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N Thaulow - One of the best experts on this subject based on the ideXlab platform.
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Delayed Ettringite Formation in swedish concrete railroad ties
Cement and Concrete Research, 2004Co-Authors: Sadananda Sahu, N ThaulowAbstract:Since the 1970s, failures of a number of precast concrete products manufactured at elevated temperatures have been reported. This article reports on a case where a petrographic examination of cracked Swedish concrete railroad ties identified Delayed Ettringite Formation (DEF) as the damaging mechanism. This was unexpected because the concrete railroad ties were steam-cured with a maximum concrete temperature below 60 deg C. The authors discuss the influence of various parameters on DEF, in light of this case. They note that DEF is not only influenced by the curing temperature, but also by various other factors, such as cement composition (alkalis, C3S, C3A, SO3, and MgO), fineness, etc. The authors conclude that if an unfavorable combination of these parameters exists, Delayed Ettringite may occur at lower temperatures than 70 deg C. The conditions that confer risk include the use of high alkali cement with high surface area, high C3S content, concrete with low water-to-cement ratio, and high cement content.
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Delayed Ettringite Formation IN SWEDISH CONCRETE RAILROAD TIES
Cement and Concrete Research, 2004Co-Authors: Sadananda Sahu, N ThaulowAbstract:Abstract A petrographic examination of cracked Swedish concrete railroad ties identified Delayed Ettringite Formation (DEF) as the damaging mechanism. This was unexpected because the concrete railroad ties were steam-cured with a maximum concrete temperature below 60 °C. The consensus in the published literature is that DEF only occurs in concrete subjected to heat curing above 70 °C. However, DEF is not only influenced by the curing temperature, but also by various other factors, such as cement composition (alkalis, C3S, C3A, SO3, and MgO), fineness, etc. If an unfavorable combination of these parameters exists, Delayed Ettringite may occur at lower temperatures than 70 °C. In this paper, the influence of various parameters on DEF is discussed with reference to the investigated concrete.
Xiao Qin - One of the best experts on this subject based on the ideXlab platform.
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Relationship between Delayed Ettringite Formation and Delayed expansion in massive shrinkage-compensating concrete
Cement and Concrete Composites, 2004Co-Authors: Peiyu Yan, Feng Zheng, Jiang Peng, Xiao QinAbstract:The possibility of Delayed expansion induced by Delayed Ettringite Formation in massive shrinkage-compensating concrete was investigated. Mortars were prepared using ordinary Portland cement and a sulfoaluminate-based expansive agent. They were cured in three different moist conditions at elevated temperature in a temperature match conditioning process to simulate the temperature development in the interior of massive concrete, and then at ambient temperature. Changes in quantity and morphology of Ettringite were examined using semi-quantitative X-ray diffraction and scanning electron microscopy. The time-dependent length change of restrained mortars was also measured. The results show that, in addition to the quantity of Ettringite, the structure of mortar, morphology of Ettringite and curing conditions also influenced expansion of mortars induced by Delayed Ettringite Formation. The expansion mechanism of Delayed Ettringite Formation and the relationship between curing conditions and length change, Delayed expansion and damage to concrete structure are discussed.
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Behaviour and the controlling factor of Delayed Ettringite Formation in shrinkage-compensating massive concrete
Magazine of Concrete Research, 2002Co-Authors: Peiyu Yan, Jiang Peng, Xiao QinAbstract:The longitudinal variance of confined shrinkage-compensating concrete was investigated under different curing conditions. A Delayed Ettringite Formation (DEF) was observed in the specimen cured with temperature match conditioning (TMC), simulating the situation in the core of massive concrete. DEF induced the loss of expansion efficiency at the early age and then Delayed the expansion at the later age in shrinkage-compensating concrete. Both behaviours are detrimental to the long-term performance of shrinkage-compensating concrete. Environmental humidity was identified as the dominating factor in controlling the occurrence of the detrimental Delayed expansion induced by DEF in shrinkage-compensating massive concrete.
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The effect of expansive agent and possibility of Delayed Ettringite Formation in shrinkage-compensating massive concrete
Cement and Concrete Research, 2001Co-Authors: Peiyu Yan, Xiao QinAbstract:The effects of expansive agent and possibility of Delayed Ettringite Formation (DEF) were determined using a temperature match condition (TMC) system in the simulated condition of shrinkage-compensating massive concrete. The expansive agent used in massive concrete cannot give full play to its shrinkage-compensating effect when curing temperature is higher than 70°C. The harmful Delayed expansion due to DEF might occur in hardened concrete.
Sadananda Sahu - One of the best experts on this subject based on the ideXlab platform.
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Delayed Ettringite Formation in swedish concrete railroad ties
Cement and Concrete Research, 2004Co-Authors: Sadananda Sahu, N ThaulowAbstract:Since the 1970s, failures of a number of precast concrete products manufactured at elevated temperatures have been reported. This article reports on a case where a petrographic examination of cracked Swedish concrete railroad ties identified Delayed Ettringite Formation (DEF) as the damaging mechanism. This was unexpected because the concrete railroad ties were steam-cured with a maximum concrete temperature below 60 deg C. The authors discuss the influence of various parameters on DEF, in light of this case. They note that DEF is not only influenced by the curing temperature, but also by various other factors, such as cement composition (alkalis, C3S, C3A, SO3, and MgO), fineness, etc. The authors conclude that if an unfavorable combination of these parameters exists, Delayed Ettringite may occur at lower temperatures than 70 deg C. The conditions that confer risk include the use of high alkali cement with high surface area, high C3S content, concrete with low water-to-cement ratio, and high cement content.
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Delayed Ettringite Formation IN SWEDISH CONCRETE RAILROAD TIES
Cement and Concrete Research, 2004Co-Authors: Sadananda Sahu, N ThaulowAbstract:Abstract A petrographic examination of cracked Swedish concrete railroad ties identified Delayed Ettringite Formation (DEF) as the damaging mechanism. This was unexpected because the concrete railroad ties were steam-cured with a maximum concrete temperature below 60 °C. The consensus in the published literature is that DEF only occurs in concrete subjected to heat curing above 70 °C. However, DEF is not only influenced by the curing temperature, but also by various other factors, such as cement composition (alkalis, C3S, C3A, SO3, and MgO), fineness, etc. If an unfavorable combination of these parameters exists, Delayed Ettringite may occur at lower temperatures than 70 °C. In this paper, the influence of various parameters on DEF is discussed with reference to the investigated concrete.
Peiyu Yan - One of the best experts on this subject based on the ideXlab platform.
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Relationship between Delayed Ettringite Formation and Delayed expansion in massive shrinkage-compensating concrete
Cement and Concrete Composites, 2004Co-Authors: Peiyu Yan, Feng Zheng, Jiang Peng, Xiao QinAbstract:The possibility of Delayed expansion induced by Delayed Ettringite Formation in massive shrinkage-compensating concrete was investigated. Mortars were prepared using ordinary Portland cement and a sulfoaluminate-based expansive agent. They were cured in three different moist conditions at elevated temperature in a temperature match conditioning process to simulate the temperature development in the interior of massive concrete, and then at ambient temperature. Changes in quantity and morphology of Ettringite were examined using semi-quantitative X-ray diffraction and scanning electron microscopy. The time-dependent length change of restrained mortars was also measured. The results show that, in addition to the quantity of Ettringite, the structure of mortar, morphology of Ettringite and curing conditions also influenced expansion of mortars induced by Delayed Ettringite Formation. The expansion mechanism of Delayed Ettringite Formation and the relationship between curing conditions and length change, Delayed expansion and damage to concrete structure are discussed.
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Behaviour and the controlling factor of Delayed Ettringite Formation in shrinkage-compensating massive concrete
Magazine of Concrete Research, 2002Co-Authors: Peiyu Yan, Jiang Peng, Xiao QinAbstract:The longitudinal variance of confined shrinkage-compensating concrete was investigated under different curing conditions. A Delayed Ettringite Formation (DEF) was observed in the specimen cured with temperature match conditioning (TMC), simulating the situation in the core of massive concrete. DEF induced the loss of expansion efficiency at the early age and then Delayed the expansion at the later age in shrinkage-compensating concrete. Both behaviours are detrimental to the long-term performance of shrinkage-compensating concrete. Environmental humidity was identified as the dominating factor in controlling the occurrence of the detrimental Delayed expansion induced by DEF in shrinkage-compensating massive concrete.
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The effect of expansive agent and possibility of Delayed Ettringite Formation in shrinkage-compensating massive concrete
Cement and Concrete Research, 2001Co-Authors: Peiyu Yan, Xiao QinAbstract:The effects of expansive agent and possibility of Delayed Ettringite Formation (DEF) were determined using a temperature match condition (TMC) system in the simulated condition of shrinkage-compensating massive concrete. The expansive agent used in massive concrete cannot give full play to its shrinkage-compensating effect when curing temperature is higher than 70°C. The harmful Delayed expansion due to DEF might occur in hardened concrete.
James J. Beaudoin - One of the best experts on this subject based on the ideXlab platform.
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Effect of Aggregate Particle Size and Composition on Expansion of Mortar Bars due to Delayed Ettringite Formation
Cement and Concrete Research, 1998Co-Authors: P.e. Grattan-bellew, James J. Beaudoin, V.-g. ValleeAbstract:The effect of aggregate composition and particle size on the expansion of mortar bars, due to Delayed Ettringite Formation (DEF), was evaluated by heat-curing mortar bars made with basalt, dolostone, granite, limestone, siliceous limestone, and pure crystalline quartz. Subsequent to heat curing, the mortar bars were subjected to 3 thermal cycles to accelerate the Formation of DEF. They were then stored in lime water for 59 days and length change was monitored. Only mortar bars made with quartz aggregate showed significant expansion. Expansion was found to be inversely proportional to the particle size of the quartz aggregate. The amount of Ettringite formed in the mortar bars was shown to be proportional to their rate of expansion.
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Microcracking as a precursor to Delayed Ettringite Formation in cement systems
Cement and Concrete Research, 1996Co-Authors: James J. BeaudoinAbstract:Abstract Concretes, made with ASTM Type I, III and V cements were subjected to different microcrack-inducing treatments i.e. drying/re-wetting, freezng/thawing and loading/unloading. Expansion of the concretes due to Delayed Ettringite Formation (DEF) was measured. Crack surface composition was studied using x-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDXA). The results confirmed that microcracking in concrete and mortar made with ASTM Type III Portland cement can lead to increased deterioration resulting from DEF subsequent to high temperature curing followed by severe thermal-drying.
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A kinetic study of Delayed Ettringite Formation in hydrated portland cement paste
Cement and Concrete Research, 1995Co-Authors: Yan Fu, Ping Gu, James J. BeaudoinAbstract:Results of a kinetic study of Delayed Ettringite Formation in hydrated Portland cement paste by XRD analysis over the temperature range 5 to 85 °C are reported. Two competitive reactions in terms of gypsum consumption are discussed. These involve both CSH gel and the hydrated calcium aluminates. An increase in temperature apparently accelerates sulphate absorption rate by C SH gel. Ettringite Formation is relatively temperature independent during the first day of hydration in the range 65 to 85 °C. A mechanism for secondary Ettringite Formation in high temperature steam cured Portland cement material is advanced. © 1995.