Evaluation of concrete fracture energy through a pull-out testing procedure

The pull-out test has been applied so far in the in-situ evaluation of concrete compression strength. In the present paper it is proposed, with the convenient procedure modifications, for the in-situ evaluation of concrete fracture energy G-F. The area enclosed between force versus displacement curve and displacement axis is approximately equal to the product of Mode I fracture energy G-F times the total cone-shaped fracture area, only when the contrast ring diameter is larger than a threshold value. In this case the failure process is dominated by tensile cracking, whereas, for smaller diameters, the failure mechanism is complex, as mortar against aggregate interlock prevails with an energy dissipation considerably higher than that strictly necessary for Mode I separation.