Compressive mechanical properties are critical indicators of the degree of hydration of concrete and are frequently used as indicators of other mechanical and durability properties. The rate of compressive mechanical response development is of importance to construction projects wherein the concrete hydration is on the critical path. Ultra-high performance concrete (UHPC), when used in field-cast connections between prefabricated bridge elements, can create robust connections that emulate monolithic components. Traditional UHPC formulations tend to express a delay prior to setting and initial mechanical property development. This research program investigated the compressive mechanical response of a new UHPC formulation intended for use in field-cast infrastructure connections. The time to initiation and rate of property development was observed to be influenced by the ambient environment surrounding the concrete during curing. At an elevated curing temperature, the UHPC was observed to reach 10,000 pounds per square inch compressive strength at 11 hours. The compressive strength, modulus of elasticity, axial strain at peak strength, and overall stress-strain response were captured under three curing conditions from early age through 56 days after casting.
The objective of this research study was to evaluate the compressive mechanical response of a rapid strengthening ultra-high performance concrete (UHPC) formulation when exposed to a range of curing conditions. This research result is critical to the broader use of UHPC-class materials as field-cast grouts in connections between Prefabricated Bridge Elements and Systems (PBES) components.