Quality evaluation of portland cement concrete at early age with Free-Free Resonant Column.

摘要

At early age, the behavior and mechanical properties of portland cement concrete changes rapidly with time due to hydration. The hydration process consists of a series of chemical reactions that accelerate nonlinearly with the rise in temperature. The hydration process consists of three stages: the dormant period, the setting time, and the hardening time. Timely opening of roads and resumption of constructions depend of the knowledge of these stages. The initial and final setting times are arbitrarily determined by a standard test (ASTM C 403). Although the setting time has been studied for many decades, the new technologies allow making more accurate and detailed description and analysis of the hydration process with time. On the other hand, the quality of portland cement concrete traditionally is evaluated by strength parameters in the hardened stage, and only standard slump test is used at very early age to evaluate workability. In this research, maturity and seismic technologies were used to evaluate and measure portland cement concrete properties. The proposed protocol evaluates the quality as well as the setting time of concrete at very early age with the Free-Free Resonant Column (FFRC) device. Several mixes were considered to study the versatility of the approach. The effects of cement content, the aggregate type, mineral admixtures, and curing condition were studied with the FFRC. Correlations of conventional standard strength test with maturity and seismic modulus from early age to hardened stage are presented. Moreover, an approach for determining the initial and final setting time is provided.