Proceedings of the International rilem conference Materials, Systems and Structures in Civil Engineering 2016

124

International RILEM Conference on Materials, Systems and Structures in Civil Engineering 

Conference segment on Service Life of Cement-Based Materials and Structures 

22-24 August 2016, Technical University of Denmark, Lyngby, Denmark 

 

characterize the cyclic damage accumulation. In addition, a continuum model to simulate 

fatigue failure can incorporate other effects that where previously discussed, notably 

shrinkage, creep, thermal strains, order effects or the influence of the mean stress as well as 

the full three-dimensional stress state. 

5. Summary 

In this paper, the importance of simulating concrete as a multiphysics and multiscale material 

have ben highlighted. It is emphasized that most scenarios (including mechanical as well as 

thermal, hygral loading or the time-dependent solidification/hardening) are not separable and 

a profound understanding of nonlinear effects requires a full coupling. The advantage is that 

otherwise phenomenologically determined interaction coeffcients are automatically included 

in the model as thus simplify the calibration of material parameters and thus the 

generalization capabilities of the model. 

References 

[1]  Khoury, G.A., Strain of heated concrete during two thermal cycles. Part 3: isolation of 

strain components and strain model development. Magazine of Concrete Research, 2006. 

58(7): p. 421-435. 

[2]  Nagai, G., T. Yamada, and A. Wada, Three-dimensional nonlinear finite element analysis 

of the macroscopic compressive failure of concrete materials based on real digital image. 

Proc. 8th ICCCBE. 2000, Stanford Univ., California, USA. 449-456. 

[3] Titscher, T. and J.F. Unger, Application of molecular dynamics simulations for the 

generation of dense concrete mesoscale geometries. Computers & Structures, 2015. 158: 

p. 274-284. 

[4]  Johannesson, B. and U. Nyman, A Numerical Approach for Non-Linear Moisture Flow in 

Porous Materials with Account to Sorption Hysteresis. Transport in Porous Media, 2010. 

84(3): p. 735-754. 

[5] Havlasek, P., Creep and shrinkage of concrete subjected to variable environmental 

conditions, in Faculty of Civil Engineering, Department of Mechanics. 2014, Czech 

Technical University, Prague. 

[6] Coussy, O., et al., The equivalent pore pressure and the swelling and shrinkage of 

cement-based materials. Materials and Structures, 2004. 37(265): p. 15-20. 

[7]  Pinson, M.B., et al., Hysteresis from Multiscale Porosity: Modeling Water Sorption and 

Shrinkage in Cement Paste. Physical Review Applied, 2015. 3(6). 

[8]  Zhang, B., D.V. Phillips, and K. Wu, Further research on fatigue properties of plain 

concrete. Magazine of Concrete Research, 1997. 49(180): p. 241-252. 

[9]  Kindrachuk, V.M., M. Thiele, and J.F. Unger, Constitutive modeling of creep-fatigue 

interaction for normal strength concrete under compression. International Journal of 

Fatigue, 2015. 78: p. 81-94. 

[10] Peerlings, R.H.J., Enhanced damage modelling for fracture and fatigue. 1999, Technische 

Universiteit Eindhoven. 

[11] 

Peerlings, R.H.J., et al., Gradient enhanced damage for quasi-brittle materials. 

International Journal for Numerical Methods in Engineering, 1996. 39: p. 3391-3403. 

[12] de Vree, J.H.P., W.A.M. Brekelmans, and M.A.J. van Gils, Comparison of nonlocal 

approaches in continuum damage mechanics. Computers and Structures, 1995. 55(4): p. 

581-588. 

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125

International RILEM Conference on Materials, Systems and Structures in Civil Engineering 

Conference segment on Service Life of Cement-Based Materials and Structures 

22-24 August 2016, Technical University of Denmark, Lyngby, Denmark 

 

RESIDUAL CONCRETE STRENGTH AFTER SUSTAINED LOAD: 

EXPERIMENTAL RESULTS AND  MODELLING APPROACH 

 

Zainab Kammouna 

(1,2)

, Matthieu Briffaut 

(1,2) 

, Yann Malecot 

(1,2)

 

 

(1)  Univ. Grenoble Alpes, 3SR, Grenoble, France 

(2)  CNRS, 3SR, Grenoble, France 

 

 

 

 

 

Abstract 

Rheological models for estimating the creep of concrete generally assume that concrete is an 

homogeneous material. Therefore, strains incompatibilities between the cement paste and 

aggregates when the concrete is subjected to a creep loading cannot be taken into account 

whereas they can generate microcracking. These microcracks may cause a decrease of the 

elasticity modulus and of the strength of concrete, and an increase in the amount of creep 

strains under the same loading level. This increase in creep strains can be considered as the 

source of nonlinearity with the stress level. To study the influence of these microcracks on the 

mechanical behaviour, compressive creep tests at different loading level (50% and 80% of the 

strength) and for different age of loading (1 and 3 month) have been performed followed by 

quasi static test to measure the residual concrete strength. Experimental results highlight 

different trends with respect to the age of loading. Besides, a viscoelastic-damageable model 

has been adopted for calculating creep using a mesoscopic meshing approach. The results 

show that a significant proportion of non-linearity can be explained by the microcracks and 

that the mesoscopic approach allows to reproduce a strength decrease for hardened concrete. 

 

 

1. Introduction 

 

The existing models for estimating creep of concrete, based on a rheological model generally 

assume that concrete is a homogeneous material (see for instance [1-3]). Therefore the 

incompatible strains between cement paste and aggregates throughout creep loading could not 

be taken into account. Recently, [4] represents concrete as a composite material which consist 

of spherical elastic inclusions (aggregate and/ or voids) imbedded in a linear viscoelastic 

matrix. Nevertheless, the model does not take into account micro-cracks at cement-aggregates 

interface level which occurs due to incompatible deformations between these two materials. 

 

Experimentally the relation between the stress level and creep is not linear. Microcracks at 

cement – aggregates interface which is directly related to the stress level could be a reason. 

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