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D. Scorza et alii, Frattura ed Integrità Strutturale, 34 (2015) 70-73; DOI: 10.3221/IGF-ESIS.34.06 73 C ONCLUSIONS rom the above tests on as-received specimens, we have obtained a peak load equal to 420.84 ± 147.93 N, a Young modulus equal to 47.83 ± 10 GPa, and a fracture toughness equal to 1.189 ± 0.299 MPa m . Then, from the tests on the thermal pre-treated specimens, we have obtained a peak load equal to 311.31 ± 56.67 N, a Young modulus equal to 34.07 ± 15.27 GPa, and a fracture toughness equal to 0.998 ± 0.243 MPa m . The degradation of the red Verona marble mechanical properties due to the thermal cycles is evident, and can be quantified in terms of mean values: the peak load reduction is equal to about 26%, the Young modulus reduction is equal to about 28.77%, and the fracture toughness reduction is about 16%. Moreover, for the first specimen type (A-type), the presence of wide portion of Fe-hydroxides: (i) eases the stable crack growth behaviour related to its petrographic nature; (ii) induces dispersion of results in terms of initial compliance and, therefore, of elastic modulus, such a behaviour being connected to its chaotic dispersion inside the matrix. On the other hand, the second specimen type (B-type) is characterised by wide portions of material with allochemical grains. Such portions: (i) partially inhibit the stable crack propagation, such a behaviour being related to its petrographic nature; (ii) produce a mechanical behaviour rather constant in terms of initial values of compliance and, therefore, of elastic modulus, such an attitude being connected to its rather homogeneous distribution inside the matrix. R EFERENCES [1] ASTM E 399-90 (Reapproved 1997). Annual Book of ASTM Standards, Vol. 03.01: Metals-Mechanical Testing; Elevated and Low-temperature Tests; Metallography (ASTM, West Conshohocken, Pennsylvania, USA, 2001). [2] Zuo, J., Xie, H., Dai, F., Ju, Y., Three point bending test investigation of the fracture behaviour of siltstone after thermal treatment, Int. J. Rock Mech. Min. Sci., 70 (2014) 133–143. [3] Ouchterlony, F., Review of fracture toughness testing of rock, SM Arch., 7 (1982) 131–211. [4] Whittaker, B.N., Singh, R.N., Sun, G., Rock Fracture Mechanics: Principles, Design and Applications. Elsevier Science Ltd, Oxford, UK, (1992). [5] ISRM Testing Commission (co-ordinator: Ouchterlony, F.) Suggested methods for determining the fracture toughness of rock, Int. J. Rock Mech. Min. Sci. Geomech. Abstr., 25 (1988) 71–96. [6] ISRM Testing Commission (co-ordinator: Fowell, R.J.) Suggested methods for determining mode I fracture toughness using cracked chevron notched Brazilian disc specimens. Int. J. Rock Mech. Min. Sci. Geomech. Abstr., 32 (1995) 57–64. [7] Jenq, Y., Shah, S., Two Parameter Fracture Model for Concrete, J. Eng. Mech., 111 (1985) 1227–1241. [8] Spagnoli, A., Ferrero, A.M., Migliazza, M., A micromechanical model to describe thermal fatigue and bowing of marble, Int. J. Solids Struct., 48 (2011) 2557–2564. [9] UNI EN 12371:2010, from EN 12371: Natural stone test methods: Determination of frost resistance, (2010). [10] UNI 11186:2008: Beni culturali - Materiali lapidei naturali ed artificiali - Metodologia per l'esposizione a cicli di gelo e disgelo, (2008). F