Monitoring early age strength gain of SCC with different supplementary cementitious materials using acoustic emission sensors

Abstract

This investigation employed acoustic emission (AE) technique to monitor the strength development at an early age of self-consolidating concrete (SCC) mixtures with different supplementary cementitious materials (SCM’s). Four types of SCM’s including fly ash (FA), metakaolin (MK), silica fume (SF) and slag (SG) were investigated in this study. A normal concrete mixture with higher coarse-to-fine aggregate ratio was also investigated for the comparison. Three prisms from each tested mixture were continuously monitored by means of attached AE sensors up to a total period of 3 days. Cylindrical samples were tested to evaluate the compressive strength gain along the tested period. The emissions resulting from the changes in the microstructure of the specimens were recorded along with the temperature variations (using thermocouples) for all mixtures. Different AE parameters were analyzed including the signal amplitude, absolute energy, peak frequency, number of AE hits and cumulative signal strength (CSS) to relate them to the rate of strength gain. Furthermore, b-value analysis was conducted on the collected AE signals to evaluate the strength development by means of the variations in the b-value. The results of the AE parameters including the number of AE hits and CSS showed a direct correlation between the rate of strength gain and these studied AE parameters. Meanwhile, the b-value analysis was found to be a useful tool for capturing the changes in the internal properties of the different tested mixtures at early ages.