Why Sugar is Added in Concrete

Concrete is an extremely used construction material that is a mixture of water, cement, sand, aggregates and sometimes admixtures are also required in suitable proportions as per construction requirements.

Durability, strength, and binding strength are some of the superior properties of cement or concrete which are dependent on the initial setting time of concrete that is again ultimately affected by weather conditions.

This leads us to the conclusion that climatic or atmospheric conditions are very vital while considering the properties of concrete. The role of Sugar In Concrete is to delay or increase the setting time of cement concrete at the construction site so as to obtain the required characteristics of concrete such as strength and durability.

This method is cheap as sugar is a readily available component beneficial in delaying the setting of concrete.

Sugar in Concrete

Sugar is basically a carbohydrate, which is composed of oxygen, carbon, and hydrogen elements. For hot weather conditions where the subsequent decrease of setting time of cement is observed, in such conditions Retarders and Accelerators such as Retarder sugar and gypsum are used to increase the setting time of concrete.

Sugar is cheap, affordable, and easily available material that shows an increase in both initial and final setting time of cement paste with its increment of 0.1%.

It has been experimentally proven that concrete with sugar has shown increments in concrete compressive strength by 22.4%, 19.6%, and 20.3% at the span of 7, 14, and 28 days respectively as compared to concrete with no sugar.

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Effect of Sugar on Setting Time of Concrete

When Sugar is used in concrete it delays the setting time of concrete acting as a retarder. Sugar of quantity 0.1% could delay the initial setting time by 116 minutes of the concrete. Hence to delay the setting time by the required amount one could adjust the value of sugar accordingly.

Sugars in concrete are categorized under “cement destroyers” which when added to concrete show an increment in concrete compressive strength by 22.4%, 19.6%, and 20.3% after the span of 7, 14, and 28 days respectively comparatively with concrete with no sugar. This is the result of the subsequent increase in the setting time of concrete.

Sugar is found to be not having an adverse effect on concrete but can delay initial and final setting time by 80 minutes and 110 minutes respectively for the value of 0.06% by weight of cement.

However, sugar is of different forms and each form acts differently in concrete. Like Trehalose does not affect concrete setting time and Lactose is only a moderate concrete retardant. Among all other sugar molecules, Sucrose is known to be the most effective retardant.

Use of Sugar as a Concrete Surface Retarder

The use of sugar as a concrete surface retarder takes into account the initial setting time of the concrete, which delays or increases it as per necessity. For the surrounding conditions to be too hot may accelerate the setting time of concrete because of surface heating.

Sugar as a Concrete Surface Retarder delays the setting time of concrete in order to obtain certain characteristics during its curing period.

It is seemingly utilized in inadequate atmospheric conditions to capitalize on the rapid coagulation due to higher temperatures.

Sugar Concrete Ratio

The quantity increment of sugar up to 0.05% by weight of concrete increases the setting time of concrete sharply, but further addition of sugar results in a decrease in the rate of setting time of concrete.

Experimental results have proved that the dosage of sugar in the range of 0.05–0.1% does not have any adverse effects and is capable of not causing any further damage to structure considering both types of cement. This specifies the Sugar Concrete Ratio of 0.05:1 as the most suitable one.

Change in Properties After Adding Sugar in Concrete

We can see the change in the properties of concrete once Sugar is added to it. Not only the initial and final setting time of concrete is changed but also the characteristics properties of concrete are affected in good cause.

The primary change that occurred by adding Sugar in Concrete is an increased flowability and compactness of the cement. The movement of adding Sugar in Concrete initiates retarding action on concrete.

There is a sufficient increase of later strength in concrete, reduction in heat of hydration is observed and formation of temperature cracks is observed. These are some of the functional changes that occurred in concrete.

Recommendations of Sugar in Concrete

Sugar in Concrete acts as a retarder if mixed in proper proportion, in the urge to obtain maximum characteristics. However, if applied in excess quantity it might result in reversing its characteristics.

The recommended quantity as per standards for applying sugar is 0.05% of the total weight of concrete. This quantity is capable of ensuring the maximum properties gain by concrete. In subsidiary of applying the required quantity in the production plant, the sugar of necessary proportion is measured precisely.

To improve the compressive strength of concrete by 3-4% after the span of 28 days, sugar of 0.06 quantities in terms of percentage with respect to the total weight of concrete is required. The same amount is required to delay the initial setting time by 80 minutes.

Delaying the sugar added by the period of 3 to 7 days ensures the safeguard of cold joints. Similar purposes of sugar are served by OPC and some salts.

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Reason for Adding Gypsum in Cement for Sugar in Concrete

Among the available four minerals responsible for coagulation Tri-calcium aluminate (C₃A) is the most reactive one in cement.

There is an increase in heat radiation noticed which is proportional to an increase in C₃A in the setting and coagulation process. This is the result of the reaction of C₃A with water occurring rapidly further manipulated by subsequent adding of gypsum.

Gypsum also recognized as crystallized CaSO4 (Sulphate content is used to express Gypsum Content) forms a surrounding around the cement particle hindering the process of reaction of cement particles with water.

In the process of hydration, Gypsum is highly reactive with C₃A forming a precipitate as calcium sulphoaluminate hydrate which in turn forms a layer of cement particles stopping the process of C₃ hydration.