Hygro‐thermo‐chemo‐mechanical modelling of concrete at early ages and beyond. Part II: shrinkage and creep of concrete

In Part I of this paper (Int. J. Numer. Meth. Eng., in print) a mechanistic model of hygro-thermo-chemical performance of concrete at early ages has been introduced. Additionally, as compared to the existing models (e.g. J. Eng. Mech. (ASCE) 1995; 121(7):785–794; 1999; 125(9):1018–1027), an effect of relative humidity on cement hydration rate and associated hygro-thermal phenomena have been taken into account. Here we deal with mechanical performance of concrete at early ages and beyond, and in particular, evolution of its strength properties (aging) and deformations (shrinkage and creep strains), described by using the effective stress concept. This allow us for explanation and modelling of phenomena known from experiments, like drying creep (e.g. Mathematical Modeling of Creep and Shrinkage of Concrete. Wiley: Chichester, 1988), or some additional strains, as compared to pure shrinkage, which appear during autogenous deformations of a maturing, sealed concrete sample (e.g. Cement Concrete Res. 2003; 33:223–232). Creep is described by means of the modified microprestress-solidification theory by Bazant et al. (J. Eng. Mech. (ASCE) 1997; 123(11):1188–1194; 1195–1201), with some modifications to take into account the effects of temperature (Comput. Struct. 2002; 80:1511–1521) and relative humidity (Int. J. Numer. Meth. Eng., in print; Proceedings of the 5th World Congress for Computational Mechanics (WCCM), Vienna, Austria, 7–12 July 2002), on concrete aging. Shrinkage strains are modelled by using the effective stress principle in the form introduced by Gray and Schrefler (Eur. J. Mech. A/Solids 2001; 20:521–538; Appl. Mech. Rev. (ASME) 2002; 55(4):351–388), giving a good agreement with experimental data also for lower values of relative humidity. Two numerical examples showing comparison of the results obtained by means of our model with some published experimental data are presented. The third one, concerning 2D axial symmetric case, proves numerical robustness of the developed software. All these examples demonstrate the possibilities of the model to analyse both autogenous deformations in maturing concrete and creep phenomena, including drying creep, in concrete elements of different age, sealed or drying, exposed to external load or without any load. Copyright © 2006 John Wiley & Sons, Ltd.

[1]  Yunping Xi,et al.  Continuous Retardation Spectrum for Solidification Theory of Concrete Creep , 1995 .

[2]  Franz-Josef Ulm,et al.  Microprestress-Solidification Theory for Concrete Creep. I: Aging and Drying Effects , 1997 .

[3]  Bernhard A. Schrefler,et al.  The effective stress principle: Incremental or finite form? , 1996 .

[4]  K. Breugel,et al.  Autogenous shrinkage in high-performance cement paste: An evaluation of basic mechanisms , 2003 .

[5]  B. Schrefler,et al.  ANN approach to sorption hysteresis within a coupled hygro‐thermo‐mechanical FE analysis , 2001 .

[6]  Luc Taerwe,et al.  Degree of hydration-based description of mechanical properties of early age concrete , 1996 .

[7]  Zdenek P. Bazant,et al.  MICROPRESTRESS-SOLIDIFICATION THEORY FOR CONCRETE CREEP. II: ALGORITHM AND VERIFICATION , 1997 .

[8]  William G. Gray,et al.  Thermodynamic approach to effective stress in partially saturated porous media , 2001 .

[9]  Bernhard A. Schrefler,et al.  Mechanics and thermodynamics of saturated/unsaturated porous materials and quantitative solutions* , 2002 .

[10]  Zdeněk P. Bažant,et al.  Viscoelasticity with Aging Caused by Solidification of Nonaging Constituent , 1993 .

[11]  Per Freiesleben Hansen,et al.  Water-entrained cement-based materials , 2001 .

[12]  B. Schrefler,et al.  The Finite Element Method in the Static and Dynamic Deformation and Consolidation of Porous Media , 1998 .

[13]  Olivier Coussy,et al.  Characterization and identification of equilibrium and transfer moisture properties for ordinary and high-performance cementitious materials , 1999 .

[14]  Anthony H. Bryant,et al.  Creep, Shrinkage-Size, and Age at Loading Effects , 1987 .

[15]  Rui Faria,et al.  Numerical modelling of concrete curing, regarding hydration and temperature phenomena , 2002 .

[16]  Olivier Coussy,et al.  Modeling of Thermochemomechanical Couplings of Concrete at Early Ages , 1995 .

[17]  Sandeep Baweja,et al.  Justification and refinements of model B3 for concrete creep and shrinkage 1. statistics and sensitivity , 1995 .

[18]  Zdenek P. Bazant,et al.  I: Formulation , 2022 .

[19]  Zdenek P. Bazant,et al.  Solidification Theory for Concrete Creep. II: Verification and Application , 1989 .

[20]  Geppino Pucci,et al.  A frontal solver tuned for fully coupled non‐linear hygro‐thermo‐mechanical problems , 2003 .

[21]  Miguel Cervera,et al.  THERMO-CHEMO-MECHANICAL MODEL FOR CONCRETE. I: HYDRATION AND AGING , 1999 .