distress, evaluation, and repair of historic concrete jarkko simonen, p.e. wiss, janney, elstner...

36
Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc.

Upload: jabari-broadwell

Post on 15-Dec-2015

217 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Distress, Evaluation, and Repair of Historic Concrete

Jarkko Simonen, P.E.Wiss, Janney, Elstner Associates, Inc.

Page 2: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Introduction

• History• Common Distress Mechanisms– Corrosion– Freeze Thaw– Material problems

• Analysis or Evaluation Methods• Repair

Page 3: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Introduction

• Cement has a long history– Certain types of cement have been

used by the Babylonians, Egyptians, and Romans

– Portland cement 1824– Reinforced concrete 1867

• In the northwest one of the early examples of concrete construction is Fort Casey - 1890

• Generally the use of concrete became common after about 1900

Page 4: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Concrete Vintage Generalizations

Older Concrete (1900 to 1945)– Multiple layers– Placement in lifts– Higher w/c (lower f ’c)– Early reinforcing

systems– Carbonation– No air entrainment

Modern Concrete (1945 to present)– Homogenous pour– Improved placement– Lower w/c (higher f ’c)– Modern reinforcing– Carbonation– Air entrainment?– Admixtures

Page 5: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Introduction

Environment• Wet• Cold• CoastalDeterioration due to the environment• Corrosion• Freeze thaw

Page 6: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Corrosion

• Common in environments that contain salt and moisture• Distress manifests as

staining, cracking, and spalling of the concrete

Page 7: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Concrete provides a great environment for steel against corrosion

Concrete

Page 8: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Problem with rust• Corrosion of the rebar causes rust to form• Rust is 6 to 10 time less dense than steel • Increased volume causes concrete to crack

Page 9: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

• Destroys natural passive oxide layer provided by portland cement paste

• Complicated chemical interactions• Hygroscopic

Effects of Chloride Contamination

Page 10: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Chloride Contamination

• Environment (soils, sea water)• Applied (deicing chemicals)• Integral (admixtures, aggregate, water)

Page 11: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

CarbonationCarbonation

CO2 + H2O + Ca(OH)2 CaCO3 + H2Oatmospheric rain cement paste limestone water

CO2

NON-CARBONATEDCONCRETE

/ H O2

DEPTH OFCARBONATION

Page 12: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Carbonation

• Advances about 1 mm per year in normal concrete• Once carbonation

reaches steel, the steel is unprotected • Corrosion can affect

large areas

Page 13: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Freeze-thaw weathering regions (ASTM C33)

Page 14: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Freeze-thaw

• Damages the near surface region of concrete• Surface flakes off typically in horizontal layers• More aggressive if surface is exposed to chlorides

Page 15: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Air entrainment can be effective in mitigating freeze-thaw

Page 16: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

ASR - Reaction between silica and hydroxyls (OH-) in the pore solution, forming silica gel. As the gel forms, it absorbs water and expands.

OH -

OH -

OH -

OH -

OH -

OH -

OH -

ALKALIS SILICA GEL (REACTION RIM)

SURROUNDINGPASTE

COARSEAGGREGATE

FINEAGGREGATE

ALKALIS SILICA GEL (REACTION RIM)

EXPANSIONCRACK

GEL ENTERINGCRACK

SURROUNDINGPASTE

COARSEAGGREGATE

FINEAGGREGATE

RADIALCRACK

Page 17: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Alkali Silica Reaction• ASR must have all three

components present to cause a problem‐ Reactive aggregates‐ Abundance of alkalis‐ Water

• In the northwest we have two out of three‐ Reactive Aggregates‐ Water‐ Generally cement has low

alkalinity• ASR aggravates F/T and corrosion

Page 18: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Assessment Methods

Field• Visual survey• Mechanical sounding survey• Corrosion assessment

‐ Half-cell potential measurements ‐ Linear Polarization Resistance Method

• Other non-destructive methods (rebound hammer, impact-echo, pulse velocity, etc.)

Page 19: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Assessment Methods

Laboratory• Chloride content• Depth of Carbonation (Phenolphthalein indicator)• Petrographic examination

Page 20: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Condition AssessmentsReferences• ACI 201.1R Guide to Making a Condition Survey of Concrete in Service• ACI 224.1R Causes, Evaluation and Repair of Cracks in Concrete

Structures• ACI 364.1R Guide for Evaluation of Concrete Structures Prior to

Rehabilitation• ACI 437.1R Strength Evaluation of Existing Concrete Buildings• ACI 546R Concrete Repair Guide• Technical Guidelines by International Concrete Repair Institute (ICRI)• Guide to Nondestructive Testing of Concrete• Others

Page 21: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Visual Survey• Identify distress mechanisms• Repair quantities• Repair locations/typesMechanical Survey• Identify hidden distress• Dislodge dangerous fragments• Gives you a better feel about the

concrete quality

Page 22: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Corrosion SurveysHalf cell surveys

– Identify potential areas of corrosion

– Repair quantities– Repair locations/types

Linear Polarization

– Corrosion rate/aggressiveness

Page 23: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

NDT Investigative Techniques• Impact echo• Pulse velocity• GPR• Magnetic rebar locators

Page 24: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Laboratory Analysis

• Initial opinion of deterioration and conditions• Type of concrete exposure• Discuss testing with petrographer/chemist• Repair type being considered• Type of testing and expected results

Page 25: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Evaluation for Chlorides

Two methods• Cores• Drill/powder samples

Testing• ASTM C 1152: Acid-

Soluble Chloride in Mortar and Concrete

• ASTM C 1218: Water-Soluble Chloride in Mortar and Concrete

Page 26: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Evaluation for Carbonation

Page 27: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Petrography • ASTM C856: Standard Practice for

Petrographic Examination of Hardened Concrete – Freeze thaw– ASR– Finishing Problems– Identify substrate materials– Etc.

Page 28: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Repair

Concrete repair• Protection/Mitigation• Patch repairs• Reconstruction

Page 29: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Protection/Mitigation

• Coatings– Prevent moisture

• Electrochemical treatments– Cathodic protection– Chloride extraction– Re-alkalinization

• Other – Sealers

• Silanes• Siloxanes

– Migratory corrosion inhibitors

Page 30: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Patch Repairs

Considerations• Compatibility– Strength– Wear– Thermal

• Appearance– Color– Texture– Finish– Profile

Page 31: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Repairs should blend in

Page 32: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Blending Repairs

• Lift lines• Form board lines• Color• Texture

Page 33: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

• Surface Preparation– Saw cuts– Rectangular

• Installation – Dry as possible

• Finishing• Curing

Page 34: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Samples and Mock-ups

• Cleaning• Coating removal• Color• Finish• Texture• Surface preparation• Design mix• All installation and finishing

procedures and• Techniques

Page 35: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

Repair

Special Considerations with Historic/Architectural Concrete• Tasks are similar of work with other concrete• Options may be more limited• Rules of good concrete repair practice apply• Original design may need to be improved• Emphasis is needed on investigation, laboratory

analysis, samples, mock-ups, and trial repairs

Page 36: Distress, Evaluation, and Repair of Historic Concrete Jarkko Simonen, P.E. Wiss, Janney, Elstner Associates, Inc

?