The development of non-proprietary Ultra-High Performance Concrete (UHPC) is one way to reduce the initial cost of construction. However, workability is a major issue for which such mixtures are not practical in field conditions. Ultra-high performance cannot be achieved in field conditions if the concrete is not placed, finished, and compacted properly during placement. In this research, six UHPC mixtures were developed (three with steel fibers and three without fibers) using materials which are readily available on the local marketplace with water-to-cementitious materials ratios ranging between 0.17 to 0.30. The workability was determined using standard ASTM flow table apparatus, and specimens were prepared to determine compressive strength, splitting tensile strength, and permeable porosity. Flow table test exhibited flow values greater than 250 mm. Such high workability of the mixtures was achieved by optimizing the silica fume content and water reducing admixture dosage. These mixtures exhibited compressive strengths greater than 120 MPa and splitting tensile strengths greater than 5.10 MPa in both ambient and elevated curing temperatures. Results indicated that UHPC can be produced with a water-to-cementitious materials ratio as high as 0.30. Steel fibers helped to increase splitting tensile strength due to fiber-matrix interactions. Very low permeable porosity (1.7–16.7%) was observed which indicates superior durability due to the significant reduction of ingress of deleterious ions.

Ultra-high performance concrete (UHPC) mixtures are typically developed using fine aggregate with a maximum size of 600 μm. From a sustainability point of view, use of larger size fine aggregate particles in UHPC mixtures should be investigated to reduce labor costs associated with sieving, to reduce wastage of sand, and to improve sustainability. This experimental research investigates the physical, mechanical, and durability properties of UHPC incorporating coarser fine aggregates with maximum particle size of 4.75 mm replacing fine sand. Both plain and fiber reinforced UHPC mixtures were developed with a target static flow of 200 mm (8 in.) and target compressive strength of 120 MPa (17,000 pounds per square inch). Three different curing regimens were investigated: moist curing, warm bath curing at 90°C, and heat curing at 90°C. Compressive and split tensile strengths, permeable porosity, and rapid chloride permeability tests were performed to study the effect of coarser fine aggregate sizes on these UHPC properties. Increasing the maximum fine aggregate particle size range did not affect the workability, compressive strength, permeable porosity, or chloride ion ingress; however, a limited decrease in split tensile strength was observed. A change in aggregate size may have a very large impact on fiber dispersion, embedment, and crack bridging. The experimental results highlight the potential of coarser fine aggregate used in UHPC.