Rheological behaviour of ultra-high performance cementitious composites containing high amounts of silica fume

This study investigates the rheological behaviour of ultra-high performance cementitious composite mortars containing 15-25 % of silica fume. The utilization of two Portland cements with different mineralogical compositions and their influence on yield stress of mortar was monitored. The coaxial rheometer was used for determination of flow curves of tested samples. It was found that besides the relation between flow and water-to-binder ratio, there is also a substantial relationship with the mortar composition, in particular with the content of silica fume. The yield stress can be described by an exponential function of volume content of solids in the mortar. Such a function can describe not only the influence of granulometry but also the impact of structure formation on early age Portland cement hydration. It was found that the estimation of yield stress can be done even by a simple modular in-field technique such as a spread flow test.