Repair and Protection of Concrete
Construction
Repair and Protection of Concrete Presented by: Sika Corporation AIA Program Number: SIK602
Sika Corporation
This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
Sika Corporation is a Registered Provider with the American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members is available upon request.
AIA/CES Program
This AIA/CES program delivers 1 learning unit of credit (1.0 LU) This program qualifies for Health, Safety and Welfare (HSW) credit Please sign the form and add your AIA member number if you wish to obtain credit for this seminar Sika will forward this information to AIA so that you will receive credit for this presentation Non-AIA members may receive CEU’s upon request
Key Learning Objectives
Review methods to diagnose problems with concrete Review repair techniques Review protection techniques
Agenda
Diagnosis Repair Techniques Concrete Protection
Preliminary Project Forensics
Visual Inspection • Spalls • Cracks • Leaks
Further investigation may entail • • • •
Water/Cement Ratio Carbonation & Chloride Levels Coverage over the Reinforcement Corrosion Rate Measurements
Preliminary Project Forensics
Why Perform all the Testing? Determine extent of required repairs and future protection • Budget Estimate • Plan for completing work with as little disturbance as possible • On-going maintenance evaluation • Determine what went wrong and why
Corrosion of the Reinforcement Steel
Why does this happen?
Steel and Concrete
Steel is passivated in concrete Alkaline environment protects steel from corrosion
Concrete pH 12.5-13.5 Reinforcing Steel Passivating Layer (Iron Oxides)
Breakdown of Passivation Layer leads to Corrosion
Corrosion is an electrochemical process How does the protective layer break down?
Typical Causes of Corrosion
Poor cover of the reinforcement steel Carbonation Chlorides Cracks not addressed
Construction
Poor Cover of the Reinforcing Steel
Sika Corporation
Construction
Carbonation
Sika Corporation
Factors Affecting Carbonation
CO2 content H2O content Cement type Permeability • • • •
Cracks W/C Ratio Placing and curing methods Protective coatings
Corrosion - Carbonation Induced
How is the Root Cause Known?
Field Test to Determine pH
Construction
Chlorides
Sika Corporation
Corrosion Due to Chlorides
Chloride Induced Corrosion
Chlorides dissolved in water penetrate through the pore system into concrete Penetrate via chloride ion diffusion At Chloride threshold limit (at the level of the reinforcing steel), corrosion begins Common threshold limit = 1.5 lbs./Cu Yd. Chlorides break up the passivating layer, but are not used up
Factors Affecting Chloride Penetration Rate
Chloride quantity Relative humidity & moisture content Type of cement • w/c ratio
Permeability of the Concrete • Cracks in concrete • Placing and curing methods • Coatings and sealers
Construction
Cracks Not Addressed
Sika Corporation
Other Possible Causes of Corrosion
Galvanic reaction Alkali Silica Reaction Breakdown of construction materials Incipient anode
Possible Galvanic Reaction
Isolate Different Metals
Alkali Silica Reaction Reaction between aggregates containing certain mineral constituents, and the alkali’s of the cement This reaction can lead to excessive expansion, creating cracking and popouts.
Breakdown of Construction Materials
Breakdown of Construction Materials
Corrosion at Incipient Anode
Also know as ring anode or halo effect
Halo Effect
What do we do? Do nothing Rout and seal cracks Remove loose concrete Repair visible spalls Repair and Protect structure as a whole
Crack Repair Options
Rout and seal Pressure inject epoxy Gravity feed epoxy Apply a crack-bridging coating
Crack Repair Options
Rout and seal with a flexible sealant
Crack Repair Options
Pressure inject with an epoxy
Crack Repair : Gravity feed with Epoxy
Repair Visible Spalls
Protection Rebar priming Concrete bonding
Repair Mortar Function
Fill spalls, restore integrity Act monolithically with the existing concrete Protect steel reinforcement
Types of Repair Mortars
Form and Pour/Pump Trowel/Screed Grade Vertical/Overhead Machine Applied Sprayable Mortars Leveling Mortars
Screed Mortar
Machine Applied Repair Mortars
Wet or Dry
Repair Only
What is happening to rebar between repair areas?
Why did the failure occur? Will failures occur again? In areas that have already been repaired? Elsewhere in the structure?
Construction
For a long term solution to the corrosion problem, we must REPAIR all the visible damage and PROTECT against the latent damage! Sika Corporation
Why Protection?
Stop Water Intrusion Prevent chloride/salts ingress Eliminate carbonation intrusion Freeze/Thaw protection Aesthetics Extend life of the structure Address cracks in the concrete
Protection for Latent Damage
Actively Mitigate Corrosion on Steel • Inhibitor • Galvanic anodes
Prevent Further Ingress of Aggressive Chemicals (Chlorides, CO2, Water) • Penetrating sealers • Protective coatings
Actively Mitigate Steel Corrosion - Inhibitor Latent corrosion may be treated with penetrating corrosion inhibitor
Sika Ferrogard 903
Penetrating Corrosion Inhibitor Features Reduces corrosion Penetrates concrete Mixed inhibitor Does not alter appearance Easy to apply
Benefits Decreases future cost No costly breakout Not ‘dangerous’ Aesthetics
Increases service life
Characteristics to Consider
Multifunctional Forms a film on the steel surface Ability to displace chloride ions from metal surfaces Ability to penetrate /diffuse throughout the concrete Ability to reach the steel
Galvanic Protection Embedded galvanic anode Reduces corrosion of reinforcing steel in concrete adjacent to repaired areas Fights ring anode effect)
Old Chloride Contaminated Concrete
New Chloride-Free Concrete Extension
Surrounding Anode Galvanically Protects Rebar is Protected Adjacent Rebar
Best Use
Deck repairs and joint replacements Ideal for full depth slab replacement and existing / new interface High chloride areas subjected to wetting Carbonated environment Corrosion prevention and control
Construction
Prevent further ingress of chlorides, CO2, and water
Penetrating Sealers
Sika Corporation
Characteristics to Consider Water Repellent Chloride Resistant Excellent concrete penetration Water vapor permeable Does not change appearance Water based, environmentally safe
Construction
Prevent further ingress of chlorides, CO2, and water
Protective Coatings
Sika Corporation
Characteristics to Consider
High resistance to carbon dioxide (CO2) Dynamic crack bridging capability even at low temperatures High UV Resistance Braethable yet waterproof Decorative, variety of colors Low maintenance requirements
Anticarbonation…yet Breathable?
Equivalent Air Thickness
Ability of a coating to provide ‘effective cover’ Thin application of the coating (mils) Provides eqivalent protection of several INCHES of concrete cover over the steel!
Leveling Mortar Function
Fill/Seal pores and bugholes Provide a suitable surface for protective coatings Prevent pinholes and blow holes in protective coatings Add to coverage over steel reinforcement Improve the aesthetics
Construction
Prevent further ingress of chlorides, CO2, and water Protective Coatings for Traffic Bearing Surfaces
Sika Corporation
Sikadur Epoxy Broadcast Overlay System Extremely Durable Long lasting Impervious to water Stops chloride ion and road salts intrusion Low Modulus Compatible with concrete Skid resistant Traffic safe Quick turnaround time Can be opened in 4-6 hours Easy to mix and apply Labor savings
Construction
Thank You!
Questions?
Sika Corporation
Summary
Traditional Repairs necessary when building allowed to deteriorate for too long Cathodic Protection for steel frame buildings can save up to 90% of cost compared with traditional repair Managed as single structure or by portfolio System can enhance the asset purchase or sale
Repair and Protection of Concrete Presented by: Sika Corporation AIA Program Number: SIK602
Sika Corporation
This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
Sika Corporation is a Registered Provider with the American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members is available upon request.
AIA/CES Program
This AIA/CES program delivers 1 learning unit of credit (1.0 LU) This program qualifies for Health, Safety and Welfare (HSW) credit Please sign the form and add your AIA member number if you wish to obtain credit for this seminar Sika will forward this information to AIA so that you will receive credit for this presentation Non-AIA members may receive CEU’s upon request
Key Learning Objectives
Review methods to diagnose problems with concrete Review repair techniques Review protection techniques
Agenda
Diagnosis Repair Techniques Concrete Protection
Preliminary Project Forensics
Visual Inspection • Spalls • Cracks • Leaks
Further investigation may entail • • • •
Water/Cement Ratio Carbonation & Chloride Levels Coverage over the Reinforcement Corrosion Rate Measurements
Preliminary Project Forensics
Why Perform all the Testing? Determine extent of required repairs and future protection • Budget Estimate • Plan for completing work with as little disturbance as possible • On-going maintenance evaluation • Determine what went wrong and why
Corrosion of the Reinforcement Steel
Why does this happen?
Steel and Concrete
Steel is passivated in concrete Alkaline environment protects steel from corrosion
Concrete pH 12.5-13.5 Reinforcing Steel Passivating Layer (Iron Oxides)
Breakdown of Passivation Layer leads to Corrosion
Corrosion is an electrochemical process How does the protective layer break down?
Typical Causes of Corrosion
Poor cover of the reinforcement steel Carbonation Chlorides Cracks not addressed
Construction
Poor Cover of the Reinforcing Steel
Sika Corporation
Construction
Carbonation
Sika Corporation
Factors Affecting Carbonation
CO2 content H2O content Cement type Permeability • • • •
Cracks W/C Ratio Placing and curing methods Protective coatings
Corrosion - Carbonation Induced
How is the Root Cause Known?
Field Test to Determine pH
Construction
Chlorides
Sika Corporation
Corrosion Due to Chlorides
Chloride Induced Corrosion
Chlorides dissolved in water penetrate through the pore system into concrete Penetrate via chloride ion diffusion At Chloride threshold limit (at the level of the reinforcing steel), corrosion begins Common threshold limit = 1.5 lbs./Cu Yd. Chlorides break up the passivating layer, but are not used up
Factors Affecting Chloride Penetration Rate
Chloride quantity Relative humidity & moisture content Type of cement • w/c ratio
Permeability of the Concrete • Cracks in concrete • Placing and curing methods • Coatings and sealers
Construction
Cracks Not Addressed
Sika Corporation
Other Possible Causes of Corrosion
Galvanic reaction Alkali Silica Reaction Breakdown of construction materials Incipient anode
Possible Galvanic Reaction
Isolate Different Metals
Alkali Silica Reaction Reaction between aggregates containing certain mineral constituents, and the alkali’s of the cement This reaction can lead to excessive expansion, creating cracking and popouts.
Breakdown of Construction Materials
Breakdown of Construction Materials
Corrosion at Incipient Anode
Also know as ring anode or halo effect
Halo Effect
What do we do? Do nothing Rout and seal cracks Remove loose concrete Repair visible spalls Repair and Protect structure as a whole
Crack Repair Options
Rout and seal Pressure inject epoxy Gravity feed epoxy Apply a crack-bridging coating
Crack Repair Options
Rout and seal with a flexible sealant
Crack Repair Options
Pressure inject with an epoxy
Crack Repair : Gravity feed with Epoxy
Repair Visible Spalls
Protection Rebar priming Concrete bonding
Repair Mortar Function
Fill spalls, restore integrity Act monolithically with the existing concrete Protect steel reinforcement
Types of Repair Mortars
Form and Pour/Pump Trowel/Screed Grade Vertical/Overhead Machine Applied Sprayable Mortars Leveling Mortars
Screed Mortar
Machine Applied Repair Mortars
Wet or Dry
Repair Only
What is happening to rebar between repair areas?
Why did the failure occur? Will failures occur again? In areas that have already been repaired? Elsewhere in the structure?
Construction
For a long term solution to the corrosion problem, we must REPAIR all the visible damage and PROTECT against the latent damage! Sika Corporation
Why Protection?
Stop Water Intrusion Prevent chloride/salts ingress Eliminate carbonation intrusion Freeze/Thaw protection Aesthetics Extend life of the structure Address cracks in the concrete
Protection for Latent Damage
Actively Mitigate Corrosion on Steel • Inhibitor • Galvanic anodes
Prevent Further Ingress of Aggressive Chemicals (Chlorides, CO2, Water) • Penetrating sealers • Protective coatings
Actively Mitigate Steel Corrosion - Inhibitor Latent corrosion may be treated with penetrating corrosion inhibitor
Sika Ferrogard 903
Penetrating Corrosion Inhibitor Features Reduces corrosion Penetrates concrete Mixed inhibitor Does not alter appearance Easy to apply
Benefits Decreases future cost No costly breakout Not ‘dangerous’ Aesthetics
Increases service life
Characteristics to Consider
Multifunctional Forms a film on the steel surface Ability to displace chloride ions from metal surfaces Ability to penetrate /diffuse throughout the concrete Ability to reach the steel
Galvanic Protection Embedded galvanic anode Reduces corrosion of reinforcing steel in concrete adjacent to repaired areas Fights ring anode effect)
Old Chloride Contaminated Concrete
New Chloride-Free Concrete Extension
Surrounding Anode Galvanically Protects Rebar is Protected Adjacent Rebar
Best Use
Deck repairs and joint replacements Ideal for full depth slab replacement and existing / new interface High chloride areas subjected to wetting Carbonated environment Corrosion prevention and control
Construction
Prevent further ingress of chlorides, CO2, and water
Penetrating Sealers
Sika Corporation
Characteristics to Consider Water Repellent Chloride Resistant Excellent concrete penetration Water vapor permeable Does not change appearance Water based, environmentally safe
Construction
Prevent further ingress of chlorides, CO2, and water
Protective Coatings
Sika Corporation
Characteristics to Consider
High resistance to carbon dioxide (CO2) Dynamic crack bridging capability even at low temperatures High UV Resistance Braethable yet waterproof Decorative, variety of colors Low maintenance requirements
Anticarbonation…yet Breathable?
Equivalent Air Thickness
Ability of a coating to provide ‘effective cover’ Thin application of the coating (mils) Provides eqivalent protection of several INCHES of concrete cover over the steel!
Leveling Mortar Function
Fill/Seal pores and bugholes Provide a suitable surface for protective coatings Prevent pinholes and blow holes in protective coatings Add to coverage over steel reinforcement Improve the aesthetics
Construction
Prevent further ingress of chlorides, CO2, and water Protective Coatings for Traffic Bearing Surfaces
Sika Corporation
Sikadur Epoxy Broadcast Overlay System Extremely Durable Long lasting Impervious to water Stops chloride ion and road salts intrusion Low Modulus Compatible with concrete Skid resistant Traffic safe Quick turnaround time Can be opened in 4-6 hours Easy to mix and apply Labor savings
Construction
Thank You!
Questions?
Sika Corporation
Summary
Traditional Repairs necessary when building allowed to deteriorate for too long Cathodic Protection for steel frame buildings can save up to 90% of cost compared with traditional repair Managed as single structure or by portfolio System can enhance the asset purchase or sale
