A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Understanding and Mitigating Effects of Chloride Deicer Exposure on Concrete
Field and laboratory investigations were conducted to examine the effects of chloride deicers on concretebridge decks and to identify and evaluate best practices and products to mitigate such effects. The concrete bridge decks exposed to KAc or MgCl2 deicer showed significant reductions in their compressive strength, splitting tensile strength and microhardness, whereas those exposed to NaCl deicer and without signs of surface distress did not. Visual inspection would be misleading for assessing the condition of concrete bridge decks exposed to MgCl2 deicer, as the chemical attack by MgCl2 generally does not exhibit apparent signs of distress. Chloride penetration as low as 0.1 in (2.5 mm) based on AgNO3 spray method does not guarantee the integrity of the concrete exposed to MgCl2 deicer. At least half of cored ODOT bridge decks exhibited air void spacing factor higher than 200 microns (0.008 inches) per the ASTM C457 test method, indicating that they no longer have a proper air-void system for freeze-thaw resistance. The role of MgCl2 in the carbonation and ASR of field concrete, if any, is not significant, but KAc may play a significant role in contributing to ASR in concrete containing reactive aggregate. The microscopic evidence further suggests that the concrete in the field environment had been affected by both physical and chemical degradation by the joint action of freeze-thaw cycles and MgCl2. A set of mortar samples can be deployed to assess the cumulative MgCl2 exposure at a given site. A simplistic empirical-mechanistic model was developed to evaluate the conditions of the current bridge decks. Surface treatments, especially penetrating sealers and water repellents should be used to protect new concrete and existing concrete without too much chloride contamination. For any surface treatment to be used, it is important to select products with high resistance to both gas and water penetration to maximize the concretes resistance to salt scaling.
Understanding and Mitigating Effects of Chloride Deicer Exposure on Concrete
Field and laboratory investigations were conducted to examine the effects of chloride deicers on concretebridge decks and to identify and evaluate best practices and products to mitigate such effects. The concrete bridge decks exposed to KAc or MgCl2 deicer showed significant reductions in their compressive strength, splitting tensile strength and microhardness, whereas those exposed to NaCl deicer and without signs of surface distress did not. Visual inspection would be misleading for assessing the condition of concrete bridge decks exposed to MgCl2 deicer, as the chemical attack by MgCl2 generally does not exhibit apparent signs of distress. Chloride penetration as low as 0.1 in (2.5 mm) based on AgNO3 spray method does not guarantee the integrity of the concrete exposed to MgCl2 deicer. At least half of cored ODOT bridge decks exhibited air void spacing factor higher than 200 microns (0.008 inches) per the ASTM C457 test method, indicating that they no longer have a proper air-void system for freeze-thaw resistance. The role of MgCl2 in the carbonation and ASR of field concrete, if any, is not significant, but KAc may play a significant role in contributing to ASR in concrete containing reactive aggregate. The microscopic evidence further suggests that the concrete in the field environment had been affected by both physical and chemical degradation by the joint action of freeze-thaw cycles and MgCl2. A set of mortar samples can be deployed to assess the cumulative MgCl2 exposure at a given site. A simplistic empirical-mechanistic model was developed to evaluate the conditions of the current bridge decks. Surface treatments, especially penetrating sealers and water repellents should be used to protect new concrete and existing concrete without too much chloride contamination. For any surface treatment to be used, it is important to select products with high resistance to both gas and water penetration to maximize the concretes resistance to salt scaling.
Understanding and Mitigating Effects of Chloride Deicer Exposure on Concrete
X. Shi (author) / N. Xie (author) / Y. Dang (author) / A. Muthumani (author) / J. Huang (author)
2014
166 pages
Report
No indication
English
Radiation Pollution & Control , Materials Degradation & Fouling , Highway Engineering , Construction Equipment, Materials, & Supplies , Physical & Theoretical Chemistry , Deicers , Magnesium chloride , Bridge decks , Sodium chloride , Cores , Scaling , Alkali silica reactions , Sealers , Water repellants , Electron microscopes , Chemical analysis , Splitting tensile strength , Condition surveys , Microhardness
Deicer Scaling Mechanisms in Concrete
| NTIS | 1970
Freeze–thaw durability of high strength concrete under deicer salt exposure
| Online Contents | 2016