| 研究課題/領域番号 |
20J20854
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| 研究機関 | 北海道大学 |
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研究代表者 |
Mizan Mahmudul Hasan 北海道大学, 大学院工学院, 特別研究員(DC1)
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| 研究期間 (年度) |
2020-04-24 – 2023-03-31
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| キーワード | Polymer cement mortar / overlaying method / premature debonding / interfacial strength / silica fume |
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| 研究実績の概要 |
Both material and member level test were conducted to evaluate the influence of silica fume on the interfacial bond performance. In material level, tests were conducted under tensile (splitting tensile) and shear (Bi-surface and direct single surface) condition. In bi-surface shear test, experimental parameters included three levels (high, medium, and low) of surface roughness, and two (low and normal) concrete compressive strengths. In splitting tensile and direct shear test, the experimental parameters included two roughness level, and with or without primer at the interface. The effect of the constituent of overlay material on bond strength was found significant on all type of test performed. The mixing of silica fume shifts the pure interface fracture to composite or mixed fracture. Considering experimental outcomes, it is confirmed that the use of silica fume can achieve adequate bond strength with substrate concretes, even with a smooth surface. Thus, silica fume seems to enhance chemical bonding between substrate concrete and overlay material. At member level, four-point bending tests was conducted with the aim to use silica fume in practical PCM strengthening technique. The inclusion of silica fume showed higher initial slope and stiffness. The yielding and ultimate load both increases with the inclusion of silica fume in all cases. Crack patterns were shifted from pure interface to crack along tensile bar with silica fume inclusion. This indicates the positive influence of silica fume application on the interfacial bond performances of the PCM strengthened RC beam.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
This research is intending to enhance the bonding strength of PCM overlaying method by the anchoring and micro filler effect at the interface due to the mixing of silica fume. The aim is to establish a target bonding method to be used in practical PCM strengthening techniques. The adhesive strength tests between the PCM used for the overlayed part and the substrate concrete were conducted under both tensile and shear stress condition. The experimental parameters were included; the presence or absence of silica fume mixed in the PCM, the roughness of the adhesive interface, and the strength of the substrate concrete, the presence or absence primer at the interface. The outcome of experimentation clarified that the micro filler and anchoring effect by silica fume exerts an excellent impact on the adhesive strength at the interface, and both the tensile strength and the shear strength are significantly improved. At member level, four-point bending tests was conducted with the aim to use silica fume in practical PCM strengthening technique where experimental parameters includes; presence or absence of silica fume mixed in the PCM, and different amount of overlay reinforcement. The RC beam reinforced with PCM mixed with silica fume has improved yield load and ultimate load compared to the RC beam reinforced by the conventional method, and this method has an excellent reinforcing effect on the members. The data accumulated from many experiments showed usefulness to achieve the purpose of this research. Therefore, it can be judged that the research has progressed as expected.
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| 今後の研究の推進方策 |
From the perspective of practical application of PCM overlaying method, long-term performance of strengthened members should be achieved, and it is more important than short-term bonding strength of newly overlaid PCM layer. Thus, the quantitative measurement of interfacial shear strength and splitting tensile strength of the composite specimen with and without silica fume will be done considering environmental conditions such as temperature and freeze-thaw cycle into account as priority basis. After preparation of the composite specimen and sufficient curing, tests (splitting tensile and shear test) will be performed with autograph measuring interface slip and opening by contact gauge to propose the interface bond-slip relationship between concrete and PCM under particular condition.
In addition, four-point bending tests of strengthened RC beam with and without silica fume as repaired material will be conducted to resemble material level test with the aim to use silica fume in practical PCM strengthening technique. Three type of strengthening material: reinforcement, CFRP grid and CFRP strand sheet will be used as a strengthening bar. To reduce end peeling to occur (one of the main failure mode observed in out preliminary test) due to high stress concentration at the end, FRP u-strip will be attached at the end of the overlay. Strain gauges will be attached to the strengthening and the main reinforcement to get strain distribution & pi-gauges will also be attached at the interface to measure the crack opening and slip during loading test.
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