Triaxial Composite Model for Basic Creep of Concrete

Abstract

This paper shows how the mechanics of elastic composite materials can be adapted to predict the basic creep of concrete with aging due to hydration. The prediction is made on the basis of the given composition of concrete, the elastic constants of the aggregate, and the aging viscoelastic properties of the portland cement mortar. The triaxial action of the composite is approximated by Dvorak's transformation field analysis. To convert the aging creep problem to an elastic problem of a composite material with inelastic strains, Granger and Bafant's approach is used. This approach relies on Bafant's age-adjusted effective modulus method that reduces the integral-type stress-strain relation for linear aging creep with nonconvolution kernel to a quasi-elastic incremental stress-strain relation with inelastic incremental strain. Explicit expressions for the aging creep properties of concrete as a composite are deduced. The model is calibrated and verified by Ward et al.'s and Counto's test data. The predictions obtained are almost as close as those recently obtained by Granger and Bafant's model. While the present model has the advantage of describing the triaxial composite action in a rational manner, it does not yet capture the effect of the deviation of the aggregate configuration from the case of a contiguous aggregate skeleton of maximum possible compactness. Further refinements in this respect are needed. Another refinement might be needed to take into account possible enhancement of creep in the interface layers between the mortar and the aggregate.

Dam and wet-screened concrete creep in compression: in situ experimental results and creep strains prediction using model B3 and composite models

“…The model is based in a simple uniaxial rheological model which is strongly related to the physical behaviour of the material. The extension to triaxial behaviour was developed later by Baweja et al [73]. It is considered that a part of the mortar is placed in series with the aggregates (related with parameter a) and another part is placed in parallel (related with parameter b) (Fig.…”

“…The first composite models applied to concrete concerned the elastic behaviour using approaches based on uniaxial rheological models [41][42][43] and on homogenization models, such as the variational approach considering spherical inclusions (HashinShtrickman bounds) [70], the self-consistent model considering ellipsoidal inclusions [71] and the MoriTanaka method [72]. The prediction of the aging viscoelastic behaviour of the materials using composite model was developed with the work of Counto and Popovics [43,48] and later with Granger, Bažant and Baweja [47,73], based on the uniaxial rheological models, and, more recently, Sanahuja and Lavergne, using homogenization concepts [74,75].…”

Prediction of concrete creep and shrinkage: past, present and future

“…Granger and Bažant, 1995;Baweja et al, 1998). Nevertheless, the best way to achieve good long-time predictions is to conduct short-time tests on the given concrete and then extrapolate them (preferebly statistically, in a Bayesian manner) on the basis of a good prediction model incorporating as much as possible of the physics of creep.…”

How Water-Aggregate Interactions Affect Concrete Creep: Multiscale Analysis

“…Choosing, in this context, a standard micromechanical representation for mortar and concrete (Scheiner and Hellmich 2009;Baweja et al 1998;Bernard et al 2003;Hellmich and Mang 2005), namely that of a composite material consisting of a (viscoelastic) cement paste matrix with (elastic) aggregate inclusions and (potentially occurring) air inclusions (Fig. 2) the (homogenized) relaxation tensor at the concrete/mortar scale, R hom , follows from those at the cement paste scale, R cp , as well as from the volume fractions of cement paste, aggregate, and (potentially occurring) air, as (Scheiner and Hellmich 2009)…”