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

Abstract

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.

Comparisons of Tensile Fracturing Behaviors of Hydraulic Fully Graded and Wet‐Screened Concretes: A Mesoscale Study

“…On the whole, it can be concluded that the increase of the specimen size does result in the variations of the macroscopic mechanical parameters related to tensile fracturing behaviors, which is consistent with the existing research results concerning the size e ect of concrete [38]. However, in view of the large variation amplitudes of the investigated parameters obtained by limited experimental studies [11] (e.g., the typical ratio of the tensile strength of HFGC specimen to that of the corresponding wet-screened concrete specimen is ranging from 0.65 to 0.85), the variation of the specimen size is not a governing factor. Figures 11 and 12 illustrate the variations of CoVs of tensile elastic modulus, peak stress, peak strain, and fracture energy with the sample number for Types I and II, respectively, from which it is noted that 50 random specimens are enough to achieve statistical convergence.…”

“…Although the wet-screening method can avoid the direct testing on large specimens, a gap inevitably exists [9] between the real mechanical parameters of HFGC specimens and those of the corresponding wet-screened specimens; that is, the standard specimens cast using the wet-screened concrete. erefore, an extrapolation procedure should be executed with the aim of acquiring the accurate characterization of the mechanical properties of HFGC [10], which necessitates a detailed comparative study on the mechanical parameters of hydraulic fully graded and wet-screened concretes [11].…”

Evolution of thermal parameters of wet‐screened dam concrete after different freeze–thaw deterioration

“…Dam concrete is mass concrete with a poor binder content (100-300 kg/m 3 ) and wet-screened concrete is obtained by removing the larger aggregates from the original concrete mix. 1 The presence of free water in the micropores of a long-term hydraulic-concrete structure produces expansion pressure and seepage pressure in freeze-thaw cycles due to the alternating action of positive and negative temperatures. This reaction can be both periodic and nonperiodic, leading to significant changes in the mechanical and thermal properties of the structure and eventually to catastrophic fatigue damage to the structure.…”

“…strength are affected by the number of freeze-thaw cycles, the current freeze-thaw test research of concrete mainly follows industry-related norms and standards. According to the Chinese code GB/T 50082-2009, 2 a freeze-thaw test is completed when one of the following conditions is met: (1) the number of freeze-thaw cycles reaches a specified value, (2) the relative dynamic modulus of elasticity decreases to 60% of the initial value, or (3) the mass-loss rate reaches 5%. According to ASTM C666-03, 3 however, such tests must continue until each specimen has undergone 300 cycles or until its relative dynamic modulus of elasticity decreases to 60% of the initial value.…”

“…Dam concrete is mass concrete with a poor binder content (100–300 kg/m 3 ) and wet‐screened concrete is obtained by removing the larger aggregates from the original concrete mix 1 . The presence of free water in the micropores of a long‐term hydraulic‐concrete structure produces expansion pressure and seepage pressure in freeze–thaw cycles due to the alternating action of positive and negative temperatures.…”