Experimental Investigation of the TRM-to-Masonry Bond after Exposure to Elevated Temperatures: Cementitious and Alkali-Activated Matrices of Various Densities

Abstract

Limited research has focused on the effect of high temperatures on the textile-reinforced mortar (TRM)-to-masonry bond. In this study, masonry prisms that were furnished with double-layered TRM strips were tested under shear bond conditions after their exposure to 200 °C and 400 °C for 1 h using the single-lap/single-prism setup. A total of four TRM systems were applied sharing the same type of textile –a dry AR glass fiber one– and different matrices: two cementitious matrices, namely a normal-weight (TRCNM) and a lightweight (TRCLM) one, and two counterpart alkali-activated matrices (TRAANM and TRAALM) based on metakaolin and fly ash. Specimens’ exposure to elevated temperatures did not alter their failure mode which was due to the sleeve fibers’ rupture along with core fibers’ slippage from the mortar. The residual bond capacity of the TRM systems decreases almost linearly with increasing exposure temperature. The alkali-activated textile reinforced mortars outperformed their cement-based counterparts in terms of bond strength at every temperature. All systems retained close to 50% of their original shear bond strength after heating at 400 °C. Per the type of binder, lightweight matrices resulted in either comparable (cement-based systems) or better (alkali-activated systems) heat protection at the TRM/masonry interface.

Shear strengthening of masonry walls with Textile Reinforced Mortars (TRM) under high temperature exposure

“…In Ref. [47] bond decreases around 50% are obtained in specimens exposed to 400 • C, studying TRMs with glass fiber textiles and four different matrices (two cement-based and two alkali-activated mortars). In Ref.…”

“…For this reason, these systems are often misperceived as fire resistant and therefore can be used without protection, when in fact this is not the case. In recent years, some published studies analyze the loss of mechanical properties of different TRMs exposed to elevated temperatures by means of uniaxial tensile coupon tests [38][39][40][41][42], or study their bonding to masonry or concrete substrates [43][44][45][46][47]. In this regard, it is fitting to note the study reported in Ref.…”

Out-of-plane performance of structurally and energy retrofitted masonry walls: geopolymer versus cement-based textile-reinforced mortar combined with thermal insulation

“…Recent attempts to reduce the environmental impact of TRM systems focused on geopolymers as new binding materials for the textiles, which have potential to become an alternative to Ordinary Portland Cement (OPC) binders ( Arce et al , 2022a ; Askouni et al , 2021 ; Cholostiakow et al , 2023a ; Ghiassi et al , 2016 ; Gkournelos et al , 2022 ; Skyrianou et al , 2022 ; Tamburini et al , 2017 ; Wang et al , 2021 ; Zhang et al , 2019 ; Zhang et al , 2022 ). Geopolymers, which can be formed by mixing silicate dry products with an alkaline solution, exhibit excellent mechanical properties, high durability, and resistance to elevated temperatures, thus making them potential candidates as an alternative to cement-based materials, but also in a variety of uses as a fireproof adhesive for fibre-reinforced composites and laminates ( Arce et al , 2022b ; Chen et al , 2021 ; Giancaspro et al , 2009 ; Giancaspro et al , 2010 ; Katakalos & Papakonstantinou, 2009 ; Mobili et al , 2016 ; Papakonstantinou et al , 2001 ; Papakonstantinou & Balaguru, 2006 ; Papakonstantinou & Balaguru, 2007 ; Papakonstantinou & Katakalos, 2009 ; Zhang et al , 2018 ).…”

Empirical Equations for Modelling Yarn–Mortar Debonding in TRM-Strengthened Masonry Walls Subjected to Out-of-Plane Loading

“…Although the bond behaviour has been the focus of several recent experimental and analytical studies (e.g., Refs. [57][58][59][60][61]), the topic still remains open; detailed finite element simulation of the mechanics at the mortar-fibre interface results in computationally intensive models. Furthermore, identifying micro-mechanical interface parameters necessitates involved experimental procedures, often resulting in significant variance.…”