful detailing of both the connection hardware and the sealant. Guidance is provided for minimizing the potential for leakage and related deterioration.

This paper develops a finite-deformation viscoelastic material model to characterize the behavior of a silicone-based sealant material. A series of relaxation tests were performed on the test specimens for different levels of age and unit extension. Based on the experimental results, a master relaxation modulus curve is constructed. Unit extension and age effects are incorporated in the master relaxation curve by using the superposition principle. The shift factor equations developed were based on the relationship first suggested by William, Landel and Ferry (WLF Equation) and traditionally used for incorporating temperature effect. The unit extension and age dependence are accounted in the “reduced time”. The material model derived is of the generalized Maxwell (in parallel) type, which is simple and can be easily applied in finite element programs for stress analysis of joint sealants in concrete pavement.

The six papers in this Symposium Publication address many different aspects of mechanistic design, such as environmental stress, improved pavement design methodology, approaches to performance-based specification, characterization of joint sealants for design purposes, characterization of concrete strength based on fracture properties, and others. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP181

From shortly before the entry of the U. S. in World War II and to the present, the author has been continuously involved in the design, testing, manufacturing, and observation of the performance of joints of all types, from pavements to bridges, and bearings of all types, from the old rockers to elastomeric, pot, disc, and then to earthquake isolation concepts. Starting out with load transfer devices buried in concrete pavement joints for state highways and airfield pavements to field molded sealants and then compression seals, the design trend in pavements has been from longer 100 ft panels (30 m) to relatively short panels of 15 ft (4.5 m). This has greatly simplified the sealing problem, since the distance changes between joint interfaces of shorter length panels obviously are much less in creep-shrink and thermal volume change. With respect to bridges, the design trend has been reversed, going from relatively short decks of 40 ft (12 m) to longer and longer spans, greatly complicating the sealing problem. It was in this confused design period that the writer worked toward developing sealing and bearing systems for every conceivable type pavement or bridge structure. Some lessons learned during the past 50 or more years are the subject of this paper.

The recently completed Strategic Highway Research Program (SHRP) included two projects that evaluated joint sealants for Portland Cement Concrete Pavements (PCCP). The major effort consisted of the innovative materials research which, among other things, evaluated silicone and hot pour sealant performance in transverse PCCP joints. This experiment provided intensive evaluations at regularly scheduled intervals. These evaluations consisted of the more traditional performance indicators of joint sealant performance such as the extent and severity of adhesive and cohesive failure, incompressibles, etc. Although fault measurements were obtained, no direct measurement of pavement performance or user satisfaction, such as ride comfort, was obtained. Similarly, no deflection testing was performed in this experiment to evaluate load transfer or to detect voids beneath the slab. The second SHRP effort was the Joint Sealant experiment (Specific Pavement Study No. 4 or SPS-4) which consisted of 500 ft sections of sealed and unsealed transverse joints in PCCP. This experiment was designed to evaluate the effect or benefit of sealing joints on pavement performance. The evaluation factors included ride comfort using an inertial profilometer, deflection testing using a falling weight deflectometer (FWD), and distress evaluations. The experiment did not include the traditional joint seal evaluation factors such as adhesive and cohesive failures. the amount of incompressibles, etc.. During discussions at an early SIIRP western regional meeting, it was requested that SHRP consider combining both the SPS-4 and innovative materials experiments pertinent to PCCP joint sealants. Unfortunately, SHRP had already developed and approved all the experiments, so this request could not be accommodated.