MSCA-COFUND-CLEAR-Doc-PhD Position#CD22-48: Multi-physical and chemical couplings in support of predicting sensitivity of concrete internal expansive reactions to environmental conditions – from lab tests to in-field structures damage

Alkali Aggregate Reaction (AAR) and Delayed Ettringite Formation (DEF) are both Internal Swelling Reactions (ISR) that can affect concrete. Though they imply different chemo-physical mechanisms, these reactions have similar macroscopic effects: they lead to concrete expansion, cracking and decrease of its mechanical properties; at the structure scale, they lead to uncontrolled displacements inducing serviceability problems and, in some cases, raise concern regarding structural integrity. In the field, ISR appear often after several years of service and develop over several years. Acting separated or combined, these reactions affect several hundred critical structures in France. To manage them, engineering tools considering a precise and quantified understanding of the mechanisms and their influencing parameters must be provided [1–3]. A number of these tools use accelerated laboratory tests as inputs to predict the field behavior of structures for many years.

These two reactions are highly influenced by exposure parameters such as temperature, presence of liquid water (incl. rainfall), moisture or chemical transfers (particularly alkalis) between the structures and the surrounding environment. These couplings are considered to accelerate the development of the reactions in the laboratory.

The objectives of this PhD project are to improve knowledge concerning the two following questions:

• What are the quantitative influences of environmental exposure conditions on the development of ISR? How can they be taken into account to predict the field expansion of concrete for many years, using accelerated laboratory test results?
• How representative are the accelerated laboratory tests (lasting some months) as compared to structures exposed to naturel ageing and subject to degradations lasting many years (sometimes many decades)? In particular, can we improve the accelerated laboratory tests and the corresponding prevention methodologies?

The PhD project will benefit of long-term research projects comparing accelerated laboratory tests and field exposure. Some of these projects are led in an international framework. The project will focus on environmental effects on the development of ISR expansions, without considering external loadings.

The PhD project will be carried out at Gustave Eiffel University, particularly within the MAST Department, that leads research in this area since more than two decades [3–10]. It will include secondment with Japanese partners involved in cooperation with Gustave Eiffel University since 2014. All results collected in these projects, complemented with the results of ongoing projects in the Department, will provide a complete database that will be analyzed to:

• Improve the understanding of the influence of temperature, humidity, liquid water or alkali transfers considered to be the most influencing parameters for these reactions. This will lead to a better knowledge of the relation between accelerated laboratory test results and the behavior of the field structures. For ongoing experimental programs, complementary physical and chemical investigations will be considered;
• Propose or improve coupling laws between ISR expansions and the above-mentioned parameters, with the final objective to improve modeling tools such as [2, 11] and help to predict field expansion using laboratory test results as inputs. These relations will be firstly implemented in simplified models (as proposed in [12]) to help performing parametric and sensitivity studies.

1. Fasseu P, Mahut B (2003) Aide à la gestion des ouvrages atteints de réactions de gonflement interne : Guide méthodologique. Laboratoire Central des Ponts et Chaussées - LCPC

2. Seignol J-F, Baghdadi N, Toutlemonde F (2009) A macroscopic chemo-mechanical model aimed at re-assessment of delayed-ettringite-formation affected concrete structures. In: 1st Int. Conf. on Computational Technologies in Concrete Structures (CTCS’09). Jeju, Korea, pp 422–440

3.Malbois M, Nedjar B, Lavaud S, Rospars C, Divet L, Torrenti J-M (2019) On DEF expansion modelling in concrete structures under variable hydric conditions. Construction and Building Materials 207:396–402. https://doi.org/10.1016/j.conbuildmat.2019.02.142

4. Larive C (1998) Apports combinés de l’expérimentation et de la modélisation à la compréhension de l’alcali-réaction et de ses effets mécaniques. Laboratoire Central des Ponts et Chaussées - LCPC

5. Multon S (2004) Evaluation expérimentale et théorique des effets mécaniques de l’alcali-réaction sur des structures modèles. Laboratoire Central des Ponts et Chaussées - LCPC

6. Brunetaud X (2005) Étude de l’influence de différents paramètres et de leurs interactions sur la cinétique de l’amplitude de la réaction sulfatique interne au béton

7.Baghdadi N (2008) Modélisation du couplage chimico-mécanique d’un béton atteint d’une réaction sulfatique interne. PhD dissertation, Ecole Nationale des Ponts et Chaussées

8. Martin R-P, Nedjar B, Toutlemonde F (2017) Eléments de calcul pour calage de cycles d’immersion – séchage, Rapport du contrat de recherche Ifsttar / EDF 3000-592002281. 45 p.

9.Al Shamaa M (2012) Étude du risque de développement d’une réaction sulfatique interne et de ses conséquences dans les bétons de structure des ouvrages nucléaires

10.Kchakech B (2015) Étude de l’influence de l’échauffement subi par un béton sur le risque d’expansions associées à la Réaction Sulfatique Interne. PhD dissertation, Université Paris Est

11.Nedjar B, Rospars C, Martin R-P, Toutlemonde F (2021) Benchmark Study Results: IFSTTAR. In: Saouma VE (ed) Diagnosis & Prognosis of AAR Affected Structures: State-of-the-Art Report of the RILEM Technical Committee 259-ISR. Springer International Publishing, Cham, pp 427–437

12.Kawabata Y, Yamada K, Ogawa S, Martin R-P, Sagawa Y, Seignol JF, Toutlemonde F (2016) Correlation between laboratory expansion and field expansion of concrete: Prediction based on modified concrete expansion test. In: 15th international conference on alkali aggregate reaction (ICAAR). Sao Paulo, Brazil, p 10