Time-Dependent Constitutive Model of Solidifying Concrete Based on Thermodynamic State of Moisture in Fine Pores

Abstract

An enhanced multi-chemo-physical model for the time-dependent deformation of concrete is proposed based on thermodynamic state of moisture in micro-pores. The moisture migration mechanism is divided into 1) moisture transport through CSH gel grains and 2) water in motion within the inter-particle spaces of hydrate micro-products. The new kinematic model makes it possible to simulate both long-and short-term concrete creep. An enhanced mechanistic law of stress path dependency is introduced to cope with a wide variety of stress and ambient histories as well. Time-dependency at elevated temperature is also investigated with current high-accuracy thermo-hygro dynamics. The instantaneous plasticity in direct connection with evaporating moisture from CSH crystal inter-layers is incorporated into the predictive system. Although some mechanisms remain unverified, drying shrinkage and creep at high temperature are fairly simulated.

Investigations into Volumetric Stability of Aggregates and Shrinkage of Concrete as a Composite

“…In this section, the multi-scale constitutive model is described in summary. Further details can be found in the literature Zhu et al 2004;Asamoto et al 2006). …”

“…Recently, a project to couple the microscopic thermo-physical information obtained from DuCOM with macroscopic structural information such as stress, strain, deformation, cracking and others as computed by a 3D FEM structural system named COM3 has been in progress. One of the targets of this project is the development of a multi-scale constitutive model that can simulate concrete time-dependent behavior such as shrinkage and creep based on the hydration reaction, pore structure and moisture state in the pores Zhu et al 2004;Asamoto et al 2006). In this section, the multi-scale constitutive model is described in summary.…”

“…The objective is to enhance a multi-scale constitutive model Zhu et al 2004;Asamoto et al 2006) by idealizing aggregate properties and behavior appropriately and to evaluate the shrinkage behavior of concrete for any mix proportion under arbitrary environmental conditions. ics and brought them together in the computer program known as DuCOM (Maekawa et al 1999).…”

Mechanism of Long-Term Excessive Deformation and Delayed Shear Failure of Underground RC Box Culverts

“…This is called as Pickett effect (Pickett 1942;Bazant 2001). This nonlinearity is consistently simulated in considering moisture transport and the constitutive model for cement paste of meso-scale (Asamoto et al 2006) before and after cracking (Maekawa et al 2008;Yoneda et al 2014Yoneda et al , 2015. The coupling of sustained stresses and drying was also found to cause an excessive deflection of long-span PC box sectional viadcuts of about 10 years after construction (Bazant et al 2010;Ohno et al 2012).…”

“…As underground box culverts are backfilled with soil, time-dependent creep of structural concrete before and after cracking has to be taken into account (Maekawa et al 2008;Asamoto et al 2006). At the same time, differential shrinkage of concrete is associated with long-term deformation and shear failure (Yoneda et al 2013), because the inside space of box culverts is rather dry but their outer surface is surrounded by wet soil fundation and/or underground water.…”