Influence of constituents on strength and flowability in ultra high-performance concrete

Ultra-high-performance concrete (UHPC) boasts superior characterizations like excellent flowability, mechanical properties and durability. These features are achieved by adopting low water-to-binder ratio (w/b), good particle packing density and high dosage of steel fibers. This study mainly focused on the development of the optimized UHPC mixes by considering locally available materials. The impact of different composition of ordinary Portland cement (OPC) with different CaO/SiO₂ ratio (4.31, 4.37, 4.49, 4.53, 4.60 and 4.82) on the compressive strength and flowability were investigated to ensure versatility across applications. The compressive strength of UHPC mixes by using various types of fine aggregates namely, manufactured sand, standard sand, river sand and quartz sand were also investigated. Also, the compressive strength as well as flowability of UHPC were studied by varying the fiber content of 0%, 1%, 1.5%, 2%, 2.5% and 3%. The results reveal that the compatibility of OPCs with varying CaO/SiO₂ ratios has minimal impact, whereas different sand types significantly influence both flowability and compressive strength of UHPC mixes. Considering cost, availability and performance, M Sand and quartz sand can be used for the development of UHPC. Also, it was observed that increase in fiber content enhances the compressive strength while negatively influencing the flowability.