Petrographical, mineralogical and chemical investigation of 17th and 19th century lime mortars in the St.-Michael's church (Leuven, Belgium)

Abstract

Petrographical, mineralogical and chemical analyses have been used to characterize historical lime mortars in the Saint-Michael's church (Leuven, Belgium). An analysis method is proposed for a mineralogical (petrography, XRD-analysis and SEM-EDX-analysis) and chemical characterization of historical mortars. Four groups of mortars have been distinguished and indications for the processes of mortar production and for the provenance of the raw materials used for these mortars have been found. Lime was burnt in vertical lime kilns and dry slaked. The provenance of the aggregate was local and the lime was imported from Namur (SW of Belgium) and Tournai (SW of Belgium). A change in binder type and properties of the lime mortars from the 17th century original mortars (air-hardening) to the 19th century restoration mortars (hydraulic) has been observed.