Laminar cracking in post-tensioned concrete nuclear containment buildings

As a critical public safety-related structure, the long-term integrity of post-tensioned concrete containment buildings (PCCs) is necessary for continued operation of the reactors they house. In 2009, during preparations for a steam generator replacement, extensive subsurface laminar cracking was identified in a portion of the Crystal River 3 (CR3) PCC in Florida, and the plant was permanently shut down in 2013. This study investigates potential contributing factors to the identified cracking with particular focus on the effects of high early-age temperatures on the cracking risk of the concrete, on the development of the concrete properties, and on the late-age structural behavior of the concrete. Two planar, full-scale mock-ups of a portion of the CR3 PCC were constructed and instrumented with temperature and strain gauges to monitor the thermal and mechanical behavior during representative concrete curing and post-tensioning loading. Standard- and match-cured concrete specimens were tested for determination of the time- and temperature-dependent development of thermal and mechanical concrete properties, and hydration parameters were determined for the mock-up cement paste for modeling the heat generation in the concrete. These properties and parameters were utilized in 3D finite element analysis of the mock-ups in COMSOL Multiphysics and compared with experimental results. Non-destructive evaluation via shear wave tomography was conducted on the mock-ups to identify flaws and determine the effectiveness of the methods for identifying delaminations between post-tensioning ducts approximately 10 inches beneath the concrete surface. Though early-age thermal stresses were determined not to have caused cracking in the mock-ups, the high early-age concrete temperatures resulted in decreased late-age mechanical properties that were shown to contribute to greater concrete cracking risk when the mock-up was post-tensioned. Tensile stresses exceeding the tensile strength of the concrete were identified along the post-tensioning ducts when biaxial post-tensioning loads were applied in finite element analysis, but the stresses decreased rapidly with increased distance from the ducts. Through parametric modeling, increasing the tensile strength of the concrete was identified as an effective means of reducing the cracking risk in PCCs. Additionally, relationships between the mechanical properties for the standard- and match-cured specimens were identified that could enable prediction of in-place or match-cured concrete properties based only on the results of tests on fog-cured specimens.

Level thesis:degree_level

Doctoral

Department dc:contributor.department

Civil and Environmental Engineering

Grantor dc:publisher

Georgia Institute of Technology

Year dc:date.issued

2016

Author dc:creator

• Dolphyn, Bradley P.

Advisors dc:contributor.advisor

• Kurtis, Kimberly E.
• Kahn, Lawrence F.

Committee members dc:contributor.committeemember

• Jacobs, Laurence J.
• Gentry, T. Russell
• Wall, James J.

• Post-tensioned concrete containment
• Nuclear power plant
• Maturity
• Match-curing
• Thermal stress
• Finite element analysis

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/1853/55017

OAI identifier oai:identifier

oai:repository.gatech.edu:1853/55017