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Standardised residuals against the estimated creep coefficient. A full-colour version of this figure can be found on the ICE Virtual Library (www.icevirtuallibrary.com)
Source publication
Besides strength and elastic modulus properties of concrete, creep and shrinkage are also important in designing structures as they can affect seriously their integrity in the long term. It is shown that design codes internationally, as well as researchers in general, have omitted to consider the influence of aggregate, in particular its stiffness,...
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Citations
... In addition, Zhou [15] developed a theoretical method based on the linear superposition principle to derive the specific creep of concrete from the compressive creep test results where a certain amount of stress has relaxed. Lye [16] proposed two empirical models to estimate the creep coefficient and shrinkage strain of concrete covering a wide range of natural, recycled, and secondary aggregates alone or in any combination. Sirtoli [17] measured the shrinkage and creep in both autogenous and drying conditions from 1 day until 1 year and compared the results with those of empirical models. ...
... To obtain findings that were similar to those of other researchers who used various fibres, cement-to-sand ratios of 1:2 and 1:1 were used (Lye et al., 2022). To obtain insight into the advantages of the fibre in a more practical situation, where it is probable that their impact on workability will need to be taken into consideration using a superplasticiser and a mix with a low w/c ratio of .3 was selected. ...
The effects of polypropylene fibres on mortar and cement-paste cracking were investigated using different amounts of fibre fractions and eccentric rings under restrained-shrinkage conditions. Eccentric-ring tests were conducted to investigate early-age shrinkage cracks. The characteristics of restricted cementitious materials were described by evaluating the cracking time and using concrete mixtures that are less likely to crack. Different fibre-volume fractions significantly enhanced the width, area, and age of cracking. Increasing the water-cement ratio and sand percentage increased the cracking age. The eccentric-ring test showed a greater susceptibility to cracking in cement-mortar composites. The mechanical strength was assessed, and the impact of polypropylene fibres was investigated.
... The estimation of shrinkage strain is not so simple since the shrinkage behaviour of concrete is closely linked to its composition [11]. The different US and European standards include a relatively easy specific formulation for the calculation of these magnitudes [2,12], but with the limitation that the concrete considered in the development of those models was vibrated and made with conventional materials such as ordinary Portland cement (OPC) and natural aggregate (NA) [13,14]. ...
Estimating the shrinkage of structural concrete is essential to calculate, at the design stage, the stresses that a structure may experience due to this phenomenon. Nevertheless, changes in composition, as well as the use of wastes as raw materials, alter the shrinkage behaviour of concrete and render invalid shrinkage-prediction models from the standards. This paper shows a procedure to estimate the shrinkage of recycled aggregate concrete made with alternative binders. This procedure is based on modifying the shrinkage estimated through the Eurocode 2 or ACI 209.2R models by multiplying it by a partial correction coefficient for every change in concrete composition. The application of this procedure to high-performance and self-compacting concretes made with various contents of recycled aggregate of different maturity, reactive magnesium oxide and ground granulated blast furnace slag showed that it is suitable for estimating long-term shrinkage with maximum deviations of ±10%. However, to obtain an adequate accuracy, it is necessary to bear in mind some tips, such as the need to consider the prediction interactions between the factors, the usefulness of the natural logarithm of the concrete age to improve the estimation accuracy or the convenience of introducing a concrete-age-dependent coefficient to reach accurate shrinkage estimations at early ages. Finally, the partial correction coefficients are found to be of a simpler nature for the ACI 209.2R model, so this model is recommended for predicting the shrinkage of recycled aggregate concrete.
Studies have found utilization of recycled aggregate concrete (RAC) for engineering use to be environmentally favorable by preserving natural resources and limiting waste reduction. However, the use of RAC has not been effectively integrated in the industry due to limited research overlying the critical areas of its creep and shrinkage behavior. Hence, this study aims to investigate the natural aggregate concrete creep and shrinkage prediction models and perform recycled concrete aggregate (RCA) replacement level and water absorption modifications to illustrate the presence and behavior of RAC. Comparative analysis was undertaken by establishing comprehensive conventional concrete and RAC experimental databases and investigating several creep and shrinkage prediction models including, ACI 209R-92, Bazant–Baweja B3, CEB MC 90, GL 2000, MC 2010, and JSCE 2010. The Bazant–Baweja B3 model was found to present the most optimal results by evaluating each conventional model against the RAC databases and performing regression analysis. Hence, the Bazant–Baweja B3 natural aggregate concrete models for creep and shrinkage were then effectively modified to illustrate the presence of RCA replacement level and water absorption. The adjusted models were verified with a set of experimental databases which successfully presented favourable results with coefficient of correlation factors increased from an average of 0.76 to 0.9.
