www.半岛软件下载www.buonovino.com

STRUCTURAL ENGINEERING FORUM OF INDIA [SEFI]

Forum SubscriptionsSubscriptionsDigestDigest PreferencesFAQFAQSearchSearchMemberlistMemberlistUsergroupsUsergroupsRegisterRegisterFAQ安全提示FAQDonate
ProfileProfileLog in to check your private messagesLog in to check your private messagesLog in to websiteLog in to websiteLog in to websiteLog in to forum
Warning: Make sure you scan the downloaded attachment with updated antivirus tools before opening them. They may contain viruses.
Use online scanners
here and here to upload downloaded attachment to check for safety.

Fly ash based concrete subjected to high temperature
Goto pagePrevious1,2,3Next
This forum is locked: you cannot post, reply to, or edit topics.This topic is locked: you cannot edit posts or make replies.Thank Post www.半岛软件下载www.buonovino.comForum Index->E-conference on Durability of Concrete - Feb 27 to March 11 - 2012
View previous topic::View next topic
Author Message
JVCSNL
...
...


Joined: 26 Jan 2003
Posts: 161

PostPosted: Fri Mar 02, 2012 8:57 am文章主题: Reply with quote

Dear Members,

If any deteriorating agent is in direct contact with concrete surface, then we will definitely protect it by applying protective coating.

The protection may be given in inside face or outside face based on severity.

My point of raising this topic was that since chemical reactions will always be continuing in concrete, though a slow process as time goes, the presence of moisture, temperature etc. will have some role in effects of this chemical process.

Chemical reaction in case of higher temperature (that to sustained) induced due to surrounding atmosphere (because of any reason, I explained in other posts) will have some effects.

Following are few more questions for which definite answers are not given.

Does Pozzolonic material react the same way as other SCMs?

How ASR will be affected in case of higher temperature? Shall we specify all the aggregates and cementitious material in case concrete will be exposed to higher temperatures?

Do we need to monitor concrete for safety in such situations?

What is the maximum temperature allowed in contact with concrete that will not effect the mechanical properties of the concrete?

While searching answers for few of the above questions, I found contradictory answers. Some research says that there is no/minor effect on concrete properties. However, some other say that there is going to be some effect and the same shall be considered by engineer.

If concrete looses the properties slowly there would be cascaded increase in deterioration.

Regards,

Jignesh V Chokshi
Back to top
View user's profileSend private message
alpa_sheth
...
...


Joined: 26 Jan 2003
Posts: 278

PostPosted: Fri Mar 02, 2012 11:35 am文章主题:Fly ash based concrete subjected to high temperature Reply with quote

Dear Mr. Moruf:

This is a very interesting thread. I had posted a mail an hour ago requesting alternative opinions re. the efficacy of HVFA concrete for improving durability.
You seem to providing a response here. Can you expand on the comparision of others SCMS with Fly ash? Which do you think would be more effective from durability point of view?

Regards,

Alpa


From:Moruf [mailto:forum@www.buonovino.com]
Sent:29 February 2012 11:01
To:econf@www.buonovino.com
Subject:[ECONF] Re: Fly ash based concrete subjected to high temperature




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.低渗氯离子进入阿奇沃ble 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

Posted via Email
Back to top
View user's profileSend private message
nwalavalkar
...
...


Joined: 18 Nov 2010
Posts: 63

PostPosted: Fri Mar 02, 2012 2:35 pm文章主题: Reply with quote

Dear Mr Moruf

I would like to seek your opinion on use of Microsilica (Silica Fume) as Supplementary Cementitious materials (SCM).

Regards

Narendra
Back to top
View user's profileSend private message
JVCSNL
...
...


Joined: 26 Jan 2003
Posts: 161

PostPosted: Fri Mar 02, 2012 5:39 pm文章主题:Fly ash based concrete subjected to high temperature Reply with quote

Dear Members,

I am appending a note from some literature regarding effects of high temperature and pressure on concrete.


"A physico-chemical transformation of the paste took place with the rise in temperature. At high temperatures, chemical transformation of the gel weakened the matrix bonding, which brought about a loss of strength and elasticity of f ly ash and silica fume concrete."


Very interesting to note this.


Up to certain percentage of fly ash will have not much effect. But larger FA will have detrimental effects.


The effect will be very crucial to note for machine foundations, which are very sensitive and are many times subjected to high temperature and pressures. Hence, use of FA based concrete is avoided.


Regards,


Jignesh V Chokshi

Posted via Email
Back to top
View user's profileSend private message
JVCSNL
...
...


Joined: 26 Jan 2003
Posts: 161

PostPosted: Fri Mar 02, 2012 5:57 pm文章主题: Reply with quote

Dear Members,

I am appending a note from some literature regarding effects of high temperature and pressure on concrete.

"A physico-chemical transformation of the paste took place with the rise in temperature. At high temperatures, chemical transformation of the gel weakened the matrix bonding, which brought about a loss of strength and elasticity of f ly ash and silica fume concrete."

Very interesting to note this.

Up to certain percentage of fly ash will have not much effect. But larger FA will have detrimental effects.

The effect will be very crucial to note for machine foundations, which are very sensitive and are many times subjected to high temperature and pressures. Hence, use of FA based concrete is avoided.

Regards,

Jignesh V Chokshi
Back to top
View user's profileSend private message
bsec
Bronze Sponsor
Bronze Sponsor


Joined: 26 Jan 2003
Posts: 202

PostPosted: Sat Mar 03, 2012 2:04 am文章主题:Fly ash based concrete subjected to high temperature Reply with quote

Dear Mr Moruf,

I would like to get the thread to the original paper by R W Burrows on the subject matter.


I am sure there will be many experts in this forum, who would not like to be in the same page with you on this issue. I am looking forward to opinions from Mr Rajmane and Mr Kulkarni on the subject.


Best Wishes


Alok Bhowmick

在星期五,Mar 2, 2012 at 7:29 PM, alpa_sheth forum@www.buonovino.com)> wrote:
Quote:
Dear Mr. Moruf:

This is a very interesting thread. I had posted a mail an hour ago requesting alternative opinions re. the efficacy of HVFA concrete for improving durability.
You seem to providing a response here. Can you expand on the comparision of others SCMS with Fly ash? Which do you think would be more effective from durability point of view?

Regards,

Alpa


From: Moruf [mailto:forum@www.buonovino.com (forum@www.buonovino.com)]
发送:29日2月2日012 11:01
To:econf@www.buonovino.com(econf@www.buonovino.com)
Subject: [ECONF] Re: Fly ash based concrete subjected to high temperature




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.低渗氯离子进入阿奇沃ble 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









Posted via Email
Back to top
View user's profileSend private message
JVCSNL
...
...


Joined: 26 Jan 2003
Posts: 161

PostPosted: Sat Mar 03, 2012 4:06 am文章主题:Fly ash based concrete subjected to high temperature Reply with quote

Dear All,

Some experimental work done in India on this topic is availablehttp://dspace.thapar.edu:8080/dspace/bitstream/123456789/144/1/8042306.pdf.

The results show that there is reduction in Compressive and Tensile capacity and Modulus of elasticity at Higher temperatures.

Regards,

Jignesh V Chokshi

Posted via Email
Back to top
View user's profileSend private message
JVCSNL
...
...


Joined: 26 Jan 2003
Posts: 161

PostPosted: Sat Mar 03, 2012 4:29 am文章主题:Fly ash based concrete subjected to high temperature Reply with quote

Dear Members,

Another interesting investigation on HSC subjected to elevated temperatures.

http://ibe.sagepub.com/content/19/6/612.refs

Regards,

Jignesh V Chokshi

Posted via Email
Back to top
View user's profileSend private message
narayan_nayak
SEFI Member
SEFI Member


Joined: 02 Mar 2012
Posts: 9

PostPosted: Sat Mar 03, 2012 11:06 am文章主题:Fly ash based concrete subjected to high temperature Reply with quote

Dear Ms. Alpa Sheth,

I refer to your query to “ALL” and your response to Mr. Moruf.

Now it is beyond doubt that addition of mineral admixtures like Fly ash, GGBS, Metakaoline, Micro Silica, improves the durability of the concrete. Reduction in water binder ratio also improves the durability.

I have no hesitation in recommending Fly Ash upto 50% replacement for foundations and sub-structures. I may restrict to lesser extent say 30 to 35% in super structures.

By adding Fly ash early strength gain will get little slow which can be overcome by addition of “Alcofine” (a ultra-fine gained GGBS) or Chemical Admixture, etc.

The attached Table -1 [from Nayak NV (2012)] gives broadly summary of effectiveness of secondary cementing material on concrete.

The Self Compacting Concrete (SCC) is used where structures are heavily reinforced and chances of honey combing are high inspite of vibration. SCC also contains secondary cementing materials like Fly ash. Presently cost difference between SCC and Normal Concrete is not very substantial if you take the advantage of reduction in cost of not providing vibration in SCC.

From sustainability and durability consideration, one should encourage use of Fly ash, GGBS, etc. in our practices.

Thanks and Regards,

NV Nayak



From:alpa_sheth [mailto:forum@www.buonovino.com]
Sent:Friday, March 02, 2012 7:30 PM
To:econf@www.buonovino.com
Subject:[ECONF] Re: Fly ash based concrete subjected to high temperature



Dear Mr. Moruf:

This is a very interesting thread. I had posted a mail an hour ago requesting alternative opinions re. the efficacy of HVFA concrete for improving durability.
You seem to providing a response here. Can you expand on the comparision of others SCMS with Fly ash? Which do you think would be more effective from durability point of view?

Regards,

Alpa


From:Moruf [mailto:forum@www.buonovino.com] ((mailto: forum半岛软件下载@www.buonovino.com))
Sent:29 February 2012 11:01
To:econf@www.buonovino.com(econf@www.buonovino.com)
Subject:[ECONF] Re: Fly ash based concrete subjected to high temperature




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.低渗氯离子进入阿奇沃ble 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






Think Green & Live green.
This e-mail is confidential and it is intended only for the addressees. Any review, dissemination, distribution, or copying of this message by persons or entities other than the intended recipient is prohibited. If you have received this e-mail in error, kindly notify us immediately by telephone or e-mail and delete the message from your system. The sender does not accept liability for any errors or omissions in the contents of this message which may arise as a result of the e-mail transmission.""

Posted via Email



Warning: Make sure you scan the downloaded attachment with updated antivirus tools before opening them. They may contain viruses.
Use online scanners
here and here to upload downloaded attachment to check for safety.
Table_A.docx
Description:

Download
Filename: Table_A.docx
Filesize: 15.29 KB
Downloaded: 435 Time(s)

Back to top
View user's profileSend private message
Moruf
SEFI Member
SEFI Member


Joined: 14 Sep 2010
Posts: 5

PostPosted: Sun Mar 04, 2012 5:25 pm文章主题:Fly ash based concrete subjected to high temperature Reply with quote

Sorry for the belated response, the attached is the requested paper by R.W Burrows

On Sat, Mar 3, 2012 at 7:31 AM, JVCSNL forum@www.buonovino.com)> wrote:
Quote:
Dear All,

Some experimental work done in India on this topic is availablehttp://dspace.thapar.edu:8080/dspace/bitstream/123456789/144/1/8042306.pdf.

The results show that there is reduction in Compressive and Tensile capacity and Modulus of elasticity at Higher temperatures.

Regards,

Jignesh V Chokshi








Posted via Email



Warning: Make sure you scan the downloaded attachment with updated antivirus tools before opening them. They may contain viruses.
Use online scanners
here and here to upload downloaded attachment to check for safety.
27a_Effect_of_Fly_Ash.pdf
Description:

Download
Filename: 27a_Effect_of_Fly_Ash.pdf
Filesize: 60.14 KB
Downloaded: 815 Time(s)

Back to top
View user's profileSend private message
Display posts from previous:
This forum is locked: you cannot post, reply to, or edit topics.This topic is locked: you cannot edit posts or make replies.Thank Post www.半岛软件下载www.buonovino.comForum Index->E-conference on Durability of Concrete - Feb 27 to March 11 - 2012 All times are GMT
Goto pagePrevious1,2,3Next
Page2of3



Jump to:
Youcannotpost new topics in this forum
Youcannotreply to topics in this forum
Youcannotedit your posts in this forum
Youcannotdelete your posts in this forum
Youcannotvote in polls in this forum
Youcannotattach files in this forum
Youcandownload files in this forum


© 2003, 2008 SEFINDIA,Indian Domain Registration
Publishing or acceptance of an advertisement is neither a guarantee nor endorsement of the advertiser's product or service.advertisement policy
Baidu
map