Effectiveness of Nondestructive Methods for the Evaluation of Structures Affected by Internal Swelling Reactions: A Review of Electric, Seismic and Acoustic Methods Based on Laboratory and Site Experiences

Abstract

Internal swelling reactions (ISR) (which mainly comprise alkali‐silica reaction, alkali‐carbonate reaction, delayed ettringite formation, etc) are damage processes that affect the long‐term durability of concrete structures. The reactions are apparently characterized by series of closely spaced, tight map cracks with wide cracks appearing at regular intervals, and excessive tensile stresses in rebars. These phenomena are alarming for affected structure managers as they deal with people safety and structures operation. Moreover, there is no easily implemented way to stop the reactions. Prediction of concrete expansion, structural degradation, and assessment of efficiency and periodicity of repair works are crucial issues. The aim of this work is to explore the applicability of some nondestructive techniques (NDT) of investigations (electric, seismic, and acoustic methods) to differentiate the structure zones affected or not by the ISR for different exposure conditions. The collected experience highlights that the coupling between some of those nondestructive (ND) methods can reduce the measurement uncertainty and eliminates the factors that may influence the characterization of the structure parts affected by ISR. Nevertheless, for a complete structure reassessment, it is also desirable to refer to global geometrical/topographical survey and to destructive analysis methods on some cored samples for chemical analysis, petrography, and residual expansion measurements.

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

“…This reduction is mainly due to (micro) crack opening in hardened cement paste. To represent this feature in the model, we use a dimensionless damage variable d such that, for a given level of expansion, the Young's modulus of the concrete is equal to: (5) where E 0 is Young's modulus for sound concrete. Based on experimental results obtained by [31], the following expression for d was proposed: (6) In this equation, d max represents the maximal damage, whereas ω governs the kinetics of degradation.…”

“…during precasting process or in massive cast-in-situ structures), the ettringite becomes unstable while the concrete is still plastic and reforms after cooling in the hardened material, thus generating swelling due to crystallisation pressure [4]. This expansive process leads to local macroscopic effects mainly consisting of material swelling, cracking and a decrease of the mechanical properties, which may cause serious structural problems due to unexpected deformations and additional stresses in concrete and reinforcement [5][6][7][8][9]. The occurrence of this expansive phenomenon in several concrete structures in the last years worldwide has identified the need for improvement of preventive measures to inhibit these reactions in affected structures.…”

Comparison of Alkali–Silica Reaction Gel Behavior in Mortar at Microwave Frequencies

“…The first two methods are rather simple, but often inaccurate and inefficient while the last two are more scientific and well-established, but are also more sophisticated. Diffused ultrasonic techniques [2], linear and nonlinear acoustic methods [3]- [5], and seismic tomography [6], [7] can be classified as seismicwave methods, while ground-penetrating radar, electrical resistivity, and capacitive methods belong to the electromagnetic techniques [8]. Each of these methods has its own benefits and limitations and none by itself is fully effective and robust.…”

Modelling the Swelling due to Delayed Ettringite Formation - Application to a Real Bridge

“…In this equation,   corresponds to the final expansion,  C and  L are the characteristic and the latency times respectively (corresponding to the swelling rate and the duration before the onset of expansion) and  and  are two parameters used to introduce a linear expansion at the end of the swelling process. These parameters are fitted on the results of a free expansion test on cores taken from the affected structure and immersed in water in laboratory for measuring the residual potential of expansion [4].…”

“…Thermal conditions can lead to ettringite destabilization, preventing its formation during cement hydration. In this case, ettringite lately develops in hardened cement paste and causes structure expansion which leads to the macroscopic local effects mainly consisting in material swelling, cracking and decreasing of the mechanical properties which may cause large structural disorders due to unexpected deformations and additional stresses in concrete and reinforcement [2][3][4][5]. Indeed, the elastic modulus and the concrete tensile strength are likely to significantly decrease which can cause major concern for massive concrete structures.…”