Rheological, hydration and mechanical characteristics of microsilica fibre reinforced cement combinations with incremental fly ash contents

Cement combinations are usually manufactured by partially replacing Portland cement with fly ash (FA) due to its pozzolanic properties and low carbon emissions. The challenge, however, is selecting an optimum FA content that is viable in terms of the sustainability, cost and performance of the combination for a given application. This paper examines the properties, microstructure and hydration of fibre reinforced microsilica cement combinations with varying FA contents. Results indicated that the addition of FA prolonged the initial and final setting times of the combinations, decreased the viscosity peaks and lowered the ettringite, C-S-H and Ca(OH)2 contents. At low FA contents, permeation and mechanical properties were still comparable to those of a reference sample. It was observed that combinations with 30% or more FA contents exhibited significant reductions in alkalinity, performance and Ca/Si ratios. Furthermore, the performance of the combinations seemed to reach a plateau regime between FA contents of 15% and 30%.