ACOUSTIC EMISSION AND BOND DEGRADATION IN REINFORCED CONCRETE DUE TO ELEVATED TEMPERATURES.

A preliminary study was made of the application of acoustic emission (AE) testing investigating the effect of elevated temperatures on the bond between the concrete and steel in reinforced concrete. The specimens studied were of the bond pull-out type having a bond length of the order of twice the maximum aggregate size to simulate local bond stress conditions. Temperatures in the range 20-600 degree C were examined using an electric furnace with a uniform slow heating rate to avoid transient effects. Specimens were maintained at a peak temperature level for an hour to provide good thermal saturation prior to cooling in air. Results of slip and AE were obtained with bond stress and comparisons made. In the residual ambient state effects of load cycling before pulling to failure were assessed.