Geomechanical, durability–hygrothermal and thermal shock properties of Kocaeli Kandira stone used as building stone in historical structures

This study investigated the mineralogical, chemical, physical, mechanical, durability–hygrothermal, thermal shock properties, and economic aspects of the Kandira stone, one of the well-known natural building stones, commonly used in many historical structures in the Marmara and Thrace regions. Especially, it has been preferred to Malta stone in historical structures in Istanbul due to economic reasons at the beginning of the 1900s. A similar appearance and lithology with Malta stone and closeness of the Kandıra stone to İstanbul made it attractive to be used as natural building stone in historical monuments and new structures. The mean physico-mechanical properties of Kandira stone yielded 2.24 g/cm³ apparent density, 2.72 specific gravity, 19.21% total porosity, 5.8% water absorption by weight, 48 MPa compressive strength, 11.4 MPa bending strength. In terms of durability properties, Kandira stone has high resistance to aging by CaCl salt mist and no or low resistance to SO₂ aging in a humid environment. Also, the freeze–thaw test of Kandira stone yielded an exceptionally low mass loss (0.11%) indicating that the stone is resistant to freeze–thaw effect. Thermal shock tests indicated that Kandira stone is mainly resistant to thermal shock cycles. Economically, the calculated probable reserve of Kandira stone resulted in 40.8 × 10⁶ tons of material and the potential economic value based on the probable reserve is calculated around 54.672 × 10⁹ TL (approximately €7.2B). In conclusion, this study defined the petrographic, geomechanical, durability–hygrothermal and thermal shock properties essential for the use of Kandira stone as building stone and restoration material.