Mechanical Properties of Modified Reactive Powder Concrete

Original Reactive Powder Concrete (RPC) - in form of a superplasticized cement mixture with silica fume, steel fibers and ground fine quartz 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 160C. 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 to high compressive strength level of RPC (200 MPa) to the absence of coarse aggregate. Both the original and modified RPC (with coarse aggregate addition) perform better - in terms of higher strength and lower drying 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. The main purpose of the present investigation was to modify RPC including some coarse aggregate in the mixture and to study the influence of the coarse aggregate on the properties of cement mixtures in terms of required mixing water, compressive and flexural strength, shrinkage, swelling and creep.