“Improving the Performance of High Early Strength Concrete by Controlling Self-Desiccation and Mitigating Shrinkage.”

Co-Major Advisors Jason Weiss, School Head and professor of infrastructure materials; Jason Ideker, associate professor of infrastructure materials. Committee Members: Burkan Isgor, professor of infrastructure materials and Jack Higginbotham (GCR). 

Abstract: HES concrete is becoming increasingly used to repair damaged pavement sections, enabling the repaired pavement to be opened to traffic within hours of placing the concrete. A common approach that is used for rapid repair consist 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 over-night so that it can be opened to traffic early the following morning. As a result, traffic delays during day-time hours are kept to a minimum. Although HES concrete repair projects are attractive, inherently they have challenges because they have strict requirements for opening, severe penalties for not achieving the target strength, simultaneous construction tasks, and extensive traffic control. As such, among other design considerations, HES concrete mixtures are typically designed with a low water-to-cement-ratio. As a result, these patches may be susceptible to self-desiccation which can lead to excessive shrinkage and early age cracking. In addition, reduced hydration can result in the reduced rate of strength gain and overestimated strength development by maturity predictions. This thesis specifically examines the impact of self-desiccation on the performance of these mixtures. This research aims, 1) to 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.