In such environments, concrete is subjected to processes of degradation whereby ion addition and exchange reactions occur, leading to breakdown of the matrix microstructure and weakening of the material

Preface
Concrete and cement-based materials are the most widely used building materials globally, finding application in such diverse situations as buildings of all kinds, civil engineering structures, water supply and drainage infrastructure, agro-industrial infrastructure, transport infrastructure, and so on. Concrete is economical and watertight, provides good mechanical strength, ensures good thermal inertia, and conforms to the health standards imposed by industry, making it a material of choice for many applications, as already indicated. However, many of the environments to which concrete is exposed are highly aggressive due to various chemical and/or biological components, and the demands being made on concrete to perform in such environments are likely to grow substantially in years to come as the built infrastructure expands and environmental pollution increases. These environments are often aqueous in nature, comprising natural environments such as soft waters, sea waters or ground waters, or man-made such as industrial environments, and treated water or wastewater and polluted environments.

In such environments, concrete is subjected to processes of degradation whereby ion addition and exchange reactions occur, leading to breakdown of the matrix microstructure and weakening of the material. Sometimes this can be extremely rapid and serious, such as in acidic environments, while in other cases degradation of the concrete matrix occurs over long periods, for example in mild or soft waters. However, in almost all cases, the scale of the problem is such that the consequences are severe. Concrete failure can adversely affect the well-being of human communities and disturb ecological balances. There are also large direct costs from the need to maintain and sometimes replace deteriorated infrastructure, and indirect costs linked with suspension of production or reduction in transport mobility during maintenance work, which place a great burden on society.

With these problems in mind, RILEM Technical Committee TC 211-PAE¹ was formed in 2005. Its aim was to address issues concerning performance of cement-based materials in aggressive aqueous environments, where the main form of degradation relates to hydrate alteration and transformation of mineralogy by ion exchange between the material and the environment, involving mass exchanges. One of the TC’s objectives was the consideration of the scientific nature of the problem. Another objective was to attempt to provide engineering approaches to addressing these problems in practice. The TC had the ambitious aim of seeking to furnish an understanding of concrete performance over a broad range of environments in terms of fundamental mechanisms and processes. It also sought to provide a generic framework for these processes, as well as guidelines for material selection and precautionary measures for adequate performance in aggressive environments. Construction and design standards were also recognized as important. The TC took a critical approach to existing standards, with a view to providing a framework within which improved standards and guidelines could be written. To a large degree, the work of the technical committee has addressed many of these aims.

This State-of-the-Art Report (STAR) is the compilation of the work of multiple authors who worked in groups to produce the requisite knowledge and information.

The focus of the TC’s work was on three main groups of aggressive waters:

• 
  Moderate to highly saline waters (other than marine waters), e.g. sulfate-bearing waters, magnesium-bearing waters.
  
• 
  Soft or acidic waters, e.g. pure natural waters, organic waters, drainage effluents such as sewers, acidic waters of various origins (inorganic and organic acids).
  
• 
  Marine waters (but with chloride ingress not being a major focus)
  

The TC considered actions on cement-based materials of these different aqueous environments. There was a lesser focus on highly aggressive industrial effluents. The approach was to recognise that all aqueous environments are aggressive to cement-based materials to a certain degree; therefore aqueous solutions should be considered as part of a continuum from pure (ion-free) waters to highly saline solutions, with intervening solutions of various salinities and ionic constituents. Indeed, some less saline solutions may be more aggressive than more highly saline solutions. In addition, the mobility of waters in regard to the attacked structures is important. While the scope of aggressive environments considered was fairly broad, certain deterioration aspects were specifically excluded from the work, such as rebar corrosion (extensively covered in other RILEM Technical Committees), alkali-aggregate reaction, and physical and cavitational damage.

RILEM TC 211-PAE met as a Committee for the first time in September 2005. Since then the committee has held several meetings, and organised two public events: an International Workshop in Ghent in September 2007², and a Final Conference in Toulouse in June 2009³. Both of these events yielded valuable Proceedings which have contributed to this STAR report. Numerous informal communications have, of course, also been held over the years between the members of the working groups.

The TC conducted its work by being organised into four Working Groups, each tackling a different aspect of the problem:

1. 
   Nature of degradation and deterioration mechanisms, including kinetics, for cement-based materials and different cementitious systems in aggressive aqueous environments, by considering the compositions of real environments.
   
2. 
   Modelling of deterioration, and Service Life Modelling, in such environments.
   
3. 
   Appropriate test methods to assess performance of cement-based materials in such environments, which can be used to characterise and rate relative performance as well as to inform long term predictions.
   
4. 
   Engineering implications and consequences of deterioration in aggressive aqueous environments, and engineering approaches to the problem.
   

Details of TC members are given at the end of this Preface. Members of the Working Groups are indicated in the following table. Each group comprised Contributing and Associate members, allowing coordination and cross-referencing between the various working groups. Other authors made contributions, and they are indicated in the relevant chapters.

Working group	Contributing members	Associate members
Nature of the problem: Characterisation and degradation aspects	Convenors: A. Bertron, F. Glasser J. Duchesne G. Escadeillas E. Menéndez M. Santhanam T. Matschei	K. Scrivener N. De Belie D. Hooton B. Lothenbach
Modeling	Convenor: E. Samson P. Le Bescop B. Lothenbach K. Snyder E. Guillon	F. Glasser
Test methods	Convenor: N. De Belie Bertron M. Castellote K. Scrivener D. Hooton M. Alexander M. Santhanam K. Van Tittelboom	P. Le Bescop C. Fourie
Engineering	Convenor: A. Chatterjee A. Goyns	M. Alexander C. Fourie

Each Working Group contributed a Part to the STAR report, which thus has four Parts. Parts I and III comprise multiple chapters, while Parts II and IV have one chapter each, giving a total of 16 chapters. The main contributing authors are acknowledged at the start of each chapter. Chapter drafts underwent a review process by other assigned members of the TC. These reviewers are also acknowledged in each chapter. The Part and Chapter titles are as follows:

Part I. Mechanisms of degradation of cementitious materials in aggressive aqueous environments

1. 
   General introduction to Part I
   
2. 
   Sulfate attack of concrete
   
3. 
   Magnesium attack of cementitious materials in marine environments
   
4. 
   Leaching of cementitious materials by pure water and strong acids (HCl and HNO₃)
   
5. 
   Ammonium nitrate attack on cementitious materials
   
6. 
   Attack of cementitious materials by organic acids in agricultural and agrofood effluents
   

Part II. Modeling degradation of cement-based materials in aggressive aqueous environments

7. 
   Modeling degradation of cement-based materials in aggressive aqueous environments
   

Part III. Methods for testing concrete degradation in aggressive aqueous environments

8. 
   General considerations
   
9. 
   Tests for leaching and degradation in soft or carbonated waters
   
10. 
    Test methods for resistance of concrete to sulfate attack – a critical review
    
11. 
    Testing for degradation by inorganic acids
    
12. 
    Bacteriogenic sulfuric acid attack of cementitious materials in sewage systems
    
13. 
    Test methods for chloride transport in concrete
    
14. 
    Test methods for magnesium attack
    
15. 
    Methods for testing cementitious materials exposed to organic acids
    

Part IV. Cement-based materials performance in aggressive aqueous environments – engineering perspectives

16. 
    Cement-based materials performance in aggressive aqueous environments – engineering perspectives
    

I wish to acknowledge with sincere gratitude the Convenors of the Working Groups for facilitating the work of their groups. I also wish to acknowledge the contributions of the members of the working groups. All these individuals have contributed large amounts of time and effort in drafting what is hoped will be a valuable addition to the literature in this area.

I wish most specifically to acknowledge the tremendous assistance and efforts of my co-editors: Dr Alexandra Bertron and Prof Nele De Belie. They have gone well beyond the call of duty in ensuring an excellent outcome to the STAR, besides acting as convenors of their own working groups. I am much obliged to them!
Prof Mark G Alexander (University of Cape Town, South Africa)

Chair of RILEM Technical Committee TC-211 PAE

Editors: M. G. Alexander (1), A. Bertron (2), N. De Belie (3)

(1) Department of Civil Engineering, University of Cape Town, Cape Town, South Africa

(2) Université de Toulouse; UPS-INSA; LMDC (Laboratoire Matériaux et Durabilité des Constructions); 135, avenue de Rangueil; F-31 077 Toulouse Cedex 04, France

(3) Magnel Laboratory for Concrete Research, Department of Structural Engineering, Ghent University, Technologiepark - Zwijnaarde 904, B-9052 Ghent, Belgium

RILEM TC 211-PAE Members

Prof Mark Alexander (Chair). Department of Civil Engineering, University of Cape Town, PO Rondebosch, 7701, South Africa. Email: Mark.Alexander@.uct.ac.za

Dr Eric Samson (Secretary). SIMCO Technologies Inc., 1400 Boul. du Parc Technologique, Suite 203, Québec (Qc), Canada, G1P 4R7. Email: [e-mail]

Dr Alexandra Bertron. Université de Toulouse, UPS-INSA, LMDC (Laboratoire Matériaux et Durabilité des Constructions), 135, Avenue de Rangueil, 31077 Toulouse Cedex 4 – France. Email: [e-mail]

Dr Marta Castellote. Instituto Eduardo Torroja, C/ Serrano Galvache, 4. 28033 Madrid, Spain.

Email: [e-mail]

Dr Anjan Chatterjee. Conmat Technologies Private Limited, CF 318, Sector 1, Salt Lake, Kolkata 700064, India. Email: [e-mail]; [e-mail]

Prof Nele De Belie. Magnel Laboratory for Concrete Research, Ghent University, Technologiepark Zwijnaarde 904, B-9052 Ghent, Belgium. Email: [e-mail]

Prof Josée Duchesne. Department of Geology and Geological Engineering, CRIB, Université Laval, Québec, Canada G1K 7P4. Email : [e-mail]

Prof Gilles Escadeillas, Université de Toulouse, UPS-INSA, LMDC (Laboratoire Matériaux et Durabilité des Constructions), 135, Avenue de Rangueil, 31077 Toulouse Cedex 4 – France. Email: [e-mail]

Prof Fred Glasser. University of Aberdeen, King's College, Engineering & Physical Sciences School, Chemistry, Aberdeen AB24 3UE, UK . Email: [e-mail]

Mr Alaster Goyns. PIPES Consultancy, PO Box 12519, Clubview, 0014, South Africa. Email: [e-mail]

Dr Emmanuel Guillon. Lafarge Centre de Recherches, 95 rue Montmurier, BP 15, F-38291 Saint-Quentin Fallavier, France. Email: [e-mail]

Prof Doug Hooton. Department of Civil Engineering, University of Toronto, 35 St George St, Toronto, Ont., Canada M5S 1A4. Email: [e-mail]

Dr Patrick Le Bescop. CEA, DEN, DPC, SECR, Laboratoire d’Etude du Comportement des Bétons et des Argiles, F-91191 Gif-sur-Yvette, France. Email: [e-mail]

Dr Barbara Lothenbach. EMPA, Ueberlandstrasse 129, CH-8600 Duebendorf, Switzerland

Email: [e-mail]

Dr Esperanza Menéndez. Instituto Eduardo Torroja, C/ Serrano Galvache, 4. 28033 Madrid, Spain. Email: [e-mail]

Dr Manu Santhanam. Department of Civil Engineering, IIT Madras, India.

Email: [e-mail]

Prof Karen Scrivener. Laboratory of Construction Materials, EPFL, CH-1015 Lausanne, Switzerland. Email: [e-mail]

Dr Kenneth A. Snyder. NIST, 100 Bureau Drive, Bldg 226, Gaithersburg, MD 20899-8615, USA. Email: [e-mail]

Student Member

Ms Kim Van Tittelboom. Magnel Laboratory for Concrete Research, Ghent University, Technologiepark Zwijnaarde 904, B-9052 Ghent, Belgium.

Email: [e-mail]

Corresponding member

Mr Clyde Fourie. 1 Yarrow Rd., Milnerton, 7441 Cape Town, South Africa.

Email: [e-mail]

Contributor

Dr Thomas Matschei. Research and Development (Holcim Group Support Ltd.), Holderbank,

Switzerland. Email: [e-mail]

(T. Matschei was an author in Part I but not formally a member of the TC.)

1 Performance of cement-based materials in aggressive aqueous environments

2 Proceedings of the RILEM TC 211-PAE Workshop, Ghent, September 2007. Ed. N De Belie

3 Proceedings of the RILEM TC 211-PAE Final Conference, Toulouse, June 2009.

(2 volumes, 598pp. ISBN 978-2-35158-071-4). Eds. M.G. Alexander & A. Bertron