| 1. |
- Berrocal, Carlos Gil, 1986, et al.
(författare)
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Characterisation of bending cracks in R/FRC using image analysis
- 2016
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 90, s. 104-116
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Tidskriftsartikel (refereegranskat)abstract
- In this study, experiments were conducted to induce bending cracks of specific surface crack width to reinforced concrete beams made of plain concrete (RC) and reinforced concrete beams made of fibre reinforced concrete (R/FRC). After injecting and impregnating the cracks with dyed epoxy resin, image processing and analysis were employed to investigate the internal crack morphology. Several crack features including crack width (accumulated, effective and maximum), branching and tortuosity were defined and quantified. The results showed that in addition to arrested crack development, the presence of fibres yielded a distinctive change in the internal crack pattern, including increased branching and tortuosity, both of which have positive implications regarding concrete permeation. Likewise, specimens with fibres exhibited reduced maximum individual crack widths near the rebar, potentially increasing the ability of autogenous crack healing and reducing the risk of corrosion initiation.
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| 2. |
- Berrocal, Carlos Gil, 1986, et al.
(författare)
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Corrosion of Steel Bars Embedded in Fibre Reinforced Concrete under Chloride Attack: State-of-the-Art
- 2016
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 80, s. 69-85
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Forskningsöversikt (refereegranskat)abstract
- This literature review summarises the influence of fibres on the main parameters governing corrosion of conventional reinforcement. The ability of fibres to suppress crack growth has proven to decrease permeation in cracked concrete while chloride diffusion, in uncracked concrete, seems to remain unaffected by the addition of fibres. Steel fibres in concrete are considered to be insulated owing to the high impedance of the passive layer. However, they will become conductive if they are depassivated. Although low carbon steel fibres may suffer severe corrosion when located near the concrete surface or bridging the cracks, embedded fibres will remain free of corrosion despite high chloride contents. Published experimental observations indicate that fibres had little influence on the corrosion rate of rebars. Steel fibres improved corrosion resistance of rebars moderately; this is mainly attributed to a reduced ingress of chlorides due to arrested crack growth.
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| 3. |
- Berrocal, Carlos Gil, 1986, et al.
(författare)
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Effect of fibre reinforcement on the crack width profile and internal crack pattern of conventionally reinforced concrete beams
- 2016
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Ingår i: Proceedings of the 9th RILEM International Symposium on Fiber Reinforced Concrete. - 9782351581872 ; , s. 355-366
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Konferensbidrag (refereegranskat)abstract
- Although fibre reinforcement is known to reduce the crack width and crack spacing of conventionally reinforced concrete elements, the impact of fibres on the crack width profile and crack morphology has not received as much attention. This paper presents experimental results of the crack width profile and internal crack pattern obtained from three-point bending test of conventionally reinforced concrete notched beams made of plain concrete and fibre reinforced concrete at low fibre dosages. The induced cracks were, under loaded conditions, injected with a fluorescent epoxy-resin. From each beam, two pieces were extracted and subjected to a second impregnation. Digital images were taken using a microscope and were then processed and analysed to extract quantitative information. The results revealed that the accumulated crack width was similar for all mixes. However, in the samples with fibres the main crack branched off into several narrower cracks compared to plain concrete, which generally exhibited a single and wider crack. Based on the known relation between permeation and crack width, this finding describes a mechanism through which fibre reinforcement can improve the water tightness of reinforced concrete structures and potentially extent their service life reducing the ingress of detrimental agents.
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| 4. |
- Berrocal, Carlos Gil, 1986, et al.
(författare)
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Influence of fibre reinforcement on the initiation of corrosion-induced cracks
- 2016
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Ingår i: Materials, Systems and Structures in Civil Engineering 2016 - Segment on Service Life. - 9782351581704 ; 1, s. 231-240
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Konferensbidrag (refereegranskat)abstract
- The initiation of corrosion-induced cracks, often running parallel to the reinforcement, becomes a turning point in the service life of a reinforced concrete (RC) structure as they promote increased corrosion rates, thus accelerating the degradation process of the structure. Compared to plain concrete, fibre reinforced concrete (FRC) provides additional confinement to the reinforcement, which has been reported to delay or even prevent the appearance of mechanically induced splitting cracks. In this study, an experimental programme has been carried out to investigate the influence of fibres on the onset of corrosion-induced splitting cracks. Cylindrical lollipop specimens with a centrally positioned Ø16 mm bar and varying cover depths from 40 to 64 mm were subjected to accelerated corrosion. A constant current of 100 µA/cm2 was impressed through the specimens and the electrical resistance between each rebar and an external copper mesh acting as cathode was monitored. Crack initiation, determined from a drop in electrical resistance, and confirmed by visual inspection, revealed that fibre reinforcement may delay corrosion-induced cracks, an effect that was more noticeable for reduced c/Ø ratios, featuring up to 50% higher corrosion levels at crack initiation compared to plain concrete.
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| 5. |
- Berrocal, Carlos Gil, 1986, et al.
(författare)
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Investigation on the influence of fibre reinforcement on chloride induced corrosion of RC structures
- 2016
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Ingår i: Proceedings of the 11th fib International PhD Symposium in Civil Engineering. - 9784990914806 ; , s. 303-310
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Konferensbidrag (refereegranskat)abstract
- Corrosion of reinforcement is the main cause of deterioration of RC structures located in marine environments or subjected to de-icing salts. In order to delay the ingress of chlorides, such structures requirethe use of thick, dense concrete covers and strict crack width limitations. Given the crack limiting effectprovided by fibres, it would be of interest to incorporate fibre reinforcement to conventionally reinforced concrete structures. Nevertheless, whereas fibre reinforcement might delay the penetration of detrimental agents into the concrete through crack control, there are other aspects which need to be addressed to determine whether fibres can improve the overall durability of RC structures.Several experiments were conducted within the present project, parts of them still ongoing, to investigatesome of these aspects, namely: (i) the effect of fibres on the diffusivity of uncracked concrete; (ii)whether fibres may affect the corrosion onset of rebars for any crack width; (iii) whether steel fibres,due to their conductive nature, might influence the resistivity and consequently the corrosion rate ofembedded rebars; and (iv) whether there is a risk of galvanic corrosion between steel fibres and rebars.Obtained results from chloride migration and bulk diffusion tests showed that fibres had no significant influence on the diffusion coefficient of concrete. Results from experiments in which RC beams were subjected to different loading conditions and thereafter naturally corroded through exposure to highlyconcentrated salt solution, showed a trend for earlier corrosion initiation with increasing crack width.Concrete mixes incorporating fibres exhibited similar or delayed corrosion onset compared to their plain concrete counterparts. While resistivity of FRC was consistently lower than resistivity of plain concrete measured under AC at 1 kHz, corrosion rate measurements based on the galvanostatic pulse technique showed no clear correlation between the presence of fibres and the corrosion rate.
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