The Experts below are selected from a list of 5034 Experts worldwide ranked by ideXlab platform
Jan Olek - One of the best experts on this subject based on the ideXlab platform.
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Sulfate Attack research whither now
Cement and Concrete Research, 2001Co-Authors: Manu Santhanam, Menashi D. Cohen, Jan OlekAbstract:Sulfate Attack research is at a critical stage. In spite of meaningful advances in the past few years, this problem is still not well understood. Due to its complicated mechanism, the reaction between cement hydration products and Sulfate-bearing solutions manifests itself in a variety of ways. In order to provide adequate means for selection of materials for concrete exposed to such aggressive environments, additional research is necessary to further clarify the interaction between concrete and Sulfate-bearing solutions. Specifically, the role of the cation in the Sulfate solution, and the effects of formation of various products like gypsum, ettringite, and thaumasite, on the extent of damage need to be investigated. The available testing methods for Sulfate Attack have been subject to some criticism lately. Although these test methods can give an indication of the mechanisms involved in Sulfate Attack, prediction of field performance using lab studies is difficult. Efforts are needed to introduce appropriate changes in the tests in order to obtain field-like conditions in the laboratory. Combined with good monitoring methods, this would enable the prediction of service life of structures exposed to Sulfate solutions. Recent advances in nondestructive testing techniques can be applied to the task of monitoring field structures, although there is a significant effort necessary to calibrate these methods for Sulfate Attack-related scenarios. In order to produce efficient concrete designs for service in aggressive environments, it is imperative to develop reliable models. Modeling can help in selecting the appropriate materials and their proportions, as well as in determining service life parameters. As a first step towards modeling, critical parameters, which serve as an indicator of deterioration, need to be recognized and established. This paper discusses these issues, and cites some interesting recent developments. Finally, some recommendations for future studies are provided.
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Sulfate Attack research — whither now?
Cement and Concrete Research, 2001Co-Authors: Manu Santhanam, Menashi D. Cohen, Jan OlekAbstract:Sulfate Attack research is at a critical stage. In spite of meaningful advances in the past few years, this problem is still not well understood. Due to its complicated mechanism, the reaction between cement hydration products and Sulfate-bearing solutions manifests itself in a variety of ways. In order to provide adequate means for selection of materials for concrete exposed to such aggressive environments, additional research is necessary to further clarify the interaction between concrete and Sulfate-bearing solutions. Specifically, the role of the cation in the Sulfate solution, and the effects of formation of various products like gypsum, ettringite, and thaumasite, on the extent of damage need to be investigated. The available testing methods for Sulfate Attack have been subject to some criticism lately. Although these test methods can give an indication of the mechanisms involved in Sulfate Attack, prediction of field performance using lab studies is difficult. Efforts are needed to introduce appropriate changes in the tests in order to obtain field-like conditions in the laboratory. Combined with good monitoring methods, this would enable the prediction of service life of structures exposed to Sulfate solutions. Recent advances in nondestructive testing techniques can be applied to the task of monitoring field structures, although there is a significant effort necessary to calibrate these methods for Sulfate Attack-related scenarios. In order to produce efficient concrete designs for service in aggressive environments, it is imperative to develop reliable models. Modeling can help in selecting the appropriate materials and their proportions, as well as in determining service life parameters. As a first step towards modeling, critical parameters, which serve as an indicator of deterioration, need to be recognized and established. This paper discusses these issues, and cites some interesting recent developments. Finally, some recommendations for future studies are provided.
Menashi D. Cohen - One of the best experts on this subject based on the ideXlab platform.
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Sulfate Attack research whither now
Cement and Concrete Research, 2001Co-Authors: Manu Santhanam, Menashi D. Cohen, Jan OlekAbstract:Sulfate Attack research is at a critical stage. In spite of meaningful advances in the past few years, this problem is still not well understood. Due to its complicated mechanism, the reaction between cement hydration products and Sulfate-bearing solutions manifests itself in a variety of ways. In order to provide adequate means for selection of materials for concrete exposed to such aggressive environments, additional research is necessary to further clarify the interaction between concrete and Sulfate-bearing solutions. Specifically, the role of the cation in the Sulfate solution, and the effects of formation of various products like gypsum, ettringite, and thaumasite, on the extent of damage need to be investigated. The available testing methods for Sulfate Attack have been subject to some criticism lately. Although these test methods can give an indication of the mechanisms involved in Sulfate Attack, prediction of field performance using lab studies is difficult. Efforts are needed to introduce appropriate changes in the tests in order to obtain field-like conditions in the laboratory. Combined with good monitoring methods, this would enable the prediction of service life of structures exposed to Sulfate solutions. Recent advances in nondestructive testing techniques can be applied to the task of monitoring field structures, although there is a significant effort necessary to calibrate these methods for Sulfate Attack-related scenarios. In order to produce efficient concrete designs for service in aggressive environments, it is imperative to develop reliable models. Modeling can help in selecting the appropriate materials and their proportions, as well as in determining service life parameters. As a first step towards modeling, critical parameters, which serve as an indicator of deterioration, need to be recognized and established. This paper discusses these issues, and cites some interesting recent developments. Finally, some recommendations for future studies are provided.
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Sulfate Attack research — whither now?
Cement and Concrete Research, 2001Co-Authors: Manu Santhanam, Menashi D. Cohen, Jan OlekAbstract:Sulfate Attack research is at a critical stage. In spite of meaningful advances in the past few years, this problem is still not well understood. Due to its complicated mechanism, the reaction between cement hydration products and Sulfate-bearing solutions manifests itself in a variety of ways. In order to provide adequate means for selection of materials for concrete exposed to such aggressive environments, additional research is necessary to further clarify the interaction between concrete and Sulfate-bearing solutions. Specifically, the role of the cation in the Sulfate solution, and the effects of formation of various products like gypsum, ettringite, and thaumasite, on the extent of damage need to be investigated. The available testing methods for Sulfate Attack have been subject to some criticism lately. Although these test methods can give an indication of the mechanisms involved in Sulfate Attack, prediction of field performance using lab studies is difficult. Efforts are needed to introduce appropriate changes in the tests in order to obtain field-like conditions in the laboratory. Combined with good monitoring methods, this would enable the prediction of service life of structures exposed to Sulfate solutions. Recent advances in nondestructive testing techniques can be applied to the task of monitoring field structures, although there is a significant effort necessary to calibrate these methods for Sulfate Attack-related scenarios. In order to produce efficient concrete designs for service in aggressive environments, it is imperative to develop reliable models. Modeling can help in selecting the appropriate materials and their proportions, as well as in determining service life parameters. As a first step towards modeling, critical parameters, which serve as an indicator of deterioration, need to be recognized and established. This paper discusses these issues, and cites some interesting recent developments. Finally, some recommendations for future studies are provided.
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does gypsum formation during Sulfate Attack on concrete lead to expansion
Cement and Concrete Research, 2000Co-Authors: Bing Tian, Menashi D. CohenAbstract:Abstract Sulfate Attack on Portland cement concrete is often said to arise from each of two major Sulfate reactions: (1) The Sulfate ions react with C 3 A and its hydration products to form ettringite with an increase in volume that results in expansion and subsequent cracking of the concrete; (2) The Sulfate ions react with calcium hydroxide (CH) to form gypsum. Even though gypsum formation is generally accepted to be harmful, the specific mechanism is not well established. Especially, the idea that gypsum formation leads to any expansion is controversial. This paper covers an investigation carried out to study the gypsum formation during Sulfate Attack and its consequences. Two parts are included: Part 1 consists of the results of a literature review describing different theories supporting and contradicting the idea that gypsum formation is expansive. Part 2 describes the laboratory investigation carried out by the authors. The results suggested that gypsum formation during Sulfate Attack may cause expansion.
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does gypsum formation during Sulfate Attack on concrete lead to expansion
Cement and Concrete Research, 2000Co-Authors: Bing Tian, Menashi D. CohenAbstract:Abstract Sulfate Attack on Portland cement concrete is often said to arise from each of two major Sulfate reactions: (1) The Sulfate ions react with C 3 A and its hydration products to form ettringite with an increase in volume that results in expansion and subsequent cracking of the concrete; (2) The Sulfate ions react with calcium hydroxide (CH) to form gypsum. Even though gypsum formation is generally accepted to be harmful, the specific mechanism is not well established. Especially, the idea that gypsum formation leads to any expansion is controversial. This paper covers an investigation carried out to study the gypsum formation during Sulfate Attack and its consequences. Two parts are included: Part 1 consists of the results of a literature review describing different theories supporting and contradicting the idea that gypsum formation is expansive. Part 2 describes the laboratory investigation carried out by the authors. The results suggested that gypsum formation during Sulfate Attack may cause expansion.
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Sulfate Attack on Concrete: Research Needs
ACI Materials Journal, 1991Co-Authors: Menashi D. Cohen, Bryant MatherAbstract:The mechanism of Sulfate Attack on portland cement concrete is not well understood. This has limited confidence that can be placed in and hence the reliability of existing standard tests and models to predict performance and service life of concrete subjected to Sulfate Attack. A systematic research effort is necessary to establish 5 criteria. This paper presents and discusses these 5 criteria. In addition, an approach for assessing the influence of pozzolans, or other cementing materials, on concrete performance and service life in Sulfate environment is presented.
Manu Santhanam - One of the best experts on this subject based on the ideXlab platform.
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Sulfate Attack research whither now
Cement and Concrete Research, 2001Co-Authors: Manu Santhanam, Menashi D. Cohen, Jan OlekAbstract:Sulfate Attack research is at a critical stage. In spite of meaningful advances in the past few years, this problem is still not well understood. Due to its complicated mechanism, the reaction between cement hydration products and Sulfate-bearing solutions manifests itself in a variety of ways. In order to provide adequate means for selection of materials for concrete exposed to such aggressive environments, additional research is necessary to further clarify the interaction between concrete and Sulfate-bearing solutions. Specifically, the role of the cation in the Sulfate solution, and the effects of formation of various products like gypsum, ettringite, and thaumasite, on the extent of damage need to be investigated. The available testing methods for Sulfate Attack have been subject to some criticism lately. Although these test methods can give an indication of the mechanisms involved in Sulfate Attack, prediction of field performance using lab studies is difficult. Efforts are needed to introduce appropriate changes in the tests in order to obtain field-like conditions in the laboratory. Combined with good monitoring methods, this would enable the prediction of service life of structures exposed to Sulfate solutions. Recent advances in nondestructive testing techniques can be applied to the task of monitoring field structures, although there is a significant effort necessary to calibrate these methods for Sulfate Attack-related scenarios. In order to produce efficient concrete designs for service in aggressive environments, it is imperative to develop reliable models. Modeling can help in selecting the appropriate materials and their proportions, as well as in determining service life parameters. As a first step towards modeling, critical parameters, which serve as an indicator of deterioration, need to be recognized and established. This paper discusses these issues, and cites some interesting recent developments. Finally, some recommendations for future studies are provided.
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Sulfate Attack research — whither now?
Cement and Concrete Research, 2001Co-Authors: Manu Santhanam, Menashi D. Cohen, Jan OlekAbstract:Sulfate Attack research is at a critical stage. In spite of meaningful advances in the past few years, this problem is still not well understood. Due to its complicated mechanism, the reaction between cement hydration products and Sulfate-bearing solutions manifests itself in a variety of ways. In order to provide adequate means for selection of materials for concrete exposed to such aggressive environments, additional research is necessary to further clarify the interaction between concrete and Sulfate-bearing solutions. Specifically, the role of the cation in the Sulfate solution, and the effects of formation of various products like gypsum, ettringite, and thaumasite, on the extent of damage need to be investigated. The available testing methods for Sulfate Attack have been subject to some criticism lately. Although these test methods can give an indication of the mechanisms involved in Sulfate Attack, prediction of field performance using lab studies is difficult. Efforts are needed to introduce appropriate changes in the tests in order to obtain field-like conditions in the laboratory. Combined with good monitoring methods, this would enable the prediction of service life of structures exposed to Sulfate solutions. Recent advances in nondestructive testing techniques can be applied to the task of monitoring field structures, although there is a significant effort necessary to calibrate these methods for Sulfate Attack-related scenarios. In order to produce efficient concrete designs for service in aggressive environments, it is imperative to develop reliable models. Modeling can help in selecting the appropriate materials and their proportions, as well as in determining service life parameters. As a first step towards modeling, critical parameters, which serve as an indicator of deterioration, need to be recognized and established. This paper discusses these issues, and cites some interesting recent developments. Finally, some recommendations for future studies are provided.
Wenhui Duan - One of the best experts on this subject based on the ideXlab platform.
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damage evolution of cement mortar with high volume slag exposed to Sulfate Attack
Construction and Building Materials, 2020Co-Authors: Yonggan Yang, Binggen Zhan, Jingfeng Wang, Yunsheng Zhang, Wenhui DuanAbstract:Abstract Sulfate Attack is one of the important reasons for the premature failure of cement-based materials. In this paper, the deterioration law of mortar by Sulfate Attack was investigated through expansion, mass change, relative dynamic elastic modulus (Erd) and the distribution of Sulfate ion content. Moreover, the pore size distribution, corrosion products and three-dimensional crack distribution were performed by Mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) and X-ray computed tomography (X-ray CT), respectively. In addition, the degradation process of mortar with slag immersed in Sulfate solution was investigated. The results showed that combined the mass change and Erd can more accurately evaluate the damage of mortar by Sulfate Attack. The increase of water-to-cement ratio significantly aggravates the mortar deterioration. Adding slag can significantly improve the pore size distribution and improve the Sulfate resistance of mortar. The deterioration process of mortar with slag by Sulfate Attack is different from that of mortar without slag. The degradation process of the mortar with slag is that the surface layer peels off first, and then the Sulfate ion continues to invade the interior of the sample to form a new expansion area.
R N Swamy - One of the best experts on this subject based on the ideXlab platform.
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Sulfate Attack and role of silica fume in resisting strength loss
Cement & Concrete Composites, 2005Co-Authors: S T Lee, H Y Moo, R N SwamyAbstract:Abstract This paper presents a detailed experimental study on the Sulfate Attack of Portland cement mortars, and the effectiveness of silica fume in controlling the damage arising from such Attack. The test solutions used to supply the Sulfate ions and cations were 5% sodium Sulfate solution and 5% magnesium Sulfate solution. Tap water was used as the reference solution. The main variables investigated in the study were the water/cementitious materials ratio, and the level of cement replacement. Compressive strength measured on 50 mm cubes was used to assess the changes in the mechanical properties of mortar specimens exposed to Sulfate Attack for 510 days. X-ray diffraction and differential scanning calorimetry were used to evaluate the microstructural nature of the Sulfate Attack. The test results showed that the presence of silica fume had a beneficial effect on the strength loss due to sodium Sulfate Attack. The best resistance to sodium Sulfate Attack was obtained with a SF replacement of 5–10%, but even then, a strength loss of 15–20% can be expected. On the other hand, mortars with silica fume were severely damaged in the magnesium Sulfate environment. Further, the compressive strength loss actually increased with increasing SF content. The test results thus showed clearly that the use of SF in concrete exposed to magnesium Sulfate solution is not recommended. The test results also showed that the w/cm ratio is the most critical parameter influencing the resistance of concrete to Sulfate Attack. All the tests reported in the study were carried out at 20 ± 1 °C.
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Sulfate Attack of Mortars Containing Recycled Fine Aggregates
ACI Materials Journal, 2005Co-Authors: S T Lee, R N Swamy, H Y Moon, S S Kim, J P KimAbstract:From both environmental and sustainability points of view, it is imperative for engineers to effectively use the increasing amounts of concrete waste available. This article reports on a study of the durability of mortar specimens made with recycled fine aggregate exposed to external Sulfate Attack. The replacement level and the type of the recycled fine aggregate were the primary variables. The mortar specimens were immersed in a 5% sodium Sulfate solution for 360 days and regularly monitored for visual damage, variation of expansion, and compressive strength. At the end of 360 days, the products of Sulfate Attack and the mechanism of Attack were investigated through x-ray diffraction and scanning electron microscopy. Results show that the use of recycled fine aggregates up to a maximum of 50% replacement level had a beneficial effect on durability against Sulfate Attack, in terms of strength loss and expansion. Mortar specimens incorporating 100% replacement level, regardless of type of recycled aggregate, suffered severe deterioration. The water absorption of the recycled fine aggregate was a major factor controlling expansion, strength loss, and the intensity of damage due to Sulfate Attack. The microstructural studies indicated that the primary cause of deterioration of the mortar specimens with recycled aggregate was the formation of thaumasite and gypsum due to Sulfate Attack. The authors hypothesize that incorporation of recycled fine aggregate possibly led to the production of a relatively weak interfacial transition zone, particularly when high replacement levels were employed. The authors conclude that, when recycled fine aggregates with high water absorption are used in concrete, the limiting level of replacement is 50%. Care in the design of concrete mixtures should be taken even when such concretes are used in normal exposure conditions.
