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[parikshit_pandya]

Y �Dear all,

what are the general thumb rules for nominal mix design?

Parikshit pandya

Posted via Email

[dipeshtanuja]

�
Hi,

Regarding nominal mix design of reinfirced concrete M20 it is 1:2:3 of cement:sand:ageeregate with watercement ratio.

On Thu, 09 Nov 2006 parikshit_pandya[AT]red... wrote :

[rajmane]

10 Nov 2004

Dear all

I do not agree that nominal mix design of reinforced concrete M20 it is
1:2:3. For RCC. We have to always note that a design mix which should
satisfy both strength (used in design of structures) and durability
requirements (max. w/c ratio, minimum cement content, minimum grade, for
a particular exposure condition) as per IS:456-2000. When we say RCC, I
feel, we mean only structural concrete. Then durability requirements of
Codes have to be ensured.

N P Rajamane Deputy Director and Head, Concrete Composites Lab,
Structural Engg Research Centre, CSIR, Taramani, Chennai 600113 (Ph :
22549152 (D), 22549150 (CCLab), Res: 224417882) Email :
rajmane[AT]ser..., rajamanenp[AT]yah...

PS : The above opinion is personal and it may not be necessarily the
view of SERC.

dipeshtanuja[AT]red... wrote:

[Akshaya.Das]

Dear Sefian,

Here is some comment from a very experienced engineer in the
construction field. I thought to share this with you all.

Regards,

Dr A K Das

________________________________

Message From Basu, Pranab
Sent: Friday, November 10, 2006 4:53 PM
To: Das, Akshaya
Subject: nominal mix design

I could not understand as to where from the discussion evolved? Unless
you know the purpose, you might not contribute significantly. However
like others, I can share my knowledge in the following manner.

1. First of all there is no terminology like Nominal Mix Design.
Nominal Mix is a recommendation by IS 456 based on statistical data from
several regions. Obviously the structural strength as well s the
durability factor remained in consideration.

The Nominal Mix for M20concrete is 1:1.5:3, for M15 is 1:2:4

2. Design Mix is a design of concrete mix where all the actual design
requirements as per the actual materials and working conditions are
taken care of. The main design considerations are Structural Strength,
Standard Deviation in strength, Durability of structure (minimum cement
content), physical and chemical properties of building materials,
exposure of the structure, workability factor and above al the available
resources for commercial viability.

Design Mix is always an economic option but require technical
competence.

I do not know how my vies can help one, if the problem or the issue is
not known.

-----Original Message-----
Message From Das, Akshaya
Sent: Friday, November 10, 2006 4:31 PM
To: Basu, Pranab
Subject: FW: nominal mix design

Interesting discusiion!!!!!

Akshay

-----Original Message-----

Message From rajmane[AT]ser... [mailto:rajmane[AT]ser...]

Sent: Friday, November 10, 2006 10:00 PM

To: Das, Akshaya

Subject: nominal mix design

10 Nov 2004

Dear all

I do not agree that nominal mix design of reinforced concrete M20 it is
1:2:3. For RCC. We have to always note that a design mix which should
satisfy both strength (used in design of structures) and durability
requirements (max. w/c ratio, minimum cement content, minimum grade, for
a particular exposure condition) as per IS:456-2000. When we say RCC, I
feel, we mean only structural concrete. Then durability requirements of
Codes have to be ensured.

N P Rajamane Deputy Director and Head, Concrete Composites Lab,
Structural Engg Research Centre, CSIR, Taramani, Chennai 600113 (Ph :

22549152 (D), 22549150 (CCLab), Res: 224417882) Email :

rajmane[AT]ser..., rajamanenp[AT]yah...

PS : The above opinion is personal and it may not be necessarily the
view of SERC.

dipeshtanuja[AT]red... wrote:

[ranna]

nominal mix for M20 is 1:1.5:3

rajmane[AT]ser... wrote:

[mkalgal]

Dear all
I agree with Mr. Rajmane. Even if strength alone is the criteria,
please do not use "thumb rules" for mix proportion!. We can get M10
with lots of water in 1:1.5:3 mix and M30 with controlled water cement
ratio, graded aggregates and good particle packing! If proper mix
design is not possible, do some trial castings.
Regards
Kalgal

在2006年11月11日11:45:57坐着,岚纳[在]bhe……< ranna[AT]bhe...> wrote:

[rajmane]

13 Nov 2004

Dear all

(1) I do not agree that nominal mixes are " The Nominal Mix for M20
concrete is 1:1.5:3, for M15 is 1:2:4". For RCC, we have to think of
durability which is ensured by suitable adoption of w/c ratio. In the
absence of inclusion of w/c ratio in defining the concrete mix or grade,
the concretes can not be taken as acceptable. Defining/describing the
concrete without w/c ratio should stop in the interest of the concrete
constructions, especially, when the cement is produced in modern cement
plants where high strength cements are easily and consistently produced
and made available to engineers without much effect on final price.

(2) I am very glad about the following observation by Shri Basu, Pranab:

"Design Mix is a design of concrete mix where all the actual design
requirements as per the actual materials and working conditions are
taken care of. The main design considerations are Structural Strength,
Standard Deviation in strength, Durability of structure (minimum cement
content), physical and chemical properties of building materials,
exposure of the structure, workability factor and above al the available
resources for commercial viability."

However, I wish to add that the words "Durability of structure (minimum cement
content)" should be replaced with "Durability of structure (minimum cement
content, max. w/c ratio, minimum grade, for a particular exposure condition)".

(3) Let us accept important observations of Prof. Kalgal. A given mix proportion can give a wide range strengths, say ranging even from as less as 10 MPa to as high as 100 MPa depending upon several factors such as type and strength of cement strength, w/c ratio, presence/absence of mineral and chemical admixtures, type of mixer machine, transportation, placing and curing operations, age, etc.

Yours sincerely

N P Rajamane Deputy Director and Head, Concrete Composites Lab,
Structural Engg Research Centre, CSIR, Taramani, Chennai 600113 (Ph :
22549152 (D), 22549150 (CCLab), Res: 224417882) Email :
rajmane[AT]ser..., rajamanenp[AT]yah...

PS : The above opinion is personal and it may not be necessarily the
view of SERC.

Akshaya.Das[AT]ake... wrote:

[sidhudaljeet]

Dear N P Rajamane
1:1.5:3 for M-20 was used for hand mixed non vibrator concretes with water cement ratio based on water (5% of aggregates + 30% of cement ) Thus water cement ratio of 0.525. I think even today if you use hand mixed concrete and don�t use vibrator 33 grade OPC cement and water cement ratio 0.525, M-20 would be a great achievement.
Daljeet
rajmane[AT]ser... wrote:

13 Nov 2004

Dear all

(1) I do not agree that nominal mixes are " The Nominal Mix for M20
concrete is 1:1.5:3, for M15 is 1:2:4". For RCC, we have to think of
durability which is ensured by suitable adoption of w/c ratio. In the
absence of inclusion of w/c ratio in defining the concrete mix or grade,
the concretes can not be taken as acceptable. Defining/describing the
concrete without w/c ratio should stop in the interest of the concrete
constructions, especially, when the cement is produced in modern cement
plants where high strength cements are easily and consistently produced
and made available to engineers without much effect on final price.

(2) I am very glad about the following observation by Shri Basu, Pranab:

"Design Mix is a design of concrete mix where all the actual design
requirements as per the actual materials and working conditions are
taken care of. The main design considerations are Structural Strength,
Standard Deviation in strength, Durability of structure (minimum cement
content), physical and chemical properties of building materials,
exposure of the structure, workability factor and above al the available
resources for commercial viability."

However, I wish to add that the words "Durability of structure (minimum cement
content)" should be replaced with "Durability of structure (minimum cement
content, max. w/c ratio, minimum grade, for a particular exposure condition)".

(3) Let us accept important observations of Prof. Kalgal. A given mix proportion can give a wide range strengths, say ranging even from as less as 10 MPa to as high as 100 MPa depending upon several factors such as type and strength of cement strength, w/c ratio, presence/absence of mineral and chemical admixtures, type of mixer machine, transportation, placing and curing operations, age, etc.

Yours sincerely

N P Rajamane Deputy Director and Head, Concrete Composites Lab,
Structural Engg Research Centre, CSIR, Taramani, Chennai 600113 (Ph :
22549152 (D), 22549150 (CCLab), Res: 224417882) Email :
rajmane[AT]ser..., rajamanenp[AT]yah...

PS : The above opinion is personal and it may not be necessarily the
view of SERC.

Akshaya.Das[AT]ake... wrote: