Abstract
Alkali Silica Reaction (ASR) is known to be a serious problem for concrete worldwide, especially in high humidity and high temperature regions. ASR is a slow process that develops over years to decades and it is influenced by changes in environmental and loading conditions of the structure. The problem becomes even more complicated if one recognizes that other phenomena like creep and shrinkage are coupled with ASR. This results in synergistic mechanisms that can not be easily understood without a comprehensive computational model. In this paper, coupling between creep, shrinkage and ASR is modeled within the Lattice Discrete Particle Model (LDPM) framework. In order to achieve this, a multi-physics formulation is used to compute the evolution of temperature, humidity, cement hydration, and ASR in both space and time, which is then used within physics-based formulations of cracking, creep and shrinkage. The overall model is calibrated and validated on the basis of experimental data available in the literature. Results show that even during free expansions (zero macroscopic stress), a significant degree of coupling exists because ASR induced expansions are relaxed by meso-scale creep driven by self-equilibriated stresses at the meso-scale. This explains and highlights the importance of considering ASR and other time dependent aging and deterioration phenomena at an appropriate length scale in coupled modeling approaches.
Highlights
Alkali-Silica Reaction (ASR), a problem of world wide nature [1], leads to internal deterioration in the form of a distributed network of cracks
In order to achieve this, a multi-physics formulation is used to compute the evolution of temperature, humidity, cement hydration, and ASR in both space and time, which is used within physics-based formulations of cracking, creep and shrinkage
It must be observed here that such deterioration is often overlooked in typical experiments because it is counterbalanced by strength increase due to cement hydration While many research efforts are directed towards a permanent cure for ASR affected structures, the currently available solutions are only in the research development stage and have many limitations
Summary
Alkali-Silica Reaction (ASR), a problem of world wide nature [1], leads to internal deterioration in the form of a distributed network of cracks. The model and accompanying experiments showed the importance of such coupling especially for large crack openings [73] Another comprehensive model considering possible migration of ASR gel and its diffusion within the concrete porous structure was recently presented by Bažant et al [10]. ASR-LDPM [65] is reviewed and extended to variable moisture conditions and is implemented within a multi-scale multi-physics framework that takes into consideration spatial and temporal distributions of humidity and temperature inside concrete All accompanying deformations, such as shrinkage, thermal and creep strains, are introduced in the numerical framework allowing the macroscopic effects of those deformations but notably the effects of creep-induced stress relaxation of ASR induced internal pressure. This can be seen for example in the model by Kawabata et al [2], which while successful in many regards, it considers macroscopic creep only
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