Reactive powder concretes

It is a revolutionary cement application, which creates a new range of concretes with a vast range of usages in the future. The compressive strength of this material ranges from 200 to 800 MPa, its tensile strength from 25 MPa to 150 MPa, the crushing energy amounts to 30,000 J/m2 and the density varies from 2500 to 3000kg/m3. It is based on the creation of a very homogeneous blend with the use of very fine materials and non-continuous gradation of proper mix so as to achieve the highest possible density (the ratio of the diameter of the various fractions is approximately 7). The W/C ratio is close to 0.15 and the workability of these mixes is controlled with high percentages of super-plasticizers, while pressure is being applied during hardening. To increase the deformation prior to crushing, steel or carbon fibers are being used. Due to the very small water/cement ratio, a considerable percentage of cement is not hydrated and is being used as an aggregate.

In the figure below, cross-sections from this new material are being compared with respective cross-sections from steel, conventional reinforced concrete and pre-stressed concrete. 

The most well-known and spectacular uses of this material to date are:
  • The 6 meters span pre-stressed pedestrian bridge in Sherbrook, Canada, with a 200 MPa compressive strength.
  • The Sakata-Mirai pedestrian bridge in Japan and the Seonyu footbridge in Seoul, spanning 120m, with a concrete compressive strength of 180 MPa (the bearing structure consists of precast and prestressed arches; Architect: Rudy Ricciotti).