2007 Volume 5 Issue 2 Pages 149-160
This paper aims to show the importance of autogenous shrinkage for the serviceability performance of reinforced high-strength concrete (HSC) flexural beams, and also the effectiveness of low-shrinkage HSCs (LS-HSC) made by using expansive additive and/or shrinkage-reducing chemical agent and/or Belite-rich low-heat Portland cement for improving the flexural serviceability performance of beam. From the design equation point of view, this paper also proposes a new concept for evaluating flexural crack width and deformation of RC beams taking into consideration the early age deformation of concrete before loading. The experimental results show that autogenous shrinkage of HSC significantly affects increases in crack width and deformation of RC beams, while LS-HSCs markedly improves their serviceability performance. The present concept, which takes into account strain change in tension reinforcement and curvature change in the cracked section before and after loading, is effective in explaining the effects of shrinkage and expansion of concrete before loading on maximum crack width and flexural deformation of RC beams. JSCE (Japan Society of Civil Engineers) code equations for predicting maximum crack width and flexural deformation into which the present concept is incorporated improve the prediction accuracy compared with conventional equations and show fairly good agreement with experimental results.