We propose the development of a simple, low cost technology for the field placement of ultra-high performance concrete (UHPC) that consists of a modified Gunite system and an improved UHPC formulation. The Gunite system includes modifications that overcome a number of problems related to the delivery of UHPC via gunnite including dust suppression and nozzle plugging associated with rapid setting fiber reinforced cementitious materials. An atomized water mist is produced that is much more effective at wetting very fine particles essential to making UHPC, improving uniformity, eliminating rebound, and producing a very dense concrete with greatly improved strength. The new system autogenously cured needing no external source of heat. The improved UHPC formulation is based on a calcium sulfoaluminate (CSA)--Portland (OPC) blended cement, anhydrite, ultra-fine fly ash (UFA), Polyvinyl alcohol (PVA) fibers, steel fibers, a proprietary accelerator and graded quartz river sand. This formulation results in a much higher rate of strength development, as well as the prerequisite total strength. The UFA provides a strong pozzolanic component and contributes to the overall density and long term strength of the final UHPC. The UHPC gunnite formulation also has superior adhesion and bonding to a range of fibers and preexisting surfaces.
Keywords: Gunite, Ultra Fine Ash (Ufa), Calcium Sulfoaluminate Cement (Csa), Rapidly Deployable, Rapid Strength Development, Superior Bonding, Fiber Reinforced, Low Cost
