Building Management Hawaii April/May 2014 - (Page 33)

ConCrete Preserving A Historic Treasure A contractor takes on concrete spall repair at Hawaii's oldest wood frame building. By Richard Malmgren B eing selected to perform concrete remedial repairs on the Hawaiian Mission Houses Historic Site and Archives' Hale Laau-which dates to 1821 and is the earliest wood frame structure still standing in the Hawaiian Islands- is both a privilege and an accolade for any contractor. Moreover, the variety of materials is not the dichotomy it might initially appear. Pre-engineered and precut on the East Coast of the U.S., Hale Laau's wood was shipped around Cape Horn from Boston in 1820 and reassembled in Honolulu by the first company of missionaries. It then became a communal home for many missionary families, who shared it with Island visitors and boarders. While the above grade structure is wood framing and siding, the basement was originally constructed of sun-dried adobe (a composite formed from clay, water and organic material whose technology was most likely brought to Hawaii by Mexican sailors). Given the height of the water table, less than five feet below grade, it did not take long for the adobe bricks to turn to mud. The perimeter basement walls were subsequently rebuilt with coral blocks. Above and below: Hale Laau In the 1900s, additional structural renovation was undertaken to preclude structural collapse. Not obvious to the average visitor walking about the basement, new reinforced concrete columns were added to support new steel beams that in turn helped to support the wood structure above. A rough surfaced texture was employed to provide the appearance of old, hand applied plaster. Over several decades, salty water soaked through the concrete and promoted rusting of the old, square shaped reinforcing steel embedded within the concrete columns. As with our newer concrete structures, the expansive forces of the rusting steel caused the concrete columns to crack and spall. In some instances, the pieces of broken concrete could Courtesy of Hawaiian Mission Houses be easily removed with minimal force using a pry bar. Square reinforcing steel not withstanding, the causes and repair procedures for the concrete spalling in this historic structure were hardly unlike those of our newer concrete office buildings and condominiums. Hawaii's salt-laden environment promotes rusting. Because rust takes up greater volume than the steel from which it was formed, it causes severe internal pressure on the surrounding concrete. This leads to cracking, spalling and, if left unaddressed, structural failure. At Hale Laau, pneumatic chipping tools were used to remove not only the delaminated concrete, but also the salt contaminated concrete surrounding the rebar. Chloride inhibitors, rust converters and bonding adhesives were brushed on in separate applications over which a patching mortar was applied, all to extend the life of the completed repair. Additional material was hand applied to match the original texture. Richard Malmgren formed RCM Construction Corporation, a Hawaii licensed general contracting company, in April 1986. RCM is equipped with an extensive arsenal of pneumatic tools, injection systems and high-tech repair materials to restore damaged concrete and eliminate initial failure. www.buildingmanagementhawaii.com BMH April-May 2014 33 http://www.buildingmanagementhawaii.com

Table of Contents for the Digital Edition of Building Management Hawaii April/May 2014

Editor’s Note By Stacy Pope
Hawaiiana Hits The Big Five-0
CONCRETE Restoration and Repairs: Maintaining A Strong Foundation
Concrete Spalls, Cracks And Leaks
Should You Repair Or Replace?
Restoring Exposed Aggregate Surfaces
Preserving A Historic Treasure
ELEVATOR Modernization: Are You Losing Energy?
Greening Your Elevators
Upgrading On A Budget
INSURANCE: Locking Down The Leaks
Navigating Property Insurance
COOLING TOWERS: HVAC Chemical Feed Pumps
Waikiki’s Oldest Hotel Keeps It Cool
Industry News or Movers & Shakers
On Site: Self-Management 101

Building Management Hawaii April/May 2014