Katelyn Freeseman

Characterization of concrete at various freeze-thaw damage conditions using SH-waves

Evaluation of migration-based reconstructions can give a qualitative characterization of large scale or excessive subsurface damage. However, for detection of stochastic damage mechanisms such as freeze-thaw damage, evaluation of the individual time-history data can provide additional information. A comparison of the spatially diverse measurements on several concrete slabs with varying freeze-thaw damage levels is given in this study. Signal characterization scans of different levels of freeze-thaw damage at various transducer spacing is investigated. The results show promise for a SH-wave classification system applicable for nondestructive characterization of freeze-thaw damage conditions.

Effect of Early Opening to Traffic on Fatigue Damage to Concrete Pavement

The current methods for determining criteria for opening a roadway to traffic are often overly conservative, causing unnecessary construction delays and user costs. This problem can be explained, in part, by the purely empirical nature of the current methods. These criteria require wait periods after concrete placement or certain levels of compressive or flexural strength, or both, after concrete placement, and specific site conditions are not accounted for. Further, the effect of early traffic-related loads on long-term pavement behavior has not been quantified. In this study, the effect of early opening on pavement damage was reexamined through a laboratory study and analytical modeling. The result was a mechanistic-based procedure for evaluating the effect of early opening to traffic on the accumulation long-term damage; this procedure also accounts for critical factors such as climate, traffic level, and pavement design characteristics. The basis of this method is a modification of the fatigue damage analysis in the Mechanistic–Empirical Pavement Design Guide; this modification enables an analysis of traffic loading on the first 28 days of pavement life. The procedure also enables an update to predictions on the basis of as-built nondestructive testing measurements of the pavement. The output of the analysis is a quantitative damage prediction that allows the road owner to do a cost–benefit analysis of the timing for opening the road on the basis of the specific site and traffic characteristics. The results presented here show how innovated opening criteria based on load restrictions can allow for early opening while mitigating any adverse effect on the long-term pavement performance.