Civil Engineering - Building Materials - Discussion

5. 

Pick up the correct statement from the following:

[A]. For thin structures subjected to wetting and drying, the water cement ratio should be 0.45
[B]. For mass concrete structures subjected to wetting and drying, the water ratio should be 0.55
[C]. For thin structures which remain continuously under water, the water-cement ratio by weight should be 0.55
[D]. For massive concrete structures which remain continuously under water, the water cement ratio by weight should be 0.65
[E]. All the above.

Answer: Option E

Explanation:

No answer description available for this question.

Deepthi said: (Aug 13, 2013)  
Strength of concrete primarily depends upon the strength of cement paste. Strength of cement paste depends upon the dilution of paste or in other words, the strength of paste increases with cement content and decreases with air and water content.

Amit Karn said: (Jun 28, 2014)  
How to use these ratios in Practical engineering work?

Please explain me!

Gundo said: (Jul 17, 2014)  
The cement:mortar ratio is important in prac engineering work because cement features, precast or not, need a specific ratio to suit its specific function. Say for instance you're building a brick wall which has an opening; your c:m ratio (the first number represents one "part" cement in my country, and the latter represents aggregates such as sand, stones etc) between the bricks which a situated above the opening must be in such a way that it is stronger than the cm of the surrounding bricks.

Madhu C N said: (Aug 11, 2014)  
AS W/C Ratio increases strength decreases right then how can we use those high ratios at important places ?

Ravi Teja Trendy said: (Oct 5, 2014)  
The reaction of cement with water is exothermic and releases lot of heat. This heat is very high in case of mass concrete structures which in turn results in failure.

So high W/C ratio is used for both workability during construction and serviceability during operation.

Shiva said: (Jan 19, 2015)  
In water, the thin like structure require 0.55 wc ratio. Why it is increasing in water every structure will given high wc ratio from a supposed one.

Navjot Patial said: (May 6, 2015)  
On high workability it easy to work on those concrete. So we use more water cement like 0.55 or 0.65.

Harsha said: (Jul 6, 2015)  
Can any one keep reference for above mentioned W/C ratios?

Pradeep said: (Aug 14, 2015)  
Why massive concrete structures which remain continuously under water w/c ratio is high as compare to drying & wetting concrete structure?

Arti said: (Sep 29, 2015)  
As the material is thin it will not require much water, even in dry as well in wet condition because it will have the tendency to fulfill its water requirement, but in case of mass concrete it will need enough water for its hydration whether in dry or wet condition, its because it is thick.

Adeleke, Abdul Waheed said: (Sep 29, 2015)  
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.

Bhargava Reddy said: (Nov 19, 2015)  
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?

Khatri, Tejinder said: (Dec 17, 2015)  
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.

Swarup said: (Dec 29, 2015)  
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.

Akhil said: (Oct 27, 2017)  
.65 wc ratio its bit high, and asking for segregation.

Husen said: (Jan 17, 2018)  
On what dose the foundation of a construction rest on?

Sanju said: (Nov 4, 2018)  
@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.

Zach said: (Nov 25, 2018)  
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.

Dilip said: (May 28, 2020)  
It's based upon IS456-2000 Exposure conditions.

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