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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 113 Abstracts search results
Document:
22-200
Date:
September 1, 2023
Author(s):
S. Fernando, C. Gunasekara, D. W. Law, M. C. M. Nasvi, S. Setunge, and R. Dissanayake
Publication:
Materials Journal
Volume:
120
Issue:
5
Abstract:
The creep and drying shrinkage of two alkali-activated concretes produced with low-calcium fly ash and rice husk ash (RHA) were investigated over a period of 1 year. The compressive strength of 100% low-calcium fly ash (100NFA) concrete and the concrete having 10% RHA replacement (10RHA) decreased from 49.8 to 37.7 MPa (7.22 to 5.47 ksi) and 30.2 to 18.3 MPa (4.38 to 2.65 ksi), respectively, between 28 and 365 days. The imbalance in the dissolution rate of the raw materials in the blended system (10RHA) could negatively influence the strength properties, which leads to poor matrix integrity and a highly porous structure when compared with 100NFA. The presence of the micro-aggregates due to the block polymerization provides the effect of increasing the aggregate content in the 100NFA concrete compared with the 10RHA concrete, which is hypothesized as one of the reasons creep and shrinkage properties deteriorated in 10RHA.
DOI:
10.14359/51738891
22-242
May 1, 2023
Brock D. Hedegaard, Timothy J. Clement, and Mija H. Hubler
3
A new semi-empirical concrete shrinkage and creep model called the CPRH Model is proposed and calibrated. The new model proposes a coupling between autogenous and drying shrinkage using a volume-average pore relative humidity and treats drying creep as an additional stress-dependent shrinkage, linking together all these phenomena. The proposed expressions are designed to facilitate traditional integral-type analysis, but also uniquely support ratetype calculations that can be leveraged by analysis software. Model calibration uses the Northwestern University (NU) database of creep and shrinkage tests to determine new model parameters. The proposed model uses minimal inputs that are often known or may be assumed by the design engineer. Comparison of the proposed model to historical time-dependent models indicates that the new model provides a superior fit over a wider range of inputs.
10.14359/51738709
22-144
March 1, 2023
Rodolfo Bonetti, Oguzhan Bayrak, Kevin Folliard, and Thanos Drimalas
2
An investigation was performed on the drying shrinkage and tensile drying creep characteristics of a nonproprietary ultra-high-performance concrete (UHPC) mixture. The mixture was formulated using metakaolin as the supplementary cementitious material (SCM) and limestone powder as the mineral filler. Cylindrical specimens with dimensions of 52 x 400 mm (2.05 x 16 in.) were fabricated and loaded at 7 and 11 days from casting to various stress levels for 90 days. Additional specimens were fabricated from a proprietary mixture with a silica fume-ground quartz formulation to study the effects of mixture composition. Simultaneous free drying shrinkage measurements were recorded in accompanying specimens placed in the same room environment. Attention was given to the effect of the casting orientation, age at loading, and mixture composition on the drying shrinkage and drying creep behavior of the samples. These tests show that the metakaolin-limestone powder mixture has significantly lower drying shrinkage and specific drying creep than the silica fume-ground quartz mixture. Additionally, the age at loading influences primary creep behavior while not affecting secondary creep at the same stress level. It seems that fiber orientation plays a significant role in the drying creep behavior of UHPC and that cracked UHPC under constant tensile stress undergoes a significant amount of fiber slip.
10.14359/51738492
20-472
November 1, 2021
Chandrasekhar Bhojaraju, Malo Charrier, and Claudiane M. Ouellet-Plamondon
118
6
A factorial experimental design plan was used to compare admixtures (high-range water-reducing admixture, viscosity-modifying agent, accelerator, calcium silicate hydrate [CSH] seeds, and nanoclay) in a cement and silica fume blend. Two methods were tested to measure the structuration rate: the constant velocity method and the creep recovery method. The measurements were performed with a rotational rheometer with a double-helical spiral geometry to reduce slippage. The evolution of yield stress and thixotropy of the mixtures at four resting times was evaluated, providing insight into the stress that the recently printed structure can withstand. The creep recovery method generally provides a higher static yield stress than the constant velocity method, except for the stronger mixtures, raising additional questions on the effect of the paste history on microstructural buildup mechanisms. When the extruder begins, shear is applied and the microstructure is broken, causing the dynamic yield stress to be lower than the static yield stress. The effect of the admixtures on thixotropy is discussed.
10.14359/51734149
18-301
March 1, 2021
Erik Stefan Bernard
It is well known that creep can affect the serviceability of concrete structures, including tunnel linings made using fiber-reinforced shotcrete (FRS). However, the possible effect of creep on the strength of structures is seldom explicitly considered in design. For cracked FRS loaded in tension or flexure, creep rupture of the fiber-concrete composite, either by pullout or rupture of fibers, can lead to structural collapse, at least when no alternative load path exists. In the present investigation, the influence of fiber geometry and surface roughness on creep rupture (expressed as the time-to- collapse) of FRS panel specimens subjected to a sustained flexural-tensile load has been assessed. The results suggest that geometric aspects of fiber design influence the propensity of the fiber composite to suffer creep rupture at a crack, and that collapse primarily occurs as a result of fiber pullout rather than tertiary creep of individual fibers. For the fibers presently investigated, geometric aspects of fiber design appear to exert a greater influence on creep rupture of the fiber composite than the properties of the material comprising the fibers.
10.14359/51730410
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