In-situ evaluation of self-healing performance of Engineered Geopolymer Composites (EGC) by ultrasonic method

This paper reports a novel method to evaluate the self-healing performance of Engineered Geopolymer Composites (EGC), the ultrasonic method which provides an in-situ evaluation of the samples. The dog-bone shaped samples were pre-loaded to 2% tensile strain at different curing ages (3d, 7d, 14d, and 28d) followed by putting them into 40 degrees C water for self-healing. Apart from the development of ultra-sonic pulse velocity (UPV), the recovery of tensile properties and residual crack characteristics were investigated to verify the effectiveness of ultrasonic method. The results show that there is an increase of UPV in all samples while A7d samples (pre-loaded at 7d) have the highest UPV after self-healing for 28d and the most significant increasing magnitude during the self-healing process indicating great self-healing performance. The similar conclusion could be found according to the traditional indicators' results of tensile properties and crack characteristics, which validates the effectiveness of ultrasonic method. Besides, there is a strong correlation between the tensile strength and UPV with R-2 close to 1, which indicates that UPV could be a prediction to tensile strength according to the fitting equations. (C) 2020 Elsevier B.V. All rights reserved.