Characterisation of roman mortars from Conímbriga with respect to their repair A.L. Velosa a, ⁎ , J. Coroado b , M.R. Veiga c , F. Rocha d a Department of Civil Engineering, University of Aveiro, 3810-193 Aveiro, Portugal b Polytechnic Institute of Tomar, Portugal c National Laboratory of Civil Engineering (LNEC), Portugal d University of Aveiro, Department of Geological Engineering, Portugal Received 15 March 2007; received in revised form 29 June 2007; accepted 29 June 2007 Abstract The need for the formulation of mortars for repair of ancient Roman renders in the archaeological site of Conímbriga brought about the need for a study of the rendering solutions existent therein. Various samples were extracted and analysed by means of acid attack followed by determination of particle size distribution, execution and visualization of thin sections, thermal analysis and mineralogical and chemical analysis using XRD and XRF. This paper presents the results of four of the Conímbriga mortars; the results show similarities in terms of the raw materials that were used and crushed ceramic particle size. © 2007 Elsevier Inc. All rights reserved. Keywords: Mortar; Conservation; Opus Signinum 1. Introduction Amidst the various building techniques used during the Roman Era, documented by Vitruvius' Ten Books of Architecture [1], a mortar made of lime and sand with the addition of potsherds, previously grounded and sieved is recommended for plastering, with the note that the added ceramic particles will make the mortar better for use. The execution of this kind of render is also suggested by the same author for specific use in the case of walls subject to continuous damp. In the absence of natural pozzolanic material such as that available in Pozzuoli and other volcanic regions, Romans employed ceramic particles and dust to fulfill the same role. Hence, dispersed throughout archaeolog- ical remains of urban conglomerations belonging to the Roman Empire, mortars of a reddish colour, usually designated as Opus Signinum, frequently exist as ren- ders used in tanks, aqueducts, pools and other water- bearing constructions. In Portugal, where no natural pozzolanic material was obtainable, the use of this technique is widespread and the main archeological sites display walls covered by Opus Signinum. This is the case at Conímbriga, which suffered Roman occupation from century 1 B.C. until sometime between the years 465 A.D. and 468 A.D. Although buried for a long period of time, the dura- bility of these mortars is still remarkable; however, in a Materials Characterization 58 (2007) 1208 – 1216 ⁎ Corresponding author. Tel.: +351 234370049; fax: +351 234370094. E-mail addresses: avelosa@civil.ua.pt (A.L. Velosa), jcoroado@ipt.pt (J. Coroado), rveiga@lnec.pt (M.R. Veiga), frocha@geo.ua.pt (F. Rocha). 1044-5803/$ - see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.matchar.2007.06.017