Quantifying the pavement preservation value of chip seals

Aging induced embrittlement of the asphalt mixtures makes them more susceptible to cracking. The oxidation and embrittlement rates are the most rapid at the surface of the pavement where the asphalt is exposed to the traffic and various environmental factors. It is envisioned that applying a surface treatment may isolate the asphalt from the environment to some extent, and thereby delay the oxidative aging processes. Asphalt Institute and Minnesota DOT launched a research study to quantify the effect of chip seal on preserving the asphalt pavements. Field cores were taken from a test track which was initially constructed in 1999 in Minnesota. A chip seal layer was applied on different sections of the test track at 1, 2, 3, and 4-year time intervals after the construction. The field core specimens were subjected to IDT creep/strength, and DC(t) tests to evaluate the effect of chip seal and its optimum application time on the low- Temperature cracking of the pavement. The overall results revealed that the application of the chip seal significantly decreased the rate of embrittlement of the asphalt layer. Furthermore, the optimum time of sealing was found to be immediately after construction of the pavement, and the advantageous effect of chip sealing diminished as the time of application was postponed to 3 years or longer after construction.