One of my friends had this question in the BARC-2014 interview. The interviewer asked him what if I threw my tea on concrete? See, that was an indirect form of what you asked. It slows the setting of the concrete. And, yes, he got it right.
In simple terms, it is based on the glucose catalytic principle. According to its formula, it belongs to the polyhydroxy group, and its surface has a strong polarity that results in solid-liquid adsorption, this molecular hydroxy group slows the hydration process by hindering the crystal contact and delays triclinium silicate hydrate reaction.
Approximately
.1 % sugar slows the rxn by ~ 5 hours.
.2 % sugar slows the rxn by 9-11 hours.
For more information watch this video
