Development of Ultra High Performance Concrete and Reactive Powder Concrete with Nanosilica

The article is dedicated to the design and production of Ultra High Performance Concrete (UHPC) and Reactive Powder Concrete (RPC) using silica fume and nanosilica. Nanosilica and fine steel fibres were used for the production of RPC. Compressive strengths of UHPC and RPC above 150 MPa have been achieved. It has been demonstrated that UHPC and RPC can be produced using standard concrete mixing system without the use of activating mixing and without a special treatment regime during maturing of the concrete. Aging of the concrete took place in a normal environment, without elevated pressure or temperature. The aging process at 20 °C allows the use of UHPC and RPC for the ready-mixed concrete when working on high volume construction projects. Even without thermal treatment, without the application of solidification pressure and without autoclaving, RPC reached a compressive strength of more than 180 MPa and a flexural tensile strength after 60 days greater than 22 MPa. The high tensile bending strength may be considered as the main advantage of RPC, as the RPC parameters allow, for instance, the use for pre-stressed structural elements where a high initial strength is also required.