Impact of origination of expansion on three-dimensional expansion crack propagation process due to DEF evaluated by mesoscale discrete model

Abstract

In this study, DEF expansion crack propagation process under different restraint condition was numerically investigated by mesoscale discrete model, which describes concrete material with coarse aggregate phase and mortar phase using 3D-Rigid Body Spring Model. The purpose of this study is to clarify the impacts of origination of expansion and aggregate on characteristic DEF expansion such as localized expansion crack and cracks localized at the ITZ between paste and aggregate. In this analysis, Single Aggregate Model and Multi-Aggregate Model were constructed to verify expansion crack propagation process and interaction between aggregate and mortar phases precisely. As a result of Single Aggregate model, it was confirmed that expansion crack tends to be localized as expansion phase ratio is lower, and cracks localized at the ITZ is appeared at the early stage of expansion. By using Multi-Aggregate Model, the analytical results of expansion crack propagation process, stress distribution change, and expansion strain change under different restraint condition were coincided with experimental observation. In addition, it was found that origination of expansion strongly influences to DEF expansion. In terms of aggregate, the existence of aggregate and grain size distribution slightly inhibit expansion strain development and crack volume development, and their impacts on DEF expansion, however, seems to be small. This is because cracks localized at the ITZ generates at the early stage of expansion process and the stress transfer mechanism between mortar and aggregate phase disappears.