A New Mix Design Method for UHPC based on Stepwise Optimization of Particle Packing Density

This paper presents a new approach which is based on stepwise optimization of particle packing density for ultra-high performance concrete (UHPC) mix design. At first the method of superplasticizer-water solution demand measurement was used to find out the compatibility of the commercial raw materials of cements, silica fumes, quartz powders and superplasticizers regarding packing density and strength. As a result, the most suitable components and the optimum cementitious pastes were determined. Subsequently the optimum cementitious pastes with a fixed volume were combined with the blended aggregate which was formed by the combination of different grain aggregates of quartz sands or (and) crushed basalts. Based on the determination of the highest self-flowability and the lowest plastic viscosity for concretes the optimum mix proportions for UHPCs were recognized corresponding to the optimum blended aggregate. Four different self-compacting UHPC series with the different maximum grain sizes of 1 mm, 2.5 mm, 4 mm, 8 mm and compressive strength higher than 190 MPa were developed. In comparison to the reference mixtures the developed optimum UHPCs were much more effective in term of materials saving and performance improving