Civil Engineering - Concrete Technology - Discussion

@Gurjant Singh Sawna.

For Hydration of cement only it requires *26% of water by Mass* for 500kg of cement it will be 130 kg of water.

Those who are saying 38% or 40% it is for (*Hydration+ gel pores filling*).

It is NOT necessary that for the process of "Hydration" the gel pores should be "saturated".

We think that fully hydration means for "chemical reaction & pores filling" both but Hydration means chemical reaction btwn cement and water only.

the question has said for hydration, not complete hydration
so, 15% water is used by cement to fill voids(pores) and 23% for hydration so for complete hydration we should use 23+15=38%
but as per question for hydration:: 500*.23= 115 so near value is 120 kg . 120 kg is right answer

Total water requirements for Complete the chemical reaction Is 38 %,

So, 38 * 500 = 19.

Because 23% of the water required for hydration process & 15 water is required for filling the gell pores.

So, total (23+15) = 38% water is required to complete the total chemical reaction.

Cement 500= 0.35 m3 ( 50 kg cement =0.035 m3 cement )
Water Req for cement 38 %.
= 0.35 * 38/woo.
= 0.133 m3 Water.

From Water Density.
1000 kg/m3 = (kg/0.133 m3).
Water = 133 kg.

Cement 500= 0.33 m3 ( 50 kg cement =0.033 m3 cement).

Water Req for cement 38 %.
= 0.33 * 38/woo.
= 0.127 m3 Water.

From Water Density.
1000 kg/m3 = (kg/0.127 m3).
Water = 127 kg.

It has been further estimated that about 15% by weight of cement is required to fill up the gel pores and 23% is used for hydation of cement process. So total 38% is required.

For complete reaction, 38% of water by weight of cement is required.
0.38 * 500 = 190 kg.

But the answer given in this option is 130kg.

How?Can anybody explain?

Normally the standard weight of cement bag = 50kg it requires 35 litres of water.

So 500 kg of cement bag required = 500*35/50 = 135 litres of water.

@All,

The question has said for hydration, not complete hydration. So we will consider 23% only.

Then, (0.23* 500 = 115) Approx = 120 kg Answer.

Actually it is 25% of corresponding water of cement.

So 500*0.25 = 125 kg. But according to option given answer will be 130 kg.