Common sugar is one of the most effective retarding agents used as an admixture for delaying the setting time of concrete without detrimental effect on the ultimate strength. Addition of excessive amounts will cause indefinite delay in setting. At normal temperatures addition of sugar 0.05 to 0.10 per cent have little effect on the rate of hydration, but if the quantity is increased to 0.2 per cent, hydration can be retarded to such an extent that final set may not take place for 72 hours or more. NOTE : When sugar is used as a controlled set retarder, the early strength of concrete is severely reduced but, beyond about 7 days, there is an increase in strength of several per cent compared with a non-retarded mix. This is probably due to the fact that delayed setting produces a denser hydrated cement gel.