Building Management Hawaii April/May 2014 - (Page 22)

ConCrete Concrete Spalls, Cracks And Leaks To better handle repairs, know the conditions that can severely damage concrete. By Alvin Nishikawa C oncrete repair approach is a rather simple process if one understands a few concepts and terminologies. However, similar to other things in life, there are considerations that may alter the repair methodology. This article is meant to present a basic overview of repair conditions that are typical of a concrete structure, including causes, concerns and repair methodology. There are three typical concrete conditions that cause concern: * Concrete delamination or spall; * Concrete cracks; and * Water leaks or infiltration through walls, ceilings and floors. Delaminated or Spalled Concrete Condition Concrete delamination ocurrs when the concrete cover separates, but is not yet detached from the parent concrete. Delaminated concrete is not always obvious by visual review. Spalled concrete, or spalling, is the void left in the parent concrete after the delaminated concrete has become detached. Concrete delamination is typically caused by the corrosion of the embedded steel reinforcement in cast-in-place, CMU block, metal lathplaster, and pre-stressed and posttensioned concrete structures. When steel corrodes, it expands many times in volume, thus generating an internal force pushing outward on the encasing concrete. The outward force placed on the concrete soon exceeds its tensile strength and the delaminated concrete condition is created. This condition progresses to the point that the delaminated concrete becomes fully detached, and there is a resulting spall (or void) in the concrete structure. Concerns regarding delaminated or spalled concrete include: * Bodily injury and property liability; * Acceleration of further delaminated or spalled conditions; * Potential water leaks; and * Repair costs. Liability concerns include personal injury and property damage caused by the falling of dislodged concrete material. Potential liabilities also arise from tripping hazards presented by deck delaminations and or or spalled conditions. Acceleration of delaminating conditions occur as corroded reinforcement steel retains moisture and chlorides, which in turn accelerates the electro-chemical corrosion process. Water leaks associated with delaminated or spalled concrete conditions may occur at joints, window perimeters and voids in waterproofing membrane systems. These include parking deck coatings and planter box membranes as well as wall coating systems. Although it may take years, repair costs can skyrocket if not addressed early. Over time, a simple nonstructural repair can become a structural concern that requires complete removal of multiple concrete sections and require supplemental shoring. These repairs are not only monetarily costly, but are also often logistically inconvenient to owners and respective patrons. Concrete Cracks Example of extreme spalling and damage around an opening in the concrete structure 22 April-May 2014 BMH There are many causes of concrete cracking. These include mix ratios, premature drying, excessive loads, settlement, heaving, temperature variations, improper or missing joints and external restraints. The main concern is that cracks in concrete allow water to migrate down to the reinforcement steel. This in turn leads to corroding conditions and

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