Rheological modeling and flow simulation to evaluate the filling ability of fresh concrete

Abstract

The construction process of concrete structures can be mainly classified into (1) structural design, (2) casting and placing, and (3) management. The structural design and maintenance technologies are relatively well understood and well-received in academia and industries, however, the studies related to the placing and casting performance of fresh concrete have scarcely been reported despite its importance in the field. The applications of rheometer are introduced to estimate the construction processes and the consequent constructability, but its field application is still limited due to inconvenience and non-robust nature. The evaluation of casting and placing performance of fresh concrete still relies on empirical and qualitative methods such as the slump test. The quantitative evaluation of the rheological properties and workability of fresh concrete is the first task required to ensure the load resistance, serviceability, and durability of concrete structures. This dissertation firstly proposes simulation-based correlation models to estimate the rheological properties of fresh concrete. Then, the casting performance of self-compacting concrete placed on the steel-plate concrete panel and the effect of vibrating compaction on flow of normal concrete are discussed. Specifically, the model to estimate yield stress and plastic viscosity of self-compacting concrete by using slump flow test results considering the partial segregation of coarse aggregates is introduced, and the porous-medium analogy generalizes flow resistance by inner shear studs in the steel-plate concrete panel, and the models to predict the filling ability of self-compacting concrete casting inside steel-plate concrete panels is provided. To evaluate the filling ability of normal concrete, the numerical simulations of the flow table test of wet-sieved mortar also are given for the estimation of plastic viscosity of normal concrete based on the multi-scale approach. In addition, this study applies the diffusion analogy to describe the attenuation of vibrating compaction, and the change of rheological behavior under vibration is formulated. Based on the generalized attenuation and rheological properties, the coupled numerical simulation can give us the change of filling height profiles by vibrating compaction. The aforementioned methods to predict the filling and casting performance of fresh concrete contain the relevant verification test results to strengthen their reliability.