A new model for the analysis of the structural/mechanical performance of concrete structures affected by DEF – Case study of an existing viaduct

Abstract

A new model for the analysis of the structural/ mechanical performance of concrete structures affected by DEF -Case study of an existing viaduct Concrete construction is becoming increasingly complex and the importance of producing structures that are both cost effective and durable in the long term has never been higher. Therefore, an understanding of concrete durability is considered fundamental to determine the service life of new or existing structures. However, at present a significant number of existing concrete structures and bridges have already been deteriorated by a chemo-mechanical process known as Delayed Ettringite Formation (DEF). This phenomenon causes expansion of the affected concrete, generally leading to cracking and a decrease of its mechanical properties. The disease or deterioration mechanism therefore induces serious problems regarding serviceability, sustainable operation and structural integrity, which makes it necessary to apply predictive models able to re-assess the mechanical state of the affected structures. In this way, chemo-mechanical modelling must be performed considering the influence of humidity, stiffness reduction and stress in the development of expansion. The elaborated 3D model was applied to an existing viaduct affected by DEF. The displacements and stresses were computed based on the experimental data obtained from the in-situ measurements. The computed results highlight the relationship between the saturation degree and the expansion. Finally, comparisons between different calculations with and without considering the anisotropy of expansion and stiffness reduction are presented and discussed.

New Methods for Assessing External Sulfate Attack on Cement-Based Specimens

“…However, the visual macroscopic deformations suffered by the cement paste samples confirm the primary role of expansion in the degradation process (cracks appeared and propagated where the specimen deformed the most). It is notable that the observed deformation shape was consistent with the results of a calculation based on the model developed at Gustave Eiffel University, based on a thermodynamic approach to describe the formation of crystals inside porous mediums [42,43] to re-evaluate the structural damage caused by internal sulfate attack (ISA). Despite the fact that each type of sulfate attack has a specific physicochemical mechanism, Gustave Eiffel's model helped to predict qualitatively the deformation of the studied specimens subjected to ESA.…”

Effect of an Early-Age Exposure on the Degradation Mechanisms of Cement Paste under External Sulfate Attack

“…by the external environment [1][2][3][4][5][6][7]. Early-age exposure can also influence the mechanisms of internal reactions, such as the well-known alkali-aggregate reaction (AAR) and delayed ettringite formation (DEF) [8][9][10]. Two phenomena, the alkali's content of the concrete and the temperature reached during the concrete hardening and relative humidity, influence the extent of degradation at an early age.…”

Influence of Reinforcing Rebar on Expansion due to Delayed Ettringite Formation along the Bonding Length – Part I: The Role of Bond on Expansive Behavior of Concrete

“…Therefore, it is important to understand the mechanical responses of reinforced concrete (RC) structures affected by DEF expansion. Thus far, however, few studies have addressed these issues (Seignol et al 2009;Karthik et al 2016a;Metalssi et al 2016).…”