Volume 38, Issue 6 (November 2010)
Tensile Creep Test of Fiber-Reinforced Ultra-High Performance Concrete
This paper describes the development and use of a high cost and space efficient tensile creep test setup for cement-based materials. This test setup features a load capacity of 6800 kg (15 000 lb), capacity for three specimens in series, and the ability to measure deformations at four points for each specimen with an accuracy of 10 micro-strains. This newly developed test setup allowed testing the long-term tensile creep of ultra-high performance concrete (UHPC) for the first time. In the experimental study, steel fiber-reinforced UHPC prisms were subjected to tensile creep to investigate the effect of different thermal treatment conditions on their viscoelastic response over a 1-year period. Results from the experimental study showed the necessity to perform tensile creep tests rather that direct tensile strength tests to predict the long-term tensile performance of UHPC. These results show that the quality of the bond between the fibers and cementitious paste was better evaluated using tensile creep than direct tension tests. Experimental results showed that specific tensile creep of UHPC decreased between 63 % and 69 % when thermal treatment of 60°C (140°F) for 72 h or of 90°C (194°F) for 48 h was applied, respectively, prior to loading. Results from this study also point to the necessity of having a standard tensile creep test similar to the currently existing compressive creep standard, especially if the tensile capacity of concrete is considered in structural design.