Atmospheric deterioration of ancient and modern hydraulic mortars

Different types of ancient and recent hydraulic mortars were collected from well-documented archaeological, historic and modern buildings in various g eographical locations turban, suburban, rural and maritime) of Italy, Spain and Belgium, representative of different environmental impacts, types and degrees of deterioration. A synthesis of the characteristics of the collect ed samples is presented, along with the identification of the formation pro ducts that occurred on the sample surfaces as a result of the reaction of t he mortars with atmospheric pollutants. The analyses were performed by mean s of optical microscopy (OM), X-ray diffractometry (XRD), scanning electron microscopy (SEM-EDX) and ion chromatography (IC). The results obtained pro ve that sulphation processes takes place on hydraulic mortars, leading to g ypsum formation on the external surface of the samples. Through the reactio n of gypsum with the aluminate hydrate of the binder, ettringite Formation was found to occur on a cement-based restoration mortar sampled in Antwerp. (C) 2000 Elsevier Science Ltd. All rights reserved.