Scale-Dependent ASR Expansion of Concrete and Its Prediction coupled with Silica Gel Generation and Migration

Abstract

This study set out to investigate the effect of gel migration through micro-pores and cracks on concrete expansion caused by alkali-silica reaction (ASR). First, sensitivity analyses with permeation of produced silica gel were conducted by using a computational scheme of multi-scale poro-mechanics. Then, silica gel movements were found to substantially affect the ASR expansion of concrete with the possibility of its scale effect being rooted in the drugging force when the silica gel is in motion. With accelerated ASR tests of mortar, the predicted scale effects were experimentally verified and the permeation of gel was inversely identified in terms of multi-scale mechanics. Here, the effect of alkali ion leaching on the scale-dependency was also discussed in view of chemo-physics as well as mechanics of produced gel migration. The measured characteristic scale-dependency in the experiment can be also simulated by nonlinear analysis of smeared cracks coupled with gel generation, migration and alkali ion leaching.

Strong Coupling of Freeze-Thaw Cycles and Alkali Silica Reaction - Multi-scale Poro-mechanical Approach to Concrete Damages -

“…In order to express the solid-liquid coexisting states, parameter β is introduced, which is the ratio of the solid phase to total ASR-gel. The proposed model has been sufficiently verified by ASR experiments, for both the uniform expansion under unconfined condition and the non-uniform expansion with confinements (Takahashi et al 2016).…”

“…Then, the hydration products together with the cement particles forms the micro pore structure, within which the moisture transport and equilibrium can be formulated. The multi-ionic transport and equilibrium for ASR, as well as the thermodynamic equilibrium of ice formation are considered also at this scale (Takahashi et al 2016;Scherer and Vallenza II 2005). Since both the alkali silica reaction and the ice formation will cause volume increase in the pore substances, the mechanical interaction between pore substances (ice, water, ASR gel) and concrete skeleton will be considered for both non-cracked and cracked conditions.…”

“…Based on the experimental data from Wang et al (1997), k 0 =10 -9 cm/s, b=4 for liquid water, while for the liquid ASR gel, the sensitivity analysis (Takahashi et al 2016) based on measured ASR expansion shows k 0 =10…”

“…Kawabata and Yamada 2015;Sannoh and Torii 2014;Costa et al 2014;Saouma 2014;Saouma et al 2014;Multon et al 2009;Bazant and Steffens 2000;Bangert et al 2004;Liaudat et al 2015;Charpin and Ehrlacher 2014). Meanwhile, based on the multi-scale chemo-hygral computational system (DuCOM-COM3, Maekawa et al 2008;Maekawa and Ishida 2002), the authors have modelled and simulated the ASR gel production by considering the multi-ionic equilibrium (Takahashi 2014;Elakneswaran and Ishida 2014), the mechanical impacts of ASR in multi-directional cracking system (Maekawa and Fujiyama 2013;Takahashi 2014), as well as the scale-dependent gel anisotropic expansion and migration (Takahashi et al 2016).…”

“…The system should start from the hydration stage in nano-scale, and then be upgraded to the physical and chemical equilibrium in porous media, and finally lead to the structural performance (Maekawa et al 2003(Maekawa et al , 2013. Based on this platform, dual impacts have been well modelled and simulated based on poro-mechanics, such as the fatigue effect of condensed water under traffic loads (Maekawa and Fujiyama 2013), the steel corrosion and crack opening caused by corrosion gels (Gebreyouhannes and Maekawa 2016), as well as the ASR expansion and damage (Takahashi et al 2016).…”