Strength and permeability of steel fibre reinforced grouts

The feasibility of using steel fibres to improve the tensile strength and durability of cement–sand grout was investigated. Initial tests focused on achieving pumpable grout mixes and 13 mm round steel fibres with a diameter of 0.16 mm were found to be compatible with a conventional grout paddle mixer and piston pump. Subsequently, grouts with 0.5% and 1% fibre volume fraction were subjected to compressive and splitting tensile strength tests, coefficient of permeability tests and wet–dry cycles. The effect of partial cement replacement with silica fume and blast furnace slag was also investigated. It was found that steel fibres were beneficial for short- and long-term tensile strength. Coefficient of permeability was not adversely affected by addition of fibres. Resistance to microcracking and increase in permeability after wet–dry cycles was also improved by steel fibres. Partial replacement of cement with blast furnace slag resulted in enhanced mechanical properties, whereas the results for silica fume were mixed.