Influence of Specimen Size on Effect of Curing Regime on Concrete Compressive Strength

The compressive strength of 70‐, 120‐, 200‐, and 250‐mm concrete cubes, subjected to four different curing regimes, was determined at the ages of 28 and 90 days, in order to study the influence of specimen size on the effect of curing regimes on cube strength. In the first curing regime the specimens were exposed unprotected to 30°C/40% RH. The second regime was similar to the first one but exposure took place at 20°C/65%. In the third regime the specimens were stored in water at 20°C to the age of seven days followed by storage in air at 20°C/65%, and in the fourth regime the specimens were continuously stored in water at 20°C. It was found that the effect of curing regimes on cube strength is related to specimen size, and it is much greater in the smaller than in the larger specimens. For example, the 28‐day strength of the concrete subject to seven days wet curing (third regime), was about twice the strength of the corresponding uncured concrete when 70‐mm cubes were tested, and only 10% greater when 250‐mm cubes were tested. Test results also include data on the effect of moisture content on cube strength and on the effect of specimen size on strength development between the ages of 28 and 90 days.