| 1. |
- Bado, Mattia Francesco, et al.
(författare)
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Distributed optical fiber sensing bonding techniques performance for embedment inside reinforced concrete structures
- 2020
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 20:20, s. 1-23
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Tidskriftsartikel (refereegranskat)abstract
- Distributed optical fiber sensors (DOFS) are modern-day cutting-edge monitoring tools that are quickly acquiring relevance in structural health monitoring engineering. Their most ambitious use is embedded inside plain or reinforced concrete (RC) structures with the scope of comprehending their inner-workings and the functioning of the concrete-reinforcement interaction. Yet, multiple studies have shown that the bonding technique with which the DOFS are bonded to the reinforcement bars has a significant role on the quality of the extracted strain data. Whilst this influence has been studied for externally bonded DOFS, it has not been done for embedded ones. The present article is set on performing such study by monitoring the strain measurement quality as sampled by DOFS bonded to multiple rebars with different techniques and adhesives. These instrumented rebars are used to produce differently sized RC ties later tested in tension. The discussion of the test outputs highlights the quasi-optimal performance of a DOFS/rebar bonding technique consisting of incising a groove in the rebar, positioning the DOFS inside it, bonding it with cyanoacrylate and later adding a protective layer of silicone. The resulting data is mostly noisefree and anomalies-free, yet still presents a newly diagnosed hitch that needs addressing in future research.
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| 2. |
- Chen, Teresa E, 1988, et al.
(författare)
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Assessment of the mechanical behaviour of reinforcement bars with localised pitting corrosion by Digital Image Correlation
- 2020
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Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 219
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion of reinforcement in concrete impairs the mechanical behaviour of rebars by decreasing their strength and deformation capacity. In this study, uniaxial tensile tests were carried out on 61 rebars taken from 22 pre- and un- cracked reinforced concrete beams subjected to drying and wetting cycles in chloride solution for over three years. A 3D-scanning technique was used to characterise the maximum local corrosion level, μmax, and different pit shape parameters. Digital Image Correlation (DIC) was used to capture the displacement field of the test bars; the engineering strain was measured through the virtual extensometers created in the DIC post-processing software. The proof and ultimate forces showed linear decreasing trends of μmax, while the proof and ultimate strengths (based on the minimum residual cross-sectional area) were not obviously affected by corrosion. The ultimate strain of corroded bars depended on the gauge length due to strain localisation in the pit. Thus, it was emphasised that the ultimate strain may be overestimated if measured based on a short gauge across the pit. It was also observed that when μmax exceeded a critical local corrosion level (μcrit depending on the ratio between the yield and ultimate strengths of the steel), the region outside the pit did not develop yielding. A lower bound of ultimate strain was further derived as a function of the mechanical parameters of uncorroded steel and maximum local corrosion level. This provided a good comparison with the experimental results. Ultimately, a hypothesis for time-dependent assessment of strain capacity is proposed, considering the evolution of corrosion morphology over time.
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| 3. |
- Chen, Teresa E, 1988, et al.
(författare)
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Correlation between concrete cracks and corrosion characteristics of steel reinforcement in pre-cracked plain and fibre-reinforced concrete beams
- 2020
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Ingår i: Materials and Structures/Materiaux et Constructions. - : Springer Science and Business Media LLC. - 1359-5997. ; 53:2
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents results on corrosion characteristics of 66 rebars extracted from un- and pre-cracked plain concrete and fibre-reinforced concrete (FRC) beams suffering from corrosion for more than 3 years. The influences of fibre reinforcement, flexural cracks, corrosion-induced cracks and loading condition on the maximum local corrosion level (defined as the maximum cross-sectional area loss percentage) and pit morphology were examined. With 3D-scanning, the corrosion characteristics were analysed, and pit types were classified based on the maximum local corrosion level and geometric parameters of pits. Corrosion pits were observed near some flexural cracks, while the bars at other cracks were free from corrosion. Most rebars in FRC had less maximum local corrosion level than those in plain concrete under the same loading condition and maximum flexural crack width. However, the maximum local corrosion level was not dependent on the maximum flexural crack width (0.1 and 0.4 mm). Longitudinal cracks (corrosion-induced cracks) aggravated the total steel loss and changed the pit morphology by promoting the pit length development. However, longitudinal cracks did not always form, even with severe pitting corrosion. A hypothesis about the time-dependent interplay between transverse and longitudinal cracks and corrosion development was proposed. Further studies on predicting the pitting corrosion evolution and experimental work on specimens exposed for longer periods are needed to understand and quantify the long-term durability of concrete structures reinforced with both conventional reinforcing bars and fibres.
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| 4. |
- Chen, Teresa E, 1988, et al.
(författare)
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Hybridarmerade konstruktioner i kloridhaltiga miljöer – beständighet, säkerhet och livscykelkostnader
- 2020
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Ingår i: Bygg och teknik. - 0281-658X. ; 2020:6, s. 14-19
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Livslängden för armerade betongkonstruktioner i kloridhaltiga miljöer kan förlängas genom att kombinera traditionell armering med fibrer i så kallade hybridarmerade lösningar. Detta visades experimentellt i ett tidigare doktorandprojekt i samarbete mellan Chalmers tekniska högskola och Thomas Concrete Group. I ett efterföljande postdocprojekt har vi nu utvecklat modeller som kvantitativt utvärderar fibrernas effekt på beständighet och säkerhet – därigenom visas de positiva resultaten i praktisk användning. Vi har också genomfört en fallstudie som visar de ekonomiska och miljömässiga fördelarna med att använda hybridarmerad betong i kantbalkar.
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| 5. |
- Gil Berrocal, Carlos, 1986, et al.
(författare)
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The effect of fibres on corrosion of reinforced concrete
- 2020
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Ingår i: American Concrete Institute, ACI Special Publication. - 0193-2527. ; SP-343, s. 361-370
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Konferensbidrag (refereegranskat)abstract
- In the present paper, long-term experiments involving natural corrosion of RC beams subjected to chloride solution cyclic exposure were carried out to investigate the effect of fibres on different aspects of the corrosion process as well as their contribution to the structural behaviour of RC elements damaged by corrosion. The long-term experiments were complemented with short-term accelerated corrosion experiments and mechanical tests to investigate the influence that low fibre contents may have on individual mechanisms that play an important role in the corrosion process of steel in concrete. These showed that fibres promote crack branching which results in a change of the internal crack pattern towards multiple thinner cracks, particularly near the reinforcement. This agrees with the long-term experiment results, which exhibited longer times to corrosion initiation for FRC beams with bending cracks and revealed a more distributed corrosion with more pits but less crosssectional loss compared to bars in plain concrete. Fibres also proved beneficial in delaying corrosion-induced cracks and preventing cover spalling, which greatly enhanced the bondbehaviour of corroded bars. Furthermore, a positive effect of the fibres was also observed on the residual flexural capacity of corroded beams, which generally increased the load-carrying capacity and rotation capacity.
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