Mechanical properties of modified reactive powder concrete

Original Reactive Powder Concrete (RFC) - in form of a superplasticized cement mixture with silica fume, steel fibers and ground fine quartz (150-400 (μm) - was studied in comparison with a modified RPC where a graded natural aggregate (max size 8 mm) was used to replace the fine sand and/or part of the cementitious binder. Original and modified RPC were manufactured at a plastic-fluid consistency, cast by vibration and cured at three different conditions: a) room temperature; b) steam-curing at 90°C; c) high pressure steam-curing at 160°C. The addition of the graded aggregate does not reduce the compressive strength provided that the quality of the cement matrix, in terms of its water-cement ratio, is not changed. This result is in contrast with the model proposed to relate the high compressive strength level of RPC (200 MPa) to the absence of coarse aggregate. Both the original and modified RPC (with the coarse aggregate addition) perform better - in terms of higher strength and lower driving shrinkage or creep strain - when they are steam cured rather than cured at room temperature. This improvement was related to a more dense microstructure of the cement matrix, particularly in the RPC specimens steam cured at 160°C.