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2020-07-14Author
Wiemer, NielsWetzel, AlexanderSchleiting, MaximilianKrooß, PhilippVollmer, MalteNiendorf, ThomasBöhm, StefanMiddendorf, BernhardMetadata
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Effect of Fibre Material and Fibre Roughness on the Pullout Behaviour of Metallic Micro Fibres Embedded in UHPC
Abstract
The use of micro fibres in Ultra-High-Performance Concrete (UHPC) as reinforcement increases tensile strength and especially improves the post-cracking behaviour. Without using fibres, the dense structure of the concrete matrix results in a brittle failure upon loading. To counteract this behaviour by fibre reinforcement, an optimal bond between fibre and cementitious matrix is essential. For the composite properties not only the initial surfaces of the materials are important, but also the bonding characteristics at the interfacial transition zone (ITZ), which changes upon the joining of both materials. These changes are mainly induced by the bond of cementitious phases on the fibre. In the present work, three fibre types were used: steel fibres with brass coating, stainless-steel fibres as well as nickel-titanium shape memory alloys (SMA). SMA fibres have the ability of “remembering” an imprinted shape (referred to as shape memory effect), triggered by thermal activation or stress, principally providing for superior performance of the fibre-reinforced UHPC. However, previous studies have shown that NiTi-fibres have a much lower bond strength to the concrete matrix than steel fibres, eventually leading to a deterioration of the mechanical properties of the composite. Accordingly, the bond between both materials has to be improved. A possible strategy is to roughen the fibre surfaces to varying degrees by laser treatment. As a result, it can be shown that laser treated fibres are characterised by improved bonding behaviour. In order to determine the bond strength of straight, smooth fibres of different metal alloy compositions, the present study characterized multiple fibres in series with a Compact-Tension-Shear (CTS) device. For critical evaluation, results obtained by these tests are compared with the results of conventional testing procedures, i.e., bending tests employing concrete prisms with fibre reinforcements. The bond behaviour is compared with the results of the flexural strength of prisms (4 × 4 × 16 cm3) with fibre reinforcements.
Citation
In: Materials Volume 13 / Issue 14 (2020-07-14) , S. 3128 ; EISSN 1996-1944Sponsorship
Gefördert durch den Publikationsfonds der Universität KasselCitation
@article{doi:10.17170/kobra-202009091757,
author={Wiemer, Niels and Wetzel, Alexander and Schleiting, Maximilian and Krooß, Philipp and Vollmer, Malte and Niendorf, Thomas and Böhm, Stefan and Middendorf, Bernhard},
title={Effect of Fibre Material and Fibre Roughness on the Pullout Behaviour of Metallic Micro Fibres Embedded in UHPC},
journal={Materials},
year={2020}
}
0500 Oax 0501 Text $btxt$2rdacontent 0502 Computermedien $bc$2rdacarrier 1100 2020$n2020 1500 1/eng 2050 ##0##http://hdl.handle.net/123456789/11795 3000 Wiemer, Niels 3010 Wetzel, Alexander 3010 Schleiting, Maximilian 3010 Krooß, Philipp 3010 Vollmer, Malte 3010 Niendorf, Thomas 3010 Böhm, Stefan 3010 Middendorf, Bernhard 4000 Effect of Fibre Material and Fibre Roughness on the Pullout Behaviour of Metallic Micro Fibres Embedded in UHPC / Wiemer, Niels 4030 4060 Online-Ressource 4085 ##0##=u http://nbn-resolving.de/http://hdl.handle.net/123456789/11795=x R 4204 \$dAufsatz 4170 5550 {{Ultrahochfester Beton}} 5550 {{Mikrofaser}} 5550 {{Memory-Legierung}} 5550 {{Mechanische Eigenschaft}} 7136 ##0##http://hdl.handle.net/123456789/11795
2020-09-10T13:38:54Z 2020-09-10T13:38:54Z 2020-07-14 doi:10.17170/kobra-202009091757 http://hdl.handle.net/123456789/11795 Gefördert durch den Publikationsfonds der Universität Kassel eng Namensnennung 4.0 International http://creativecommons.org/licenses/by/4.0/ high-performance concrete fibre reinforcement shape memory alloys pullout strength fibre/matrix bond 500 Effect of Fibre Material and Fibre Roughness on the Pullout Behaviour of Metallic Micro Fibres Embedded in UHPC Aufsatz The use of micro fibres in Ultra-High-Performance Concrete (UHPC) as reinforcement increases tensile strength and especially improves the post-cracking behaviour. Without using fibres, the dense structure of the concrete matrix results in a brittle failure upon loading. To counteract this behaviour by fibre reinforcement, an optimal bond between fibre and cementitious matrix is essential. For the composite properties not only the initial surfaces of the materials are important, but also the bonding characteristics at the interfacial transition zone (ITZ), which changes upon the joining of both materials. These changes are mainly induced by the bond of cementitious phases on the fibre. In the present work, three fibre types were used: steel fibres with brass coating, stainless-steel fibres as well as nickel-titanium shape memory alloys (SMA). SMA fibres have the ability of “remembering” an imprinted shape (referred to as shape memory effect), triggered by thermal activation or stress, principally providing for superior performance of the fibre-reinforced UHPC. However, previous studies have shown that NiTi-fibres have a much lower bond strength to the concrete matrix than steel fibres, eventually leading to a deterioration of the mechanical properties of the composite. Accordingly, the bond between both materials has to be improved. A possible strategy is to roughen the fibre surfaces to varying degrees by laser treatment. As a result, it can be shown that laser treated fibres are characterised by improved bonding behaviour. In order to determine the bond strength of straight, smooth fibres of different metal alloy compositions, the present study characterized multiple fibres in series with a Compact-Tension-Shear (CTS) device. For critical evaluation, results obtained by these tests are compared with the results of conventional testing procedures, i.e., bending tests employing concrete prisms with fibre reinforcements. The bond behaviour is compared with the results of the flexural strength of prisms (4 × 4 × 16 cm3) with fibre reinforcements. open access Wiemer, Niels Wetzel, Alexander Schleiting, Maximilian Krooß, Philipp Vollmer, Malte Niendorf, Thomas Böhm, Stefan Middendorf, Bernhard doi:10.3390/ma13143128 Ultrahochfester Beton Mikrofaser Memory-Legierung Mechanische Eigenschaft publishedVersion EISSN 1996-1944 Issue 14 Materials 3128 Volume 13 false
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