A wide spectrum of sealant types commonly used in the United States were installed in eight different test sites using two types of sealing treatment techniques. The performance of sealants was monitored after each winter for three years to determine a performance index (PI) consisting primarily of adhesive, cohesive, and overband wear. Field samples were collected from the sites to conduct laboratory testing and validate the sealant grading system. According to the field results, most sealants failed below a PI threshold of 70% after three years. In general, rout and seal sections performed better than the clean and seal sections. Field performance results highlighted the importance of test site selection, especially for clean and seal application.
Statistical correlations of tests parameters with the field performance were performed. A composite score approach, combining ranking and correlation, was used to develop a quantitative scale for determining the level of acceptance. Based on the composite score, a strong or acceptable correlation was obtained between field performance and laboratory test parameters for field test sites. After confirming the correlation between field performance and lab results, the thresholds for test method were selected or fine-tuned.
In addition to test methods validation, an investigation was also conducted to evaluate the short-term and long-term aging effects of hot-poured crack sealants through a differential aging test. Rheological and mechanical properties of sealants at different aging stages were monitored to characterize the aging effects. Laboratory aging of sealants was studied using three different aging methods: Kettle aging, melter aging, and vacuum oven aging (VOA). The aging index was used to evaluate the effect of these aging methods. Comparing the stiffness master curves obtained from the crack sealant bending beam rheometer (CSBBR) test for field-aged samples and laboratory-aged samples, VOA was validated as a reasonable aging method for simulating two-five years of field aging.
Finally, sealant rheological, mechanical and chemical properties were analyzed, implementing different performance-based tests and FTIR test to characterize sealants aging. A set of eight types of crack sealants was exposed to approximately four years of weathering conditions. Aging mechanisms were investigated by comparing the critical properties with those obtained at the time of installation inside a small kettle. Samples were collected every six months after installation for laboratory characterization. Laboratory characterization includes low temperature stiffness, high temperature modulus, viscosity, and FTIR spectrum. According to the results of the experimental program, a consistent increase was observed in the low temperature stiffness and high temperature shear modulus of crack sealants due to weathering. The study showed that the low- and high-temperature properties of surface portion are significantly influenced by weathering effects even within a short period of life time. A superposition rule analogous to time–temperature superposition for viscoelastic materials was applied to develop master curves. A phenomenological aging model was developed as a function of aging time. Based on their aging potential, sealants were categorized into three groups at low and high temperatures with increasing aging potential: Type A, Type B, and Type C. FTIR analysis showed that rate of carbonyl index was significantly higher at the crust of crack sealants. On the other hand, the bottom part of field-aged crack sealants exhibited a higher sulfuxide index
