Abstract The paper contains quantitative characteristics of changes in the porosity and mechanical properties of RPCs caused by applying different pressures during concrete mixing, i.e. atmospheric pressure and pressure reduced to 500 and 40 mbar. The effect of curing conditions was determined as well: the impact of curing in water (Tmax = 20 °C), steaming (Tmax = 90 °C) and autoclaving (Tmax = 250 °C) on the porosity, compressive strength and flexural tensile strength of the materials tested. In addition, the maximum volumetric proportion of 6 and 14 mm steel micro-fibres which can be introduced in a standard manner, i.e. during the production of the RPC mix, was determined depending on their length. Besides the basic mechanical characteristics, tests of mechanical properties of RPCs containing fibres included the determination of the following parameters: σLOP (limit of proportionality), σMOR (modulus of rapture), Wf (work of fracture) and the toughness indices. Test results clearly confirm the considerable impact of pressure during RPC mixing and curing conditions on the durability and mechanical properties of the hardened composites. The maximum volumetric proportion of micro-fibres introduced during mixing was 8%. Steel fibre reinforcement was found to be more effective when longer fibres were used.
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