Shrinkage prediction of recycled aggregate structural concrete with alternative binders through partial correction coefficients

Abstract

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.