Mode I fracture toughness of the thermally pretreated red Verona marble by means of the two-parameter model

The paper aims to analyse the effects of pretreatment thermal cycles on both mechanical and fracture parameters of the red Verona marble, which is a natural stone of sedimentary formation. The effects of the thermal pretreatment, consisting of freeze/thaw cycles and simulating the atmospheric ageing on the material, are evaluated in terms of changes of the aforementioned parameters. Note that a wide variety of both specimen types and methods to determine mode I plain strain fracture toughness of rocks are available in the literature. The two-parameter model originally proposed for plain concrete is herein adopted. Such a method, based on the experimental data obtained from three-point bending tests on single edge-notched specimens, is able to take into account the slow nonlinear crack growth occurring before the peak load, typical of quasibrittle materials, and presents the advantages of easy specimens preparation and simple test configuration.