Date: Thursday, Feb 19th
Presenter: Jason Ideker, Asst. Professor, OSU Civil and Construction Engineering/Materials Science
Compared to the knowledge base for ordinary portland cement concrete (OPCC), relatively little information exists for calcium aluminate cement concrete (CACC), despite its existence for over 100 years. There is particularly a lack of knowledge related to early-age behavior of CACC, specifically volume change and cracking potential in field applications. To assess these early-age properties, two unique pieces of equipment were developed and employed: a rigid cracking frame and free deformation frame which enabled quantification of restrained stress generation and unrestrained autogenous deformation, respectively. An overview of calcium aluminate cement chemistry and hydration will be presented. Then the results of recent research assessing early-age properties will be given.
It was found that CACC samples cured at discrete isothermal temperatures up to 30 °C developed tensile forces in the rigid cracking frame and exhibited shrinkage phenomena in the free deformation frame. At temperatures above 30 °C, the converse was true and significant compressive forces developed in restrained testing and expansion was observed in unrestrained testing. It was found that this was a direct result of microstructural development related to the formation of metastable phases (associated with shrinkage) and stable phases (expansion as a result of conversion from metastable to stable phases). This behavior has profound implication on the behavior of the material under realistic curing conditions and a brief treatment of these issues will be given.