Durability estimation of porous building stones from pore structure and strength

The influence of both pore structure and strength on the estimation of stone durability is evaluated. Salt crystallisation may limit the durability of porous building stones because it can be considered as one of the most powerful weathering agents. Salt crystallisation produces stress over the pore surface. Consequently, stone durability is closely related to both pore structure and strength, which is the material resistance to crystallisation pressure. We propose a novel petrophysical durability estimator (PDE) as the ratio between parameters and estimators, which are based on pore structure and the strength of the material. In this study, we have used stone parameters and estimators that have an influence on durability and depend only upon pore structure, i.e., connected porosity, water absorption, the water absorption coefficient, specific surface area (SSA), the saturation coefficient, the durability factor, the durability dimensional estimator (DDE) and others derived from porosity, such as microporosity and adjusted microporosity. We also used stone parameters and estimators with an influence on strength: flexural strength, uniaxial compressive strength, Young's dynamic modulus and compressional wave velocity. These parameters and estimators, and the proposed petrophysical estimator are compared with a salt weathering test. Our study shows that there is a very strong correlation between salt weathering and the proposed petrophysical estimator, whereas only moderate correlation exists with the estimators that depend on pore structure and strength. We conclude that the proposed estimator contains the information necessary to understand and estimate the durability of porous materials which have an impact on buildings, civil constructions and historical monuments. (C) 2004 Elsevier B.V. All rights reserved.