Analysis and laboratory tests to evaluate the composition and the behaviour of some dehumidifying mortars used in the restoration field

Abstract

The aim of this work is to study some commercial products, defined dehumidifying mortars, in order to verify their composition and their performance characteristics in comparison with the technical specifications supplied by the industries. In fact, the real composition and the properties of the commercial products often differ from those declared by the suppliers. In the field of conservation the commercial products are widely used and the restorers choose the most appropriate one also on the base of the declared characteristics. So it is of particular relevance in conservation and restoration applications to know the real composition and the performance characteristics of a commercial product. Starting from these general remarks, 20 commercial products were examined, in collaboration with the Society Mapei, in order to verify their composition and their physical-mechanical characteristics. The analyses of the mortars were carried out in the Laboratory of Diagnostics for Conservation and Restoration of University of Tuscia and in the Mapei's research laboratories in Milano. The analyses and tests were performed on the products and on the specimens prepared according to the specifications referred in the technical data sheets supplied together with the mortars. In particular, the following analyses were undertaken: 1) Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), X-ray diffraction (XRD), thermo gravimetric (TG) and differential scanning calorimetry (DSC), and Fourier Transform Infrared spectroscopy (FTIR) in the Mapei's laboratories, and 2) granulometry analysis, colour measurements, pH and conductance measurements, FT-IR spectroscopy, in the laboratories of University of Tuscia.Moreover, some specific tests were carried out to study the mechanical and physical-chemical properties of the specimens: capillarity water absorption (UNI 10859: 2000), water absorption due to total immersion (imbibition capability, NORMAL 7/81), drying index measurement (NORMAL 29/88), and micro drilling tests. The results of this study indicate that the examined dehumidifying mortars not always respect the requisites required to a product to be used in the restoration of historical buildings. This suggests the necessity to verify the composition and the characteristics of the commercial products used in the conservation applications in order to choose the most appropriate materials and procedure to guarantee the safeguard of the historical buildings