Evaluation of dry mortar ratio as mix design parameter for steel fibre reinforced self compacting concrete

This paper provides a study whose aim is to validate the dry mortar ratio Dm concept in order to simplify the mix design of steel fibre reinforced self compacting concrete (SFRSCC). For this purpose, steel fibres with diameters and thickness, 30/0.50 and 60/0.80, were added to concrete in volumes of 0.5%, 1.0% and 1.5%. The fresh SFRSCC properties such as consistence, viscosity and passing ability and the hardened properties such as compressive strength, modulus of elasticity, equivalent flexural tensile strengths and sorptivity are measured. The steel fibres dispersion is also evaluated by counting method. The results demonstrate that the dry mortar ratio is dependent of fibre factor content. The increasing of steel fibres volume modifies the slump-flow, but this influence is not significant on the SFRSCC viscosity and passing ability, if an adequate dry mortar ratio is provided. The dry mortar ratio allowed sufficient homogeneous fibre dispersion for all tested fibre factor. In general, the steel fibre volume variation brings no relevant influence on the SFRSCC sorptivity coefficient. However, this coefficient is influenced by W/B ratio increasing and by fine content reduction in the mixtures. Finally, the results of SFRSCC fresh and hardened properties confirm the effectiveness of dry mortar ratio as a parameter to control the design of self compacting mixtures.