Investigating entrained air voids and Portland cement hydration with low-temperature scanning electron microscopy

Corr, David J.; Juenger, Maria; Monteiro, Paulo J.M.; Bastacky, J.

doi:10.1016/j.cemconcomp.2004.02.035

Cited by 23 publications

(10 citation statements)

References 5 publications

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“…This shows that a low content of AEA can have some beneficial effects on enhancement of the corrosion potential, resulting in a reduced permeability. This can be confirmed by the findings of previous studies, which indicate that if there is a high amount of air bubbles in cement paste, the voids will be filled more expressively with hydration products. In fact, incorporating high AEA content causes a greater porosity of the cement paste, leading to the presence of capillary channels and micropores in the vicinity of the pores, and the greater ease of water flow between them.…”

Section: Resultssupporting

confidence: 84%

Corrosion behavior and optimization of air‐entrained reinforced concrete, incorporating microsilica

Ghanei

Eskandari‐Naddaf

Davoodi

2018

Structural Concrete

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Nowadays, corrosion evaluation of steel embedded in reinforced concrete (RC) plays an important role in repair, protection and maintenance of RC structures. Air‐entraining agent (AEA) and microsilica (MS) are among the most important admixtures, which affect the corrosion rate (CR) of RC. Specifically, 12 mix designs incorporating different contents of AEA (ie, 0, 0.7, 1.4, 2.1, 2.9, and 3.6% by weight), half with 10% MS, were constructed. The corrosion behavior of RC specimens after exposure to 3.5% NaCl environment was investigated using half‐cell potential (HCP) and electrical resistance (ER) as conventional tests and Tafel polarization as a more powerful corrosion test. Moreover, an optimization process was conducted on the mix design parameters using Taguchi and Factorial methods to analyze the effective factors and sensitivity of CR to each factor. The results of Tafel test indicate that they are noticeably more reliable and reasonable as compared to HCP and ER tests. Moreover, the results show that incorporating a low content of AEA (up to 0.7%) effectively improves the corrosion behavior of RC specimens, while the mix design containing 0.7% AEA together with 10% MS is the optimal design in terms of a decreased CR. The results also show that Factorial is a more applicable method in the field of corrosion evaluation of RC, due to the yield of more accurate findings as compared to Taguchi.

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Section: Resultssupporting

confidence: 84%

Corrosion behavior and optimization of air‐entrained reinforced concrete, incorporating microsilica

Ghanei

Eskandari‐Naddaf

Davoodi

2018

Structural Concrete

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“…This agrees with previous shell formation studies (Atahan et al, 2008;Rashed and Williamson, 1991). It has been reported that unhydrated fine particles make up the shell at early hydration of a freeze-dried cement paste, and form various hydration products at a later stage (Corr et al, 2004).…”

Section: Morphology Of Entrained Air-voids In Cement Pastessupporting

confidence: 92%

Effect of sodium sulfate and sodium nitrite on air-void system in air-entrained concrete

Yang

2016

Magazine of Concrete Research

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The purpose of this work was to explore the effect of sodium salts on the air-void structure in air-entrained concrete, and to observe the morphology of the air voids in the presence of sodium sulfate (Na 2 SO 4 ) and sodium nitrite (NaNO 2 ) as well as the use of sodium abietate. The foam index test was used in analysing the foam stability of sodium abietate, microscopic determinations of the Powers spacing factor in hardened air-entrained concrete and the air-void distribution were characterised, and a microscopic evaluation was carried out using scanning electron microscopy for the morphology of air voids in cement paste. The foam index test indicated that the introduction of either sodium sulfate or sodium nitrite results in a drop in foaming power, but has no effect on foam stability. The addition of sodium salt was found to lead to a decrease in the pore size of air voids in air-entrained concrete. Adding sodium sulfate in conjunction with sodium abietate was found to gradually increase the Powers spacing factor, while the corresponding results for sodium nitrite were the reverse. Regardless of the sodium salt used, a distinct shell was observed to form around the entrained air voids. However, with the addition of sodium sulfate, more needle-like crystals were formed on the surface.

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“…The Since fresh concrete is a heterogeneous mixture with different phases, every constituent of the system affects the stability of air bubbles, and the corresponding mechanisms involved are complex. Generally, the factors affecting air bubble's stability in concrete include the properties of basic concrete components [33,34], the mix proportion of concrete [35][36][37], the mixing process [33,38], temperature [39], atmospheric pressure [20,40], air-entraining agents [41][42][43], other chemical additives [44][45][46], mineral admixtures [47][48][49][50], and the quality of mixing water [15]. Each constituent of the system, either internal or external, influences bubble stability to a varying extent.…”

Section: Formation Of Bubbles In Concretementioning

confidence: 99%

A Review on Bubble Stability in Fresh Concrete: Mechanisms and Main Factors

et al. 2020

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In order to improve the stability of air bubbles in fresh concrete, it is of great significance to have a better understanding of the mechanisms and main influencing factors of bubble stability. In the present review, the formation and collapse process of air bubbles in fresh concrete are essentially detailed; and the advances of major influencing factors of bubble stability are summarized. The results show that the surface tension of air–liquid interface exerts a huge impact on bubble stability by reducing surface free energy and Plateau drainage, as well as increasing the Gibbs surface elasticity. However, surface tension may not be the only determinant of bubble stability. Both the strength of bubble film and the diffusion rate of air through the membrane may also dominate bubble stability. The application of nano-silica is a current trend and plays a key role in ameliorating bubble stability. The foam stability could be increased by 6 times when the mass fraction of nano-particle reached 1.5%.

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Investigating entrained air voids and Portland cement hydration with low-temperature scanning electron microscopy

Cited by 23 publications

References 5 publications

Corrosion behavior and optimization of air‐entrained reinforced concrete, incorporating microsilica

Corrosion behavior and optimization of air‐entrained reinforced concrete, incorporating microsilica

Effect of sodium sulfate and sodium nitrite on air-void system in air-entrained concrete

A Review on Bubble Stability in Fresh Concrete: Mechanisms and Main Factors

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