Compressive and Tensile Creep and Shrinkage of Synthetic FRC: Experimental Results and Comparison to Codes

The mechanical properties of FRC mixes, namely compressive and tensile strength, are generally improved with respect to their unreinforced counterparts due to the contribution of fibres. This has implications in aspects like crack propagation or the development of time-deferred strains such as those resulting from creep and shrinkage, which in turn influence the long-term deformation of structural elements. The effect of fibres on compressive creep has been studied by various researchers, and codes and guidelines for the design of concrete structures include provisions to predict creep under compression. However, tensile creep of FRC has not attracted the same level of coverage despite its relevance to the loss of tension stiffening. This paper presents the results of an experimental study in concrete specimens reinforced with synthetic fibres were subjected to constant loading in uniaxial tension and in compression in order to evaluate the effect that increasing dosages of synthetic fibres have on the resulting time-dependent strains. The evolution of shrinkage, creep strains and the creep coefficient were analyzed in relation to the fibres dosage. The experimental strain-time curves were compared to the theoretical curves from the models adopted in the Eurocode 2, the Model Code, or by the ACI Committee 209.