Concrete with High Volume of Recycled Concrete Aggregates and Fly Ash: Shrinkage Behavior Modeling

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Title: Concrete with High Volume of Recycled Concrete Aggregates and Fly Ash: Shrinkage Behavior Modeling

Author(s): Rawaz Kurda, Jorge de Brito, and José D. Silvestre

Publication: Materials Journal

Volume: 116

Issue: 1

Appears on pages(s): 83-94

Keywords: fly ash; modeling; recycled concrete aggregates; shrinkage

Date: 1/1/2019

Abstract:
The objective of this research is to understand the shrinkage of concrete mixtures produced with high content of fly ash (FA) and recycled concrete aggregates (RCAs), individually and jointly, with low (with superplasticizer [SP]) and high (without SP) water-binder ratio (w/b). In this study, the behavior and ultimate shrinkage of the concrete mixtures were studied up to 1 year and the results compared to Eurocode 2 and ACI 209.2R. The shrinkage increased with the amount of RCA content and the opposite occurred with the use of FA. Shrinkage due to the summed individual effect of RCA and FA was at least 10% higher than the effect of combining RCA and FA. Therefore, there is a positive synergy between RCA and FA in concrete. Moreover, in most concrete mixtures, the predicted shrinkage calculated by both Eurocode 2 and ACI 209.2R models was higher than the experimental values. Therefore, this study suggests decreasing the coefficient ultimate shrinkage strain (USS) in the standard model by 45%. Then, to confirm the correction factor, apart from the results of this study, it was applied to the results of 19 studies and it seems that the experimental and calculated shrinkage are quite similar after the correction suggested by this study. Further correction factors are suggested for the concrete mixtures made with different incorporation ratios of FA and/or RCA, with or without SP, for constant target workability.