One of the most important phenomena of the delayed behaviour of mass concrete used in dams is creep, i.e., the increase in deformation over time when subjected to constant stress. Although several studies concerning concrete creep were carried out throughout the last decades in a structural and material level, the physical and chemical phenomena are yet to be fully understood. This paper presents a study on the Alqueva dam’s concrete deformability in which a parameter evaluation was performed using the Baz̆ant and Panula’s basic creep function, based on both in situ and laboratory creep test results. In the first part of the paper, the approach and material properties that better fit the experimental data of a dam’s mass concrete are presented. In the second part, the fitted function for each in situ test was validated using a finite element numerical model that takes into account the time‐dependent behaviour, the applied stress and the monitored temperatures.

These recommendations have been prepared by the corresponding working group within RILEM TC 287-CCS ''Early-age and long-term crack width analysis in RC structures'', following work by the previously ceased RILEM TC 254-CMS ''Thermal cracking of massive concrete structures''. This recommendations document is developed in complementarity to the state-of-the-art report of RILEM TC 254-CMS and aims to provide expert advice and suggestions to engineers and scientists interested in modelling the thermo-chemo-mechanical behaviour of massive concrete structures since concrete casting. Recommendations regarding geometrical characteristics and complexities, concrete properties and appropriate material models, boundary conditions and loads, and numerical model peculiarities with relevance to the simulation of the thermo-chemo-mechanical behaviour of massive concrete structures are given herein. The recommendations have been reviewed and approved by all members of the TC 287-CCS.These recommendations have been prepared within a framework of RILEM TC 287-CCS. The recommendations have been reviewed and approved by all members of the TC 287-CCS.

This paper proposes a methodology for the prediction of the compressive creep strains of dam concrete based on wet-screened experimental results at constant elevated temperature conditions measured in situ. Due to its large aggregate dimensions, the experimental characterization of dam concrete has particular constraints. The wet-screened concrete, obtained by sieving the aggregates larger than a given dimension, after mixing, is used to cast standard specimens and to embed monitoring devices. An experimental in situ installation using creep cells was used to obtain the compressive creep strain development over time for the maturing conditions of the dam core. The study of the effect of wet-screening procedure on creep in compression considers three types of concrete, dam concrete and two wet-screened concretes tested at three loading ages, 28, 90 and 365 days. The comparison between different types of concrete at different maturing conditions requires the definition of a reference state given by the maturity method, using the equivalent age, and relies on the fit of compressive creep strains to the RILEM recommended model B3. To take into account the effect of the aggregate content on the deformability properties of dam concrete, an equivalent two-phase composite model was applied. The equivalent composite model considered the equivalent matrix as the wet-screened concrete and the inclusions as the larger aggregates that are removed during the wet-screening procedure. Predictions obtained with the composite model are close to the dam concrete experimental results, for the tested loading ages.

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