258-AAA : Avoiding alkali aggregate reactions in concrete - Performance based concept

Technical Committee 258-AAA

General Information

Chair: Prof. Børge Johannes WIGUM
Deputy Chair: Dr. Jan LINDGÅRD
Activity starting in: 2014

Subject Matter

The purpose of this proposed Technical Committee (TC) is to develop and promote a performance based testing concept for the prevention of deleterious Alkali Aggregate Reactions (AAR) in concrete. Strong emphasis will be put on the implementation of the RILEM methods and recommendations as national- and international standards.

Avoidance of AAR in future structures is of great importance, and the ways to achieve this will be covered by the work programme proposed by this TC. Development of performance test methods to examine the potential alkali reactivity of particular concrete mixes to be used in a project has already been focused on in the work programme of a previous TC, i.e. TC219-ACS. In the work programme of TC 219-ACS, it was taken into account the mitigating effect of supplementary materials such as fly ash or slag etc., or the specification of low alkali levels in the mix. By using such mitigation measures, a much wider selection of aggregates can be used safely while increasing the sustainability of the concrete and aggregate industry. Although such draft performance tests have been under preparation, there is still a necessity to finalize and validate these test methods by international inter-laboratory trials and correlate the performance test results with field exposure sites. Performance testing of special types of concrete (e.g. containing lightweight or recycled aggregates, fibres etc) also needs to be studied further. As soon as the necessary validation is finished, it is the intention to publish these methods as RILEM Recommendations.

An important additional tool in validation of the performance testing concept is to make an assessment of the link between the accelerated results from the laboratory and behaviour of these concrete mixtures in real field structures. Tins will be carried out by compiling the main findings from exposure sites worldwide, preparing an overview of "lab-field correlation" from exposure sites and real concrete structures in services. The objective is to establish a link between outdoor exposure sites dedicated to AAR investigations and located in different parts of the world, in order to generate an international database on the effect of environmental conditions on the kinetics of AAR. Ultimately, this will allow the development of new specifications for reducing the risk of deleterious expansion and cracking development in concrete structures due to ASR in different environments.

One of the important "missing links" in the international AAR research is how to measure the amount of potential alkalis to be released from various types of aggregates in the laboratory, under accelerated conditions. It is also of important to evaluate the potential alkali recycling which in some instances have been reported. This is of particular importance for massive structures having long-service life, e.g. dams, where the contribution of alkalis from aggregates is believed to produce damaging AAR despite the fact that the concrete has been designed to meet current specifications for avoidance of AAR. Various test methods have already been proposed, and it is the intention in this proposed TC to finalise and validate a test method for alkalis released by aggregates, while compiling results from exposure sites and concrete structures worldwide in order to assess the "true" levelof alkali released from various aggregates. As soon as the necessary validation is finished, it is the intention to publish this method as a RILEM Recommendation.

It is well known that synergistic reactions such as freezing and thawing and delayed ettringite formation (DEF) can exacerbate the effects of AAR and can complicate its diagnosis and management. It is however not the intention in this proposed TC to include these issues.

Terms of reference

The proposed TC will work for the full 5 years of its allowed life, based upon the nature of the performance tests. Much of th eground work for these performance tests has been carried out by the previous TC 219-ACS, in the form of draft test methods and State-of-the-Art Reports. However, due to the nature of AAR, being a slow reaction, it is necessary to validate these performance test results with exposure site measurements which necessitate the full 5 year term to reach reliable correlations.

The objective of finalizing and validating the performance testing concepts to avoid AAR in future structures will be achieved by organised international inter-laboratory trials and round-robin testing. This will make use of the wide body of expertiseavailable through the participating members and their entities. 

The main objective of estimating the alkali release from aggregates is to achieve an assessment of the total (reactive) alkali content in concrete. A proposed RILEM AAR-8 test method is considering different test parameters of measurement. It is necessary to investigate and obtain more experience with a common method that takes into account different parameters like, different temperatures, size of aggregate particles, extraction solution, etc. The analysis of different aggregates could give information about the more realistic test method to estimate the potential contribution of alkalis in the field concrete. It is necessary to carry out a round robin test to analysis the possible dispersion of the method and the accuracy of the results. For the round robin test it is necessary about two years for selection of different types of aggregate, test them and analyses the results to extract conclusions. Finally, the validated test methods that reliably estimate the total alkali content of concrete will be published as a RILEM recommendation.

Main of the members will be invited from TC 219-ACS on AAR, though new members are encouraged and will be welcome.The TC is aiming to have a wide international membership which helps to promote the eventual international use of RILEM methods and recommendations. Thus, much communication will be by e-mail and making use of web-site solutions. However, physical meetings will still be the centre of its activities and wherever possible these will be co-ordinated with major relevant international conferences to facilitate attendance. Meetings will also be arranged in locations where laboratories are carrying out performance testing and/or have established outdoor exposure sites. The TC will also apply new ways of electronic communication during the meetings, enabling participation of members without physically being at the venue of the meeting.

Detailed working programme

WP1: Performance testing; Accelerated testing in laboratory.

Proposed task group leader; Dr. Terje F. Rønning, Heidelberg Cement Northern Europe, Oslo, Norway.

Milestones

Deliverables

Expected delivery (end of)

Procedures for boosting of alkalis.

 

Report

2016

Validate preferred test(s) by international inter-laboratory trials and by field exposure sites.

Report

2017

Evaluate the proposed performance test for predicting the effectiveness of AAR inhibitors (e.g. pozzolans, slags, chemical admixtures etc.).

Report

2018

Evaluate the effect of 'lower carbon" Portland cement on AAR & AAR testing.

Report

2018

Evaluate performance testing of special concretes (e.g. containing lightweight or recycled aggregates, fibres etc).

Report

2018

Finalize and validate performance test methods for potential alkali reactivity of various concrete mixes.

Application document.

Publish methods as RILEM Recommendations. 

2019

 

WP2: Performance testing; Laboratory vs. field; Exposure site.

Proposed task group leader; Professor Benoît Fournier, Geology and geological engineering Department, University Laval Quebec. Canada.

Milestones

Deliverables

Expected delivery (end of)

Establish links between existing exposure sites (databases) - add specimens with common aggregates (North America ↔ Europe)

Report

2015

Prepare an overview of correlation between performance testing in the laboratory and field performance in concrete structures under outdoor exposure conditions (input to WP1) → develop recommendations to improve reliability of performance testing in the laboratory

Report

2015

Prepare an overview of main findings from AAR-dedicated outdoor exposure sites worldwide (input to WP1) → appraisal of the effects of environmental conditions on expansion due to AAR.

- Evaluating potential reactivity of concrete aggregates

- Evaluating the long-term efficacy of supplementary cementing materials to prevent deleterious expansion due to AAR

Report

2016

Make recommendations for changes in existing specifications that consider environmental conditions (temperature, relative humidity)

Application document.

Publish methods as RILEM Recommendations.

2019

 

WP3: Performance testing; Assessment of detailed alkali household in concrete, including internal aggregate release,recycling and external supply.

Task group leader; Dr. Esperanza Menéndez Méndez, Institute of Construction Science, "Eduardo Torroja" (CSIC), Madrid,Spain.

Milestones

Deliverables

Expected delivery (end of)

Initiate and organize an international survey of international exposure sites and alkali release from aggregates.

Report

2015

Collect the bibliography results of releasable alkalis from the aggregates and the potential contribution to the quantity of alkalis in the field concrete.

STAR report

2016

Make a round robin test with different representatives' aggregates of alkali composition, reaction ratio and mineralogy. Analyses of the different parameters of test in relation with the classes of aggregates. Define the best relation between results and the number and conditions of test.

Report

2017

Comparison between the laboratory tests and the field concrete experience.

Report

2018

Characterization of potential alkali-releasing common constituent minerals in concrete aggregate, e.g. feldspars, micas and clay minerals, their potential release capacity in kg/m³, and the prerequisite exposure conditions, mineral qualities or properties promoting such release.

Report

2018

Validate a test method for alkalis released by aggregates. It is necessary analyse the influence of different parameters of test in the results of the alkali release with different type of aggregates and related them with real behaviour of similar aggregates. For this proposal it is necessary to analyse the influence of temperature, size of particles, extraction solutions, and time to test, liquid: solid ratio, agitation, etc. Also, it is necessary to analyse the behaviour of aggregates with different mineralogy and quantity of alkalis and with slow, medium and high reaction ratio.

Application document.

Publish methods as RILEM Recommendations.

2019

Technical environment

In previous TCs, a comprehensive set of test methods and specifications for avoidance of damaging AAR in normal concrete structures has been developed and published as RILEM Recommendations and guidance on diagnosis and management of structures published as RILEM reports. Work on performance tests and tests for alkali release from aggregates has been started but needs to be completed.

In addition, particular attention is given within Canadian Standards Association and ASTM to link field performance evaluation and development of reliable performance test methods for establishing efficient long-term preventive measures against AAR in new concrete constructions. The collaboration between North American researchers and practitioners involved in the above standards committees and the other international members of tiiis new TC, e.g. with CEN, will enable the development of the specifications to construct infrastructures rick-free of AAR.

Expected achievements

The expected deliverables will be RILEM Recommendations and Reports as set out in (4). The intention will be initially to publish these test methods and guidance as RILEM Recommendations in Materials and Structures and as RILEM Reports. Additionally, periodic specialised seminars will be held, where particularly students and young researchers will be encouraged to present their work for common discussion.

It is possible, and even likely, that these methods and guidance will be adopted by international Standards bodies such as CEN.

Collaboration and participation in specialized congresses directly related with the AAR, like ICAAR. Attend special sessions on concrete durability congress to spread the works of the TC.

Group of users

The target audience will be the industry, practising engineers and researchers from testing laboratories and national- and international regulatory bodies. The wide membership of the previous TC 219-ACS, which will be maintained in the new TC means that it has important liaisons with bodies such as CEN, ASTM, ICOLD and the organising committee of the series of international conferences on AAR, ICAAR. The work activities presented in this application has particularly been supported by Robin Charlwood; Chairman of ICOLD; Committee on Concrete Dams.

Specific use of the results

The results will be used to improve the specification of concrete to ensure more durable and sustainable structures and to improve the management of existing structures to maximise their economic life. Some countries have already adopted the RILEM Test methods and Specifications and a specific objective of the new TC will be to encourage the wider adoption bynational standard bodies for use in tiieir country or region.

Active Members

  • Prof. Mark G. ALEXANDER
  • Mr. Ricardo antonio BARBOSA
  • Mr. Anthony F. BENTIVEGNA
  • Mr. Mario BERRA
  • Dr. Violeta BOKAN-BOSILJKOV
  • Ingmar BORCHERS
  • Dr. Maarten BROEKMANS
  • Dr. Rene BRUECKNER
  • Dr. Oguzhan COPUROGLU
  • Dr. João CUSTÓDIO
  • Dr. Mario DE ROOIJ
  • Prof. Klaartje DE WEERDT
  • Prof. Josée DUCHESNE
  • Dr. Rui Miguel FERREIRA
  • Prof. Benoît FOURNIER
  • Dr. Sue FREITAG
  • Prof. Mette GEIKER
  • Dr. Eric GIANNINI
  • Dr. Colin GIEBSON
  • Prof. Dr. Michal A. GLINICKI
  • Bent GRELK
  • Prof. R. Doug HOOTON
  • Assoc. Professor Jason H. IDEKER
  • Dr. Yuichiro KAWABATA
  • Prof. Kurt KIELSGAARD HANSEN
  • Dr. Stefan KRISPEL
  • Prof. Dr. Selmo C. KUPERMAN
  • Dr. Andreas LEEMANN
  • Lech LEWCZUK
  • Dr. Jan LINDGÅRD
  • Prof. Tung Chai LING
  • Dr. Qing-Feng LIU
  • Dr. Renaud-Pierre MARTIN
  • Dr. Esperanza MENENDEZ MENDEZ
  • Dr. Birgit MENG
  • Dr. Oliver MIELICH
  • Dr Urs MÜLLER
  • Dr. Christoph MÜLLER
  • Prof. Cecilia OLAGUE
  • Dr. Bård M. PEDERSEN
  • Dr. Gilles PLUSQUELLEC
  • Dr Terje F. ROENNING
  • Prof. Leandro SANCHEZ
  • Dr. Antonio SANTOS SILVA
  • Prof. Victor E. SAOUMA
  • Dr. Cyrille SAUVAGET
  • Dr. Ignacio SEGURA
  • Mrs Katrin SEYFARTH
  • Dr. Zhenguo SHI
  • Dr. Ian SIMS
  • Prof. Gintautas SKRIPKIUNAS
  • Dr. Suvimol SUJJAVANICH
  • Prof. Michael D. A. THOMAS
  • Dr. Frank WEISE
  • Prof. Børge Johannes WIGUM
  • Dr. Jonathan WOOD
  • Dr. Kazuo YAMADA