ANCIENT GYPSUM MORTARS FROM ST ENGRACIA (ZARAGOZA, SPAIN) - CHARACTERIZATION - IDENTIFICATION OF ADDITIVES AND TREATMENTS

The ancient mortars coming from the alabaster main facade of the St. E ngracia !: Basilica (XVI century). The research has been carried out a bout the original joint mortars and the repairing mortars of several r estorations. The characterization of different types of mortars was ma de by the application of optical microscopy, scanning electronic micro scopy with EDX, X-ray diffraction, infrared spectroscopy and laser gra nulometry. Gypsum is the main component. There has been studied; on th e mortars: the composition, the binder/aggregate ratio, the granulomet ry of the binders and the aggregates, and the identification of the ad ditives (organic compounds,..) used in the mortars. The design of the restoration mortars has been achieved by the knowledge of the studied mortars.