SEPTEMBER 13, 2017
Mr. Alfredo E. (Al) Bustamante is a Principal and the Director of Restoration of Walker’s Mid-South region. He is a registered Professional Engineer in Texas and Louisiana. He received his Bachelor of Science in Civil Engineering from Old Dominion University in Norfolk, VA and Master of Science in engineering with structural engineering emphasis from University of Illinois at Urbana-Champaign, Illinois. Mr. Bustamante has over sixteen years of experience as a project manager for a variety of projects related to structural, architectural, and material distress. His experience includes the evaluation, design, and construction phase services of many precast concrete parking garage structures.
Mr. Bustamante is a licensed professional engineer in Texas, past President of the Houston/Gulf Coast Chapter of SEAoT, past Chair of the FPA SC-02-0 subcommittee - Test Methods For Evaluating Existing Foundations (2007-2010), a member of the International Concrete Repair Institute (ICRI), the American Concrete Institute (ACI), the American Society of Civil Engineers (ASCE), The National Society of Professional Engineers (NSPE), National Academy of Forensic Engineers (NAFE), the American Institute of Steel Construction (AISC).
To an audience of about 60 at the HESS Club, Mr. Bustamante gave a slide presentation titled, “ASR and DEF Cracking - It Is Not As Bad As It Seems.”
Concrete columns that are part of any structure exposed to moisture (e.g., 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.
Mr. Bustamante discussed the cracking mechanism in concrete columns caused by ASR/DEF, giving an introduction to a comprehensive approach to investigating this type of cracking, and describing 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.
Some points made by Mr. Bustamante included:
Mr. Bustamante presented a case history of a Houston area 12-story precast concrete parking garage built in 1983 using non-prestressed reinforcing steel. The exterior load bearing columns experienced ASR/DEF cracking while the adjacent architectural precast columns did not. The column cracks were unsightly and mostly vertical (see attached photo), and were limited to the thickness of the concrete cover, i.e., the concrete outside the column reinforcing steel. Cracks were mapped, cores were taken, and nondestructive testing was done in accordance with ICRI’s Guideline No. 2010.4-2009, “Guide for Nondestructive Evaluation Methods for Condition Assessment, Repair and Performance Monitoring of Concrete Structures” to determine the cause of the cracking.
Mr. Bustamante’s repair plan allowed the columns to be saved and cost $250,000 to implement, while column replacement would have cost 24 times that amount. The repair steps were to blast clean the cracked surfaces, apply Silane with 100% solids (as a water repellant), seal the cracks and joints with a flexible sealant, coat the columns with an elastomeric coating, and implement an annual monitoring program.
To download Mr. Bustamante's slide presentation, click here.