<strong>Rendre</strong> <strong>compatible</strong> <strong>les</strong> <strong>techniques</strong> traditionnel<strong>les</strong> <strong>et</strong> <strong>les</strong> <strong>modernes</strong>Compatibilizar técnicas tradiciona<strong>les</strong> y modernasCombining traditional and modern <strong>techniques</strong>Reproduction of hydraulic lime mortarsbased on the traditional productiontechnology of ancient mortarsfrom CyprusI. Ioannou, M. Philokyprou, G. Papadouris, K. KyriakouIoannis Ioannou is a lecturer at the Department of Civil and EnvironmentalEngineering of the University of Cyprus. His research interestslie in the field of traditional building materials technology. His workfocuses on the characterisation of mortars, stone and brick. He isparticularly interested in water-mediated processes affecting theweathering of masonry materials and m<strong>et</strong>hods for the protection andrestoration of cultural heritage monuments.Address:75 Kallipoleos Str., P.O. Box 20537, 1678 Nicosia, CyprusE-mail:ioannis@ucy.ac.cyTelephone:+357 22 89 2257IntroductionUntil the beginning of the 19 th century, mud, air hardening lime,hydraulic lime and lime mixed with natural or artificial pozzolanas (e.g.crushed brick) were the most popular binders and renders used inthe construction of buildings. After the discovery of Portland cementin 1824, the latter and its derivatives became the dominant bindingand rendering materials in the building industry, mostly due to thestandardisation of their production [1]. As a result, during the lastcentury, there has been a gradual replacement of traditional mortarsby highly hydraulic cement-based mortars.The uncontrolled use of cement-based mortars for restoration purposesresulted, in many cases, in extensive damage to cultural heritage,mainly because of their incompatibility with the traditional material [2-8]. Cement is hard, rigid and impermeable. It also contains significantamounts of soluble salts which can be harmful to historic buildings.These salts not only produce non-aesth<strong>et</strong>ic efflorescences uponcrystallisation on the façade of a building, but they can also developlarge damaging pressures when they crystallise behind the surfaces ofmasonry materials.Reported damage cases, tog<strong>et</strong>her with the principle of “authenticity”,defined in the ICOMOS Venice Charter [9], resulted in a renewedinterest in the use of (hydraulic) lime mortars in the field of restoration.In the research study described in this paper, a physicochemicalcharacterisation of ancient mortar samp<strong>les</strong> from Cyprus wasundertaken in order to find out the provenance of their raw materialsand to d<strong>et</strong>ermine their composition and properties. An experimentalstudy was also carried out to design <strong>compatible</strong> mortars for restorationand conservation purposes.Materials and M<strong>et</strong>hodsMortar sampling was performed on excavations, monuments andtraditional buildings. Part of each sample was ground and used for X-ray diffraction (XRD) and X-ray florescence (XRF) analyses to identifymineral constituents and to d<strong>et</strong>ermine quantitatively the major oxidespresent in the mortars. A slice was used for the preparation of a thinsection which was used for p<strong>et</strong>rographic examination of the mortars.A scanning electron microscope (SEM), equipped with an EnergyDispersive X-ray (EDX) microanalyser, was also used to examine themicrostructure and texture of the mortars, while a significant group of15 samp<strong>les</strong> underwent thermal analyses (DTA/TG) to d<strong>et</strong>ermine theirhydraulicity. The most important physical properties of the ancientmortars (i.e. vacuum saturation porosity and capillary absorptioncoefficient) were also measured using water as the w<strong>et</strong>ting liquid.The analytical study of ancient mortar samp<strong>les</strong> was followed by thelaboratory preparation and testing of experimental mortars withsimilar compositions. The laboratory mixes were prepared using awater/binder (w/b) ratio enabling the mortar to achieve a constantflow of 165 ± 10 mm. The proportion of binder (lime and ceramicpowder) to aggregates was equal to 1:3 w/w. This was selected as theproper mixture ratio for restoration syntheses since it is matching withtechnologies of homologous mortars found in ancient monuments ofthe wider Mediterranean area [6, 10-11].In all experimental samp<strong>les</strong>, the aggregates comprised siliceous andcalcareous sands. The mixing of the aggregates and binder with tapwater was mechanical and always uniform. Compaction of the samp<strong>les</strong>was carried out in accordance to EN 196-1:1995 [12]. It was consideredcritical to use the same batch preparation for all specimens to avoid anydifferences which might occur from batch to batch. Such differenceshave been shown to exist for hydraulic mortars in previous studies [13].The samp<strong>les</strong> were prepared using standardised prismatic steel moulds ofdimensions 40 x 40 x 160 mm. After casting, the moulds containing thespecimens were covered with a glass plate to prevent loss of water byevaporation. Specimens were removed from the moulds after 7 days andthey were kept covered with a w<strong>et</strong> burlap until testing. The performanceefficiency of the experimental mortars was evaluated by a series of testsdesigned to measure their physical and mechanical properties.Results and DiscussionCharacterisation of ancient mortarsLaboratory examination of the ancient mortars under a stereoscoperevealed in most samp<strong>les</strong> the presence of small (angular, sub-angularand rounded) reddish inclusions in a compact (fine-grained) matrix(Fig. 1). These inclusions were identified by SEM/EDX analysis as regionsof silica-alumina composition (i.e. clay brick ceramic).P<strong>et</strong>rographic observations provided evidence that the mortars mostlyconsisted of fine to medium aggregates of quartz, feldspars, pyroxeneand plagioclase. Carbonate compounds and broken shells were alsoobserved in some samp<strong>les</strong>.Microscopic observations also provided ample evidence of productsof boundary reactions. Reaction rims were observed at the interfaceb<strong>et</strong>ween the binding matrix and the ceramic fragments. These weredispersed in the form of veins along the matrix, filling the vacancies and552
<strong>Rendre</strong> <strong>compatible</strong> <strong>les</strong> <strong>techniques</strong> traditionnel<strong>les</strong> <strong>et</strong> <strong>les</strong> <strong>modernes</strong>Compatibilizar técnicas tradiciona<strong>les</strong> y modernasCombining traditional and modern <strong>techniques</strong>discontinuities of its structure. The presence of hydration rims aroundindividual hydraulic phases is indicative of the existence of a strongcohesion b<strong>et</strong>ween the constituent elements of the mortars [14].The results of the mineralogical (XRD) analysis showed that the bindingmaterial of the ancient samp<strong>les</strong> was almost exclusively calcitic. Thepresence of quartz and other accessory minerals was also evidenced inall samp<strong>les</strong>. Salt crystallisation was observed in some cases where haliteand/or gypsum were present. Gehlenite was also evidenced in some ofthe ancient mortars. This is characteristic of the use of natural hydrauliclime burnt at low temperatures (
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