A Review of the Combined Effect of Recycled Steel Fibers and Waste Nano Glass On the Technical Performance of Self-Compacting Concrete

There are many advantages to using fibers in self-compacting concrete (SCC) in terms of their structural behavior or mechanical properties, but the porosity in all types of concrete is still a major problem. Thus, continuous research is needed to find solutions to reduce these pores and improve their strength and durability. Self-compacting concrete's (SCC) performance has been greatly enhanced using nanomaterials and recycled steel fibers, however, there are still many unanswered questions to explore their potential fully. The majority of current research focuses on recycled fibers or nanomaterials, with little investigation into how these two elements work together to affect the mechanical properties and durability. It found that the purpose of adding nanomaterials to fibrous concrete is to improve the microstructure, including the interfacial transition zone (ITZ) because it reduces the porosity and boosts hydration products, which will increase the amount of Calcium Silicate Hydrate (C-S-H) gel. In contrast, steel fibers enhanced the mechanical properties of self-compacting concrete and avoided undesirable brittle failure. This work attempts to improve the performance of SCC using a combination of steel fibers taken from scrap tires with nano glass that is taken from the waste of glass. The impacts of fibers and nanomaterials on the structural behavior and mechanical characteristics of SCC were reviewed separately, and then studied their combined effect. Finally, the review recommends adding the nano glass as a partial replacement for cement to benefit from the silica found in the glass composition, which is expected to increase the hydration products and reduce the porosity, because the pozzolanic interaction of glass becomes very active when it reaches a smoothness of (75 µm) due to the increase in surface area. On the other hand, it will improve the bonding strength between steel fibers and cement paste, increasing the ductility and improving the structural behavior to help minimise the brittle fracture and, thus, the associated risks.