Non-uniform moisture distribution during early age drying and curing of protective concrete overlays for Savannah River Site reactors decommissioned in-situ were expected to result in differential shrinkage that lead to tensile stresses and possible cracking. The goal was to not exceed the concrete tensile strength of 2.8 MPa or compressive strength of 23.8 MPa. An experimental study was performed on the development of shrinkage and creep strains in concrete slab specimens embedded with strain gages and relative humidity sensors at controlled ambient temperature and relative humidity conditions. The experimental data was used to verify the validity of available physics-based methods and code calculations to predict early age shrinkage and creep strains, respectively. Data on the expansive effect of a shrinkage compensating admixture based on CaO was also obtained. Prediction of the surface stress in the test specimen suggests that without the shrinkage compensating admixture, the tensile strength would be slightly exceeded. However with the admixture, the combined effects of shrinkage, creep and expansion due to the admixture is predicted to result in all compressive stresses within the full scale slab, eliminating the possibility of cracking.
- Pressure Vessels and Piping Division
Testing and Analysis of Early Age Stress-Strain Development of Concrete Overlay for Reactor In-Situ Decommissioning
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Guerrero, HN, Langton, CA, & Restivo, ML. "Testing and Analysis of Early Age Stress-Strain Development of Concrete Overlay for Reactor In-Situ Decommissioning." Proceedings of the ASME 2011 Pressure Vessels and Piping Conference. Volume 5: High-Pressure Technology; Nondestructive Evaluation; Nuclear Engineering. Baltimore, Maryland, USA. July 17–21, 2011. pp. 363-370. ASME. https://doi.org/10.1115/PVP2011-57902
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