Investigation of the Effect of Nanometakaolin on the Compression Behavior of Concrete by Acoustic Emission.

To investigate the influence of nanometakaolin (NMK) on the compression behavior of concrete, acoustic emission (AE) is applied to monitor the development of cracks on ordinary concrete as a control sample and concrete with the addition of 1% or 3% NMK during the whole compressive process. The AE parameters (event, count, RA-AF, etc.) and Gaussian Mixture Model (GMM) were analyzed. The results show that the addition of NMK results in a decrease of crack number and crack width. Compared to the control concrete, the concrete with NMK inhibits the initial crack, increases the crack initiation stress and crack damage stress, and improves the energy of crack propagation. Correspondingly, we proposed a critical point where the ringing counts and amplitude fit parameters are less than a certain threshold. This index can be used as a failure precursor for crack instability. According to the criterion and the GMM, what is found from the relation between RA and AF is that the resistance to tensile and shear is improved in the case of the concrete with NMK.