Investigating Early Age Behavior of Portland Cement Concrete in Arid Regions
The early-age behavior and properties of portland cement concrete change rapidly over time as a result of the hydration process. Comprised of a series of chemical reactions, this process accelerates nonlinearly with the curing temperature. Gaining knowledge and understanding of the phases of the hydration process (i.e., dormant, setting, and hardening) plays an important role in the timely opening of roads, resuming of construction, and achieving long-term performance. Standard tests such as ASTM C403 arbitrarily define the time of initial and final setting of concrete. Despite decades of studies concerning setting times, actual predictions still span hours, while the quality of concrete is customarily evaluated by its compressive strength at 28-days. New technologies provide an accurate and detailed understanding of the hydration process. In this research, maturity concept, along with seismic and infrared technologies, were used to measure and evaluate portland cement concrete properties. The setting times and quality of early age concrete were evaluated using seismic and maturity tests. The thermal profiles of concrete specimens were observed during the first 48-hours to monitor the heat dissipation during the hydration process. The versatility of the approach was studied by conducting tests under varied environmental curing conditions on a reference mix as well varying the water-cement ratio, chemical admixtures, and gradation of coarse aggregates. Correlations of both the maturity and seismic modulus to conventional compressive strength test at 1-, 3- and 7-days are presented. Additionally, thermal profiles of concrete for different curing conditions and mixes are shown. Lastly, an approach for determining the initial and final sets is provided which, when coupled with the strength testing, validates the need for redefining sets based on measureable concrete properties.
Wolf, Evan Lee, "Investigating Early Age Behavior of Portland Cement Concrete in Arid Regions" (2018). ETD Collection for University of Texas, El Paso. AAI10842584.