9 - Deformation of Concrete Containing Recycled Concrete Aggregate

Abstract

The effects of using coarse recycled concrete aggregate (RCA) as a replacement for natural aggregate (NA) on the load-dependent deformation properties of concrete in the form of elastic modulus and creep of concrete, and load-independent deformation in the form of shrinkage of concrete, are assessed in this chapter. Owing to the presence of adhered cement paste, RCA concrete potentially has a lower resistance against all forms of deformation compared with the corresponding NA concrete. The change in the deformation properties was shown to be affected by aggregate content, concrete strength and other factors. On average, at 100% RCA content, the elastic modulus of concrete can be expected to be reduced by 16% with respect to the corresponding NA concrete, whilst both the creep and the shrinkage can be expected to be increased by about 30%. Most of the existing models used in the design codes and those proposed by individual researchers were on the whole found not to consider the aggregate’s effects in estimating the deformation properties of concrete, and this affected their estimation accuracy. Three recently developed empirical models, essentially based on aggregate stiffness in the form of aggregate absorption, for estimating the deformation of concrete made with both RCA and NA suitable for use in structural applications are discussed in some detail in this chapter.