Fracture Toughness of Concrete: K_Ic Revisited

It is now widely accepted that many of the experimental investigations into the applicability of linear elastic fracture mechanics to cement paste, mortar, and concrete were performed before specimen size limitations were understood. Another less recognized problem was the lack of a simple but accurate stress-intensity factor analysis capability necessary to calibrate non-standard test configurations. In this paper, the results of a significant experimental investigation of a decade ago, one which concluded that linear elastic fracture mechanics concepts are not directly applicable to paste, mortar, and concrete, and reevaluated on the basis of a correct stress-intensity factor calibration not then available. The simplicity and accuracy of currently available analysis techniques for problems in linear elastic fracture mechanics are detailed. It is shown that, when evaluated with the corrected analysis, the previously reported experimental results indicate exactly the opposite of what had previously been concluded.