Behavior of Fiber Reinforced Cementitious Matrix Elements under Combined Thermo-Mechanical Loads

Typical strengthening of concrete structures is currently achieved with fibre reinforced polymers (FRP), which uses organic resin (epoxy) in the process of application. But towards the end of the last century, an upgraded system was introduced as an alternative for FRP for the rehabilitation of historic and damaged concrete and masonry structures known as fibre reinforced cementitious matrices (FRCM). FRCM systems are made from different materials like glass, steel, and carbon fibre meshes that each has a different strengthening capacity and temperature resistivity. The mesh of this system is formed from fabric grids and cementitious matrix components that are functioning as a matrix and binder. The inorganic cementitious mortar used by FRCM systems can be advantageous in harsh environments due to its excellent thermal behaviour and binding characteristics. Several small and large size beams were initially strengthened with FRCM systems and tested mechanically under four point bending. One and two layers of FRCM, as well as steel net material were used, and compared with a control beam. The observed results confirmed the higher flexural capacity and stronger bond when FRCM system replaces FRP composites in strengthening of concrete beams. In addition, several concrete specimens reinforced with FRCM and steel net were tested under a combination of mechanical loads representing gravity and controlled elevated temperatures. The results confirmed the specimens strengthened with FRCM outperformed those using typical FRP composites, mainly because of the superior thermal performance of the cementitious inorganic resin. Further, a new numerical finite element model was developed to investigate the structural response of FRCM-strengthened specimens under thermo-mechanical loads. The model was validated against the derived experimental data. The model was then used to investigating the different parameters affecting the behaviour of FRCM systems, especially at higher temperatures. The study demonstrates the viability of using FRCM systems as the strengthening and replacement material for FRP composites, particularly under elevated temperatures.