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This paper studies the time dependence of corrosion resistance in belitic calcium sulfoaluminate (BCSA) cement concrete. BCSA is a hydraulic cement that sets rapidly and has a lower carbon footprint than portland cement (PC). Some studies suggest that BCSA concrete is highly susceptible to chloride-induced corrosion, but these claims are based on testing at 28 days. No later-age results have been reported. We con昀椀rm that BCSA cement concrete exhibits poor corrosion resistance when tested at 28 days, which can be attributed to an immature microstructure with weak resistance to chloride ingress and a pore solution that does not support passivation. We further show that corrosion resistance improves signi昀椀cantly as the BCSA system matures, achieving good corrosion resistance between 90 and 180 days. This improvement relates to the slow hydration of belite, which results in signi昀椀cant later-age microstructure re昀椀nement and probably alters the pore solution in a way that promotes or enhances steel passivation.
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Beyond the chloride threshold concept for predicting corrosion of steel in concrete
All existing models to forecast the corrosion performance of reinforced concrete structures exposed to chloride environments are based on one common theoretical concept, namely, a chloride threshold, as a sharply defined trigger for corrosion, followed by a period of active corrosion. We critically review the resulting treatment of corrosion initiation and propagation as two distinct, successive stages. We conclude that this concept presents a major barrier for developing reliable corrosion forecast models, and that a new approach is needed. In reality, steel corrosion in concrete is a continuous process, that is, rarely separable into uncoupled, sequential phases. We propose that the focus be placed on the quantification of the time- and space-variant corrosion rate from the moment steel is placed in concrete until it reaches the end of the service life. To achieve this, a multi-scale and multi-disciplinary approach is required to combine the scientific and practical contributions from materials science, corrosion science, cement/concrete research, and structural engineering.
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- Award ID(s):
- 1728358
- PAR ID:
- 10588246
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- Applied Physics Reviews
- Volume:
- 9
- Issue:
- 1
- ISSN:
- 1931-9401
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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