Synergistic effects of cementitious nanocomposites grouts fused with epoxy coatings for restoring concrete structures

Grouting techniques are used in retrofitting structures to improve the structural integrity and performance of existing structures. The recent era of nanotechnology enabled the development of high-performance nanocomposite based cementitious grouts, epoxy grouts, and polyurethane grouts which enhance the strengths, durability, and life span on structures. However, use of only nanocomposite cement grouting is inadequate to bridge micro-cracks, densify the interfacial transition zone (ITZ) after retrofitting. In this study, a novel two-step hybrid crack restoring approach for concrete structures is introduced by combining injected Multi-Walled Carbon Nanotube (MWCNT) reinforced cementitious grout for nanoscale crack-bridging and ITZ densification with an epoxy coating for surface sealing for treating cracks as an integrated nano-micro-surface system. The main objective of the study is improving the mechanical performance and structural integrity of retrofitted concrete structures by assessing their synergistic effect on load-carrying capacity, deformation, and durability. The experimental study is carried out to evaluate the mechanical properties such as load carrying capacity, stress, strain, ductility, sulfate attack and influence of elevated temperature. The results demonstrate that the rupture strength of crack-restored specimens increased by 27.27, 33.33, and 20% compared to plain concrete specimens subjected to controlled room temperature, elevated temperature of 400 °C, and sulfate exposure, respectively. The microstructural analysis reveals that nanoparticle fill-up cracks in the cement composite, enhancing interaction at the interfacial zone. This study highlights the effectiveness of nanomaterial-infused grouting techniques as an innovative and efficient solution for structural retrofitting by offering improved strength, longevity, and resistance to environmental conditions.