Author
B. MIDDENDORF and D. KNOFEL
Laboratory for Chemistry of Construction Materials (BCS)
University of Siegen

Abstract
The fabric of many historic brick buildings is in part heavily damaged. The paper gives mainly chemical and mineralogical results of analyses of mortars from buildings in Northern Germany , Gypsum-anhydrite mortars as well as lime mortars were used, the former mainly for religious buildings. Because of their higher initial strength, complicated parts of a building like brick arches or vaults could be built with these gypsum-anhydrite mortars. Mortars for restoration of joints have been tested. They are based on a- and/or B-hemihydrate and hydraulic or latent hydraulic additives, partly mixed with lime hydrate and retarders. The properties of hardened mortars tested were: dynamic modulus of elasticity, drying shrinkage and expansion, compressive strength and bending tensile strength as well as the solubility in water.