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Stefan Jacobsen - One of the best experts on this subject based on the ideXlab platform.
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frost durability of high strength concrete effect of Internal Cracking on ice formation
Cement and Concrete Research, 1996Co-Authors: Stefan Jacobsen, Erik J Sellevold, Seppo MatalaAbstract:Abstract Ice formation measurements using low temperature calorimetry (CAL) were made on non-air entrained high strength concretes (HSC) before and after exposure to rapid freeze/thaw cycles in water (ASTM C666 proc. A). The purpose was to explore the relationship between water absorption during test, changes in ice formation and deterioration, to investigate the deterioration mechanism of non-air entrained HSC in the ASTM C666 test. CAL results showed zero or very little ice formation in the concretes ( w b = 0.40 and 0.35, 0, 5 and 8 % silica fume ) before C666 testing in the temperature range of the test (−20 °C). After the test (DF = 10–11) significant water absorption had taken place. Only one half or less of the absorbed water was freezeable to −20 °C, i.e. only part of the absorbed water goes into the created cracks and contributes to the deterioration by freezing there. The rest of the water is freezeable at lower temperatures or so tightly bound that it does not freeze at all to −55 °C. The freezeable water to −20 °C after test constitutes 3–7 vol-% of the cement paste. CAL measurements at intermediate stages of deterioration show very rapid transitions between no and significant amount of freezeable water and indicate a progressive mechanism of deterioration, starting at the surface in contact with water and moving inward. Apparently very little ice formation can initiate the process and result in major damage. Water storage after freeze/thaw testing results in self healing characterized by significant recovery of dynamic Emodulus and decreased amounts of ice formation. However, compressive strength recovery is much smaller than the recovery of E-modulus.
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effect of Cracking and healing on chloride transport in opc concrete
Cement and Concrete Research, 1996Co-Authors: Stefan Jacobsen, J Marchand, L BoisvertAbstract:The effects of Cracking and self healing on chloride migration and compressive strength were investigated on wc = 0.40 concrete. Internal Cracking due to rapid freeze/thaw exposure resulted in a compressive strength reduction of 68-40 % and a reduced Ultrasonic Pulse Velocity (UPV) to 78-45 % of undamaged values. The rate of chloride migration through 15 mm thick slices under a 10 volt electric field was increased by 2.5–8 times and the chloride penetration time through the slices was reduced from 64 to 0 hours for the most severe Cracking. The increased chloride transport due to Cracking could be predicted fairly well by characterizing the cracks using a square grid crack pattern model. Self healing by storage of cracked specimens in lime saturated water at 20 °C for three months after stop of freeze/thaw exposure gave recovery in UPV of 50 –100 %, but compressive strength recovered only 0–10 % of the initial value. Rate of chloride migration in the self-healed concretes was reduced by 28–35 % and penetration time was increased compared to newly cracked concrete. The chloride migration through an air entrained concrete with the same wc ratio (no Internal Cracking after more than 300 cycles of rapid freeze/thaw exposure), was unaffected by freeze/thaw.
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self healing of high strength concrete after deterioration by freeze thaw
Cement and Concrete Research, 1996Co-Authors: Stefan Jacobsen, Erik J SellevoldAbstract:Abstract Some experiments have been performed to investigate the self healing of concretes deteriorated by Internal Cracking in the ASTM C666 procedure A rapid freeze/thaw test. Six different well cured concretes were deteriorated to various degrees. Then the specimens (concrete beams) were stored in water for 2–3 months. Resonance frequency, weight, volume and compressive strength were measured during deterioration and self healing. Concretes that lost as much as 50% of their initial relative dynamic modulus during freeze/thaw could recover almost completely during subsequent storage in water, somewhat varying with concrete composition and degree of deterioration. Compressive strength showed reductions of 22–29% on deterioration, but only 4–5% recovery on self healing. Freeze/thaw tests on deteriorated and self-healed specimens in partly sealed condition showed clearly that the deterioration was governed by the ability to take up water; the more water that leaked through the plastic foil during freeze/thaw, the larger the deterioration. Self healing may be an important factor giving concrete better frost durability in field than when submitting specimens to freeze/thaw cycles in water.
Katsuyoshi Kondoh - One of the best experts on this subject based on the ideXlab platform.
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suppression of hydrogen induced damage in friction stir welded low carbon steel joints
Corrosion Science, 2015Co-Authors: Yufeng Sun, Hidetoshi Fujii, Hisashi Imai, Katsuyoshi KondohAbstract:Abstract Hydrogen-induced damage including blister and Cracking in friction stir welded low carbon steel were evaluated by the cathodic hydrogen charging method. After hydrogen charging for 2 h, irreversible dome-shaped blisters and Internal Cracking began to appear on the surface of the base metal. However, after hydrogen charging for 16 h, Cracking formed along the thermo-mechanically affected zone boundary, while the blisters or Cracking were hardly observed in the stir zone. In addition, the stir zone showed a plasticity reduction from 38% to 28%, much less than that of the base metal reduced from 48% to 2%.
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Effect of Welding Parameters on the Hydrogen Embrittlement of Cathodic Hydrogen-Charged Friction Stir Welded High Carbon Steel Joints
Corrosion, 2015Co-Authors: Hidetoshi Fujii, Hisashi Imai, Katsuyoshi KondohAbstract:The hydrogen embrittlement behavior in terms of hydrogen-induced surface blistering and hydrogen-induced Internal Cracking of the friction stir welded high carbon steel plates was evaluated by the cathodic hydrogen charging method. The welding processes were performed at different revolutionary pitches of 0.83, 0.5, and 0.25 mm/rev and therefore, the stir zones of the welds had various microstructures accordingly. After hydrogen charging for 4 hours, the base metal showed large quantities of irreversible dome-shaped blisters on the sample surface. On the contrary, the blisters were hardly observed in the stir zone regardless of the welding parameters and only a small number of microcracks were formed. Compared with the base metal, the stir zones produced at 0.83 mm/rev and 0.5 mm/rev had less ductility reduction after hydrogen charging for the same time. It revealed that the stir zones showed higher resistance to hydrogen embrittlement than the base metal. However, the specimen welded at 0.25 mm/rev showe...
Erik J Sellevold - One of the best experts on this subject based on the ideXlab platform.
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frost durability of high strength concrete effect of Internal Cracking on ice formation
Cement and Concrete Research, 1996Co-Authors: Stefan Jacobsen, Erik J Sellevold, Seppo MatalaAbstract:Abstract Ice formation measurements using low temperature calorimetry (CAL) were made on non-air entrained high strength concretes (HSC) before and after exposure to rapid freeze/thaw cycles in water (ASTM C666 proc. A). The purpose was to explore the relationship between water absorption during test, changes in ice formation and deterioration, to investigate the deterioration mechanism of non-air entrained HSC in the ASTM C666 test. CAL results showed zero or very little ice formation in the concretes ( w b = 0.40 and 0.35, 0, 5 and 8 % silica fume ) before C666 testing in the temperature range of the test (−20 °C). After the test (DF = 10–11) significant water absorption had taken place. Only one half or less of the absorbed water was freezeable to −20 °C, i.e. only part of the absorbed water goes into the created cracks and contributes to the deterioration by freezing there. The rest of the water is freezeable at lower temperatures or so tightly bound that it does not freeze at all to −55 °C. The freezeable water to −20 °C after test constitutes 3–7 vol-% of the cement paste. CAL measurements at intermediate stages of deterioration show very rapid transitions between no and significant amount of freezeable water and indicate a progressive mechanism of deterioration, starting at the surface in contact with water and moving inward. Apparently very little ice formation can initiate the process and result in major damage. Water storage after freeze/thaw testing results in self healing characterized by significant recovery of dynamic Emodulus and decreased amounts of ice formation. However, compressive strength recovery is much smaller than the recovery of E-modulus.
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self healing of high strength concrete after deterioration by freeze thaw
Cement and Concrete Research, 1996Co-Authors: Stefan Jacobsen, Erik J SellevoldAbstract:Abstract Some experiments have been performed to investigate the self healing of concretes deteriorated by Internal Cracking in the ASTM C666 procedure A rapid freeze/thaw test. Six different well cured concretes were deteriorated to various degrees. Then the specimens (concrete beams) were stored in water for 2–3 months. Resonance frequency, weight, volume and compressive strength were measured during deterioration and self healing. Concretes that lost as much as 50% of their initial relative dynamic modulus during freeze/thaw could recover almost completely during subsequent storage in water, somewhat varying with concrete composition and degree of deterioration. Compressive strength showed reductions of 22–29% on deterioration, but only 4–5% recovery on self healing. Freeze/thaw tests on deteriorated and self-healed specimens in partly sealed condition showed clearly that the deterioration was governed by the ability to take up water; the more water that leaked through the plastic foil during freeze/thaw, the larger the deterioration. Self healing may be an important factor giving concrete better frost durability in field than when submitting specimens to freeze/thaw cycles in water.
Atsushi Teramoto - One of the best experts on this subject based on the ideXlab platform.
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temperature dependence of autogenous shrinkage of silica fume cement pastes with a very low water binder ratio
Cement and Concrete Research, 2013Co-Authors: Ippei Maruyama, Atsushi TeramotoAbstract:Ultra-high-strength concrete with a large unit cement content undergoes considerable temperature increase inside members due to hydration heat, leading to a higher risk of Internal Cracking. Hence, the temperature dependence of autogenous shrinkage of cement pastes made with silica fume premixed cement with a water–binder ratio of 0.15 was studied extensively. Development of autogenous shrinkage showed different behaviors before and after the inflection point, and dependence on the temperature after mixing and subsequent temperature histories. The difference in autogenous shrinkage behavior poses problems for winter construction because autogenous shrinkage may increase with decrease in temperature after mixing before the inflection point and with increase in temperature inside concrete members with large cross sections.
Hidetoshi Fujii - One of the best experts on this subject based on the ideXlab platform.
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suppression of hydrogen induced damage in friction stir welded low carbon steel joints
Corrosion Science, 2015Co-Authors: Yufeng Sun, Hidetoshi Fujii, Hisashi Imai, Katsuyoshi KondohAbstract:Abstract Hydrogen-induced damage including blister and Cracking in friction stir welded low carbon steel were evaluated by the cathodic hydrogen charging method. After hydrogen charging for 2 h, irreversible dome-shaped blisters and Internal Cracking began to appear on the surface of the base metal. However, after hydrogen charging for 16 h, Cracking formed along the thermo-mechanically affected zone boundary, while the blisters or Cracking were hardly observed in the stir zone. In addition, the stir zone showed a plasticity reduction from 38% to 28%, much less than that of the base metal reduced from 48% to 2%.
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Effect of Welding Parameters on the Hydrogen Embrittlement of Cathodic Hydrogen-Charged Friction Stir Welded High Carbon Steel Joints
Corrosion, 2015Co-Authors: Hidetoshi Fujii, Hisashi Imai, Katsuyoshi KondohAbstract:The hydrogen embrittlement behavior in terms of hydrogen-induced surface blistering and hydrogen-induced Internal Cracking of the friction stir welded high carbon steel plates was evaluated by the cathodic hydrogen charging method. The welding processes were performed at different revolutionary pitches of 0.83, 0.5, and 0.25 mm/rev and therefore, the stir zones of the welds had various microstructures accordingly. After hydrogen charging for 4 hours, the base metal showed large quantities of irreversible dome-shaped blisters on the sample surface. On the contrary, the blisters were hardly observed in the stir zone regardless of the welding parameters and only a small number of microcracks were formed. Compared with the base metal, the stir zones produced at 0.83 mm/rev and 0.5 mm/rev had less ductility reduction after hydrogen charging for the same time. It revealed that the stir zones showed higher resistance to hydrogen embrittlement than the base metal. However, the specimen welded at 0.25 mm/rev showe...
