Exploring mechanical and durability properties of ultra-high performance concrete incorporating various steel fiber lengths and dosages

Ultra-high performance concrete (UHPC) is a new generation of steel fiber-reinforced concrete with superior mechanical and durability properties. However, limited data is available on the influence of the steel fiber length and dosage on UHPC mechanical and durability performance. Therefore, in this study, a number of UHPC mixtures with varying steel fiber lengths (8 mm (0.31 in), 12 mm (0.47 in) and 16 mm (0.62 in)) and dosages (1%, 3% and 6%) by mixture volume were tested. Mechanical properties of UHPC including compressive, splitting tensile and flexural strengths were assessed. Moreover, its resistance to chloride ions penetration and mechanical degradation under various chloride exposures (i.e. 3.5% and 10%) were evaluated. Results showed an increase in mechanical properties as the fiber dosage increased. UHPC mixtures incorporating short steel fibers exhibited enhanced flexural properties compared to that of mixtures with similar volume of longer steel fibers. At higher fiber dosage, UHPC mixtures exhibited relatively improved durability. Moreover, no degradation in UHPC mechanical properties was observed after exposure to various chloride ions solutions.