Mode I Fracture Toughness Determination of Rock and Concrete via Pull-Off Test

In this paper, the Pull-Off Test (POT) was analyzed as a method for determining the mode I fracture toughness (K-Ic) of rock and concrete. POT is submitted to tensile load (which causes a simpler stress state than tests submitted to bending and compression load) and its execution is easy, replicable and can be performed in laboratory and in situ (being its great advantage). A ratio between the dimensions of the POT was proposed to meet the Linear Elastic Fracture Mechanics requirements and the POT literature recommendations. Parametric studies were performed using numerical analysis and it was concluded that the POT is suitable for K-Ic testing, since mode I prevails in the test, and an equation was proposed for determining K-Ic in homogeneous rock and concrete (micro-concrete and mortar). A practical example of the method application was provided and K-Ic was determined for some homogeneous rocks. A similar result was achieved between POT and Semi-Circular Bending test.