Durability Performance of Micro-Titanium Dioxide and Steel Fibre Modified Recycled Aggregate Concrete

Recycled aggregate concrete (RAC) represents a sustainable alternative to conventional concrete; however, its broader application is constrained by reduced durability associated with the porous nature of recycled aggregates. This study investigates the effectiveness of micro-titanium dioxide (micro-TD) and steel fibres (SF) in enhancing the durability, structural response, and functional performance of RAC. Nine concrete mixes were prepared using 25%, 50%, and 100% replacement of natural coarse aggregate with recycled coarse aggregate by volume, micro-TD dosages of 5%, 10%, and 15% as partial cement replacement by weight, and a constant steel fibre content of 1%, incorporating the two-stage mixing approach. Durability properties, including water absorption, sorptivity, and resistance to acid, alkali, and sulphate attack, were evaluated alongside rebound hammer response, beam performance, photocatalytic activity, and microstructural characteristics. The results indicate that increasing recycled aggregate content adversely affects durability, whereas incorporating micro-TD significantly improves matrix densification and resistance to aggressive environments. Optimum performance was achieved with a mix containing 25% recycled aggregate, 10% micro-TD, and 1% SF, demonstrating enhanced durability, structural behaviour, and photocatalytic properties. The findings confirm that the combined use of micro-TD and steel fibres is an effective strategy for producing durable and functional RAC suitable for sustainable construction applications.