Shrinkage of concrete stored in natural environments

Abstract The paper reports on the influence of the natural environment on the drying shrinkage of a range of concretes, with and without steel fibre reinforcement. A combination of increasing cement content, the addition of silica fume (SF) and reduced water/binder ratio was used to obtain a wide range (C30–C70) of concrete strengths. Both prism and cylinder test specimens were used in the study and a fibre concentration of 2% (by weight) was used in the fibre reinforced concrete (FRC) mixes. The experimental results have been compared with predicted shrinkage strains obtained from the ACI 209 model. The results show that the effect of varying relative humidity and temperature in the natural environment had only a limited effect on the drying/autogenous shrinkage. The addition of 2% fibre to the various mixes had a negligible effect on shrinkage for the lowest strength (C30) but the restraint on the development of shrinkage was enhanced as the strength of the concrete was increased. Comparison between experimental results and predicted shrinkage strains was not good for the high-strength concretes, although good correlation was observed for the lower strengths (C30–C45). Further research is required to improve the prediction models for use with high-strength concretes with particular emphasis being given to the rapid development of drying/autogenous shrinkage during the first month after casting the concrete.