Identification of damage mechanisms in cement paste based on acoustic emission.

Acoustic emission (AE) monitoring during compressive loading was employed to investigate micro-crack formation and coalescence in cement paste specimens. To establish a correlation between damage and AE activity, the data was categorized on the basis of amplitude and cumulative signal strength (CSS). Three distinct stages of crack behavior, illuminated by changes in the slope of the cumulative signal strength versus time relationship, were identified. Micro-crack initiation, crack extension, and unstable crack growth (crack coalescence) were assigned to these stages. An unsupervised pattern recognition approach was employed to separate the data into signal subsets which were then classified and assigned to differing mechanisms. To gain further insight into the crack growth network and behavior, specimens were loaded to varying levels of ultimate capacity and micro-CT scanning was employed to investigate the dimensional extent of micro-cracking and to correlate the images with AE data. [ABSTRACT FROM AUTHOR]