Pore Solution Composition and Chloride Effects on the Corrosion of Steel in Concrete

Yonezawa, Takayuki; Ashworth, V.; Procter, Rob

doi:10.5006/1.3583967

Cited by 133 publications

(46 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Many subsequent investigations involving the use of secondary electron imaging SEM have confirmed the presence of portlandite-enriched interfacial zones of segregation at mild steel or stainless steel fracture surfaces that had been in contact with Portland cement pastes, mortars and concretes [27][28][29][30][31][32][33][34][35] though the morphology and degree of continuity of the portlandite have been found to vary, as has the distribution of C-S-H and other hydrate phases that have been identified. Thus, for example, Bentur and Diamond [28] reported the presence of continuous thin duplex films of portlandite backed by C-S-H in contact with steel fibres while, in a subsequent study, Bentur and Odler [34] observed steel fibres, surrounded by a discontinuous portlandite layer with pockets of C-S-H and occasionally some ettringite.…”

Section: Concretementioning

confidence: 99%

Initiation of chloride‐induced corrosion of steel in concrete: role of the interfacial zone

Page

2009

Materials & Corrosion

View full text Add to dashboard Cite

This paper provides a brief review of research aimed at characterising the steelconcrete interfacial zone (SCIZ) and its influence on the susceptibility of the metal to pitting corrosion when concrete is exposed to environments that cause ingress of chloride ions accompanied by leaching of hydroxyl ions. For reinforced concrete made from Portland cements, exposed to aqueous solutions of sodium chloride, the buffering effect of solid calcium hydroxide (portlandite) at pH $12.6 has been shown to restrain the gradual decline in the hydroxyl ion concentration of the concrete pore solution phase at depths corresponding to the embedded steel. When the concrete is produced under laboratory conditions that are carefully controlled to exclude macroscopic defects from the SCIZ and the steel is cleaned before being embedded, this can lead to observed chloride threshold levels being consistently greater than 1% chloride by mass of cement. The buffering action of cement hydration products formed in the SCIZ is believed to be partly responsible for this high tolerance to chloride-induced corrosion because it counters the generation of 'anodic acidity' that is a necessary condition for stable growth of pits to occur. Translating this behaviour of laboratory specimens to the performance of full-scale reinforced concrete structures has often proved difficult in the past and there is a need for further research in this area, particularly in relation to the role of non-traditional cements.

show abstract

Section: Concretementioning

confidence: 99%

Initiation of chloride‐induced corrosion of steel in concrete: role of the interfacial zone

Page

2009

Materials & Corrosion

View full text Add to dashboard Cite

show abstract

“…This is of huge importance in concrete technology, where a critical ratio of OH -to free Cl -exists, below which corrosion of the steel reinforcement is inevitable. 15 In the 1976 paper there is a section dealing with the inhibiting effect of sulfate ions on pitting of stainless steel, where Galvele shows that in a reaction/diffusion/migration model, the double charge on the sulfate leads to a spectacular enrichment, relative to chloride, at the bottom of a pit, consistent with complete inhibition. Probably he considered this as a special case, and his hesitation to generalize such an inhibition model in the 1976 paper may be another consequence of his view that critical pit chemistries were not, in general, especially concentrated in Me n+ .…”

Section: Newman (Continued From Previous Page)mentioning

confidence: 99%

Pitting Corrosion of Metals

Newman

2010

Electrochem. Soc. Interface

View full text Add to dashboard Cite

Pitting corrosion of metals is one of the most important electrochemical corrosion phenomena. Corrosion of steel reinforcement in concrete is always in the news, and it starts off as pitting, caused by chloride ions-so it is feasible that pitting is the most costly form of corrosion. Such an assessment might not be the same in every decade, and it is hard to measure the cost of corrosion Synthetic Diamond: Emerging CVD Science and Technology Edited by K. E. Spear and J. P. Dismukes (1994) 688 pages. ISBN 978-0-471-53589-8 Electrochemical Oxygen Technology by K. Kinoshita (1992) 444 pages. ISBN 978-0-471-57043-1 ECS Members will receive a discount. All prices subject to change without notice.

show abstract

“…23 This was then supported by some experimental works. 22 However, the hydration products at the interface were quantified using backscattered electron image analysis and it was shown that calcium hydroxide is present at the interface at only 5-9%, challenging the hypothesis. 24 Voids are often generated by bleeding and/or settlement underneath the embedded steel, perpendicular to the direction of casting, and then corrosion initiates in these voids when chlorides or aggressive ions penetrate cover concrete to the depth of the steel.…”

Section: Voidsmentioning

confidence: 99%

“…21 The most important factor influencing the CTL includes the environment at the steel-concrete interface. 22 The importance of the steel-concrete interface has been postulated, as a dense continuous cement-rich layer containing precipitated calcium hydroxide could be formed at the interface. This layer restricts the tendency for a decrease in pH to occur at anodic areas and reduces the mobility of chloride ions.…”

Section: Voidsmentioning

confidence: 99%

Variation in the chloride threshold level for steel corrosion in concrete arising from different chloride sources

Ryou

Ann

2008

Magazine of Concrete Research

View full text Add to dashboard Cite

In order to compare the role of chlorides from internal and external sources in corroding, the steel bar in concrete/ mortar, the chloride threshold level (CTL), corrosion resistance, chloride transport, observation of the steelconcrete/mortar interface and the pH-dependent release of bound chlorides were examined. As binders, ordinary Portland cement (OPC), 30% pulverised fuel ash (pfa), 60% ground granulated blastfurnace slag (ggbs) and 10% silica fume (SF) were used. For external chlorides, the onset of corrosion was detected by a jump of the galvanic current and for internal chloride the corrosion rate was measured using a polarisation technique to determine the CTL. As a result, the variation in the CTL was marginal, despite the different chloride source, but binder type greatly affected the corrosion behaviour and the CTL: OPC concretes/mortars provided the highest resistance to chloride-induced corrosion and the highest CTL, and the polarisation resistance was also the greatest before depassivation, compared to the mixtures with pozzolanic materials. For the rate of chloride transport, 60% ggbs concretes produced the lowest diffusivity, while OPC produced the highest. The visual examination of the steelconcrete interface showed that corrosion always starts in the voids in contact with the steel bar, because of a higher reactive environment. In addition, it was found that acid soluble chlorides indicate only about 90% of total.

show abstract

Pore Solution Composition and Chloride Effects on the Corrosion of Steel in Concrete

Cited by 133 publications

References 0 publications

Initiation of chloride‐induced corrosion of steel in concrete: role of the interfacial zone

Initiation of chloride‐induced corrosion of steel in concrete: role of the interfacial zone

Pitting Corrosion of Metals

Variation in the chloride threshold level for steel corrosion in concrete arising from different chloride sources

Contact Info

Product

Resources

About