Creep and shrinkage prediction model for analysis and design of concrete structures - model B3
01 Jul 1995-Vol. 28, Iss: 180, pp 357-365
TL;DR: In this paper, a model for the characterization of concrete creep and shrinkage in the design of concrete structures is recommended, which is simpler, agrees better with the experimental data and is justified better theoretically than the previous models.
Abstract: A model for the characterization of concrete creep and shrinkage in the design of concrete structures is recommended. It is simplier, agrees better with the experimental data and is justified better theoretically than the previous models. The model complies with the general guidelines recently formulated by RILEM TC 107. Justification of the model and various refinements are to be published shortly in two parts.
Citations
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TL;DR: In this article, a new physical theory and constitutive model for the effects of long-term aging and drying on concrete creep is proposed, in which the viscosity of the flow term of the compliance function is a function of a tensile microprestress carried by the bonds and bridges crossing the micropores (gel pores) in the hardened cement gel.
Abstract: A new physical theory and constitutive model for the effects of long-term aging and drying on concrete creep are proposed. The previously proposed solidification theory, in which the aging is explained and modeled by the volume growth (into the pores of hardened portland cement paste) of a nonaging viscoelastic constituent (cement gel), cannot explain long-term aging because the volume growth of the hydration products is too short-lived. The paper presents an improvement of the solidification theory in which the viscosity of the flow term of the compliance function is a function of a tensile microprestress carried by the bonds and bridges crossing the micropores (gel pores) in the hardened cement gel. The microprestress is generated by the disjoining pressure of the hindered adsorbed water in the micropores and by very large and highly localized volume changes caused by hydration or drying. The long-term creep, deviatoric as well as volumetric, is assumed to originate from viscous shear slips between the opposite walls of the micropores in which the bonds or bridges that cross the micropores and transmit the microprestress break and reform. The long-term aging exhibited by the flow term in the creep model is caused by relaxation of the tensile microprestress transverse to the slip plane. The Pickett effect (drying creep) is caused by changes of the microprestress balancing the changes in the disjoining pressure, which in turn are engendered by changes of the relative humidity in the capillary pores. Numerical implementation, application and comparison with test data is relegated to a companion paper that follows in this issue.
418 citations
TL;DR: In situ creep behavior of calcium–silicate–hydrates (C–S–H), the nano-meter sized particles that form the fundamental building block of Portland cement concrete, is measured and it is demonstrated that the creep rate is likely due to the rearrangement of nanoscale particles around limit packing densities following the free-volume dynamics theory of granular physics.
Abstract: Concrete, the solid that forms at room temperature from mixing Portland cement with water, sand, and aggregates, suffers from time-dependent deformation under load. This creep occurs at a rate that deteriorates the durability and truncates the lifespan of concrete structures. However, despite decades of research, the origin of concrete creep remains unknown. Here, we measure the in situ creep behavior of calcium–silicate–hydrates (C–S–H), the nano-meter sized particles that form the fundamental building block of Portland cement concrete. We show that C–S–H exhibits a logarithmic creep that depends only on the packing of 3 structurally distinct but compositionally similar C–S–H forms: low density, high density, ultra-high density. We demonstrate that the creep rate (≈1/t) is likely due to the rearrangement of nanoscale particles around limit packing densities following the free-volume dynamics theory of granular physics. These findings could lead to a new basis for nanoengineering concrete materials and structures with minimal creep rates monitored by packing density distributions of nanoscale particles, and predicted by nanoscale creep measurements in some minute time, which are as exact as macroscopic creep tests carried out over years.
366 citations
TL;DR: The introduction of statistical methods into the analysis of aeronautical experimental data, whether for quality control in production, for the interpretation of the results of structural and aerodynamic laboratory experiments, or for airline operation, has been brought about only in recent years, it may by now be fair to assert that their advantages are no longer in dispute.
Abstract: WHILE the introduction of statistical methods into the analysis of aeronautical experimental data, whether for quality control in production, for the interpretation of the results of structural and aerodynamic laboratory experiments, or for airline operation, has been brought about only in recent years, it may by now be fair to assert that their advantages and even their indispensability are no longer in dispute. Hitherto, investigations on these lines have usually involved, explicitly or implicitly, only the ‘normal curve of error’ and allied considerations; owing, it may be thought, to the controllability of the various manufacturing or laboratory techniques, but also perhaps to the scarcity of data hitherto available. It may well be, however, that with the accumulation of information arising out of investigations planned with particular reference to the statistical analysis of their results the whole range of the apparatus for statistical analysis, usually confined to such fields as those of biology or economics, will be called into full play.
350 citations
TL;DR: In this article, the characterization of cementitiously stabilized layers and the properties that influence pavement performance are discussed, as well as performance-related procedures for characterizing these layers and performance-prediction models for incorporation into the mechanistic-empirical pavement analysis methods.
Abstract: This report presents information on the characterization of cementitiously stabilized layers and the properties that influence pavement performance. It also contains recommended performance-related procedures for characterizing these layers and performance-prediction models for incorporation into the mechanistic–empirical pavement analysis methods. Individual chapters highlight pavement distresses of hot-mix asphalt pavements and concrete pavements, laboratory tests and model development, and model calibration. The material contained in the report will be of immediate interest to state materials, pavement, and construction engineers and others involved in the different aspects of pavement design and construction.
270 citations
TL;DR: In this paper, the creep properties of calcium silicate hydrates (C-S-H) are assessed by means of nanoindentation creep experiments on a wide range of substoichiometric cement pastes.
231 citations
References
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Book•
01 Jan 1988
TL;DR: Buyukozturk et al. as mentioned in this paper presented a state-of-the-art in mathematical modelling of creep and shrinkage in concrete: physical mechanisms and their mathematical description, Z.P.Bazant et al analysis of structures, O.G.Tsubaki et al conclusions for structural analysis and for formulation of standard design recommendations.
Abstract: Part 1 Memorials: Robert L'Hermite and his legacy, M.Fickelson the impact of Robert L'Hermite on the evolution of creep and shrinkage theory, Z.P.Bazant a tribute to Douglas McHenry, B.Bresler Hubert Rusch and his legacy, H.Hilsdorf. Part 2 State-of-the-art in mathematical modelling of creep and shrinkage in concrete: physical mechanisms and their mathematical description, J.F.Young et al material models for structural creep analysis, Z.P.Bazant et al creep and shrinkage analysis of structures, O.Buyukozturk et al finite element analysis of creep and shrinkage, C.A.Anderson et al probabilistic models, T.Tsubaki et al conclusions for structural analysis and for formulation of standard design recommendations. Part 3 Summaries of discussions from the symposium: physical mechanisms and their mathematical description, U.Schneider material models, P.E.Roelfstra structural analysis, V.Kristek finite element analysis, L.Cedolin uncertainty of creep and shrinkage predictions, S.G.Reid current research in material modelling, J.W.Dougill current research in structural analysis, B.Espion. Appendices: list of lectures and papers presented at the symposium list of participants.
445 citations
01 Apr 1972
TL;DR: In this paper, the authors present a rigorous formulation of the effective modulus method and extend it to the case of a variable elastic modulus and an unbounded final value of creep.
Abstract: • IN THE CREEP ANALYSIS OF concrete structures two kinds of errors are involved. One stems from the inaccurate knowledge of the creep law, and its minimization is a problem of materials re search. The second error is caused by the simpli fication of analysis, which designers introduce to avoid the complexities of an exact analysis. In the sequel, only accuracy or exactitude in the latter sense will be of concern. The simplest and the most widespread among the simplified methods of analysis is the well known effective modulus method, whose error with regard to the theoretically exact solution for the given creep law is known to be quite large when aging of concrete, i.e., the change of its properties with the progress of hydration, is of significance (see Table 2 discussed below). How ever, a surprisingly simple way of refinement of this method has been recently discovered by Trost, 1 on the basis of approximate and mostly intuitive considerations. The intent of this paper is to present a rigorous formulation of this method and to extend it to the case of a variable elastic modulus and an unbounded final value of creep.
445 citations
Book•
01 Jan 1983
TL;DR: The creep of plain and structural concrete as mentioned in this paper, a.k.a., the "deformation of concrete", is a metaphor for the "creep of plain concrete" and "decrease of structural concrete".
Abstract: Creep of plain and structural concrete , Creep of plain and structural concrete , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
418 citations
TL;DR: In this article, a general constitutive law for creep is presented, in which the aging due to continuing hydration of cement is taken into account in a simple manner, and better justified than in existing theories.
Abstract: A new general constitutive law for creep is presented, in which the aging due to continuing hydration of cement is taken into account in a simple manner, and better justified than in existing theories. Microchemical analysis of the solidification process is used to show that the aging may be modeled as a growth of the volume fraction of load-bearing solidified matter (hydrated cement), which may be described as a nonaging viscoelastic material. It was found that a history integral should be used to express the rate, rather than the total value of the viscoelastic strain component. Other study findings are also discussed.
367 citations
TL;DR: The introduction of statistical methods into the analysis of aeronautical experimental data, whether for quality control in production, for the interpretation of the results of structural and aerodynamic laboratory experiments, or for airline operation, has been brought about only in recent years, it may by now be fair to assert that their advantages are no longer in dispute.
Abstract: WHILE the introduction of statistical methods into the analysis of aeronautical experimental data, whether for quality control in production, for the interpretation of the results of structural and aerodynamic laboratory experiments, or for airline operation, has been brought about only in recent years, it may by now be fair to assert that their advantages and even their indispensability are no longer in dispute. Hitherto, investigations on these lines have usually involved, explicitly or implicitly, only the ‘normal curve of error’ and allied considerations; owing, it may be thought, to the controllability of the various manufacturing or laboratory techniques, but also perhaps to the scarcity of data hitherto available. It may well be, however, that with the accumulation of information arising out of investigations planned with particular reference to the statistical analysis of their results the whole range of the apparatus for statistical analysis, usually confined to such fields as those of biology or economics, will be called into full play.
350 citations