Estudio del comportamiento mecánico del hormigón de ultra-altas prestaciones (UHPC) reforzado con fibras híbridas y con consumo reducido de cemento

R Christ,H Ehrenbring,B.F Tutikian,F Pacheco,M Mancio,U Quinino

doi:10.4067/s0718-50732019000200159

R Christ, H Ehrenbring + Show 4 more

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https://doi.org/10.4067/s0718-50732019000200159

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Abstract

This article evaluated mechanical behavior of ultra-high performance concrete (UHPC) reinforced with hybrid steel and polypropylene fibers, with cement consumption of 250 kg/m³ and application of confining pressure in fresh state. The consistency of the mixture was analyzed, as well as mechanical properties of compressive strength, flexural strength and toughness. The percentages of hybridization were 50 to 100% of metal fibers and 0 to 50% of polypropylene fibers. Results showed that the compressive strength of the composite was 180 MPa (26100 psi), despite its low cement consumption of 250 kg/m³ (2.08 lb/gal), with 80% steel fibers and 20% polypropylene fibers. The combination of fibers increased the mixture’s toughness. For the composition with 80% steel fibers and 20% polypropylene fibers, the strength for large deformations increased by 191% compared with the mixture with 100% steel fibers, pointing out the benefits of hybridization

Highlights

It is known that concrete has limitations towards its ability to resist tensile stresses, which can be compensated by the addition of steel bars or fibers that allow this material to be used in the most diverse structures (Yoo et al, 2017)( Yu et al, 2015a)
As polypropylene fibers are smaller than steel fibers – the diameter of a polymer fiber, for instance, is about 95% lower than the diameter of steel fibers – the resulting composite has higher fiber concentration, which yields larger specific area
90%, and polypropylene fibers by 20% and 10%, Based on the test results for reactive powder concrete samples reinforced with hybrid steel-polypropylene fibers and respectively, provide increased toughness of the reinforced material for larger displacements

Summary

Introduction

It is known that concrete has limitations towards its ability to resist tensile stresses, which can be compensated by the addition of steel bars or fibers that allow this material to be used in the most diverse structures (Yoo et al, 2017)( Yu et al, 2015a). Ultra-high performance concrete (UHPC) has shown up as a promising civil construction material for the 21st century, as several studies have been developed regarding their structural behavior and other characteristics (Yoo et al, 2017)(AFGC, 2013)(Guo et al.,2018)(Safdar et al, 2016)(Shin et al, 2017). Concerning high consumption of binder, cement consumption turns out to be between 1100 and 1300 kg/m3 in most studies (Torregrosa, 2013) This high amount of cement is not necessarily the main factor that guarantees the material’s mechanical properties, which are linked to other factors such as low porosity, high mixture compactness and reinforcement’s usage (Alkaysi et al, 2016)(Christ, 2014)(Wille and Boisvert-Cotulio, 2015). A substitution of 50 to 60% of fly ash with respect to cement mass can improve the mixture’s consistency, reduce water consumption and improve cracking behavior due to the reduction of heat from cement hydration (Wang and Park, 2015)

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