Influence of visco-elasticity on the stress development induced by alkali-silica reaction

Cyrille Dunant, Alain Benjamin Giorla, Karen Scrivener
Pergamon-Elsevier Science Ltd, 2015
Journal paper

Abstract

The alkali-silica reaction causes long-term degradation in the microstructure of affected concrete as well as macroscopic expansion. In this paper, a micro-mechanical model based upon an explicit representation of the microstructure has been used to simulate the role of creep on the expansion and damage induced by the reaction. The model accounts for the coupling between damage propagation and stress relaxation in the cement paste. This study indicates that the influence of the visco-elastic nature of the material on the overall expansion is within the experimental scatter. However, it is shown that creep can explain the comparatively low amount of damage in the cement paste as observed experimentally. Creep also increases the amount of damage in the aggregates when the rate of reaction increases. Overall, the results presented in this paper indicate that accelerated experiments may not be representative of the degradation in the field at equivalent degrees of reaction. (C) 2014 Elsevier Ltd. All rights reserved.

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https://infoscience.epfl.ch/record/207266?ln=en

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In this study, we investigate the mechanical behavior of large concrete structures affected by the alkali-silica reaction. Particularly, concrete dams are explored. Their permanent contact with water, and thus increased humidity, promotes the ASR. Seasonal variation of the environmental temperature causes different levels of concrete damage in “cold” and “warm” zones. In order to study the behavior of such structures, a thermo-mechanical multi-scale numerical model is developed. It is based on the algorithm proposed by CubaRamos. Simulations are performed at the macro- and meso-scales, both of which are handled by the finiteelement method. An elastic thermo-mechanical simulation, performed at the macro-scale, results in a temperature and displacement field. This information at every integration point of the macro-scale is communicated to a corresponding representative volume element (RVE) at the meso-scale. The temperature value is used to determine the gel expansion rate for the following time step. Advancement of the ASR at the level of RVEs leads to gel expansion, deformation of the matrix, and growth of cracks. Given the solution of an RVE problem, homogenized material properties are extracted and communicated to the corresponding integration point of the macro-structure. In the next loading step, the latter behaves according to local states of material throughout a structure.Concrete damaging process is locally driven by gel volume increase, which in its turn depends on therate of alkali-silica reaction. An equation used to relate the ambient temperature and the amount of available reactants to the gel strain rate is inspired by the Arrhenius law. Parameters of this equation are calibrated based on the experiments by Gautam & Panesar. Cracks in concrete are handled by a continuum damage model. Convergence of the static solution in the presence of multiple cracks is achieved by modification of the sequential linear analysis proposed by Rots and Invernizzi. The cement paste at the meso-scale behaves viscoelastically, which causes relaxation of stresses and reduction in the level of damage. For this purpose, an algorithm coupling the SLA with the general viscoelastic model is developed.

2019

Relation of expansion due to alkali silica reaction to the degree of reaction measured by SEM image analysis

Mohsen Ben Haha, Emmanuel Gallucci, Amor Guidoum, Karen Scrivener

Scanning Electron Microscopy Image Analysis (SEM-IA) was used to quantify the degree of alkali silica reaction in affected microbars, mortar and concrete prisms. It was found that the degree of reaction gave a unique correlation with the macroscopic expansion for three different aggregates, stored at three temperatures and with two levels of alkali. The relationships found for the concretes and the mortars overlap when normalised by the aggregate content. This relationship seems to be linear up to a critical reaction degree which coincides with crack initiation within the reactive aggregates. © 2007 Elsevier Ltd. All rights reserved.

2007

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The Alkali-Silica Reaction (ASR) in concrete is a chemical reaction, which produces an expansive product, generally called “ASR gel”, and causes cracking and damage in concrete over time. Affecting numerous infrastructures all around the world, ASR has been the topic of much research over the past decades. In spite of that, many aspects of this reaction are still unknown. In this numerical-investigation paper, a three-dimensional concrete meso-structure model is simulated using the finite-element method. Coarse aggregates, cement paste, and ASR gel are explicitly represented. A temperature dependent eigen-strain is applied on the simulated ASR gel pockets to capture their expansive behavior. This applies pressure on the surrounding aggregates and the cement paste, leading to cracks initiation and propagation. Free expansion of concrete specimens due to ASR is modeled and validated using experimental data. Influence of different key factors on damage generation in aggregates and paste and macroscopic expansion are discussed.

2021

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2019