Achieving Durability in Concrete

siennatearfulUrban and Civil

Nov 25, 2013 (3 years and 10 months ago)

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Presented by: Peter Emmons,

Achieving Durability in Concrete
Repairs

Learning Outcomes


At the end of this webinar, you will be able
to:


Recognize when a repair method needs to be
defined on a concrete substrate


Describe proper repair methods


Describe types of repair materials available

Introduction


This webinar focuses on concrete conditions
that require removing some or all of the
concrete before standard surface preparation
for coating application.

Method of Repair


When the selecting the method and equipment
for repair you should consider:


The size of the area to be repaired


Is there cracking


Is there exposed reinforcing steel (rebar)


Location of the floor (indoor/outdoor)


The ambient conditions


The specified ICRI Concrete Surface Profile (CSP)


The coating or coating system that will be applied
over the repair areas

Repair Conditions


Before a successful repair project can begin,
several key issues need to be addressed:


Determine the cause of concrete deterioration
or damage


Determine the most suitable repair method,
equipment and materials


Determine if there is an industry standard to
follow (SSPC, ICRI, ASTM, ACI)


Determine if the project should involve a
structural engineer and/or architect

Method of Crack Repair


Cause of cracking must be determined
before a crack repair method can be
selected


Is there a likelihood of further movement?

Settlement Cracking


Cracks resulting from settlement of the
structure with a low likelihood of further
movement can be repaired by epoxy
pressure injection

Dynamic Cracks


Cracks that will continually move due to:


Thermal expansion


Thermal contraction


Absence of adequate expansion joints




Damage Due to Thermal
Property Changes

Expansion Joint

Cracks Causing Water Intrusion


The sources of water intrusion vary


Water may be coming through


Cracks in the


Concrete structure


Between concrete and piping through the concrete
structure


Through honeycombs in the concrete


Through control or expansion joints


Water Intrusion

Photo Courtesy of Tnemec

Reinforcement Repair


The most frequent cause of damage to
reinforcing steel is corrosion

Spalling


Spalling of reinforced concrete is commonly
associated with corrosion of the rebar


The increase of volume due to the corrosion
product causes the outer layers of the concrete
to detach


Reinforcement Repair


Proper steps to prepare the reinforcement
will help insure that the repair method is a
long
-
term, rather than temporary, solution


Remove concrete surrounding steel


Clean the reinforced steel by wire brushing


Repair of reinforcement



Replace the reinforcement


Supplement the reinforcement


Coat the reinforcement

Deteriorated Concrete


A repair or rehabilitation project will usually
involve removal of deteriorated, damaged
or defective concrete

Methods to Remove
Deteriorated Concrete


Classification of concrete removal methods
are:


Blasting


Cutting


Impacting


Milling


Hydrodemolition


Prospecting


Abrading


Surface Preparation


One of the most important steps in the
repair of a concrete floor is the preparation
of the surface to be repaired

ICRI Guideline No. 310.2


ICRI Guideline No. 310.2, Selecting and
Specifying Concrete Surface Preparation for
Sealers, Coatings and Polymer Overlays provides
designers, specifiers, contractors and
manufacturers with the tools needed to select and
specify the methods for preparing concrete
surfaces prior to the application of sealer, coating
and polymer overlay systems

ICRI Guideline 310.2

ICRI Guideline 310.2


Photo Courtesy of Tnemec

Surface Preparation Methods


Chemical cleaning


Acid etching


Mechanical
preparation


Abrasive preparation


Material Selection


Things to consider when selecting which repair
material to use are:


Coefficient of thermal expansion


Shrinkage


Permeability


Modulus of elasticity


Chemical properties


Electrical properties


Color properties


Selecting the Repair Product


Repair systems include:


Cast
-
in
-
place concrete


Pre
-
placed aggregate
concrete


Troweling and dry
packing


Injection grouting


Cement grouting


Chemical grouting


Bonding Methods


Repair materials may require a separate
bonding agent


Application must be done with care in order
to avoid premature cure creating a bond
breaker with the new repair material


Cement based


Epoxy and latex based

Surface Treatments


The objective is to limit corrosion by
establishing conditions that reduce the free
water in the concrete while preventing
further moisture or chloride intrusion

Surface Treatments


Generically classified as:


Sealers


Coatings


Membranes


Overlays

Sealers


Penetrating


After application material penetrates within
the substrate of the concrete


Surface


Thin film that lays on the surface of the
concrete

Penetrating Sealers


Such products include, but are not limited
to:


Boiled linseed oil


Silanes


Siloxanes


Epoxies


Methacrylates

Surface Sealers


Such products include, but are not limited
to:


Epoxies


Polyurethanes


Methyl methacrylates


Moisture
-
cured urethanes


Acrylics

Coatings


Materials with a DFT greater than 10 mils
and less than 30 mils

Coatings


Such products include, but are not limited
to:


Acrylics


Styrene
-
butadienes


Polyvinyl acetates


Chlorinated rubbers


Urethanes


Polyesters


Epoxies

Membranes


Materials with a DFT greater than 30 mils
and less than 250 mils

Membranes


Such products include, but are not limited to:


Urethanes


Acrylics


Epoxies


Neoprenes


Cement


Polymer concrete


Methyl methacrylates


Asphaltic products

Overlays


Materials with a DFT greater than 250
mils

Overlays


Such products include, but are not limited
to:



Polymer concrete


Concrete


Epoxies


Methyl methacrylates


Polymer modified concrete


Summary


This webinar has outlined important components
of repairing concrete, resources for concrete
repair and examples of how to successfully repair
concrete. Proper identification of the cause of
damage to concrete as well as the selection of
appropriate repair methods and materials is
important not only to successful patching but also
to successful surface preparation and coating
application