THURSDAY June 15, 2017 at HESS (Houston Engineering and Scientific Society), 5430 Westheimer, Houston 77056. Tel: 713 627 2283
6:00 pm – Social – Sponsored by Walker
6:30 pm – Dinner
7:00 pm – Program
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Concrete columns that are part of any structure exposed to moisture (i.e. bridge and parking structure perimeter columns) present a seemingly ugly picture when subjected to apparently severe cracking due to internal expansive forces from alkali-silica reaction (ASR) and delayed ettringite formation (DEF). Based on the presenter’s experience, and supplemented by several independent research studies, the apparently severe cracking in concrete elements subject to expansion forces from either ASR or DEF, or both, is often not as detrimental to the structural integrity of the column elements as it seems. The distress caused by internal expansion forces resulting from ASR and DEF primarily affects the concrete cover, but the core of the concrete columns confined by mild steel reinforcement is generally not significantly compromised. This presentation will discuss the cracking mechanism in concrete columns caused by ASR/DEF, present an introduction to a comprehensive approach to investigating this type of cracking, and describe a proven repair and monitoring program. The comprehensive approach to evaluate the significance of the cracking on existing precast concrete columns consists of up-close field observations, non-destructive testing, material sampling, inspection openings, petrographic studies, structural analysis, and reporting.
The presenter will discuss a repair program for column elements that are deemed to be structurally adequate, which consists of surface preparation, sealing cracks with flexible sealant, application of a clear sealer, and application of a silicone based paint system. The general goal of the repair approach is to maintain the relative humidity in the concrete column below the threshold that triggers the ASR and/or DEF mechanisms. The presenter will also discuss one or two case studies.
Presented by former SEAoT Houston/Gulf Coast Chapter President Al Bustamante