Optimizing Ultra High-Performance Concrete Mixtures Adopting the Modified Andreassen Approach

Abstract

This paper addresses the mixture design and assessment of properties related to cost-effective ultra high-performance concrete (UHPC), targeting densely compacted cementitious matrices. The modified Andreasen and Andersen particle packing model was employed to define boundaries between binder and aggregate content. Optimization was initially performed for mortar followed by concrete. Mortar mixtures involved ternary replacement of cement by silica fume, metakaolin and limestone at various volume percentages of 35% to 55%. Adding basalt to mortar allowed 20-30% volume replacement to obtain a unique UHPC mixture that satisfied the requirements of particle packing models and performance-based approaches with minimal impact of compressive strength. The results show that the modified Andreasen and Andersen particle packing could represent the formwork of UHPC mixture design while the performance-based approach is necessary to reach the optimum mix. The addition of 2% volumetric ratio of short double-headed steel fibers improved the compressive and tensile strengths by up to 13% and 50%, respectively. Steam curing accelerated the gain of concrete strength compared to normal and hot curing methods.