SPECIAL WORKSHOP “CHEMICAL EXPANSION OF …civil.colorado.edu/~saouma/AAR/Library/Granada-2007/Granada-2007/1... · Eric Bourdarot , EDF, CHAMBERY, France. ... Options for diagnosis

SPECIAL WORKSHOP

“CHEMICAL EXPANSION OF CONCRETE IN DAMS & HYDRO-ELECTRIC PROJECTS”

October 18 & 19, 2007Granada, Spain

Sponsored by

ICOLD COMMITTEE ON CONCRETE DAMS, SPANISH COMMITTEE ON CONCRETE FOR DAMS and

INTERNATIONAL JOURNAL ON HYDROPOWER & DAMS

13 March 2008 1Robin Charlwood Presentation to RILEM ACS Committee - Valencia

ChairmenRobin Charlwood, Chairman ICOLD Committee on Concrete Dams

& Principal, Robin Charlwood & Associates, SEATTLE, USA; and

Juan Manuel Buil Sanz

– Chairman, SPANCOLD Committee on Concrete for Dams

& Endesa Generación, BARCELONA, Spain

The Organizing Team also includedArturo Gil, Iberdrola Generación,

SALAMANCA, SpainAlison Bartle, Editor, International Journal of Hydropower & Dams

Other Contributors to the Planning included:Eric Bourdarot , EDF, CHAMBERY, France

Paddy Grattan-Bellew, NRC, OTTAWA, CanadaBernard Goguel, Coyne et Belier, PARIS, France

Victor Saouma, University of Colorado, Boulder, USAIan Sims, STATS Limited & Secretary, RILEM TC ACS, UK

13 March 2008 Robin Charlwood Presentation to RILEM ACS Committee - Valencia 2

ObjectivesThis workshop “Chemical Expansion of Concrete in

Dams and Hydroelectric Projects” is to:• Provide an international review the understanding of

expansion phenomena in concrete dams and hydroelectric projects, and

• Provide a basis to review and, if appropriate, update and amplify the information of the ICOLD Bulletin 97 and the USCOLD 1995 Conference.

It will consider all kinds of chemical expansion phenomena in concrete dams, including that due to alkali aggregate reactions (ASR and ACR), as well as reactions in which free lime or magnesia has a role, and those due to sulphur compounds.


Some Dam AAR Milestones….• USBR’s Stewart Mountain Dam• TVA’s Fontana Project and cored slots 1970• NB Power’s Mactaquac project and diamond wire saw cut

slots 1988• Chambon Dam with slot cuts +upstream membrane• ICOLD Bulletin 79 on AAR published in 1991 by Committee

on Concrete• 1992 CANCOLD/CEA 1st International Conference on AAR in

Hydroelectric Plants and Dams - Fredericton, NB, Canada• 1995 USCOLD 2nd International Conference in Chattanooga,

TN, USA• 2007 U Colorado Boulder Short Course on AAR• Now time for an ICOLD/SPANCOLD Review…..• New ICOLD Bulletin on Expanding Concrete in Dams


USBR’s Stewart Mountain Dam


Three US Dams


Three USBR examples of ASR where expansions have ceased after about 25 to 30 years

Stewart Mountain Dam


Repairs to crest and thrust block plus vertical anchors to maintain seismic stability

TVA’s Fontana Dam


Over 10 cmUS movement

since 1940

Over 7.5-cm VERTICAL expansion

since 1940

Spillway Gate Binding

Unit misalignmentproblems in Powerhouse

TVA Drilled Slots in 1970….


Shear stress and slot cut

ASSR movements have continued at a constant rate for nearly 50 years…

NB Power’s Mactaquac Project….


Dam crest rise of 10 cm

SW gate jamming

Powerhouse substructure crack, unit misalignment and discharge ring ovalling

ASSR strain rates of up to 145 μ-strain/a in most concrete structures for 30 years

Cracking in end pier of intake

Mactaquac Diamond Wire Saw Cutting 1988….


Mactaquac Diamond Wire Saw Cutting 1988….


Chambon Dam slot cutting + membrane


Chambon Dam slot cutting + membrane


Carpi membrane reduces uplift and improves stability

The membrane now 20 years old – is it slowing the reaction?

ICOLD Bulletin 79 on AAR 1991


ICOLD Bulletin 79 on AAR 1991


ICOLD Bulletin 79 & CSA identifies:

1.Alkali-Silica Reaction (ASR) – forms sodium silicate gels which leads to EXPANSION, CRACKING, EXUDATION OF GEL AND DETERIORATION OF STRUCTURE;2.Alkali-Silica-Silica te Reaction (ASSR) – “slow/late ASR”

a) if alkalis are in excess then a swelling gel is formed leading to EXPANSION, CRACKING, EXUDATION OF GEL AND DETERIORATION,

b) if lime is in excess a less expansive gel results in EXPANSION, CRACKING AND DETERIORATION OF STRUCTURE

3.Alkali-Carbonate Reaction (ACR) – forms brucite (Mg(OH)2 ) without an expansive gel but leads to WEAKENING OF BOND BETWEEN CEMENT PASTE AND AGGREGATES, MICROCRACKING

Acres database of over 100 International AAR Cases with significant damage - 1995


Acres’ database of AAR Cases – 1995 now at: http://www.hatchenergy.com/Company/Expertise/ExpHydroAAR/indcnt.htm


http://www.hatchenergy.com/Company/Expertise/ExpHydroAAR/indcnt.htm

2007It is time for an ICOLD review, since there has

been a significant number of additional cases and particularly to consider all

possible kinds of chemical reactions that may be causing expansion in dams.

There appear to be a number of cases where ASR or ACR does not explain behavior….


Granada ProgramThursday, October 188:30 a.m. –

10:30 a.m.

Session 1: Introduction and Objectives

10:50 a.m. –

12:30 p.m. Session 2: Chemical Reactions and Processes

1:30 p.m. –

3:50 pm Session 3: Case Histories 4:10 p.m. –

6:10 p.m.

Session 4: Numerical Modelling

Friday, October 19

8:30 p.m. -

10:30 p.m

Informal No-Host

Reception/Dinner 8:30 a.m. –

10:30 a.m.

Session 5: Remedial Actions & Prevention

11:00 a.m. –

12:30 p.m.

Session 6: Panel Discussion –

Lessons learned

1:30 p.m. –

3:30 p.m.

ICOLD/SPANCOLD Committee Meeting


Granada Workshop• There were a number of very interesting

cases reported from around the world• Presentations are on the web at:

http://www.dam-research.org/Granada-2007/index.html

• In some, small rates of what were considered ASR expansion were causing serious problems

• There were several cases of Internal Sulphate Attack reported

• Samples…



Workshop Panel Questions A - IMPORTANT REACTIONS:1. What are the important chemical reactions? Causes, interactions,

mechanisms, effects?2. Options for diagnosis and testing in new & existing structures?

B - CONTROL & MANAGEMENT:3. Effectiveness of control or management in affected structures? 4. Remaining or residual expansion strains and deterioration?

C - MODELLING & MONITORING:5. Can the available numerical models treat all the important reactions?6. Can existing models reliably forecast future behaviour of existing

structures?7. What instrumentation and testing for modelling and monitoring?

D - PREVENTION & REMEDIATION:8. Options for and efficacy of remediations in existing structures?9. Effectiveness of prevention in new structures?10. What are effective laboratory criteria for prevention by testing?11. How big can be an expansion can be tolerated for a mass concrete

element or structures? In terms of μstrains? Or Cracks openings?

E - RESEARCH & DEVELOPMENT:12. R & D needs including controlled prototype testing?13 March 2008 Robin Charlwood Presentation to RILEM ACS

Committee - Valencia 22

Panel Responses – Lessons LearnedA - IMPORTANT REACTIONS:1. What are the important chemical reactions? Causes, interactions,

mechanisms, effects?RESPONSES:1. The most important chemical reactions are alkali aggregate reactions

with siliceous aggregates, this affects up to 30% of dams in some countries.

2. A more minor reaction is of aggregates containing sulfide minerals (e.g. pyrite) which may oxidize to sulfate leading to internal sulfate attack. This is reported in a handful of cases.

3. Although massive deposits of ettringite have also been observed, these are a common feature of old concrete (especially when saturated) and degradation due to delayed ettringite formation is very unlikely as this occurs only when the temperature during hydration exceeds 70°C (on a conservative basis) and more realistically 80 or 90°C.

Q: To what extent can these various reactions co-exist? It appears that they can co-exist if the required minerals and alkalis are present, e.g. siliceous aggregates as well as pyrites could cause simultaneous ASR and ISA.

18/19 October 2007 Robin Charlwood & Juan Manuel Buil Sanz 23

Panel Responses – Lessons LearnedA - IMPORTANT REACTIONS:2. Options for diagnosis and testing in new & existing structures?RESPONSES:1. In the case of new structures, it is a matter of assessing materials and

mix combinations in advance, to ensure an absence of potentially expansive reactions.

2. Dams require long term tests well in advance of construction. 3. RILEM has published guidance on assessing aggregate combinations

for AAR potential and is now developing a practicable and universally reliable performance test; it will be important to ensure its applicability to dam structures.

4. RILEM is also preparing guidance on the diagnosis of AAR in existing structures, stressing the key value of experienced petrographic examination of suitable samples, which can also identify other deteriorative mechanisms.

5. Further guidance is also planned for the appraisal of affected structures, including tests to assess any residual potential for continued expansion; again it will be essential to ensure that the guidance makes allowance for the special circumstances of large concrete dams.


Panel Responses – Lessons LearnedB - CONTROL & MANAGEMENT:3. Effectiveness of control or management in affected structures? RESPONSES:1. At this time there is no known intervention method to curtail or stop the

expansive reactions within the concrete mass, either ASR, ACR or ISA.2. Lithium salts injection has been suggested in lab tests but it is not feasible to

get uniform distribution in large dams3. In some ASR cases the reactions have ceased after about 30 years. What

about ACR or ISA?4. Some dams have been waterproofed with upstream membranes. It is not yet

known if this will significantly reduce the expansive reactions.5. Chambon Dam has geo-membrane upstream for the top 60 m for 20 years

but there are still other moisture access paths available.6. San Esteban Dam also coated with geo-membrane Q: Long term (maybe 10 to 20 years?) observations may provide indications of

the effects of sealing but a carefully controlled prototype experiment is required to derive reliable results.


Panel Responses – Lessons LearnedB - CONTROL & MANAGEMENT:4. Remaining or residual expansion strains and deterioration?RESPONSES:1. Some reports indicate that structural problems may occur in dams with

expansions as low at 0.01% (0.1mm/m). 2. Such low levels of expansion are general regarded as below the threshold for

deleterious effects in most test methods and at this stage the signs of ASR in petrographic analysis may be difficult to detect.

3. Similarly many cases of expansion reported appeared to initiate after several decades and to be advancing at a linear rate with no sign of leveling off.

4. Total free alkali test results are likely to be quite variable because of the large aggregate size (some areas contain a lot of aggregate others less).

5. In terms of kinetics, there is considerable evidence that this follows the Arrhenius law (R=Ro exp(-Ea /RT))with increasing temperature and the activation energy seems to be fairly constant in reported studies, so extrapolation to lower temperatures should be fairly reliable.

Q: Can residual expansion can be measured on cores taken from the structure if care is taken to avoid leaching?In cases where expansion continues unabated, the alkalis may be being re- supplied from certain aggregates, eg. feldspars, and may continue indefinitely and in which case measuring residual expansion is a redundant issue.


Panel Responses – Lessons LearnedC - MODELLING & MONITORING:5. Can the available numerical models treat all the important reactions?RESPONSES:1. Most previous models were simply mechanical expansion models and if they

were calibrated based on deformations and stresses, then the type of reaction was not considered an issue.

2. Newer kinetic models include explicit relations regarding temperature and moisture. In theory these will require recalibration for each case of each reaction type.

3. It is possible that the extent of enhanced creep will vary depending on the damage effects of the particular reaction type

4. Similarly stress-dependency of the expansion may be related to the driving mechanism and therefore reaction type specific

Q: This topic requires further investigation.


Panel Responses – Lessons LearnedC - MODELLING & MONITORING:6. Can existing models reliably forecast future behaviour of existing structures?RESPONSES:1. Historically, “heuristic” models (such as GROW3D and CANT) developed in the 80’s

and 90’s have met a pressing need of industry.2. We are all indebted to the excellent experimental research program on AAR undertaken

in France by the LCPC (Larive, Multon, Toutlemonde) which cast the problematic of AAR into a formalism rooted in Chemistry, Thermodynamics, and Mechanics.

3. As a result of this work, there are a number of codes based on this model developed in France (LRPC/CESAR/Seignol, EdF/Grimal), and US (Colorado/Merlin/Saouma). However, these models are more complex, and certainly more accurate, than the current ones widely used in practice. They are being adopted in Europe and Japan.

4. Practically any Finite Element code has sufficient number of “parameters” which can be fine-tuned to give numerical results which appear to match experimental observations. Great care is required on calibrating the model before forecasting.

Q: We should design a test of uniqueness of calibration and reliability for forecasts. Maybe an ICOLD Numerical Methods Benchmark Topic where models are calibrated for an existing condition and future forecasts are compared?


Panel Responses – Lessons LearnedC - MODELLING & MONITORING:7. What instrumentation and testing for modelling and monitoring?RESPONSES:1. Mechanical models require “free” and “restrained” expansion rates as inputs.

Measurements of vertical expansion provide a reasonable approximation to “free” expansion.

2. Longitudinal strain rates on affected structures are required and are usually the most reliable inputs.

3. To determine expansion rates at least three years of high accuracy data are required to allow the trend to be filtered from the cyclic data.

4. Deformation data accuracy of about 1 με/year is required5. In-situ stress measurements are required to calibrate a model. Accuracy is

usually limited to about 0.7 MPa (100psi) but is sufficient.6. Offsets at cracks or construction joints are very valuable. Accuracy of about

0.5 mm/year is required.7. RH is not a reliable indicator of water supply for the reaction. Need alternative

measure of available moisture. Degree of saturation?Q: Need more info on stress dependency and anisotropy of expansion and

enhanced creep parameters 18/19 October 2007 Robin Charlwood & Juan Manuel Buil Sanz 29

Panel Responses – Lessons LearnedD - PREVENTION & REMEDIATION:8. Options for and efficacy of remediations in existing structures?RESPONSES:1. Options for remediation depend upon the impacts of the expansion on the

structure and associated equipment.2. In some cases continued monitoring suffices, whereas in other examples

some sort of protection, strengthening, or actions such as slot cutting to accommodate movement or partial replacement might be necessary.

3. Affected structures can usually be managed and AAR has rarely, only about 4 known cases, been the sole cause of actual failure.

4. In dams and related water-retaining construction, complete exclusion of water is not feasible and water-resistant coatings can sometimes cause new problems for concrete rather than having a beneficial effect.

5. RILEM is preparing guidance on appraisal and management of structures affected by AAR.

Q: Need to make sure RILEM guidance is relevant to large dams!


Panel Responses – Lessons LearnedD - PREVENTION & REMEDIATION:9. Effectiveness of prevention in new structures?RESPONSES:1. There is extensive knowledge about ASR and various forms of expansive

sulfate action (ISA) , so that prevention ought to be effective when materials and mixes have been adequately assessed in advance and these are then properly monitored during construction.

2. Carbonate aggregates need more research and RILEM is presently conducting a review; it is thought possible that, in at least many cases, expansion apparently associated with carbonate aggregates might be a special case of ASR. RILEM has established that many of the preventative measures that are usually effective at controlling conventional ASR are not similarly reliable in the case of expansion associated with carbonate aggregates.


Panel Responses – Lessons LearnedD - PREVENTION & REMEDIATION:10. What are effective laboratory criteria for prevention by testing?RESPONSES:1. RILEM has devised a scheme - AAR-0 - for assessing aggregate

combinations for AAR potential, including petrographic assessment, screening tests and dependable concrete expansion tests, with one version - AAR-4 - being capable of interpretation after just 3 or 4 months and therefore practically useful for projects.

2. Criteria have been tentatively suggested in AAR-0, but these might need to be reviewed in respect of large dams. RILEM has also drafted an international specification - AAR-7 - which assesses the level of precaution required on the basis of structure type and environment, with dams falling into the highest risk category, and then provides a menu of prevention measures.

Q: However, the current criteria in AAR-7 might need to be reconsidered for large dam structures.


Panel Responses – Lessons LearnedD - PREVENTION & REMEDIATION:11. How big can be an expansion can be tolerated for a mass concrete element

or structures? In terms of μstrain? or crack openings? or..?RESPONSES:1. Tolerable accumulated expansion depends on the dam configuration, size,

function (incl water access etc) and time frame (100 years +)2. Some recent cases in Switzerland with very wide mild curvature gravity

arches show serious issues with only 100 μstrain free expansion3.

In other cases the expansion is restrained expansion of much larger values of “free expansion”

can be accommodated


Panel Responses – Lessons LearnedE - RESEARCH & DEVELOPMENT:12. R & D needs including controlled prototype testing?RESPONSES:1. Understanding of slow expansion mechanisms with low alkali content (eg dam

with <1 kg/m3 free alkali and 20 – 50 μstrain/year!!)2. Clarification of potential interactions or co-existence of different expansion

reactions (ASR, ACR, ISA, DEF and ??)3. Techniques for estimating remaining expansion in existing dams4. Understanding of indefinitely continuing expansion mechanisms (alkali

“resupply” from aggregates etc)5. Material properties:

a) Clarify volumetric vs anisotropic expansion mechanismsb) Need creep parameters for expanding concretec) Need to know stress dependency of expansiond) Effects of global and local temperature fieldse) Dependency on water, RH, degree of saturation, …

6. Modeling reliability – test use of “calibrated” models for forecasts7. A large scale, very long term, prototype test of a sealed dam to examine

effectiveness of sealing which appears to be the only option.18/19 October 2007 Robin Charlwood & Juan Manuel Buil Sanz 34

Panel Responses – Lessons Learned

Workshop PPTs are at:http://www.dam-research.org/Granada-2007/index.html

hosted by Victor Saouma at University of Colorado in Boulder

Acres, now Hatch Energy, AAR cases database at:http://www.hatchenergy.com/Company/Expertise/ExpHydroAAR/indcnt.htm



http://www.hatchenergy.com/Company/Expertise/ExpHydroAAR/indcnt.htm

Proposed ICOLD Bulletin Contents1.

Nature and Extent of the Problem

2.

Chemical reaction causes, factors (at micro level)3.

Physical Effects and Factors for Each Reaction Type (at meso and macro level)

4.

Diagnosis5.

Mathematical modelling

6.

Management Options7.

Prevention

8.

Conclusions and Recommendations

• Appendices: • A –

A Model Investigation Program

• B -

Case Histories 18/19 October 2007 Robin Charlwood & Juan Manuel Buil Sanz 36

Thank you for your attention,and thanks as well as from my Grand-daughter Somer,

the future Geologist who has an opinion!


You civil engineers really should pay more attention to the

geology and mineralogy!

ICOLD• ICOLD: International Commission on Large Dams• Established 1928 in Paris by France, UK, USA, India• Presently 85 countries members• Congresses every 3 years, last in Barcelona in 2006, next in Brasilia 2009, then China in 2012..• Many technical committees, meet each year at least• Volunteer work• Main products are Bulletins –

Older ones available free

from ICOLD website

13 March 2008 38Robin Charlwood Presentation to RILEM ACS Committee - Valencia

ICOLD Committee on Concrete Dams• Previously Committee on Concrete for Dams• Charlwood Chairman since 1997• Currently 25 members (1 per country + Co-Opted)• Terms of reference:

• Alkali-Aggregate Reactions in Concrete Dams –

1991 –

Bertacchi, IT • Roller Compacted Concrete –

2003 –

Dunstan, UK• Specification and QC of Concrete for Dams –

2007 –

Berthelsen, NO• Physical Properties of Hardened Concrete –

2008 –

Berra, IT• Assessment of Materials for Concrete Dams –

2009 –

Pichler, AT• Expanding Concrete in Dams –

NEW –

Charlwood, US + Buil, ES• Waterstops

in Concrete Dams -

? –

Jia, CHINA• Sustainable Concrete Dam Construction -

? –

Jabarooti, IRAN• Decommissioning of Concrete Dams –

Options for Recycling -

?, IT• Technologies for Raising Dams -

? –

Rogers, US13 March 2008 39Robin Charlwood Presentation to

RILEM ACS Committee - Valencia

Documents

SPECIAL WORKSHOP “CHEMICAL EXPANSION OF …civil.colorado.edu/~saouma/AAR/Library/Granada-2007/Granada-2007/1... · Eric Bourdarot , EDF, CHAMBERY, France. ... Options for diagnosis