This is why sugar is added to concrete...

                                                                                                                                                                               SUGAR IN CONCRETE!

                        "WHY DO THEY ADD IT ??"

     You might be wondering that, what this sugar is going to do with concrete, right ?? Ya, then you are at the right place.Here we go.

transit_mixer_carrying_RMC

Let us think about this situation when some transit mixer transporting RMC gets stuck in the mid of traffic for a long time then what will be your remedy in avoiding concrete from getting set... yeah, this is the case where sugar comes in handy by acting as a retardant, making concrete more plastic.For your surprise, you can even add some sort of cold or soft drinks to the concrete for delaying the setting time of concrete.

So, How does it work?

There are diversified theories in explaining this 'sugar in concrete' concept. Some of the most significant theories are as follows.

• Theory 1: Formation of sugar coat

In the process of setting of concrete water has to react with cement. But the addition of sugar to concrete hinders this reaction by forming a coat around the cement particles(molecules).

• Theory 2: Formation of insoluble complexes

Due to the addition of sugar to concrete, the conc. of  Al & Ca gets reduced, since sugar forms complexes with these elements.Thus reaction between Al, Ca, water is hindered.

• Theory 3: Glucose Catalytic Principle

Since the surface of sugar has strong polarity it results in solid liquid adsorption thus it hinders the crystal contact and tricalcium silicate hydrate reaction.

 Those theories sounds complex right :D 

• In Layman's terms:

Hydration reaction between water and cement is prevented by sugar thus it delays the concrete setting process.

Results based on Tests:

1. It is tested that usage of >1% of sugar conc. might completely delay the process of concrete setting for days.
2. The sugar content of 0.06% by weight to concrete, can improve compressive strength by 3.26% in 28 days and delays initial setting time by 94 min.
3. The addition of OPC(ordinary Portland cement) would give retardation of 4hrs.
4. The addition of 0.04% of sugar by weight to cement will almost double the setting time.
5. Sugars like glucose, lactose, raffinose act as good retarders.
6. For your surprise, even some types of salts act the same purpose.

Conclusions:

1. Sugar owns the property of water reducing & set retarding mixture.

               For crystallisation or hydration of cement, it should contain at least 25% of water by weight to cement.But too much content of water might decrease the strength.This can be avoided with the help of sugar(due to its property as explained in point 1).

     2. Due to its action with concrete, it can be regarded as delayed accelerator rather than retarder.
     3. Usage of sugar in concrete doesn't show any effects on durability, absorption, shrinkage properties of concrete.

Uses:

1. Useful during construction in summer, during which temperature cracks are seen due to the uncontrollable temperature difference between inside & outside mainly resulting from the heat of hydration of cement.
2. Sugar acts as a retarder.
3. Flowability & compactibility of concrete is increased.
4. Hydration heat is decreased.
5. overall strength of concrete is increased.

Incidents in relation:

Victoria Line:(London)

             

victoria line_concrete_control room

Engineers working in Victoria Line used sugar for removing the concrete that was accidentally poured over the signalling equipment during upgrade work of Victoria station.

Baramati:

 A slab got collapsed in Baramati after construction due to the usage of river water for construction works which was polluted by wastes of the nearby sugar industry.(As sugar enhance setting time of concrete, it took more time to achieve strength).

That's all for the topic.Hope you got some info.

Signing off,

Yours UCY

THANK YOU.