Nineteenth century hydraulic restoration mortars in the Saint Michael's Church (Leuven, Belgium): Natural hydraulic lime or cement?

Abstract

This research focuses on the characterization of nineteenth century hydraulic restoration mortars used in the Saint Michael's Church in Leuven (Belgium). The mortars were used as restoration mortars for weathered mortar joints. A historical study of old work descriptions and mineralogical, petrographical and chemical analyses have been used to characterize these hydraulic mortars. The different hydraulic phases are identified using petrographical analysis, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDX) and chemical analyses. Based on the presence of gehlenite (C 2AS), the dominance of C 2S, the large amounts of portlandite, the chemical analyses and on the historical sources, these hydraulic mortars are characterized as natural hydraulic lime mortars.