Geopolymers and polymers in the conservation of tile facades Sara Moutinho a,⇑ , Cristiana Costa b , Ângela Cerqueira c , Fernando Rocha b , Ana Velosa d a Civil Engineering Department, RISCO, University of Aveiro, Portugal b Geosciences Department, GeoBioTec & RISCO, University of Aveiro, Portugal c Geosciences Department, GeoBioTec, University of Aveiro, Portugal d Civil Engineering Department, RISCO & GeoBioTec, University of Aveiro, Portugal highlights  Geopolymers visual observation showed that the GEO-MKZL had the better behaviour (without cracking or salt formation).  Compressive strength showed that Geo-MKZL have a desired compacted structure.  Polymers showed a better behaviour only in the bonding tile fragments.  Geopolymers showed a better adhesion to ceramic body than polymers.  Geopolymers showed potential to be applied into ceramic glazed tiles. article info Article history: Received 7 June 2018 Received in revised form 22 October 2018 Accepted 7 November 2018 Keywords: Tiles Geopolymers Polymers Conservation Lacunae abstract The most commonly used materials to fill gaps/lacunae in glazed tiles are lime mortars or organic resins, which have some disadvantages regarding their compatibility and durability, failing to guarantee the desired characteristics. Therefore, there is a need to develop new materials with compatible characteris- tics, able to withstand exposure to variations in climatic conditions. This scientific work focuses on the possibility of using geopolymers, aiming to evaluate the possibility of the use of these materials in the intervention process of historic tiles conservation as compatible materials that may be used to fill gaps. Different geopolymer pastes were developed changing the source of aluminosilicates, the type of alkaline activators and the pH. To evaluate the geopolymers, polymers and tiles, several tests were carried out. The results suggest that the geopolymers are a possible option for the filling of tile gaps, given the char- acteristics that can be achieved, ensuring compatibility and durability properties. Ó 2018 Elsevier Ltd. All rights reserved. 1. Glazed tiles as a coating of facades Glazed tiles (azulejos) are characteristic elements of the Por- tuguese built heritage, being part of the historical identity of Por- tuguese culture [1]. They are characterized by their dimensions, their aesthetic expression and also by the raw materials used and manufacturing procedures employed [2,3], which condition the performance of the parts produced in terms of water beha- viour, wear and resistance. This material that started to be used in Portugal is composed by two parts – a tardoz (ceramic body) – and a glazed surface [4]. The composition of the ceramic body influences the performance of the tile, being evident that a new tile and an old ceramic tile have different characteristics and conse- quently different performance, due both to an initial difference in materials and porous structure and the action of degradation agents and adverse environmental conditions [4]. Therefore, it is important to study the behaviour of old tiles and to improve the properties of the materials used in the conservation of the built heritage, ensuring the compatibility of the employed solutions. For several centuries Netherlands, Italy, England and Portugal tile claddings have been used although they express differences in terms of the decorative elements and also of architectural expression [5]. Since the 16th century they have been used in the national territory and it in the mid-19th century were consid- ered a traditional coating material in several Portuguese cities, with a particularly pronounced expression in city of Oporto. In order to meet the evolution in terms of building demands, there was a differentiation in tile production, resulting from the technological innovations in ceramic production. Through the times there have been changes concerning the pictorial layer of the tile as well as the ceramic body. https://doi.org/10.1016/j.conbuildmat.2018.11.058 0950-0618/Ó 2018 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: sara.moutinho@ua.pt (S. Moutinho), cristianacosta@ua.pt (C. Costa), angelamcerqueira@ua.pt (Â. Cerqueira), tavares.rocha@ua.pt (F. Rocha), avelosa@ua.pt (A. Velosa). Construction and Building Materials 197 (2019) 175–184 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat