Influence of cracking on oxygen transport in UHPFRC using stainless steel sensors

[EN] Reinforced concrete elements frequently suffer small cracks that are not relevant from the mechanical point of view, but they can be an entrance point for aggressive agents, such as oxygen, which could initiate the degradation processes. Fiber-Reinforced Concrete and especially Ultra High Performance Concrete increase the multi-cracking behavior, reducing the crack width and spacing. In this work, the oxygen availability of three types of concrete was compared at similar strain levels to evaluate the benefit of multi-cracking in the transport of oxygen. The types of concrete studied include traditional, High-Performance, and Ultra-High-Performance Fiber-Reinforced Concrete with and without nanofibers. To this purpose, reinforced concrete beams sized 150 x 100 x 750 mm(3) were prepared with embedded stainless steel sensors that were located at three heights, which have also been validated through this work. These beams were pre-cracked in bending up to fixed strain levels. The results indicate that the sensors used were able to detect oxygen availability due to the presence of cracks and the detected differences between the studied concretes. Ultra High Performance Concrete in the cracked state displayed lower oxygen availability than the uncracked High Performance Concrete, demonstrating its potential higher durability, even when working in cracked state, thanks to the increased multi-cracking response. The authors would like to express their gratitude to the Spanish Ministry of Science and Innovation for the pre-doctoral scholarship granted to Ana Martinez Ibernon (FPU 16/00723), to the Universitat Politecnica de Valencia for the pre-doctoral scholarship granted to Josep Ramon Lliso Ferrando (FPI-UPV-2018), and the European Union's Horizon 2020 ReSHEALience project (Grant Agreement No. 760824). Martínez-Ibernón, A.; Roig-Flores, M.; Lliso-Ferrando, JR.; Mezquida-Alcaraz, EJ.; Valcuende Payá, MO.; Serna Ros, P. (2020). Influence of cracking on oxygen transport in UHPFRC using stainless steel sensors. Applied Sciences. 10(1):1-17. https://doi.org/10.3390/app10010239 Front Matter. (2013). fib Model Code for Concrete Structures 2010, I-XXXIII. doi:10.1002/9783433604090.fmatter Yoo, D.-Y., & Banthia, N. (2016). Mechanical properties of ultra-high-performance fiber-reinforced concrete: A review. Cement and Concrete Composites, 73, 267-280. doi:10.1016/j.cemconcomp.2016.08.001 Wittmann, F., & Van Zijl, G. (Eds.). (2011). Durability of Strain-Hardening Fibre