2021 Fiscal Year Research-status Report
Modeling and re-corrosion evaluation of patch repaired concrete subjecting to chloride attack
| Project/Area Number |
19K04547
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| Research Institution | Saitama University |
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Principal Investigator |
欒 堯 埼玉大学, 理工学研究科, 助教 (20725288)
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| Project Period (FY) |
2019-04-01 – 2023-03-31
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| Keywords | chloride migration / patch repaired concrete / blast furnace slag / water repellent agent / water penetration / silica fume |
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| Outline of Annual Research Achievements |
In FY2021, the study on the influence of cracks on chloride penetration of patch repaired concrete was continued experimentally. In addition to the specimens made from repair mortar that were studied last fiscal year, the specimens made from ordinary concrete and those blended with supplementary cementitious materials were studied using electrophoresis test for chloride migration. Three types of concrete specimens with ordinary Portland cement (OPC), slag blended cement (BFS), and silica-fume (SF) blended cement were induced with crack width in the range of 0 to 0.6 mm and tested for the effective diffusion coefficient. It was confirmed that the effective diffusion coefficient without crack followed the order of OPC > BFS > SF, while the influence of crack significantly increased with the increasing crack width, playing a dominant role at big crack widths. In addition, chloride binding capacity was studied for repair mortar made from slag blended cement with the replacement ratio of 0 to 70%, showing that the chloride binding capacity strongly depended on slag blending ratio, which may influence the chloride penetration under real conditions.
In addition, the multi-scale approach for capillary absorption of cracked cementitious materials, which were developed in the last fiscal year, was enhanced for the application of water repellent agent to cracked concrete. The analysis indicated that water penetration through cracks was greatly retarded when water repellent agent was added in the mixtures, leading to highly increased water resistance for the repaired structures.
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| Current Status of Research Progress |
Current Status of Research Progress
4: Progress in research has been delayed.
Reason
The progress of experimental and analytical studies on water and chloride penetration of patch repaired concrete generally followed the research plan. On the other hand, regarding the study on the corrosion of steel bars in patch repaired concrete, which was included in the original plan, it was difficult to start experimental study because of the Covid-19. Some necessary apparatuses were delayed being delivered, while the international students who was planned to perform the study couldn’t come to Japan by April, 2022, because of entry closing. Therefore, this study will be focused on FY2022.
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| Strategy for Future Research Activity |
In the FY2022, immersion test of patch repaired concrete for steel bar corrosion will be conducted to study the influence of cracks on corrosion. Measurement of weight loss and natural potentials for steel bars will be carried out, while chloride profiles will also be measured. The numerical models will also be extended to steel corrosion.
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| Causes of Carryover |
Some part of the remained amount will be spent on purchasing experiment materials, such as cement, steel bars, chemicals, and so on. The other part will be spent for travel and registration fees for academic conferences.
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