XV International Conference on Durability of Building Materials and Components DBMC 2020, Barcelona C. Serrat, J.R. Casas and V. Gibert (Eds) Effect of Mortar Age on the Textile-to-Mortar Bond Behavior Ali Dalalbashi 1 , Bahman Ghiassi 2 , and Daniel V. Oliveira 3 1 PhD Student, ISISE, University of Minho, Department of Civil Engineering, Azurém, 4800-058 Guimarães, Portugal. E-mail: alidalalbashi@gmail.com 2 Assistant Professor, Centre for Structural Engineering and Informatics, Faculty of Engineering, University of Nottingham, Nottingham, United Kingdom. E-mail: bahman.ghiassi@nottingham.ac.uk 3 Associate Professor, ISISE & IB-S, University of Minho, Department of Civil Engineering, Azurém, 4800-058 Guimarães, Portugal. E-mail: danvco@civil.uminho.pt Abstract. Textile-reinforced mortar (TRM) composites have received extensive attention as a sustainable solution for seismic strengthening of masonry and historical structures. This new system is composed of textile fibers embedded in an inorganic matrix and is applied on the masonry and the concrete substrate surface as an externally bonded reinforcement (EBR) system. The bond at the textile-to-mortar interfaces is the main stress-transfer mechanism and, therefore, should be thoroughly investigated. Furthermore, the effectiveness of TRMs in improving the seismic performance of existing structures is highly dependent on the durability of its components, materials, textile-to-mortar bond, and their long-term behavior. Due to the novelty of these materials in application to masonry structures, several aspects related to the durability and long-term performance of them are still not clear. To that end, a new study has been launched that looks at the time effect on the mechanical properties and bond behavior between fiber and mortar. For this purpose, two different hydraulic lime-based mortars, as well as steel and glass fibers, are used to investigate the effect of mortar age on the TRM system after 180 days. The results show that at the early age of mortars, their mechanical properties, and the bond behavior of textile-to-mortar have been increased. Another critical point to remember is that by increasing the mortar age, textile-to-mortar bond and mortar strength are decreased. Keywords: Textile-to-Mortar Bond Behavior, Durability, Long-Term Behavior, Degradation Mechanism. 1 Introduction The advantages of textile reinforced mortar (TRM) composites to fiber-reinforced polymers (FRPs) are the fire resistance, the vapor permeability, the removability, and the compatibility with masonry and concrete substrates (Carozzi and Poggi, 2015; Papanicolaou, Triantafillou, Papathanasiou, and Karlos, 2007). Thus, these advantages have made TRM composites very interesting for externally bonded reinforcement of masonry and reinforced concrete structures. Mechanical properties of the TRMs and structural components strengthened with TRMs are strongly dependent on the properties of both the mortar and the fiber, the interfacial bond behavior of the fiber-to-mortar, and the interfacial bond behavior between the TRM composite and masonry substrate (Ghiassi, Oliveira, Marques, Soares, and Maljaee, 2016). Although mechanical characterization of TRMs (Leone et al., 2017; Lignola et al., 2017), or the bond between TRM and masonry substrate (Ascione, De Felice, and De Santis, 2015; Razavizadeh et al., 2014) have been the subjects of several studies, the fiber-to-mortar bond