Effects of Chemical admixture and Mineral admixture on the Penetration of Chloride Ion and Chloride Binding Capacity

Tsuyuki, Naomitsu; Umemura, Yasuhiro

doi:10.3151/coj1975.39.7_19

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“…Cement particles have surface charges which causes them to flocculate when in contact with water while the addition of chemical admixtures into the fresh concrete mix releases the trapped bound water within the gel matrix [22,23]. However, other research reports that the effect of these chemical admixtures is to increase the amount of bound chloride when chloride diffusion into hardened concrete occurs from external sources [30,31]. This is due to the greater surface area of the hydration products produced by the flocculation of cement particles and release of bound water caused by the admixtures [30,31].…”

Section: Introductionmentioning

confidence: 99%

“…However, other research reports that the effect of these chemical admixtures is to increase the amount of bound chloride when chloride diffusion into hardened concrete occurs from external sources [30,31]. This is due to the greater surface area of the hydration products produced by the flocculation of cement particles and release of bound water caused by the admixtures [30,31].…”

Section: Introductionmentioning

confidence: 99%

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Free and bound chloride relationships affecting reinforcement cover in alkali activated concrete

Mangat

Ojedokun

2020

Cement and Concrete Composites

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This paper investigates the free chloride profiles, diffusion parameters and chloride binding capacity of an alkali activated concrete (AACM) together with a control Portland cement (PC) concrete. Ggbs based AACM concrete specimens with different molarity of activator were exposed to a 5% NaCl solution for 540days to determine their free chloride diffusion properties. The relationships between the free and bound chloride concentration were determined by applying Freundlich and Langmuir isotherms. The required cover to steel reinforcement for corrosion prevention is derived to satisfy the limiting thresholds of free and bound chloride concentrations.The results show that Fick's second law of diffusion applies to the free chloride profiles of AACM concrete and provides higher values of diffusion coefficients than a similar grade of PC concrete. The relationship between the free and bound chlorides is defined by the Langmuir isotherm. PC concrete has higher chloride binding capacity than AACM concrete for both water and acid soluble chlorides. Less concrete cover to steel reinforcement is required in AACM than PC concrete when calculated by using the bound chloride concentration threshold limit. The values of cover based on the corresponding free chloride limit in AACM concrete are higher than its bound chloride values. Ca 6 Fe 2 O 6 .CaCl 2 .10H O kuzel's salt (KS) ISE ion selective electrode D ref diffusion coefficient at reference time t t ref reference age (days) m age factor C ref surface chloride concentration corresponding to the time k constant for surface chloride concentration C-S-H calcium silicate hydrate CH portlandite AFm monosulfoaluminate AFt ettringite C-S-H calcium silicate hydrate N-A-S-H sodium aluminosilicate hydrate SCMs supplementary cementitious materials

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