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2023 (English)In: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 72, article id 106619Article in journal (Refereed) Published
Abstract [en]
Autogenous self-healing of post-fire damaged concrete enables structure performance auto-recovery leading to reduced repair costs, less generated waste, and lower CO2 emissions. In this paper, to improve the efficiency of this process and understand the underlying mechanism, the self-healing of 0.1 wt% MWCNT-modified and pure cement paste subjected to novel environmental stimulators was tested. High-temperature damage was induced at 200 °C and 400 °C, followed by a self-healing cyclic treatment with water, a mixture of water with phosphate-based retarding admixture, and limewater. The self-healing efficiency of the proposed solutions were compared based on crack closure, strength regains, porosity, and chemical composition changes. The surface crack closure after 200 °C varied between 33% and 60%, whereas for 400 °C, only retarding admixture exposure obtained over 50% crack closure and the most considerable decrease in average crack width of 33% for MWCNT-modified paste. The highest values of compressive strength recovery, equal to 18% and 14%, exceeding the intact specimen's compressive strength, were observed for the MWCNT-modified paste healed in water and limewater. Water exposure with an extended wetting phase enhanced the compressive strength recovery of the MWCNT-modified materials. Strong (r = 0.87) and moderate (r = 0.52) positive correlations were observed between temperature loading and compressive and flexural strength recovery parameters, respectively. Higher porosity and interconnected crack network, caused by high temperature, facilitated the self-healing process. Porosity changes before and after healing were pronounced in contrast to the amount of unhydrated cement, which did not exhibit noticeable changes. The healing mechanism included three processes: calcite formation, further hydration inside the cracks, and rehydration of the bulk cement paste.Previous article in issue
Place, publisher, year, edition, pages
Elsevier Ltd, 2023
Keywords
Compressive strength, Concrete repair, Multi-wall carbon nanotubes (MWCNT), Post-fire recovery, Re-curing, Sustainable structures
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-97064 (URN)10.1016/j.jobe.2023.106619 (DOI)001058443100001 ()2-s2.0-85154535482 (Scopus ID)
Funder
Swedish Transport AdministrationSvenska Byggbranschens Utvecklingsfond (SBUF)
Note
Validerad;2023;Nivå 2;2023-05-10 (joosat);
Licens fulltext: CC BY License
2023-05-102023-05-102024-03-07Bibliographically approved