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Mike Rhodes
Land and property valuer and auctioneer
Asked a question last year

Sugar is act as an accelerator or retarder in concrete?

Sugar is act as an accelerator or retarder in concrete?

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Ricardo Kuhn
Construction Foreman

Introduction : Hydration is the process in which cement mixes with sand, gravel and water to harden and form the mixture we call concrete.

Sugar (yes, the white sugar used in households) behaves like a Retarding Admixture and reduces the rate of hydration reaction of cement.

Sugar is very effective, even in minute quantities. To such an extent that, an excess of sugar content in the concrete mix by weight of 0.2% will impede the hydration reaction completely. As a result, the concrete will never set, and collapse immediately once the shuttering is removed. This process is known as Killing of Set.

It is generally done in hot weather conditions to counter the hardening process due to high temp.

Sugar based soln’s are sometimes added to the mix when workers need to keep the mix moist.

The setting time increases with the increase in % of sugar up to 0.06%.

The delay in setting of concrete could be useful in preventing cold joints & in reducing early setting of cement in hot weather concreting.

Sugar when used in right proportions acts as retarder but when it is used in excess, it reverse the property i.e., becomes accelerator.

Sugar above 0.08% by wt of cement accelerated the setting time with nominal gain in initial strength.

So a careful using of sugar can be economical compared to chemical retarder products

Ross Kim
Geotechnical engineer

Sugar is retarding agent.

Retarders are type of admixture that extend the hydration induction period, thereby increasing the setting times. Sugar is a carbohydrate, a substance composed of carbon, oxygen and hydrogen. It can be useful when concrete used in hot weather.

  • Sugar is used as a retarder for a concrete mix.
  • The setting time of concrete increases with increase in the percentage of sugar up to 0.06% by weight of cement. Beyond 0.06% use of sugar it is found that the both initial and final setting times drastically reduces. Sugar when used in correct proportion acts as retarder.
  • Sugar upto 0.06% helps to delay the setting of cement at construction site during hot weather concreting.
  • It is cheap and readily available. If used carefully, it could be economical in comparison with other retarders.
  • Furthermore, most of the studies conducted on the use of sugar as a set retarder focused on the setting time of such concretes, without much emphasis on the effect of adding sugar on strength. Still some studies observed that, the concrete mixture with 0.06% of sugar had more 28-day compressive strength, by about 14.64 MPa, as compared to the concrete without sugar.

Sugar meddles with the concrete restricting cycle in the solid. Note that solid and concrete are not equivalent. Concrete is made by consolidating concrete, water and a filler material called a "total," like rock or sand. Most concrete is produced using limestone and dirt. It responds with water to frame a solidifying glue that ties the total together to create hard concrete. This solidifying cycle is called hydration.

One hypothesis recommends that when the solid combination contains sugar, the sugar particles connect themselves to the hydrating solidify and repress the synthetic responses associated with hardening the material.

sugar builds the centralizations of calcium, aluminum, and iron in concrete. The sugar particles consolidate with these metals to frame insoluble compound buildings that coat the concrete grains. A few key synthetic cycles that solidify the solid are then hindered. Hydration hinders the cycle and the solid takes more time to set. Thus, sugar is known as a retarder. Retarders increment the setting season of cement.

Refined white sugar is extraordinary compared to other retarders. Lactose, the sugar found in milk, is a moderate retarder. Trehalose, a sugar created by different parasites, is non-hindering and doesn't influence setting time.

Sugar is mainly famous as retardant of concrete and thus is often used to help adjust the setting times, especially in emergencies. Retardants are used to slow down the setting of concrete, mainly in warm weather, to make it more plastic and provide them more time to work with the material.

Here in sugar, the setting process is slow down because it interferes with the chemical reaction that causes cement to set when water is added. Sugar is composed of carbon, oxygen and hydrogen atoms which can interfere with the hydration process by binding with the minerals and slow down the reaction. There are also some theories that the sugar-metal complexes that form can also create an insoluble layer around the cement grains that impedes the reaction necessary for hardening. All type of sugars are not efficient at this. But Glucose, a simple sugar that is mainly formed through the breakdown of starch and is the main component of corn syrup, and lactose, which is found in milk, are considered to be good cement retarders.