What happens when sugar is added in to concrete?

When sugar is added to concrete it delays the setting time of concrete as it acts as the retarder.

When sugar is added to the concrete, it acts as a retarding agent, and it delays the setting time of concrete. Sugar is one of the traditional retarding agents used in concrete. If the Sugar dosage level is approximately 0.06% by weight of the cement then it increases the setting time up to 1.33 hrs

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Basically, the principle followed is the glucose catalytic principle. According to its formula, it belongs to the polyhydroxy group and its surface has strong polarity. This results in solid-liquid adsorption. Hence the molecular hydroxy group slows the hydration process by hindering the crystal contact and delays tricalcium silicate hydrate reaction.

Some of the functions of sugar in concrete are as follows;

• Increase in flowability and compactness.
• Retarding action on concrete.
• Reduction in hydration heat and temperature cracks.
• Increase in later strength of concrete.

In simple terms, sugar acts as a retarder and delays the setting time of concrete.

This is the reason why transit mixer drivers are sometimes advised to add some soft drink to the concrete mix if the vehicle gets stuck up in the traffic for too long.

Technically speaking,

Sugars have been categorized as ‘cement destroyers’ and when sugar is added to Portland cement paste at the onset of mixing, hardening may be delayed indefinitely.

Concrete hardens due to formation of calcium silicate hydrate.

The retarding action of sugar is probably by the prevention of the formation of calcium silicate hydrate.

Sugar exceeding 0.2% by weight of concrete will slow down the reaction drastically.

Sugar increases the setting time of cement up to 1.33 hrs at dosage level of 0.06% by wt of cement. There will be no effect on workability, compaction by the use of sugar as admixture in concrete. Higher long-term compressive strength is achieved in concrete by the use of sugar as admixture.