2023 Fiscal Year Research-status Report
A multi-scale approach for modeling self-healing concrete by coupling water ingress and crack healing process
| Project/Area Number |
22K04257
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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) |
2022-04-01 – 2025-03-31
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| Keywords | self-healing / crack / water penetration / fiber / superabsorbent polymer / X-ray CT / multi-scale model |
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| Outline of Annual Research Achievements |
In FY2023, experimental study was performed on the performance of strain-hardening cementitious composites (SHCC) with the addition of superabsorbent polymers (SAPs), which were expected to accelerate self-healing of SHCCs. Uniaxial tensile test was performed to induce multiple fine cracks, subsequently immersing the specimens in water for self-healing. Three types of SAPs were used, respectively, with experiment showing difference in self-healing rate depending on water absorption property of SAP. In addition to microscopic observation on crack healing at surface, X-ray computed tomography (CT) was applied to study the internal healing inside specimens. Based on the information of initial cracks and crack healing rate from the experiment, simulation based on multi-scale models coupling crack healing and water ingress were carried out for the SHCCs with SAPs, reasonably representing self-healing process and the consequent water ingress reduction. Furthermore, the multi-scale model was enhanced to consider the incorporation of integral silane treatment on water repellency of cracked SHCCs, which has been shown effective to increase water resistance for durability. Comparison between the performed simulation and test data from past studies showed the validity of the simulation on water absorption behaviors of treated SHCCs.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Based on the multi-scale model developed in last fiscal year, more complicated conditions that influence water ingress or self-healing were taken into account in the simulation by enhancing the present model from microscale, such as the influence of SAPs and the incorporation of silane treatment. The simulation on those cases were compared with experiment performed in this year or test data from past studies, indicating the reasonability of the simulation result. It can be said that the scope of the model has been extended for more applications.
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| Strategy for Future Research Activity |
In FY2024, self-healing experiment will be performed under outdoor condition for longer time using SHCC specimens with the addition of SAPs, i.e. above half year compared to several weeks of current experiment. It is expected that the self-healing process could be much slower than experiment in laboratory, because of less available water outdoor. Meanwhile, self-healing experiment in laboratory will be continued using SAP-added SHCCs under high relative humidity of atmosphere. It is expected that water release from SAPs at high relative humidity will promote self-healing, even that the rate may be much less than immersion in water. Thermogravimetric analysis (TG) and X-ray computed tomography (CT) will be used to analyze chemical composition of healing product and crack morphology, respectively. Neutron radiography will be used to observe water distribution in cracks. Based on the experiment results, it is planned to enhance the multi-scale model for simulation under outdoor condition as well as the influence of high relative humidity.
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| Causes of Carryover |
In FY2024, some amount will be paid for purchasing necessary consumables for experiments. Also, devices will be purchased to facilitate the experiment, for example, a tensile creep loading device that can induce cracks with sustained load for investigating the influence of load on self-healing. XRD and computed tomography (CT) will be performed using devices in Saitama Industrial Technology Center and RIKEN, so the service fee will be paid.
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