Material design of economical ultra-high performance concrete (UHPC) and evaluation of their properties

Coupling of separate optimizations of binder and aggregate phases to produce sustainable and economical ultra high-performance concrete (UHPC) mixtures is reported. Binders containing commonly available cement replacement materials with a (mass-based) cement replacement level between 30% and 50% are selected using microstructural packing- and rheology-based criteria. These binders are used along with aggregate sizes/amounts selected based on maximum packing density predicted by a compressible packing model to produce UHPC mixtures having a compressive strength > 150 MPa. Three coarse aggregate sizes (maximum nominal size of 6.25 mm, 4.75 mm, and 2.36 mm) and two fine aggregate sizes (d₅₀ of 0.6 mm and 0.2 mm) are used in the optimization process, which is implemented in a computer program. Packing considerations relevant for polydisperse mixtures and the presence of fibers are incorporated. The high compressive and flexural strengths of these mixtures coupled with very high resistance to moisture and ionic transport validates the material design procedure. A preliminary cost analysis is also presented to demonstrate that UHPC mixtures can be proportioned at a fraction of the cost of proprietary mixtures using a fundamental materials science-based design approach.