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ASR : Risk assessment of concrete mixture designs with alkali-silica reactive (ASR) aggregates

Technical Committee


General Information

Chair: Prof. Jason H. IDEKER
Deputy Chair: Prof. Klaartje DE WEERDT
Activity starting in: 2020
Cluster D

Subject matter

The overall goal of the proposed TC is to develop a framework for risk assessment of mixture designs for concrete prone to alkali-silica reaction (ASR). This includes validating current test methods for aggregate reactivity, efficacy of SCMs and alkali balance in the concrete system.  The data from these validation efforts (WP 1 and WP 2) will inform a framework (WP 3) that is a starting point for the development of decision-making models. This framework would allow the user to enter known data about a particular aggregate-cementitious materials composition, concrete alkali content from various (external/internal) sources, the expected exposure environment, service-life needs and structural classification and to determine a pathway for mixture designs with reduced risk for deleterious ASR. 

Assessing aggregate reactivity alone is no longer particularly meaningful in the absence of considering the context of the entire concrete system.  The expansion behaviour by ASR can be different depending on aggregate character (rock type and its combination, size, alkali-absorbing/releasing properties, mix proportion), alkali inventory and age of the concrete. The framework should encompass the entire concrete system (WP1 – aggregate reactivity; WP2 – alkali inventory).

In addition, the framework should account for the environmental conditions to which the concrete is exposed. Hereto, the access to field stations with a large variety of climates is crucial (WP1). As the world is currently facing climate change, exposure conditions can change rapidly. In the long-term the framework should enable estimations of ASR expansion at various environmental conditions.

Preventive measures currently adopted are established based on accelerated laboratory conditions that do not consider any temperature/moisture cycling and bench-marked against numerous field experiences. Further validation of these preventive measures is needed, including a time scale and variation of effectiveness in different environments [1]. This will be included in the framework (WP3).  

The group assembled for this TC has a very strong tie to their respective national standards organizations (e.g. AASHTO, ASTM, ACI, CSA, JSA, CEN, FIB and others).  Many of these members are active participants and leaders in the organizations.  This ensures strong cross-collaboration between the groups and where possible sharing of knowledge and improvement to test methods and standards. 

 

  1. Rajabipour, F., Giannini, E., Dunant, C., Ideker, J.H., and Thomas, M.D.A., Alkali–silica reaction: Current understanding of the reaction mechanisms and the knowledge gaps. Cement and Concrete Research, 2015. 76: p. 130-146.

Terms of reference

The proposed work will fill the normal 5-year lifespan of a TC (see Table 1). Given the current COVID-19 situation it is proposed that a first meeting be held virtually in the Spring of 2021 and the second meeting will be held in Mexico commensurate with the RILEM week in the Fall of 2021.  The TC comprises 3 work packages (WP). It is proposed that WP 1 will take place in years 1-3, WP 2 will occur in years 1-4 and WP 3 will take place in years 3-5 of the proposed TC. A proposed list of 46 members with broad global representation (all interested, helped in proposal development and committed to the TC) is provided in Section 9.  Several Postdoctoral Scholars are included in this list.  We have recruited 5 (five) new members to this TC who are also new to RILEM.  We will be open and will invite other current RILEM members who have ongoing projects and/or expertise in ASR as well.  In this TC there will be literature-based research, new information coming from the various ongoing and/or new projects outlined in Section 10 as well as development of a framework to be the basis for a decision-making model.  No round-robin testing is anticipated as part of this TC. The industrial relevance for this TC will be in the form of validation/verification of existing RILEM test methods for ASR determination (reactivity) and prevention and particularly in the framework that will be developed.  This framework will establish a new protocol for selecting mixture designs that will be resistant to ASR that includes factors such as exposure, structural classification and lifespan of the concrete structures.  This is not currently done and is of great interest to the industry.

Detailed working programme

The goal of the proposed TC is to develop a framework for risk assessment of mixture design for concrete containing alkali silica-reactive aggregates.

Central in such a framework is the determination of the uncertainty of the selected accelerated performance-based test methods by comparing to field performance (WP1), as well as systemizing the impact of the different alkali sources on both reactivity and prevention (WP2).    

The  framework (WP3) would provide the user with a risk-assessment process relying on known information about a particular aggregate-cementitious materials composition, its expected exposure environment, service-life needs and structural classification (risk of ASR resulting in deleterious expansion) to determine a mixture design and risk levels associated with the potential for deleterious alkali-silica reaction.

Figure 1 gives a schematic overview of the work packages and how they are connected. The timeline for the TC is presented in Table 1. In the following sections the activities in the different work package are explained in further detail.

Figure 1 : Schematic overview of the work program of the TC

WP 1 Validation of Accelerated Laboratory Methods against Field Performance and Outputs Interpretation

Now that a mature suite of RILEM test methods exist (following the work of previous TCs) the user needs guidance on how to choose which RILEM method (s) is (are) appropriate for the project under consideration and how this interfaces with local/national guidance/standards/test methods.  Not only does a user need to know which methods to choose but what the implications of a result are from that test method and how test results from different methods should be interpreted.

An inventory of relevant existing field structures and exposure sites was compiled during TC 258-AAA. As the exposure sites are maturing, we are able to gain valuable information to further benchmark and refine our interpretation of accelerated test methods. Benchmarking will for example provide crucial information regarding the reliability of laboratory methods to predict preventive measures that have successfully and unsuccessfully prevented ASR in the field. This will include traditionally used SCMs such as fly ash, slag, silica fume as well as lightweight aggregates, natural pozzolans, ground glass and calcined clays. 

We will investigate and compare the reliability of accelerated test methods for the determination of the reactivity level of an aggregate, and efficacy of preventing effect of SCMs. It is known that the current available and recommended methods do not necessarily provide the same assessment of the alkali-reactivity potential of concrete aggregates or preventive effect of SCMs [2, 3]. When comparing the different test methods, we will focus on the uncertainty associated with the performance test methods as well as the time required for testing.

To further support the work in WP1 valuable information will provide from a series of projects as well as access to data from exposure sites. The involved Project Investigators are interested and committed to being involved in the proposed TC.

Table 2 : Projects that will provide input to WP1

 

Name

Country

Year

Participants

1

NCHRP 10-103 - Improving Guidance of AASHTO R 80/ASTM C 1778 for Alkali-Silica Reactivity (ASR) Potential and Mitigation

USA

Started 9/2019

Thano Drimalas (PI), Kevin Folliard, Benoit Fournier, Jason H. Ideker, Michael D.A. Thomas

2

PARTNER - Project Results from the post-documentation program

EU

 

 

3

ASR KPN – COIN "linking performance testing to field"

Norway

 

Lindgård, Rønning, Wigum

4

LNEC-cube study initiated under Norwegian R&D project “ASR - Reliable concept for performance testing” (KPN-ASR) and RILEM TC-258-AAA activities

Portugal Norway

 

 

5

AKR Performance - Linking Field Performance and RILEM AAR-2 and RILEM AAR-3

Austria

 

Stefan Krispel Smart Minerals GmbH, TU Wien

6

RADCON International V4-Korea Joint Research Program “The effect of chemical composition of concrete on its long-term performance in irradiated environment” (including radiation induced ASR)

Korea

Poland

 

Glinicki – IPPT PAN

7

Existing exposure sites that members have access to for long term data:
Custódio (Vila Real, Portugal), Ideker (Corvallis, OR, USA), Thomas (Fredericton, NB, Canada, BRE, UK), Drimalas and Folliard (Austin and Port Aransas, Texas), Hooton (U. Toronto, Picton, Kingston, Canada), Fournier (U. Laval, CANMET), Silva and Custódio (LNEC), Borchers, Lindgård, and Fournier (PARTNER Project), Lindgård (SINTEF), Yamada and Kawabata (Japan), Wigum (Iceland), Ferreira (Finland, VTT)

Deliverable:  A report on the comparison of the reliability of a selection of performance test methods with regard to aggregate reactivity and preventive impact of SCMs will be produced. The report will contain formal recommendations to AAR-0 and revisions to and/or new test methods will be made. The report will be included as a chapter in the overall STAR produced from this TC.

WP 2 Alkali Inventory in Concrete and Impact on Reactivity and Prevention

Essential work was started in TC258-AAA to develop a test method (RILEM AAR-8) to assess alkali release by aggregates.  The test method was developed and a round robin study was completed.  Now, it is important to determine the implication of the results from this test method in concert with the total alkali inventory from the concrete (alkalis from cement, SCMs, aggregates, chemical admixtures, potential for external sources) and the important role of alkali threshold needed to initiate ASR which varies based on aggregate mineralogy/reactivity.  To accomplish WP 2 the following tasks are envisioned:

Task 1:  Assessing the implication and interpretation of results from the test method RILEM AAR-8 (2020) Determination of Potential Releasable Alkalis by Aggregates in Concrete. The remaining question from RILEM AAR-8 is “how does the user interpret the results of the test?” This links in part to WP 1 in terms of the reliability and selection of the proper accelerated test method (s). We will look into the impact of releasable alkalis from both reactive and non-reactive aggregates [4].

Task 2:  Determining the threshold alkali content for specific aggregate types to initiate reaction. We will be looking into a standard test method to assess this e.g. RILEM AAR-10 and/or AASHTO T380 Miniature Concrete Prism Test, at different alkali contents (pH in the range 13 to 13.7). Mortar bar tests should not be used. We will contribute to build a database of alkali thresholds for different aggregate mineralogy.

Task 3:  Quantifying and determining the impact of SCMs on the alkali inventory with a focus on fly ash, slag, natural pozzolans, calcined clays and ground glass, by focusing on pore solution data from existing and new studies on concrete, mortar and paste [5, 6]. Experimental data will be combined with thermodynamic modelling (GEMS).  

Task 4:  Assessing the significance of external sources of alkalis (potential modification to RILEM AAR-12) such as de-icing salts used on road pavements or de-icers used on airport pavements.

To further support this work several projects can provide valuable information to WP2 and those Project Investigators are interested and committed to being involved in the proposed TC.

Table 3 : Projects that will provide input to WP2

 

Name

Country

Year

Participants

1

NCHRP 10-103 - Improving Guidance of AASHTO R 80/ASTM C 1778 for Alkali-Silica Reactivity (ASR) Potential and Mitigation

USA

Started 9/2019

Thano Drimalas (PI), Kevin Folliard, Benoit Fournier, Jason H. Ideker, Michael D.A. Thomas

2

Synergia - Role of aluminium release by SCM on aggregate dissolution

Switzer-
land

 

Leemann, Scrivener

3

ARA - Verification of alkali release from aggregates, Pre-project

Norway

2020

De Weerdt, Rønning, Wigum and Lindgård

4

NEWSCEM - impact of new SCMs on ASR

Norway

2018-2023

Wigum, De Weerdt, Lindgård, Rønning, Hemstad

5

Ground glass and ASR

Canada

2020

Fournier

6

Champlain Bridge Deconstruction Program (Montreal, Canada); alkali profiling assessments in various (exposed / un-exposed) elements of an existing structure affected by ASR

Canada

2020-

Fournier

7

Alkali-release of 40 German aggregates and their impact on concrete performance (also with Ottersbo aggregate from Norway to link our results to the LNEC cube study)

Germany

 

Borchers

8

Influence of different extents of ASR-damage on freeze-thaw-resistance of concrete

Germany

 

Borchers

9

Implementation of ASR performance testing with external alkalis for highly-trafficked concrete pavements in Poland with collaboration of GDDKiA

Poland

 

Glinicki – IPPT PAN

Deliverable:  A report summarizing findings from literature and ongoing projects related to alkali threshold, impact of SCMs on the alkali inventory and external alkali will be produced. The report will in addition contain formal recommendations for the interpretation of the results from RILEM AAR-8. The report will be included as a chapter in the overall STAR produced from this TC.

WP 3 Framework for Risk Assessment of Mixture Designs Incorporating Alkali-silica Reactive Aggregates

In this Work Package the information developed in WP 1 and WP 2 will directly feed the development of a framework for risk assessment of mixture design for concrete containing alkali-silica reactive aggregates. The framework will link the following parameters:

  • The uncertainty from different AAR test methods (RILEM, ASTM, CSA, JSA, etc.) and impact of minor differences between the test methods (WP 1)
  • The level of aggregate reactivity (WP 1)
  • The chemical composition of the binder and the alkali inventory of the concrete (WP2)
  • Role of environment in the expected field conditions of the structure to be built, with a particular focus on temperature and moisture (rainfall and/or RH) (take from WP1, and TC 258-AAA STAR)
  • Structural classification (adapt from ASTM C1778, AASHTO R80) and service life

The development of the framework can encompass:

  • Treatment of large data sets, data mining, and deep learning which may attract new RILEM members.
  • Material/Structural modelling approach for more explicit risk assessment [7]

During the development of the framework we will coordinate with the TC led by Menéndez Méndez for data from that TC which may be useful in refining the framework.

In the long term, the framework could provide a base for probabilistic risk assessment of the influence of climate change on ASR expansion, by combining numerical modelling and climate data (optimistic/pessimistic scenario available from IPCC).

Projects that can support WP3 and in which proposed TC members are involved are reported in the table below.

Table 4 : Projects that will provide input to WP3

 

Name

Country

Year

Participants

1

Modelling of environmental conditions in terms of ASR expansion

Japan

 

Kawabata

2

Existing unpublished data triaxial anisotropic restraint

 

 

Dunant

3

Multi-phase, multi-species modelling of ASR and electrochemical treatment for ASR affected concrete - A National Natural Science Foundation of China (NSFC) Project

China

2020-2024

Liu

4

Towards improved assessment of safety performance for LTO of nuclear civil engineering structures - EU ACES, H2020/EURATOM

EU

2020

Miguel Ferreira and Jabbour

5

Micromechanical modelling of expansion with 3-dimensional discrete model

France Japan

 

Multon, Miura (Nagoya Univ.), and Kawabata

6

Modelling of environmental conditions for linking laboratory and field expansions

Japan

2021-

Kawabata, Yamada, Sagawa (Kyushu Univ.)

Deliverable:  A report and set of flow charts presenting the framework for performing risk assessment of mixture design comprising the key parameters from WP1 and WP2. The report will be included as a chapter in the overall STAR produced from this TC.

Final TC Deliverable:  A STAR that incorporates Work Packages 1-3 culminating in the development of the framework for risk assessment of mixture designs.  Further, formal recommendations on revisions RILEM AAR-0 and AAR-8, and potentially other RILEM AAR test methods will be provided.

 

  1. Thomas, M.D.A., Fournier, B., and Folliard, K.J., Alkali-aggregate reactivity (AAR) facts book. 2013, Federal Highway Admininstration (FHWA), US Department of Transportation. p. 212.
  2. Golmakani, F. and Hooton, R.D., Impact of pore solution concentration on the accelerated mortar bar alkali-silica reactivity test. Cement and Concrete Research, 2019. 121: p. 72-80.
  3. Einarsdottir, S.E and Hooton, R.D., Factors Affecting the Alkali Release from Concrete Aggregates. in Proceedings, 16th International Conference on Alkali-Aggregate Reaction, . 2021. LIsbon, Portugal.
  4. Vollpracht, A., Lothenbach, B., Snellings, R., and Haufe, J., The pore solution of blended cements: a review. Materials and Structures, 2016. 49(8): p. 3341-3367.
  5. Fily-Paré, I., To Be Published: Behaviour of concrete incorporating Ground Glass (GG) and alkali reactive aggregates, in Département de géologie et de génie géologique. 2020, Université Laval: Québec, Canada.
  6. Liu, Q.-f., Shen, X., Jiang, W.-Q., Xia, J., Hou, D., Hu, Z., and Li-Xuan, M. Coupled Deterioration Mechanisms under Various Degradation Processes. 2020 [cited 2020 08/09/2020]; Available from: https://www.researchgate.net/project/Coupled-Deterioration-Mechanisms-under-Various-Degradation-Processes.

 

Technical environment

This proposed TC builds directly from four previous TCs including: 

  • TC-106 (1988-2001): focused on petrographic examination and accelerated test method development, AAR-2 and AAR-3;
  • TC 191-ARP (2001-2006): focused on accelerated test methods (AAR-4), specialized procedures for ACR, and broadening international consistency in diagnosis (AAR-6), specifications (AAR-7) and alkali release (AAR-8);
  • TC 219-ACS (2006-2014): focused on the entire concrete mixture, assessment of the binder impacts on AAR (performance testing); in this TC overall recommendations were first provided as AAR-0, and AAR-1 to AAR-5 were published; other new test methods were proposed and significant work was made in publishing a petrographic atlas
  • TC 258-AAA (2014-2020): comprised of four work packages including WP1 - performance testing, WP2 - link between performance testing and field experience, WP3 - detailed alkali inventory including alkali release from aggregates and WP4 - Verification of alkalis released from aggregates. [8]

This proposal was developed from an exploratory team formed from TC 258-AAA TC meeting in Delft, NL, December 2019 Chaired by Michael Thomas and including team members:  Børge Wigum, Klaartje De Weerdt, Terje Rønning, Jan Lindgård, Renaud-Pierre Martin, Ian Sims, Kazuo Yamada, Yuichiro Kawabata, Stephan Krispel, Benoit Fournier and Jason Ideker.  After a draft proposal was developed by the exploratory team it was then reviewed by the entire TC 258-AAA as well as the newly recruited members.  This TC has a very strong link to previous TCs particularly the link to development of RILEM AAR methods. We are aware of the joint proposal with Esperanza Menéndez Méndez and Leandro Sanchez and we will work together to coordinate the TCs and make sure there is no overlap.  To make the organization clear this TC will oversee all current RILEM AAR Methods including AAR-0.  For any new test methods developed by the TC led by Esperanza Menéndez Méndez and Leandro Sanchez we will work with them to incorporate interpretation of those new methods into AAR-0 and this TC will approve those changes through standard RILEM voting procedures.

This newly proposed TC is also linked to standardization efforts at ASTM, CSA, ACI AASHTO, JSA, CEN, FIB.  The proposed Chair of the TC and many members are active and in leadership positions in many of these organizations so that influential change already has been and will continue to be made through the shared involvement in RILEM.

 

  1. Wigum, B.J., Lindgård, J., Sims, I., and Nixon, P., Rilem activities on alkali–silica reactions: from 1988–2019. Proceedings of the Institution of Civil Engineers - Construction Materials, 2016. 169(4): p. 233-236.

Expected achievements

Deliverables from this TC will include: 

  1. State-of-the-art-Report will include:
    • Chapter (s) from each of the Work Packages outlined in Section 4.
    • Recommendations about interpretation of RILEM test methods and proposed changes (if merited) to RILEM AAR-0.
    • Recommendations for the interpretation of results from RILEM AAR-8.
    • Other recommendations may be made for modifications to the various RILEM AAR methods based on the outcomes particularly of WP 1 in this TC.
    • A framework for risk-assessment of mixture design for concrete with alkali-silica reactive aggregates.
  2. A condensed version of the most relevant results and recommendations will be published as (a) paper(s) to be submitted to Materials and Structures to reach a larger audience.

Group of users

The outcomes of the TC will be of particular benefit to:

  • WP 1, 2 and 3: academics, testing laboratories (academic, industrial and government), practitioners and Ph.D. students
  • WP 3: Industrial sector, government agencies, private industry, standards/code/specification organizations

Specific use of the results

The results from this TC will be used to improve related concrete standards and specifications (WP 1 and 2) and to ensure new concrete is highly resistant to ASR (WP 3); the results from WP 3 may also ultimately inform a new way to design concrete mixtures to be ASR resistant and this may ultimately be placed into standards/codes/specifications. Assessment of the significance of external sources of alkalis will provide tools for competitive concrete solutions for pavements, bridge decks and two-layered road pavements of increased durability. Such a development is very much desired by drivers plagued by notorious road work and traffic delay. The deliverables will also strengthen environmentally conscious concrete technology by supporting durable concrete mixture design approaches and providing tools for more effective selection of aggregates and binders for concrete. The impact of climate change on future performance will also be included.

The work of this TC will help to provide wider adoption of RILEM Test Methods and specifications globally. It also ensures that the international community is moving forward with as close as possible “similar” approach to AAR detection and prevention. For countries where overseas technical experts are sought (e.g. New Zealand) the benefit of RILEM test methods and supporting guidelines are particularly useful because they clearly identify aspects we need to consider in the local context when deciding on a test regime and interpreting test results.  It helps them to avoid commercial interests and remove bias from their testing approaches. This benefit will continue to be experienced by countries that may not have extensive AAR background at the national/local level. 

The proposed Chair of the TC, Jason Ideker is leading, along with members of TC 258-AAA and other international researchers, an effort to establish a website where all of the International Conference on Alkali Aggregate Reactions in Concrete Proceedings can be searched and downloaded for free (https://icaarconcrete.org/).  This will significantly broaden the access and dissemination of knowledge related to AAR. The benefits of this and the tie that this community has to the International Conference on Alkali Aggregate Reactions cannot be underestimated.  Perhaps no other premature concrete deterioration mechanism is represented by such a large community that can readily share data because so much of the laboratory and field testing/evaluation we do is based on a common set of test methods and standards.