Investigating the Viability of Using Relative Humidity-Based Moisture Sorption Isotherms to Generate Moisture Profiles of Concrete Highway Bridge Decks

Many deterioration mechanisms within concrete structures are moisture related. This is primarily true for those structures which are subjected to natural weathering cycles. This thesis focuses on investigating the viability of using relative humidity—based moisture sorption isotherms to determine moisture [profiles] in concrete structures, with specific application in concrete bridge structures. Based on current literature, the principle obstruction to using this method has to do with incompatibility between a method that was developed under static environmental conditions and a concrete structure having an internal environment that is dynamic and continuously evolving due to the natural moisture and temperature cycles to which it is exposed.

Through experimental testing the author was able to determine that if a concrete structure is sufficiently massive and the environment surrounding the sensor probe placed inside the concrete bridge deck is sufficiently small, then compatibility between the method and the system may be assumed. However, during the investigation, the author determined that there is a definite upper limit to the applicability of a moisture sorption isotherm. Beyond the upper limit, there is potential for the existence significant additional moisture that will not be uniquely identifiable by the moisture sorption isotherm. If a system contains an initial moisture level beyond the identifiable levels within the limits of the moisture sorption isotherm, then the obtained data will consistently indicate the maximum level relative humidity and the true moisture level cannot be determined.