Shrinkage Cracking Propensity of UHPC

It is widely accepted that ultra-high performance concrete (UHPC) provides better mechanical and durability properties than high performance or conventional concrete. The high cementitious materials and fiber contents are key to its change in properties, making this type of material suitable for a wide range of structural applications. However, because of its very low water-to-cementitious materials ratio range (i.e, 0.18-0.22) compared to that of high strength and/or conventional concrete (typically higher than 0.30), this type of material can be more prone to autogenous shrinkage cracking. This paper will examine the shrinkage cracking propensity of several commercially-available UHPC materials compared to that of a typical high strength concrete, a conventional concrete, and a cementitious grout. A dual ring test will be used for this purpose, which offers the possibility to not only assess the tensile stress developed in the material due to restrained autogenous shrinkage, but also to estimate the stress reserve capacity of the materials (that is, how near the materials are to cracking). The results will help UHPC designers and end users better understand the cracking behavior of these materials under restrained conditions.