# Civil Engineering - Building Materials - Discussion

Discussion Forum : Building Materials - Section 1 (Q.No. 5)
5.
Pick up the correct statement from the following:
For thin structures subjected to wetting and drying, the water cement ratio should be 0.45
For mass concrete structures subjected to wetting and drying, the water ratio should be 0.55
For thin structures which remain continuously under water, the water-cement ratio by weight should be 0.55
For massive concrete structures which remain continuously under water, the water cement ratio by weight should be 0.65
All the above.
Explanation:
No answer description is available. Let's discuss.
Discussion:
20 comments Page 1 of 2.

Mukul said:   9 months ago
How is it possible? For underwater?

For thin structures which remain continuously underwater, the water-cement ratio by weight should be 0.55.

Dilip said:   4 years ago
It's based upon IS456-2000 Exposure conditions.

Zach said:   5 years ago
That 0.65 is way too more. For massive structures, we will keep w/c ration very less. Because as w/c ratio increases strength decreases. Just google for WC ratio vs strength, you will get the graph to understand. And for underwater structures, we always try to make WC less.
(2)

Sanju said:   5 years ago
@All.

As we see in the IS Code-10262, it,s clear that the W/C ratio is fixed based on the experience (d/mix done earlier if any for that area) and trail mix for the particular Gr of concrete. It also depends on the workability (i.e, the reqd. Slump).

W/C ratio normally increases for the higher Gr. of Concrete. The Selection of Gr.of concrete basically depends on the factor like- (a) Types of structure (b) Location of structure (i.e, exposure condition) )to be constructed (c) Strength required for the Concrete.

So, confirming the W/C ratio without considering the above factors is not practically acceptable.
(1)

Husen said:   6 years ago
On what dose the foundation of a construction rest on?

Akhil said:   6 years ago
.65 wc ratio its bit high, and asking for segregation.

Swarup said:   8 years ago
In case of under water mass concrete structure, w/c ratio should be high as the concrete needs high degree of work ability. Similarly for thin concrete structures also.
(1)

Khatri, Tejinder said:   8 years ago
Any one please elaborate why there is a need of higher w/c ratio in case of underwater concreting?

Since the structure is already under water so the heat of hydration that gets generated will be taken care of by the curing water itself.

Please correct me if I am wrong.

Bhargava reddy said:   8 years ago
I have one doubt, water cement ratio of m20 concrete is 0.55. My question is 0.55 means how many bags of cement and how many bags of water we should use. Please anyone can answered my doubt?

ADELEKE, Abdul Waheed said:   9 years ago
The reason for high w/c in massive concrete under water is due mainly on work ability. Practically most of the concrete work under water need casing, and for proper compaction to be achieved the poured concrete has to be self compacted.