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

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.

In July 1986, the Arizona Transportation Research Center coordinated the installation of a joint sealant test site near Flagstaff, on the southbound lanes of Interstate 17. The original project was constructed in 1974, with 8 inches of portland cement concrete pavement over 6 inches of cement treated base. The test site consisted of 200 transverse joints. The objective of the project was to evaluate the performance of five joint sealants: Dow Corning 888, Superseal 888, Allied Koch 9005, Crafco Roadsaver 231, and W.R. Meadows Sof-Seal. The highway sections abutting this test site were also rehabilitated and their pavement joints were sealed with Superseal 444 which, at that time, was a specified sealant in the Arizona Department of Transportation standards. Field evaluations of the joint sealants were conducted periodically. The final evaluation was conducted eight years after construction. The evaluations were based on: (i) sealant flexibility, (ii) length of joint with missing sealant, (iii) adhesive and cohesive failure of sealant, (iv) joint width and sealant depth, (v) joint spatting, (vi) sealant recess, (vii) structural tests made with a Falling Weight Deflectometer, and (viii) slab faulting. After about eight years of service, all five sealants had exhibited comparable performance level. Clearly, all test sealants performed better than Superseal 444.

This four-year project was carried out in an aim to conduct a mid- to long-term, large-scale study on selected field-moulded sealants in concrete joints at different hydraulic structures under extremely cold climatic conditions. Other objectives were to specify installation techniques, carry out periodic inspections, evaluate the performance of various types of such sealants that could be of value to all potential users. The project also included a cost effectiveness study. General and specific guidelines were prepared for sealant selection and their installation. Based on these guidelines, different types of sealants, polyurethanes, polysulphides, silicone (1- and 2-component), were selected for the study. They were installed in horizontal, vertical and inclined joints at different locations on five Hydro-Quebec dams, mostly on the crest, and were periodically inspected for their performance. The findings are presented in this paper.