Chloride penetration in concrete subject to wet–dry cycling: influence of pore structure

Arya, Chanakya; Vassie, P R; Bioubakhsh, Samira

doi:10.1680/stbu.12.00067

Cited by 13 publications

(12 citation statements)

References 19 publications

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“…05 Cl (% by weight of concrete) (Life-365, 2008)) were actually 13, 15, 22, 22 and 24 mm after 1, 6, 12, 18 and 24 wet-dry cycles respectively. The same trend was observed in all other sets of specimens; this confirms earlier findings that, after the first wetting, chloride penetration away Modelling chloride penetration in concrete subjected to cyclic wetting and drying Arya, Vassie and Bioubakhsh from the near-surface zone is largely diffusion controlled (Arya et al, 2013(Arya et al, , 2014.…”

Section: Effective Porositysupporting

confidence: 89%

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Modelling chloride penetration in concrete subjected to cyclic wetting and drying

Arya

Vassie

Bioubakhsh

2014

Magazine of Concrete Research

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Corrosion of steel in concrete structures remains a major problem worldwide, and surfaces periodically wetted with chloride solution are particularly vulnerable. BS 8500-1 cover requirements have been calculated using the error function solution to Fick's second law of diffusion. However, the values of surface chloride content (Cs) assessed via the diffusion coefficient are rather low, suggesting the cover thicknesses may have been underestimated, which could account for the high incidence of reinforcement corrosion. This paper investigates the influence of a number of factors on Cs and the diffusion coefficient and considers the implications for modelling chloride ingress. Concrete cubes made from 100% CEM I, 70% CEM I + 30% pfa (pulverised fuel ash) and 50% CEM I + 50% GGBS (ground granulated blastfurnace slag) cements were subjected to either one-week (1 d wetting with 3%, 10% or 50% sodium chloride solutions and 6 d drying at 20°C) or two-week (2 d wetting with 50% sodium chloride solution and 12 d drying at 20°C, 30°C or 40°C) cycles, in both cases for 24 weeks during which time their mass was monitored. Identical specimens were totally immersed in 3%, 10% and 50% sodium chloride solutions, also for 24 weeks. The distribution of chloride with depth was measured. The specimens subjected to wet–dry cycling initially appeared to have high diffusion coefficients that quickly reduced to values comparable with the fully submerged specimens, suggesting that the former values are predominantly a function of moisture content and the latter a function of pore structure. The results further show that Cs increases with an increasing number of wet–dry cycles, the final value being a function of the diffusion coefficient, effective porosity and concentration of the chloride solution. Cs exerts a strong influence on the depth of chloride penetration and current estimates of Cs do not appear to be suitable for prediction purposes.

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Section: Effective Porositysupporting

confidence: 89%

“…Recent studies on wet-dry cycling (Arya et al, 2013(Arya et al, , 2014 have indicated the following.…”

Section: Introductionmentioning

confidence: 99%

Modelling chloride penetration in concrete subjected to cyclic wetting and drying

Arya

Vassie

Bioubakhsh

2014

Magazine of Concrete Research

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“…This paper reports on the effect that factors relevant to moisture content have on capillary absorption. The effect of factors related to pore structure will be considered in a companion paper (Arya et al, 2013). The moisture condition of the specimens prior to their first wetting is represented by the effective porosity, defined as the ratio of the available pore volume at any given time to the total volume of concrete.…”

Section: Introductionmentioning

confidence: 99%

“…The results of this study should, therefore, be of interest to engineers engaged in the design of new structures as well as repair and refurbishment work where there is a constant requirement to predict the residual service life of existing structures. Nevertheless, given that it is contemporary engineering practice in the UK and some other countries to build structures exposed to chlorides in cyclic wetting and drying environments using concrete made with fly ash (pulverised fuel ash (PFA)) and ground, granulated blastfurnace slag (GGBS), the performance of these concretes has also been investigated; however, because of space limitations, the results will be reported separately (Arya et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Chloride penetration in concrete subject to wet/dry cycling: influence of moisture content

Arya

Bioubakhsh

Vassie

2014

Proceedings of the Institution of Civil Engineers - Structures

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Concrete structures suffer from corrosion if chloride ions in the environment penetrate to the depth of reinforcing steel; surfaces periodically wetted with chloride solution are at most risk, when chloride ions can enter concrete by combined diffusion and absorption. BS8500-1 recommended minimum cover requirements primarily assume that chloride ingress is diffusion controlled, and absorption is only partly accounted for, so cover values may be inadequate. This paper investigates factors that influence absorption of chloride ions into concrete and how this affects distribution of chloride at different depths from the surface. Concrete cubes (CEM I cement; water/cement ratio 0 . 45) are subjected to repeated wetting (with 50% saturated salt solution) and drying cycles, during which their mass is monitored. The effective porosity, weight and distance sorptivity and chloride penetration depths are calculated for a number of curing, conditioning and drying conditions. Samples are extracted from the cubes at a range of depths and analysed for chloride content. Results show that the quantity of chloride entering the concrete, and in particular surface chloride content, is very sensitive to effective porosity/drying conditions immediately before wetting; also as much as 31% of the protection provided by concrete cover can be lost after exposure to just one wet/dry cycle, thereby significantly reducing time to corrosion of concrete structures.

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“…The third paper, by Arya et al (2014) investigates corrosion damage on concrete structures, such as bridges, car parks and maritime structures, exposed to cyclic wetting and drying with chloride solutions. Cubes of 100 mm were used in the tests to determine the required concrete cover for a working life of 100 years.…”

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confidence: 99%

Editorial

Puthli¹

2014

Proceedings of the Institution of Civil Engineers - Structures

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Chloride penetration in concrete subject to wet–dry cycling: influence of pore structure

Cited by 13 publications

References 19 publications

Modelling chloride penetration in concrete subjected to cyclic wetting and drying

Modelling chloride penetration in concrete subjected to cyclic wetting and drying

Chloride penetration in concrete subject to wet/dry cycling: influence of moisture content

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