Physico-chemical adhesion and cohesion bonds in joint mortars imparting durability to the historic structures

Abstract

It is well known that even though historic mortars present low strength and elastic moduli they confer durability to the structures surviving today. The present work investigates the durability of historic mortars in relation to the production technologies employed. Thermal analysis allows for classification of historic mortars in both lime and hydraulic types. Mineralogical data, concerning fabrication and texture, along with thermal analysis provide criteria on specific classification, for: typical lime, crushed brick–lime, cementitious, rubble masonry, hot lime technology and gypsum mortars. The correlation of the measured tensile strength (fmt, k) with the estimated CO 2/structurally bound water ratio, indicates direct proportionality to the levels of the hydraulicity. Physico-chemical adhesion and cohesion bonds, studied by SEM-TEM/EDX, developed at the matrix and at the binder/aggregate interface, respectively, becomes the key factor in interpreting the considerable durability that the historic mortars confer to the structures as bearing elements.