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
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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
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