Influence of flowability, casting time and formwork geometry on fiber orientation and mechanical properties of UHPFRC

Zhou, Bo; Uchida, Yoshiyuki

doi:10.1016/j.cemconres.2017.02.017

Cited by 95 publications

(33 citation statements)

References 16 publications

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“…Along with compressive strength, the superior flexural or tensile strength is another advantage of UHPC because it provides a minimum reinforcement in the concrete [ 1 ]. It has been also previously reported that the distribution and orientation of included fibers will have a decisive effect on its performance, rather than applied HT conditions [ 40 , 41 , 42 ].…”

Section: Discussionmentioning

confidence: 99%

Microstructural Investigation of Heat-Treated Ultra-High Performance Concrete for Optimum Production

et al. 2017

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Abstract:For optimum production of ultra-high performance concrete (UHPC), the material and microstructural properties of UHPC cured under various heat treatment (HT) conditions are studied. The effects of HT temperature and duration on the hydration reaction, microstructure, and mechanical properties of UHPC are investigated. Increasing HT temperature accelerates both cement hydration and pozzolanic reaction, but the latter is more significantly affected. This accelerated pozzolanic reaction in UHPC clearly enhances compressive strength. However, strength after the HT becomes stable as most of the hydration finishes during the HT period. Particularly, it was concluded that the mechanical benefit of the increased temperature and duration on the 28 day-strength is not noticeable when the HT temperature is above 60 • C (with a 48 h duration) or the HT duration is longer than 12 h (with 90 • C temperature). On the other hand, even with a minimal HT condition such as 1 day at 60 • C or 12 h at 90 • C, outstanding compressive strength of 179 MPa and flexural tensile strength of 49 MPa are achieved at 28 days. Microstructural investigation conducted herein suggests that portlandite content can be a good indicator for the mechanical performance of UHPC regardless of its HT curing conditions. These findings can contribute to reducing manufacturing energy consumption, cost, and environmental impact in the production of UHPC and be helpful for practitioners to better understand the effect of HT on UHPC and optimize its production.

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Section: Discussionmentioning

confidence: 99%

Microstructural Investigation of Heat-Treated Ultra-High Performance Concrete for Optimum Production

et al. 2017

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“…and the distribution state of the fibers inside the concrete (volume ratio, direction, degree of dispersion, etc.) have a decisive effect on flexural or tensile properties [ 73 , 74 , 75 , 76 ], but the difference between these factors could be neglected in this study. Apart from such promotion of the pozzolanic reaction and the change in fiber parameters, the effect of the mixture composition on tensile strength has also been reported.…”

Section: Resultsmentioning

confidence: 99%

Performance Comparison between Densified and Undensified Silica Fume in Ultra-High Performance Fiber-Reinforced Concrete

2020

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Silica fume (SF) is a key ingredient in the production of ultra-high performance fiber-reinforced concrete (UHPFRC). The use of undensified SF may have an advantage in the dispersion efficiency inside cement-based materials, but it also carries a practical burden such as high material costs and fine dust generation in the workplace. This study reports that a high strength of 200 MPa can be achieved by using densified SF in UHPFRC with Portland limestone cement. Additionally, it was experimentally confirmed that there was no difference between densified and undensified SFs in terms of workability, compressive and flexural tensile strengths, and hydration reaction of the concrete, regardless of heat treatment, because of a unique mix proportion as well as mixing method for dispersing agglomerated SF particles. It was experimentally validated that the densified SF can be used for both precast and field casting UHPFRCs with economic and practical benefits and without negative effects on the material performance of the UHPFRC.

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“…Vom Einfluss der Probekörperschlankheit und ‐größe zu trennen sind Auswirkungen auf die Druckfestigkeit, die bei faserbewehrtem Beton durch eine abweichende Faserorientierung in unterschiedlichen Probekörpern oder Bauteilen sowie durch unterschiedliche Belastungsrichtungen hervorgerufen werden können. Die Faserverteilung und ‐orientierung innerhalb eines Betonvolumens werden dabei maßgeblich durch die Probekörper‐ oder Bauteilgeometrie (Schalungswände), das Fließverhalten des Frischbetons (Konsistenz) sowie die Art des Befüllens der Schalung und das Verdichten bestimmt .…”

Section: Einführungunclassified

Einfluss der Faserorientierung und des Fasergehalts auf die Druckfestigkeit von ultrahochfestem Beton

Riedel

2020

Beton und Stahlbetonbau

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Effect of Fibre Orientation and Fibre Volume Fraction on the Compressive Strength of Ultra-High Performance Concrete Depending on the geometry and casting method, structural members made of fibre reinforced concrete may (locally) show very different fibre orientation. As a result, the fibre reinforced concrete no longer behaves isotropically, but shows different tensile and compressive behaviour depending on the direction of loading. This aspect is of special importance for ultra-high performance concrete (UHPC), since UHPC is typically applied with high fibre volume fraction. While the influence of fibre orientation on the tensile behaviour of UHPC has already been subject of numerous studies, there was a lack of meaningful data so far in order to be able to quantify the anisotropy in compression caused by the fibres. Thus, the influence of fibre orientation and fibre volume fraction on the failure pattern and on the compressive strength of fine-and coarse-grained UHPC was investigated in a series of tests. The results show that with predominantly unidirectional alignment of fibres in the plane perpendicular to the loading direction, the compressive strength increases significantly with increasing fibre volume fraction. In contrast, the influence of fibre volume fraction is marginal with predominantly unidirectional alignment of fibres in the direction of loading. Depending on the loading direction, the compressive strength tested on cubes differs by up to 26 MPa and 14 %, respectively. The difference between cube and cylinder compressive strength increases with increasing fibre volume fraction. Based on the results, a proposal for classifying UHPC in the DAfStb Guideline "Ultra-High Performance Concrete" is provided.

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Influence of flowability, casting time and formwork geometry on fiber orientation and mechanical properties of UHPFRC

Cited by 95 publications

References 16 publications

Microstructural Investigation of Heat-Treated Ultra-High Performance Concrete for Optimum Production

Microstructural Investigation of Heat-Treated Ultra-High Performance Concrete for Optimum Production

Performance Comparison between Densified and Undensified Silica Fume in Ultra-High Performance Fiber-Reinforced Concrete

Einfluss der Faserorientierung und des Fasergehalts auf die Druckfestigkeit von ultrahochfestem Beton

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