Abstract
A new experimental method which allows the direct separation of the components of drying creep due to microcracking and stress-induced shrinkage is developed, demonstrated and validated. The basic idea is to compare the curvature creep of beams subjected to the same bending moment but very different axial forces. The results confirm that drying creep has two different sources: microcracking and stress-induced shrinkage. The latter increases continuously, whereas the former first increases and then decreases. The test results are fitted using a finite element model. The results validate the present model for drying creep. The microcracking is described by an established model, and the free (unrestrained) shrinkage of a material element is shown to depend approximately linearly on the humidity drop.
Resume
On a développé, démontré et validé une nouvelle méthode expérimentale permettant d'identifier directement les composantes du fluage au séchage dû à la microfissuration et à la contrainte de retrait. L'idée de base est de comparer le fluage en flexion de poutres soumises au même moment fléchissant mais de faire varier les différentes forces axiales.
Les résultats confirment que le fluage au séchage a deux origines différentes: la microfissuration et le retrait sous contrainte. Celui-ci augmente de façon continue alors que celle-là augmente d'abord, puis diminue. On a utilisé un modèle d'élément fini pour ajuster les résultats d'essai qui valident le modèle actuel pour le fluage au séchage. On décrit la microfissuration par un modèle établi; quant au retrait libre (non empêché) d'un élément de matériau, on montre qu'il dépend de la chute d'humidité de façon approximativement linéaire.
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References
Pickett, G., ‘The effect of change in moisture content of the creep of concrete under a sustained load’,J. ACI 38 (1942) 333–355.
Bažant, Z. P. and Wu, S. T., ‘Creep and shrinkage law for concrete at variable humidity’,J. Engng Mech. ASCE 100 (1974) 1183–1209.
Becker, J. and Bresler, B., ‘Reinforced concrete frames in fire environments’,J. Struct. Div. ASCE 103 (1977) 211–224.
Wittmann, F. H. and Roelfstra, P. E., ‘Total deformation of loaded drying concrete’,Cem. Concr. Res. 10 (1980) 601–610.
Iding, R. and Bresler, B., ‘Prediction of shrinkage stresses and deformations in concrete’, in ‘Fundamental Research on Creep and Shrinkage of Concrete’, edited by F. H. Wittmann (Martinus Nijhoff 1982).
Bažant, Z. P. and Chern, J. C., ‘Concrete creep at variable humidity: constitutive law and mechanism’,Mater. Struct. 18(103) (1985) 1–20.
Bažant, Z. P. and Chern, J. C., ‘Strain-softening with creep and exponential algorithm’,J. Engng Mech. ASCE 111(3) (1985) 391–415.
Bažant, Z. P. and Chern, J. C., ‘Stress-induced thermal and shrinkage strains in concrete’, —Ibid.113(10) (1987) 1493–1511.
Hwang, C. L. and Young, J. F., ‘Drying shrinkage of Portland cement pastes, I. microcracking during drying’,Cem. Concr. Res. 16 (1984) 584–594.
Bažant, Z. P. and Raftshol, W. J., ‘Effect of cracking in drying and shrinkage specimens,’ —Ibid,12 (1982) 209–226.
Suzuki, K., Ohno, Y. and Ohra, H., ‘Influence of the degree of restraint on cracking of concrete due to drying shrinkage’,Cem. Ass. Jap. Rev. (1982) 145–147.
Beaudoin, J. J., ‘Effect of humidity on subcritical crack growth in cement paste’,Cem. Concr. Res. 15 (1985) 871–878.
Cohen, M. D., Olek, J. and Dolch, W. L., ‘Mechanism of plastic shrinkage cracking in Portland cement and Portland cement-silica fume paste and mortar’ —Ibid,,20 (1990) 103–119.
Bažant, Z. P., ‘Constitutive equation for concrete creep and shrinkage based on thermodynamics of multiphase systems’,Mater. Construct. 3(13) (1970) 3–36.
Bažant, Z. P., ‘Thermodynamics of interacting continua with surfacesand creep analysis of concrete structure’,Nucl. Engng Design,20 (1972) 477–505.
Bažant, Z. P., ‘Long-term modeling and prediction’, Slide presentation at NSF Center for Advanced Cement-Based Materials, Center Industrial Affiliates Meeting, June 7 (Northwestern University, Evanston, IL, 1989); private communication by Y. Xi to S. G. Ried, Visiting Scholar at Northwestern University, June 1989.
Bažant, Z. P., Xi, Y. and Molina, L., ‘Moisture diffusion in concrete and mechanisms of drying’, in Proceedings of the ASCE Engng Mech. Specialty Conference (Columbus, OH, May 20–22, 1991) pp. 1146–1148.
Bažant, Z. P. and Xi, Y., ‘New test method to separate microcracking from drying creep: curvature creep at equal bending moments and various axial forces’, in Proceedings of the 5th International Symposium on Creep and Shrinkage of Concrete, edited by Z. P. Bažant and I. Carol (Chapman & Hall, London, 1993) pp. 77–82.
Bažant, Z. P., ‘Mathematical Modeling of Creep and Shrinkage of Concrete’ (John Wiley, New York, 1998).
Bažant, Z. P. and Xi, Y., ‘Continuous retardation spectrum for solidification theory of concrete creep’,J. Engng Mech. ASCE (1994) in press.
Bažant, Z. P. and Prasannan, S., ‘Solidification theory of concrete creep, I. formulation’, —Ibid,115(8) (1989) 1691–1703.
Bažant, Z. P. and Prasannan, S., ‘Solidification theory of concrete creep, II, verification and application’, —Ibid,115(8) (1989) 1704–1725.
Bažant, Z. P. and Cedolin, L., ‘Stability of Structures: Elastic, Inelastic, Fracture, and Damage Theories’ (Oxford, New York, 1991).
Bažant, Z. P. and Panula, L., ‘Practical prediction of time-dependent deformation of concrete’,Mater. Struct. Parts I and II,11(65) (1978) 307–328; Parts III and IV,11(66) (1978) 415–434; Parts V and VI,12(69) (1979) 169–183.
Thelandersson, S., ‘On the multiaxial behavior of concrete exposed to high temperature’, in Transactions of the 7th International Conference on Structural Mechanics in Reactor Technology (1983) Vol. H, H3/1.
Thelandersson, S., ‘On the multiaxial behavior of concrete exposed to high temperature’,Nucl. Engng Design 75 (1983) 271–282.
Brockenbrough, J. R. and Suresh, S., ‘Constitutive behavior of a microcracking brittle solid in cyclic compression’,J. Mech. Phys. Solids,35(6) (1987) 721–742.
Budiansky, B. and O'Connell, R. J. ‘Elastic moduli of a cracked solid’,Int. J. Solids Struct.,12 (1976) 81–97.
Laws, N. and Brockenbrough, J. R., ‘The effect of microcrack systems on the laws of stiffness of brittle solid’, —Ibid.,,23(9) (1987) 1247–1268.
Evans, A. G. and Fu, Y., ‘Some effects of microcracks on the mechanical properties of brittle solids—II, microcrack toughening’,Acta metall.,33(8) (1985) (1525–1531).
Xi, Y., Bažant, Z. P., Molina, L. and Jennings, H., ‘Moisture diffusica in cementitious materials: Moisture capacity and diffusivity’,J. Adv. Cement Based Mater. (1994) in press.
Ali, I. and Kesler, C., ‘Mechanisms of creep in concrete’, ACI Special Publication SP-9, pp. 35–37 (American Concrete Institute, 1964).
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Bažant, Z.P., Yunping, X. Drying creep of concrete: constitutive model and new experiments separating its mechanisms. Materials and Structures 27, 3–14 (1994). https://doi.org/10.1007/BF02472815
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DOI: https://doi.org/10.1007/BF02472815