ACI 239R-18 Ultra-High-Performance Concrete: An Emerging Technology Report.
The durability of UI-I PC is superior to that of conventional concrete. This is due to the dense matrix, discontinuous microstructure. and well-dispersed microcracking of the material. Ul-IPU demonstrates improved resistance to many kinds of harmful gases and liquids, chloride attack, frost action, and freezing-and-thawing cycles. These improvements are related to the higher density of’ the hydration products and of the transition zone between the matrix and the aggregates (Schmidt and Fehling 2005). The porosity of Ul-IPC is approximately 9 percent when compared to 15 percent for conventional concrete (Roux ci al. 1996). In addition, there are very few to no capillary pores in UI-WC (Uheyrezy et al. 1995), which leads to a largely discontinuous pore structure. Research has shown thai the water permeability coetlicient is approximately one to two orders of magnitude lower than thai of conventional concrete, even when the UHPC exhibits some microcracking (Roux ci al. 1996: Charron et al. 2007).
The dense matrix oIUFIPC slows the penetration of deleterious solutions into the microstructure, and so the mechanisms duit can cause conventional concrete to deteriorate are mitigated (Thomas ci al. 2012). Consequently, durability properties, as measured by permeability tests, freezing- and-thawing tests, scaling tests, abrasion tests, resistance to chloride ingress, alkali-silica reaction, and carbonation are significantly better than those of conventional concrete Russell and Graybeal 2013). 1HPC has a high ohmic resistance in comparison to conventional concrete, which further reduces the corrosion risk of embedded steel reinforcing (Rouxetal. 1996).
The superior performance ol’ UH PC has been confirmed with field experiments where two different Ul-IPC mixtures were placed at the mid-tide level of the marine exposure site at Treat Island, ME. under severe exposure conditions. Test results after exposure periods of 5 and 15 years showed no observed degradation of mechanical or durability properties and confirmed the excellent durability properties of UI-IPC (Thomas et al. 2012). Monitoring of LTHPC beams placed in the aggressive environment of the water-cooling tower of the Cattenom nuclear power plant in France for over 10 years also demonstrates the excellent durability of UHPC (Toutlemonde et al. 2009). Similar satistuictory durability results have been obtained l’or Sakata Miral pedestrian bridge and Hourg-lès-Valence road bridges (Kono ci al. 2013: ToLitlemonde ci al. 2013).
Numerous studies have addressed fire resistance of UHPCs (Russell and Graybeal 2013). Special formulations may be developed for enhanced fire resistance. In some cases, polypropylene fibers have been shown to increase the fire resistance of this class of materials.ACI 239R pdf download.