• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.557-564
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• 2004

This paper introduces a study carried out to investigate sodium sulfate attack caused by various reactive products. Experiments were performed on mortar and paste specimens made with ordinary Portland cement (OPC) conforming to KS L 5201 Type I. The water-cement ratios were varied from 0.35 to 0.55. It was found from the laboratory study that the water-cement ratio may be a key to control the deterioration of OPC matrix during sodium sulfate attack. Furthermore, X-ray diffraction (XRD) confirmed that ettringite, gypsum and thaumasite were the main products formed by sodium sulfate attack. These findings were well supported by thermal analysis through differential scanning calorimetry (DSC), and confirmed the long-term understanding that deterioration mechanism by sodium sulfate attack is a complicated process. Most importantly, deterioration due to sodium sulfate attack is characterized as the drastic reduction in compressive strength as well as the expansion (especially in cement matrix with a higher water-cement ratio).

• Geomechanics and Engineering
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• v.10 no.6
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• pp.807-826
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• 2016

In this study, aiming to investigate the effects of sulfate attack on cement stabilized highly plastic clay; an experimental study was carried out considering the effects of cement type, sulfate type and its concentration, cement content and curing period. Unconfined compressive strength and chloride-ion penetration tests were performed to obtain strength and permeability characteristics of specimens cured under different conditions. Test results were evaluated along with microstructural investigations including SEM and EDS analyses. Results revealed that use of sulfate resistance cement instead of normal portland cement is more plausible for soils under the threat of sulfate attack. Besides, it was verified that sulfate concentration is responsible for strength loss and permeability increase in cement stabilized montmorillonite. Finally, empirical equations were proposed to estimate the unconfined compressive strength of cement stabilized montmorillonite, which was exposed to sulfate attack for 28 days.

• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.441-447
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• 2009

This paper presents a detailed experimental study on the sulfate resistance of specimens made with portland cement exposed to sulfate attack. The mortar specimens were immersed in a 5% sodium sulfate solution for 360 days and regularly monitored for visual damage, compressive strength loss and expansion. In addition, at the end of 360 days, the products of sulfate attack and the mechanism of attack were investigated through X-ray diffraction, TG&DSC and scanning electron microscopy. The test results indicated that the sulfate deterioration data was ordinary portland cement > sulfate resistance portland cement > low heat portland cement. The microstructural studies indicated that the main reaction product of deterioration of the mortar specimens was the formation of ettringite, gypsum and thaumasite due to sulfate attack. For portland cement matrices, a low heat cement matrix containing the lowest C3A and silicate ratio (C/S) was beneficient against the sulfate attack.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.209-212
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• 2006

Until now, sulfate attack is not completely understood. The purpose of this study is to provide a fundamental data to understand deterioration mechanism by sulfate attack. Chemical processes for products formed by sulfate attack were explained in this study. ASTM C1012 test and microstructural observations such as XRD and BSE analysis were carried out to manifest behavior and role of the products formed during sulfate attack. Regarding the dominant causes of sulfate attack, the main deterioration modes could be divided into 3 types; (1) expansive type, (2) onion-peeling type, and (3) acidic type.

• Computers and Concrete
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• v.19 no.2
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• pp.143-152
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• 2017

This paper has numerically investigated the changes of loading-induced stress in concrete with the corrosion time in the sulfate-containing environment. Firstly, based on Fick's law and reaction kinetics, a diffusion-reaction equation of sulfate ion in concrete is proposed, and it is numerically solved to obtain the spatial and temporal distribution of sulfate ion concentration in concrete by the finite difference method. Secondly, by fitting the existed experimental data of concrete in sodium sulfate solutions, the chemical damage of concrete associated with sulfate ion concentration and corrosion time is quantitatively presented. Thirdly, depending on the plastic-damage mechanics, while considering the influence of sulfate attack on concrete properties, a simplified chemo-mechanical damage model, with stress-based plasticity and strain-driven damage, for concrete under axial loading and sulfate attack is determined by introducing the chemical damage degree. Finally, an axially compressed concrete prism immersed into the sodium sulfate solution is regarded as an object to investigate the time-varying stress in concrete subjected to the couplings of axial loading and sulfate attack.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.63-69
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• 2015

It has been well known that concrete structures exposed to chloride and sulfate attack environments lead to significant deterioration in their durability due to chloride ion and sulfate ion attack. The purpose of this experimental research is to evaluate the resistance against chloride ion and sulfate attack of the cementless concrete replacing the cement with ground granulated blast furnace slag. For this purpose, the cementless concrete specimens were made for water-binder ratios of 40%, 45%, and 50%, respectively and then this specimens were cured in the water of $20{\pm}3^{\circ}C$ and immersed in fresh water, 10% sodium sulfate solution for 28 and 91 days, respectively. To evaluate the resistance to chloride ion and sulfate attack for the cementless concrete specimens, the diffusion coefficient for chloride ion and compressive strength ratio, mass change ratio, and length change ratio were measured according to the NT BUILD 492 and JSTM C 7401, respectively. It was observed from the test results that the resistance against chloride ion and sulfate attack of the cemetntless concrete were comparatively largely increased than those of OPC concrete with decreasing water-binder ratio.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.4
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• pp.121-128
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• 2007

The present study evaluates the resistance to sulfate attack of cement matrix with or without silica fume. The main variable was the replacement levels of silica fume. In order to introduce sulfate attack to cement matrix, mortars and pastes was exposed to sodium sulfate solution for 510 days. Visual examination, expansion and compressive strength loss of mortars in addition to characteristics of pore for the paste samples were regularly investigated. From the test results, it was clearly observed that the cement matrix with silica fume was very resistant to sulfate attack irrespective of the replacement levels of silica fume. However, the severe deterioration due to sulfate attack was found in cement matrix without silica fume.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.704-709
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• 2000

This study is to test effects of sulfate attack on deterioration of cement mortar. Four tests have been carried out with four types of mortars mixed by ordinary portland cement and sulfate-resistant portland cement containing blast-furnace slag and fly-ash. It was immersed in sulfate solution for 7, 28, 91, and 180 days. from the test results, sulfate attack resistance of cement mortar was improved by admixtures (blast-furnace slag and fly-ash), sulfate-resistance portland cement mortar showed high resistance than ordinarily portland cement at compressive strength, and similar the resistance of sulfate attack with ordinarily portland cement mortar with admixtures.

• Journal of the Korean Ceramic Society
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• v.44 no.9
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• pp.465-470
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• 2007

This paper presents an experimental study of the sulfate resistance of mortars and pastes exposed to sodium sulfate solutions up to one year. In order to check deterioration modes due to sulfate attack, the sodium sulfate solution was varied at three concentration steps (3,380, 10,140 and 33,800 ppm of $SO_4^{2-}$ ions), and maintained at ambient temperature. The tests include a visual examination, expansion and compressive strength loss measurements as well as x-ray diffraction tests. The experimental data indicated that the use of cement with a low $C_3A$ content and low silicate ratio has a beneficial effect on the sulfate attack of mortars. In contrast, the mortars with a high $C_3A$ content and high silicate ratio became severely degraded due to the formation of ettringite, gypsum and/or thaumasite in the cement matrix.

• Advances in concrete construction
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• v.8 no.1
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• pp.39-45
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• 2019

Durability of strengthened reinforced concrete (RC) beams with CFRP sheets under wetting and drying cycles of magnesium sulfate attack is investigated in this research. Accordingly, 18 RC beams were designed and made where 10 of them were strengthened by CFRP sheets at their tension side. Magnesium sulfate attack and wetting and drying cycles with water and magnesium sulfate solution were considered as exposure conditions. Finally, flexural performance of the beams was measured before and after 5 months of exposure. Results indicated that the bending capacity of the strengthened RC beams was reduced about 10% after 5 months of immersion in the magnesium sulfate solution. Wetting and drying cycles of magnesium sulfate solution reduced the bending capacity of the strengthened RC beams about 7%. Also, flexural capacity reduction of the strengthened RC beams in water and under wetting and drying cycles of water was negligible.