Current knowledge of external sulfate attack

Whittaker, Mark; Black, Leon

doi:10.1680/adcr.14.00089

Cited by 98 publications

(26 citation statements)

References 105 publications

(67 reference statements)

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“…This can be attributed to the inadequate wet curing provided to the mortars and the formation of gypsum (CaSO 4 ·2H 2 O) due to reaction of sulfate ions with CH and formation of ettringite (3CaO·Al 2 O 3 ·3CaSO 4 ·32H 2 O). The above formation of gypsum and ettringite is expansive which caused microcracking in mortars and hence, affected the measured compressive strength . The addition of NS also improved the compressive strength of all fly ash mortars at all ages similar to that observed in wet‐ and steam‐cured specimens.…”

Section: Resultsmentioning

confidence: 62%

Effects of fly ash fineness, nano silica, and curing types on mechanical and durability properties of fly ash mortars

Arel

Shaikh

2017

Structural Concrete

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The effects of nano silica (NS), three different fly ash contents, two curing types and exposure to sulfate solution on mechanical and durability properties of two types of fly ash mortars are evaluated in this study. Results show that the wet-cured mortars containing finer fly ash exhibited higher compressive strength at all ages than that containing coarser fly ash. The addition of colloidal NS improved the compressive strength of both types of fly ash mortars at all ages with significant improvement at early ages. The effect of steam curing slightly improved the 3-day compressive strength of control cement mortar and both fly ash mortars with reduction starts from 7 days onwards. However, the addition of NS improved the compressive strengths at all ages of all fly ash concretes subjected to steam curing. The exposure to sulfate solution adversely affected the compressive strength at all ages of all fly ash concretes irrespective of fly ash contents, fineness types, and NS addition. Fly ash mortars containing finer fly ash exhibited slightly higher drying shrinkages but lower rate of water sorption than the mortars containing coarser fly ash. The addition of NS significantly increased the drying shrinkage and decreased the rate of water sorption of both types of fly ash mortars containing all fly ash contents. K E Y W O R D Scompressive strength, finer fly ash, nano silica, sorptivity, steam curing, sulfate attack

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Section: Resultsmentioning

confidence: 62%

Effects of fly ash fineness, nano silica, and curing types on mechanical and durability properties of fly ash mortars

Arel

Shaikh

2017

Structural Concrete

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“…The calculation of resultant mass loss (dM R ) is similar to the resultant expansion, by considering the effects from the specimens immersed in a saturated lime solution. Mass variation correlates with the expansive product recrystallization, which has a greater molarity (Whittaker and Black, 2015). Figure 9 shows the comparative mass variation history of all the series.…”

Section: Mass Lossmentioning

confidence: 99%

“…gypsum and ettringite (Skalny et al, 2002). Whittaker and Black (2015) defend that the presence of gypsum and ettringite is not enough to cause degradation. Although, after a certain period, a threshold concentration is reached and it initiates a pressure on the pore walls, which leads to expansion, cracking, spalling, loss of mechanical properties and the complete deterioration of the composite due to the concrete's low tensile strength (Monteiro and Kurtis, 2003;Neville, 2016;Idiart et al, 2011;Whittaker and Black, 2015).…”

mentioning

confidence: 99%

“…The type of cation associated with SO 4 2modifies the mechanisms and the consequences of the attack (Neville, 2004). Additionally, a higher sulfate external concentration leads to a faster diffusion generating a more severe attack (Whittaker and Black, 2015). Temperature and the pH of the solution are also determinant in the products formation (Navarro et al, 2000;Zhou et al, 2006;Liu et al, 2013;Hou et al 2015;Neville, 2016).…”

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confidence: 99%

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Sodium sulfate attack on Portland cement structures: experimental and analytical approach

et al. 2018

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The industrial development and the advance of the primary sector in Brazil generated an increase in the cases of structures damaged by sulfate attacks. A reduction in material lifetime is one of the most costly factors in the construction field. Therefore, it is necessary to understand the sulfate attack mechanism in order to provide repairs and prevent further attacks. This article aims to understand how the environmental condition and the material properties influence the attack's severity. Hence, it combined an experimental program and analytical model to measure those parameter effects. Experiments show that cement with a higher amount of tricalcium aluminate (C 3 A), as the CP V ARI, presented a more pronounced deterioration. Visual changes such as cracking, crystallization of expansive products and a complete disintegration were also observed. In addition, loss of resistance occurred in the specimens with low slag content. Moreover, the model is useful to predict the delamination depth and to identify the most critical factors influencing the attack through sensitive analysis. Its results were compared with real cases based on literature and verifying the model reliability.

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“…Sulfate attack can be described as a series of chemical interactions that occur between hardened cement paste and sulfates. The degradation of cement-based materials in sulfate-bearing environments has been of concern to concrete technologists since the early 19 th century [1][2][3]. In most cases, the deterioration that was caused by the sulfate attack resulted in formation of ettringite or gypsum.…”

Section: Introductionmentioning

confidence: 99%

The failure process of mortars during sulfate attack

et al. 2019

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External sulfate attacks on concrete structures may cause serious damage and it has attracted a wide range of attention from numerous researchers over the past decades. However, many studies have been concentrated on the sample which has been already destroyed. This paper investigated the entire deterioration process of mortars that were immersed in Na2SO4 solution containing 3 gSO4 2-/L and 33.8g SO4 2-/l at 20 o C up to 600 days. The study on time-varying regularity of expansion, cracks, compressive strength and mineral phases was investigated. Back scattered electron image was used to further examine the evolution of microstructures of the mortars during the attack process. The results showed that damage process of mortars can be described as induction stage, surface damage, bulk damage and then completely damage stage. Fine ettringites that were formed in restricted spaces, approximately 2-5 μm, result in surface damage. At the bulk damage stage, cracking was the main characteristic of mortar which leads to obvious expansion. In this stage, some large ettringite crystals (>20μm) were just deposited in the formed cracks. At the later stage, gypsum can be easily formed at interfacial transition zones as the consumption of calcium hydroxide, which mainly contributed to completely strength failure rather than expansion.

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Current knowledge of external sulfate attack

Cited by 98 publications

References 105 publications

Effects of fly ash fineness, nano silica, and curing types on mechanical and durability properties of fly ash mortars

Effects of fly ash fineness, nano silica, and curing types on mechanical and durability properties of fly ash mortars

Sodium sulfate attack on Portland cement structures: experimental and analytical approach

The failure process of mortars during sulfate attack

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