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Fly ash based concrete subjected to high temperature
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JVCSNL
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PostPosted: Tue Feb 28, 2012 5:14 pm    Post subject: Fly ash based concrete subjected to high temperature Reply with quote

Dear Members,

In most of the building works use of fly ash in concrete is encouraged for better concrete durability.

Can any one highlight effects of sustained temperature ( in range of 150 deg. c. to 200 deg. c.) on concrete with fly ash content of 20%?

What would be effects of high temperature on modulus of elasticity, strength, creep, etc?  Will it be same as that of concrete made with OPC?

Sustained high temperature (atmospheric) and temperature effects due to radiation is usually ignored in many designs.  Under ground tanks with various liquid levels at different times in the service life will be exposed to sustained temperature due to internal temperature rise.  How such considerations are taken in to account in design as well as during construction.

Little is covered in the available literature.

Regards,

Jignesh V Chokshi
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PostPosted: Tue Feb 28, 2012 5:20 pm    Post subject: Reply with quote

Dear Jignesh V,
You have raised an important query. It will be interesting to list real life scenarios where concrete will be under the temperatures of the range 150 degree c to 200 degree C for long period of time.
Best Regards
Sanjeev
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JVCSNL
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PostPosted: Tue Feb 28, 2012 5:42 pm    Post subject: Reply with quote

Dear Er. Sanjeev,

Many of the industrial machinery which is operated using high temperature steam, fuel oil, natural gases etc. are provided with enclosures, where high temperature potential exists.

Also, at many of the steam exhaust chambers, the temperature rises.  

Many of the high temperature equipment supported on concrete experience high temperature at base of the equipment.  Equipment is insulated to such temperatures, but the base plate, which requires to be in contact with grout is subjected to temperature transfer from equipment.

In many of the solar plants, the heat of radiation would be very high.  
Concrete member sizes of large machine foundations are very large and in order to control the temperature of concrete, many contractors insist use of fly ash in concrete.  However, not much knowledge is available on the effects of such exposure.  

The point becomes more interesting when we have to use fly ash near marine environment but the concrete is subjected to high temperature.  This conflicting situation makes more interesting, as on one hand we have to recommend fly ash in concrete but on other hand, we also have to account temperature effects.  

Hence, the topic was raised to gather opinions and knowledge of members about the concrete with fly ash subjected to high temperature.

Regards,

Jignesh V Chokshi
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bsec
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PostPosted: Tue Feb 28, 2012 5:49 pm    Post subject: Fly ash based concrete subjected to high temperature Reply with quote

Dear All,

Attached please find a PPT presentation prepared by me on durability provisions of latest IRC:112-2011, which might be of use for the budding young engineers.


Best Wishes


Alok Bhowmick

On Tue, Feb 28, 2012 at 10:44 PM, JVCSNL <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear Members,

In most of the building works use of fly ash in concrete is encouraged for better concrete durability.

Can any one highlight effects of sustained temperature ( in range of 150 deg. c. to 200 deg. c.) on concrete with fly ash content of 20%?

What would be effects of high temperature on modulus of elasticity, strength, creep, etc? Will it be same as that of concrete made with OPC?

Sustained high temperature (atmospheric) and temperature effects due to radiation is usually ignored in many designs. Under ground tanks with various liquid levels at different times in the service life will be exposed to sustained temperature due to internal temperature rise. How such considerations are taken in to account in design as well as during construction.

Little is covered in the available literature.

Regards,

Jignesh V Chokshi
     



     


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PostPosted: Tue Feb 28, 2012 6:20 pm    Post subject: Re: Fly ash based concrete subjected to high temperature Reply with quote

Dear Er Alok Bhowmick,

Very nice presentation covering a number of points related to durability! Should be very useful to young engineers.

Regards
NS
bsec wrote:
Dear All,

Attached please find a PPT presentation prepared by me on durability provisions of latest IRC:112-2011, which might be of use for the budding young engineers.


Best Wishes


Alok Bhowmick

On Tue, Feb 28, 2012 at 10:44 PM, JVCSNL <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
            Dear Members,

In most of the building works use of fly ash in concrete is encouraged for better concrete durability.

Can any one highlight effects of sustained temperature ( in range of 150 deg. c. to 200 deg. c.) on concrete with fly ash content of 20%?

What would be effects of high temperature on modulus of elasticity, strength, creep, etc? Will it be same as that of concrete made with OPC?

Sustained high temperature (atmospheric) and temperature effects due to radiation is usually ignored in many designs. Under ground tanks with various liquid levels at different times in the service life will be exposed to sustained temperature due to internal temperature rise. How such considerations are taken in to account in design as well as during construction.

Little is covered in the available literature.

Regards,

Jignesh V Chokshi
     



     


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malayala_sivaramkapil
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PostPosted: Tue Feb 28, 2012 7:58 pm    Post subject: No Title Reply with quote

Dear Jingesh,

As Flyash content increases in concrete obviously it will reuce
HOH,There will not be any affect on strength if un burnt carbon in
Flyash is under prescribed limits.

Creep and Modulus Of elasticity is going to be enhanced due to proper
particle packing as compared to Pure OPC
As you are planing to reduce or control temperature It is better to go
with higher replacement level but not with Flyash here it is
prefereble to use GGBFS.

Correct me If I am wrong.

Regards,

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chetan sakariya
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PostPosted: Wed Feb 29, 2012 2:58 am    Post subject: Fly ash based concrete subjected to high temperature Reply with quote

What is GGBSF ?
Limit for carbon content is how much? On Feb 29, 2012 8:19 AM, "malayala_sivaramkapil" <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear Jingesh,

As Flyash content increases in concrete obviously it will reuce
HOH,There will not be any affect on strength if un burnt carbon in
Flyash is under prescribed limits.

Creep and Modulus Of elasticity is going to be enhanced due to proper
particle packing as compared to Pure OPC
As you are planing to reduce or control temperature It is better to go
with higher replacement level but not with Flyash here it is
prefereble to use GGBFS.

Correct me If I am wrong.

Regards,
     



     



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Moruf
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PostPosted: Wed Feb 29, 2012 5:14 am    Post subject: Fly ash based concrete subjected to high temperature Reply with quote

On Wed, Feb 29, 2012 at 5:48 AM, malayala_sivaramkapil <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear Jingesh,

As Flyash content increases in concrete obviously it will reuce
HOH,There will not be any affect on strength if un burnt carbon in
Flyash is under prescribed limits.

Creep and Modulus Of elasticity is going to be enhanced due to proper
particle packing as compared to Pure OPC
As you are planing to reduce or control temperature It is better to go
with higher replacement level but not with Flyash here it is
prefereble to use GGBFS.

Correct me If I am wrong.

Regards,
     



     



Thanks for this initiative. Concrete durability is something really important to reduce the cost of retrofitting and extension of structural service life. However, the recent research output has proved the following regarding fly-ash usage towards improving concrete durability. These are among the conclusions  made by R.W Burrows (member ACI committee 222 which I also belong) :
1. Fly-ash does not help the concrete due to damage from drying because microcracks caused by drying shrinkage open up rather than heal autogenously if fly ash is present
2.It decreases resistance to freezing and thawing
3. low permeability to chloride ingress is achievable due to long curing but disappears when if the concrete is weathered by cycle of wetting and drying.
4. If chloride comes in contact with steel, the fly-ash aggravates corrosion rate.
5.Performance due to creep, thermal contraction, alkali-silica reaction among others are not really satisfactory compare to other Supplementary Cementitious materials (SCM)
 
-

Moruf O. Yusuf, CCE,PMP,MNSE
Project Department
King Fahd University of Petroleum and Minerals
P.O.Box 5019
+96638604703
 

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malayala_sivaramkapil
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PostPosted: Wed Feb 29, 2012 2:38 pm    Post subject: Fly ash based concrete subjected to high temperature Reply with quote

Can you please explain it in detail
regarding
 why it cant heal microcracks? As the heat of hydration reduces with Flyash so that overall crack formation can be reduced.
How It decreases resistance to freezing and thawing?



On Wed, Feb 29, 2012 at 11:01 AM, Moruf <forum@sefindia.org (forum@sefindia.org)> wrote:
[quote]  On Wed, Feb 29, 2012 at 5:48 AM, malayala_sivaramkapil forum@sefindia.org (forum@sefindia.org))> wrote:
--auto removed--

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dipak_bhattacharya
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PostPosted: Thu Mar 01, 2012 5:19 pm    Post subject: Fly ash based concrete subjected to high temperature Reply with quote

Issues raised by Mr. Chokshy on temperature is very important, but he should have clarified the question with specific focus.

Handling liquid in the range of 150deg.-200deg Celsius definitely is not related to water at least, may be super heated steam and may pertain only to the tail race / condenser of steam turbines of thermal power plants. 


More common problem, I find, in concrete tanks handling cooling system-water which is much near + 65 deg. celsius or , may be above.It's effect on reinforcements, also needs to be known- both for puzzolona and for OPC as well.


Thanks,


Dipak Bhattacharya.

 

On 29 February 2012 11:01, Moruf <forum@sefindia.org (forum@sefindia.org)> wrote:
[quote]            On Wed, Feb 29, 2012 at 5:48 AM, malayala_sivaramkapil forum@sefindia.org (forum@sefindia.org))> wrote:
      --auto removed--

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