Structural Designs that Accelerate Corrosion - PowerPoint

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Structural Designs that Accelerate Corrosion - PowerPoint Powered By Docstoc
					Achieving Durability in Concrete
Presented by: Peter Emmons,
 Learning Outcomes
• At the end of this webinar, you will be able
  – Recognize when a repair method needs to be
    defined on a concrete substrate
  – Describe proper repair methods
  – Describe types of repair materials available
• 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
  – 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
     • 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 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
  –   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
• 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
   – Troweling and dry
   – 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
• Penetrating
  – After application material penetrates within
    the substrate of the concrete
• Surface
  – Thin film that lays on the surface of the
Penetrating Sealers
• Such products include, but are not limited
  – Boiled linseed oil
  – Silanes
  – Siloxanes
  – Epoxies
  – Methacrylates
Surface Sealers
• Such products include, but are not limited
  – Epoxies
  – Polyurethanes
  – Methyl methacrylates
  – Moisture-cured urethanes
  – Acrylics
• Materials with a DFT greater than 10 mils
  and less than 30 mils
• Such products include, but are not limited
  – Acrylics
  – Styrene-butadienes
  – Polyvinyl acetates
  – Chlorinated rubbers
  – Urethanes
  – Polyesters
  – Epoxies
• Materials with a DFT greater than 30 mils
  and less than 250 mils
• Such products include, but are not limited to:
  – Urethanes
  – Acrylics
  – Epoxies
  – Neoprenes
  – Cement
  – Polymer concrete
  – Methyl methacrylates
  – Asphaltic products
• Materials with a DFT greater than 250
• Such products include, but are not limited
  – Polymer concrete
  – Concrete
  – Epoxies
  – Methyl methacrylates
  – Polymer modified concrete
• 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

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