Investigating the fracture behavior of Portland limestone: an experimental study

Abstract

An experimental investigation of the mechanical and fracture characteristics of the ‘Grove Whitbed’ Portland limestone is undertaken aiming to enhance understanding of the structural behavior of this natural building stone, commonly used in both new and restoration projects in Edinburgh, Scotland. A series of prismatic specimens, bearing a machined notch at their mid-span and comprising combinations of three different geometries (span/depth ratios) and three different sizes (span lengths) were subjected to three-point bending testing. The effect of specimen shape and size on flexural strength, deflection at mid-span, crack mouth opening displacement (CMOD) and fracture energy was studied. Despite the scattering of results which is significant but common in studies of the mechanical behavior of similar geomaterials, trends observed comprise (a) the negative correlation between the flexural strength of Portland limestone test specimens and their span lengths for all three shapes and (b) the positive correlation between fracture energy and specimen size. Conclusions drawn are in good agreement with similar ones for other quasibrittle materials and contribute to the assessment of the fracture behavior of full size structural members that are often beyond the range of possible failure testing.