Slide 1: Concrete Repair
CONCRETE REPAIR RANDALL KRATZ – DISTRICT MANAGER MD/DC/N.VA SIKA CORPORATION – REFURBISHMENT, SEALING & BONDING WITH SIKA SINCE 1991 GRADUATE DREXEL UNIVERSITY - COMMERCE & ENGINEERING 410-336-3757 KRATZ.RANDALL@US.SIKA.COM
Slide 2: Agenda – Concrete Repair (Spall Repair)
AGENDA – CONCRETE REPAIR (SPALL REPAIR) ▪ Brief review ▪ Root causes of deterioration ▪ Conducting condition survey ▪ Determining a repair and protection strategy ▪ Discuss available application methods ▪ Focus on material properties and benefits for proper selection
Slide 3: Causes of Deterioration, Condition Survey, Repair and Protection Strategy
CAUSES OF DETERIORATION CONDITION SURVEY REPAIR AND PROTECTION STRATEGY
Slide 4: Causes of Concrete Deterioration
CAUSES OF CONCRETE DETERIORATION ▪ Impact ▪ Abrasion ▪ Freeze/thaw cycles ▪ Chemicals/sulfates ▪ Biological (micro-organisms) ▪ Reactive aggregates (ASR) ▪ Dissimilar metals ▪ Steel reinforcement corrosion
Slide 5: Steel Reinforced Concrete
STEEL REINFORCED CONCRETE ▪ Concrete and steel are compatible ▪ Steel is passivated in concrete ▪ Alkaline environment protects steel from corrosion despite moisture and oxygen
Slide 6: Root Causes of Reinforcement Corrosion
ROOT CAUSES OF REINFORCEMENT CORROSION ▪ Chlorides and carbonation destroy the passivating layer ▪ As steel corrodes it expands causing cracking and spalling of the concrete Cl- CO2 Cl- CO2 Cl- CO2 CO2 Cl- Cl- CO2 Cl- CO2 CO2 Cl- Cl- CO2 Cl- Cl- Cl- Cl- CO2 CO2 Cl- CO2 Cl- Cl- Cl-
Slide 7: Understanding the Conditions
UNDERSTANDING THE CONDITIONS Learn the condition of the concrete ▪ Strengths ▪ Air entrainment ▪ Chloride content ▪ Carbonation depth ▪ Reactive aggregates Evaluate the status of the steel ▪ Depth of cover ▪ Contaminated or non- contaminated environment Quantify the existing damage ▪ Identify spalls
Slide 8: Selecting a Repair and Protection Strategy
SELECTING A REPAIR AND PROTECTION STRATEGY Now that we know the conditions, we can design a solution to best meet the project requirements Basic approach Considerations ▪ Remove the unsound concrete ▪ Short or long term goals ▪ Clean or replace the steel ▪ Safety and liability ▪ Coat the steel ▪ Cov
Slide 9: Concrete Repair
CONCRETE REPAIR
Slide 10: Concrete Repair
CONCRETE REPAIR ▪ Choose method of application ▪ Select repair materials ▪ Reinforcement coating ▪ Bonding agent ▪ Repair mortar/concrete ▪ Prepare substrate and reinforcement ▪ Install the repair materials
Slide 11: Application Methods
APPLICATION METHODS Trowel ▪ Smaller areas ▪ Shallower repairs Form and pour ▪ Larger volumes ▪ Easy to pour and enter formwork Form and pump ▪ More difficult access to formwork ▪ Need to move material from source through line to formwork ▪ Soffit repairs Spray (wet/dry, high/low pressure) ▪ Large v
Slide 12: Selecting the Repair Materials
SELECTING THE REPAIR MATERIALS ▪ Resist the causes of damage, perform in the environment ▪ Meet time constraints ▪ Consider the role in the overall repair and protection strategy ▪ Allow for most productive installation Cl- CO2 Cl- CO2 Cl- CO2 Cl- CO2Cl- CO2 Cl- Available Cover
Slide 13: Factors Influencing Longevity of Repair Material
FACTORS INFLUENCING LONGEVITY OF REPAIR MATERIAL ▪ Cracks in (and around) repair material allow quickest access of chlorides and carbonation to reach reinforcement ▪ Permeability of repair material determines rate of chloride and carbonation penetration through repair material to reach reinforcement
Slide 14: Crack Concerns and Types
CRACK CONCERNS AND TYPES ▪ Unsightly ▪ Leakage (ACI 224.R.72 Guideline maximum allowable width for water retaining structures is 4 mils) ▪ Structural ▪ Widen ▪ Corrosion (ACI 224.R.72 Guideline maximum allowable width for exposure to deicing chemicals is 7 mils) [Sheet of 20# paper is 4 mils thick]
Slide 15: Common Cracking in Concrete Repair
COMMON CRACKING IN CONCRETE REPAIR Design - Reflective Cracking Avoid ▪ Installing repair material over a crack ▪ Completely chip out cracks during or joint in the substrate will result in surface preparation the crack propagating through repair ▪ Epoxy inject the cracks material ▪ Honor existing jo
Slide 16: Common Cracking in Concrete Repair
COMMON CRACKING IN CONCRETE REPAIR Design - Reflective Cracking Avoid ▪ Installing repair material over a crack ▪ Completely chip out cracks during or joint in the substrate will result in surface preparation the crack propagating through repair ▪ Epoxy inject the cracks material ▪ Honor or create j
Slide 17: Common Cracking in Concrete Repair
COMMON CRACKING IN CONCRETE REPAIR Design - Reflective Cracking Avoid ▪ Installing repair material over a crack ▪ Completely chip out cracks during or joint in the substrate will result in surface preparation the crack propagating through repair ▪ Epoxy inject the cracks material ▪ Honor or create j
Slide 18: Common Cracking in Concrete Repair
COMMON CRACKING IN CONCRETE REPAIR Design - Stress Cracking Avoid ▪ Try to design around (core later) ▪ Weak points increase ▪ Select low shrinkage repair material likelihood of cracking such as at ▪ Respect the mix re-entrant corners and around ▪ Honor material limitations penetrations ▪ Use finish
Slide 19: Common Cracking in Concrete Repair
COMMON CRACKING IN CONCRETE REPAIR Design - Stress Cracking Avoid ▪ Create rectangular repairs (up to 2:1) ▪ Poor geometrics ▪ Select low shrinkage repair material ▪ Respect the mix ▪ Honor material limitations ▪ Use finishing aid ▪ Cure
Slide 20: Common Cracking in Concrete Repair
COMMON CRACKING IN CONCRETE REPAIR Design - Stress Cracking Avoid ▪ Create rectangular repairs (up to 2:1) ▪ Poor geometrics ▪ Select low shrinkage repair material ▪ Respect the mix ▪ Honor material limitations ▪ Use finishing aid ▪ Cure
Slide 21: Common Cracking in Concrete Repair
COMMON CRACKING IN CONCRETE REPAIR Design - Stress Cracking Avoid ▪ Create rectangular repairs (up to 2:1) ▪ Poor geometrics ▪ Select low shrinkage repair material ▪ Respect the mix ▪ Honor material limitations ▪ Use finishing aid ▪ Cure
Slide 22: Common Cracking in Concrete Repair
COMMON CRACKING IN CONCRETE REPAIR Shrinkage cracking Avoid ▪ Select low shrinkage repair material ▪ A race between developing ▪ Respect the mix tensile strength versus ▪ Honor material limitations shrinkage stress ▪ Use finishing aid ▪ Shrinkage stress comes from ▪ Cure volume decrease as water eva
Slide 23: Shrinkage Testing
SHRINKAGE TESTING (a) ASTM C1581/C 1581M: Ring shaped specimens (b) Length change measured per ASTM C 157/C 157M used for determining age at cracking and induced tensile modified in ICRI TDS Protocol using 3” X 3” X11 4" mold stress of mortar and concrete under restrained shrinkage (c) Length change
Slide 24: Mix Water Versus Water for Hydration
MIX WATER VERSUS WATER FOR HYDRATION Common mix water of ▪ Polycarboxylate superplasticizer 8 pints replaces water used for workability Mix water of 6.5 pints 19% reduction Mix water of 4.5 pints 44% reduction
Slide 25: Finishing Aid
FINISHING AID ▪ Use instead of finishing water ▪ Slickens better ▪ Reduces moisture loss and crusting ▪ Repair materials often stickier and set faster ▪ Very economical ▪ Remove before coating or sealing
Slide 26: Curing
CURING ▪ Start curing as soon as possible after applying finish ▪ Objective is to keep moisture in the repair material ▪ Burlap needs to remain wet ▪ Soakers and misters can be used ▪ Polyethylene needs to lay flat ▪ Burlene needs to lay flat
Slide 27: Curing
CURING ▪ Keep curing until at least 75% of design strength is reached ▪ Vertical surfaces are hard to keep in contact with burlap ▪ Forms can prevent moisture loss
Slide 28: Curing
CURING ▪ Curing compounds meeting ASTM C-309 are effective ▪ Use water based curing compounds with materials containing polymers ▪ Curing compounds need to be removed before applying coatings and sealants
Slide 29: Common Cracking in Concrete Repair
COMMON CRACKING IN CONCRETE REPAIR Perimeter Separation Avoid ▪ Select low shrinkage repair material ▪ Cement has weak bond to ▪ Respect the mix smoother saw cut surface ▪ Honor material limitations profile (usually ½” deep) ▪ Use finishing aid ▪ Cure ▪ Tool and seal perimeter ▪ Use epoxy bonding ag
Slide 30: Common Cracking in Concrete Repair
COMMON CRACKING IN CONCRETE REPAIR Perimeter Separation Avoid ▪ Select low shrinkage repair material ▪ Cement has weak bond to ▪ Respect the mix smoother saw cut surface ▪ Honor material limitations profile (usually ½” deep) ▪ Use finishing aid ▪ Cure ▪ Tool and seal perimeter ▪ Use epoxy bonding ag
Slide 31: Common Cracking in Concrete Repair
COMMON CRACKING IN CONCRETE REPAIR Perimeter Separation Avoid ▪ Select low shrinkage repair material ▪ Cement has weak bond to ▪ Respect the mix smoother saw cut surface ▪ Honor material limitations profile (usually ½” deep) ▪ Use finishing aid ▪ Cure ▪ Tool and seal perimeter ▪ Use epoxy bonding ag
Slide 32: Corrosion Process
CORROSION PROCESS ▪ Current flows between cathode and anode through steel and concrete ▪ Electrical current flow is governed by Ohm’s Law ▪ V = IR Potential Difference (V) = Current (I) x Resistance (R) ▪ V = IR Current (I) is the concern ▪ I = V/R Current (I) = Potential Difference (V) / Resistance
Slide 33: Resistance of Repair Materials
RESISTANCE OF REPAIR MATERIALS ▪ Resistance (Permeability) of repair materials is measured in coulombs ▪ Typical concrete about 3,000 – 4,000 coulombs (moderate) ▪ A repair turns the anode to a cathode ▪ Increased corrosion activity around perimeter of repair referred to as ‘incipient anode’, ‘anodi
Slide 34: Resistance of Repair Materials
RESISTANCE OF REPAIR MATERIALS ▪ Increase resistance using a higher resistant (lower permeability) repair material ▪ Repair materials available with < 500 coulombs (very low) ▪ 6 times better resistance than moderate permeability repair materials to currents and intrusion of chlorides and carbonatio
Slide 35: Reinforcement Coating
REINFORCEMENT COATING ▪ This epoxy coated rebar was investigated after 30 years, revealing protective value ▪ Using epoxy coated rebar on top mat of garage decks and uncoated rebar on bottom mat, has resulted in corrosion and spalling on the underside where chloride content is lower
Slide 36: Reinforcement Coating
REINFORCEMENT COATING ▪ Reinforcement coatings add substantially more barrier properties and resistance ▪ Epoxy, epoxy-cement, enhanced-cement, and zinc-rich materials Adjacent area becomes anode Repair becomes cathode
Slide 37: Integral Corrosion Inhibitor
INTEGRAL CORROSION INHIBITOR ▪ Integral corrosion inhibitor protects within the repair and migrates inches outside repair to reduce incipient anode corrosion (amino alcohol) ▪ Corrosion inhibitor electrochemically bonds to steel surface and excess remains in concrete to replenish itself Adjacent are
Slide 38: Compatibility with Parent Concrete
COMPATIBILITY WITH PARENT CONCRETE ▪ If mix is chiefly Portland cement and silica aggregates, then it will be thermally compatible ▪ Low modulus epoxy mortars are acceptably compatible up to ½” depth ▪ Neat epoxy and high modulus resins generally acceptable up to ¼” depth ▪ Interior/temperature stab
Slide 39: Freeze/Thaw Resistance
FREEZE/THAW RESISTANCE ▪ Air entrainment (usually 4-7%) provides tiny voids (where liquid water does not enter) around pores where liquid water does enter. When the water freezes in the pores, it can expand into the air entrainment voids. ▪ Air entrainment can be worked out of surface from excess fi
Slide 40: Strengths
STRENGTHS ▪ Select materials with appropriate adhesion and physical properties for the application ▪ Generally, similar or higher strengths than parent concrete
Slide 41: Repair Material Selection
REPAIR MATERIAL SELECTION Application Premium High/Speed Quality Performance Performance Performance Vertical/Overhead SikaTop 123 PLUS SikaQuick VOH SikaRepair 223 Trowel Mortar SikaRepair 224 Pour/Pump Sikacrete 211 SCC Plus Sikacrete 421 CI Rapid Sikacrete 100 CI Concrete Sikacrete 211 Pour/Pump
Slide 42: Repair Material Selection
REPAIR MATERIAL SELECTION Application Premium High/Speed Quality Performance Performance Performance Vertical/Overhead SikaTop 123 PLUS SikaQuick VOH SikaRepair 223 Trowel Mortar SikaRepair 224 Pour/Pump Sikacrete 211 SCC Plus Sikacrete 421 CI Rapid Sikacrete 100 CI Concrete Sikacrete 211 Pour/Pump
Slide 43: Performance Analysis
PERFORMANCE ANALYSIS Property SikaTop 123 PLUS SikaQuick VOH SikaRepair 223 Components 2 1 1 Compressive 28 day 7,000 psi 5,500 psi 7,500 psi Polymer Yes - liquid Yes - dry No – optional liquid Fibers No Yes No Permeability <500 coulombs < 1000 No data (3000-4000) Corrosion Inhibitor Yes – Data (>65
Slide 44: Price and Value Analysis (Example)
PRICE AND VALUE ANALYSIS (EXAMPLE) ▪ Example of a typical 2” vertical trowel-applied repair assuming installed price without repair material to be $50.00/SF. ▪ Corrosion resistance in equivalency to 3,000 coulomb concrete. Property SikaTop 123 Plus SikaQuick VOH SikaRepair 223 Price/SF at 2” Depth $
Slide 45: Price and Value Analysis (Example)
PRICE AND VALUE ANALYSIS (EXAMPLE) ▪ Example of a typical 2” vertical trowel-applied repair assuming installed price without repair material to be $50.00/SF. ▪ Corrosion resistance in equivalency to 3,000 coulomb concrete. Property SikaTop 123 Plus SikaQuick VOH SikaRepair 223 Price/SF at 2” Depth $
Slide 46: Specification Do's & Don'ts – Prepackaged Materials
SPECIFICATION DO’S & DON’TS – PREPACKAGED MATERIALS DO SPECIFY PERTANENT PROPERTIES DON’T SPECIFY A MIX DESIGN ▪ Strengths ▪ Water-cement ratio ▪ (> 5,000 psi … ASTM C-109) ▪ Aggregates ▪ Shrinkage ▪ Air entrainment ▪ (< .06% ... ASTM C-157) ▪ Polymer modified ▪ Permeability ▪ Microsilica/Silica fum
Slide 47: Available Related Presentations
AVAILABLE RELATED PRESENTATIONS ❑ Concrete Repair & Protection ✓ Concrete Repair (Part 1 – Materials) ❑ Concrete Repair (Part 2 – Installation) ❑ Crack Repair ❑ Concrete Protection
Slide 48: Thank You for Your Attention!
Baltimore Design School – 2014 ICRI Sustainability Award Winner THANK YOU FOR YOUR ATTENTION! RANDALL KRATZ 410-336-3757 KRATZ.RANDALL@US.SIKA.COM