Abstract The effects of C3A content, fineness, gypsum content, C3S:C2S ratio, and alkali content of the cement on the correlation between 1-day accelerated and 28-day normal strength of concrete were investigated. The accelerated testing method used was that developed by the Institution of Civil Engineers (ICE) Accelerated Testing Committee [1]. Both C3A and alkali content did not affect the correlation between accelerated and 28-day strength. Increased fineness caused the predicted 28-day strength to be less than actual. Increased gypsum content could cause an increase in accelerated strength and at the same time a decrease in 28-day strength. The ICE correlation was not applicable when cements of low C3S:C2S ratio were used.