Study on drying shrinkage of blended cement concretes

This paper presents the results of an experimental study on the mechanical properties of blended cement concrete. The work was part of a larger study examining the effects of new generations of cements on the early and long term behaviour of concretes. The aim of the study was to determine the effect of binary combinations of PC with fly ash, ggbs, and silica fume on the fresh and hardened properties of concrete. The work focussed on concrete mixes with water-cement ratios, 0.4, 0.5, and 0.6 and a cement content of 515, 410 and 340 kg /m³ respectively. Fly ash, ggbs and silica fume were used at 30%, 50% and 10% by mass of the total cement, respectively. The mechanical properties evaluated were development of cube strength, and strain due to drying shrinkage. A normalization procedure was used to compare the concretes at the same standard cube strength and water/cement ratio. It was noted that there was a decrease in 28 day compressive strengths with fly ash and ggbs and an increase with silica fume for all w/c ratios. Fly ash concretes showed a decrease in drying shrinkage and silica fume concretes showed an increase in drying shrinkage compared to equivalent PC mixes. There was no significant difference in ggbs and PC concretes.