High early strength (HES) concrete is becoming increasingly used to repair damaged concrete pavement sections. The use of HES concrete enables the repaired pavement to be opened to traffic within hours of placing the concrete. A common approach used for the rapid repair of concrete pavement consists of closing a pavement section after evening rush hour traffic, repairing the damaged pavement with a HES concrete, and opening the repaired pavement when the target strength is achieved. The HES concrete is expected to have gained the target strength by the time the road is opened to traffic early the following morning (typically before morning rush hour traffic begins). As a result, traffic delays during busy day-time hours are kept to a minimum. The rapid repair of concrete pavement is attractive because the traveling public is not delayed by the repair of the pavement, and costs associated with traffic delays are kept to a minimum.
Although HES concrete repair projects are attractive, inherently they have challenges due to strict requirements for opening, simultaneous construction tasks, extensive traffic control, and severe penalties for not achieving the target strength. In addition, the bid price is adjusted to account for the costs of the penalties, requiring higher average bid prices for these types of projects. Ultimately, jurisdictions and owners incur the increased costs associated with rapid repair concrete pavement projects.
HES concrete mixtures are typically designed with a low water-to-cement-ratio. As a result, these concrete patches are susceptible to self-desiccation which can lead to shrinkage, stress development, and early age cracking. In addition, self-desiccation can lead to a reduction in the rate of cement hydration, resulting in the reduced rate of strength gain and overestimation of strength development through the use of conventional maturity predictions. This thesis specifically examines the impact of self-desiccation on the performance of these mixtures.
This research aims to: 1) develop an experimental procedure to determine accurate quantifications of self-desiccation through the internal relative humidity of concrete at early ages, 2) mitigate self-desiccation through internal curing, thereby improving the performance of HES concrete, 3) account for self-desiccation in modified maturity predictions, thereby resulting in more accurate strength estimations of in place HES concrete, 4) minimize shrinkage and cracking potential in cementitious systems at early ages with expansive cementitious additives.