Bond of textile-reinforced belite calcium sulfoaluminate cement mortar to concrete substrate

The fast aging of existing building stock requires effective and sustainable strengthening solutions. Textile-reinforced mortars (TRM) have already proved to be very effective as well as versatile retrofitting solutions for reinforced concrete and masonry structures. TRMs can enhance the load bearing capacity of reinforced concrete structures; however, current TRM systems are based on standard Portland cement-based binders, which largely contribute to global human-induced CO₂ emissions. This work, for the first time, explores the use of belite calcium sulfoaluminate (BCSA) binder for carbon textile reinforcement through a cross-disciplinary study combining structural engineering and materials science. An experimental study was carried out on concrete block members with externally bonded strips of carbon textile-reinforced mortars, similar to a typical TRM retrofitting system for concrete beams. The textiles were embedded in an ordinary Portland cement-based (OPC) binder or in a BCSA-based binder to compare the bond behaviour to the concrete substrate. The tests revealed a superior bond between the BCSA mortar and the concrete, as well as outstanding adhesion to the textiles achieved using the BCSA binder, with performance levels largely surpassing those measured in their counterparts that used the OPC-based binder. Scanning Electron Microscopy, X-ray diffraction, and thermogravimetric analyses were used to understand this behaviour difference and it was concluded that the ettringite phase is responsible for the enhanced performance in the studied system. The results of this study suggest that BCSA binders have the potential to be a more effective and “greener” alternative to the standard binders based on Portland cement in TRM strengthening applications.