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Alternatives to early strength cements for controlling Cr
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alpa_sheth
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Joined: 26 Jan 2003
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PostPosted: Fri Mar 02, 2012 10:23 am    Post subject: Alternatives to early strength cements for controlling Cr Reply with quote

Dear All:  

In one of Prof P K Mehta’s papers, http://icjonline.com/views/2001_01_Mehta.pdf, he has mentioned that in earlier times (pre-1930s) when there was coarser ground portland cements with lesser C3S, deterioration in concrete was due to factors other than cracking (leaching etc.). In recent times due to demand of early strength cements, the cements have gotten finer. This has lead to increased cracking and while the relationship between cracking and deterioration in concrete is not mathematically established, it is indisputable that cracking causes deterioration. He further laments the undue importance given to the strength – durability relationship which in his opinion sidetracks the issue.  

Dr. Mehta panacea to the durability pains is use of lesser water content, use of coarser Portland cements and use of HVFA. I am aware Prof Dr Mehta has expanded much on this since


<![if !supportLists]>a) <![endif]> I would like the opinion of cement experts on the validity of this stand, 10 years after the paper was published. Are all conc. technologists on the same page with Prof Mehta or there are other equally valid theories?  
<![if !supportLists]>b) <![endif]>If there is concensus, why has HVFA concrete not taken on as it should have?  
<![if !supportLists]>c) <![endif]>What is better for durability, self compacting concrete or HVFA concrete?  
<![if !supportLists]>d) <![endif]>Is there any chance that expensive self-compacting concrete/viscosity-controlling admixtures will become more affordable and thus more prevalent as a more durable alternative?  




Best regards,
Alpa

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dipak_bhattacharya
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PostPosted: Fri Mar 02, 2012 4:59 pm    Post subject: Alternatives to early strength cements for controlling Crack Reply with quote

The issues have been raised time and again from time immemorial.Let me summarize what I have learnt till date:

ROLE AND USE OF FLY ASH HAS NOTHING TO DO WITH ENHANCEMENT OF QUALITIES( so called'Durabilty") OF CONCRETE.The concept of introduction of fly ash was primarily to economize the consumption of cement.As a result, the price of puzzolona cement should have been less(because of replacement of cement by trash materials like Fly ash,Blast Furnace Slag etc. ) but it has not happened.


All the qualities of puzzolona cement have been systematically publicised, circulated, and advertised through seminars by vested interests. For the same motive,33 grade, 43 grade, 53 grade cement was introduced in the market with subsequent increase of prices.Very silently then, 33 grade cement was removed from the production schedule and hence from the market.Why?
..........               ...........             .........        ........      ..........        ..........


Durability consists of two aspects, protection of concrete and protection of reinforcements.Introduction of TMT bars is a good approach for protection of reinforcements. However, Sulphate Resistant cement for protection of concrete is a costly proposition unless you're compelled in adverse soils of underground/ subsurface constructions like those in GCC countries.The approach should be to produce/ use concrete as impermeable as possible.To some extent Superplasticizers may help but again it is costly.


  With same qualities of aggregates and cement, denser is the mix, better will be impermeability, better will be strength -- summarily, a better Mix Design.It is not easy, but the approach is a honest one.
Thanks, 


Dipak Bhattacharya.
-- 


   

On 2 March 2012 19:28, alpa_sheth <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear All:

In one of Prof P K Mehta’s papers, http://icjonline.com/views/2001_01_Mehta.pdf, he has mentioned that in earlier times (pre-1930s) when there was coarser ground portland cements with lesser C3S, deterioration in concrete was due to factors other than cracking (leaching etc.). In recent times due to demand of early strength cements, the cements have gotten finer. This has lead to increased cracking and while the relationship between cracking and deterioration in concrete is not mathematically established, it is indisputable that cracking causes deterioration. He further laments the undue importance given to the strength – durability relationship which in his opinion sidetracks the issue.

Dr. Mehta panacea to the durability pains is use of lesser water content, use of coarser Portland cements and use of HVFA. I am aware Prof Dr Mehta has expanded much on this since


a) I would like the opinion of cement experts on the validity of this stand, 10 years after the paper was published. Are all conc. technologists on the same page with Prof Mehta or there are other equally valid theories?
b) If there is concensus, why has HVFA concrete not taken on as it should have?
c) What is better for durability, self compacting concrete or HVFA concrete?
d) Is there any chance that expensive self-compacting concrete/viscosity-controlling admixtures will become more affordable and thus more prevalent as a more durable alternative?




Best regards,
Alpa
     



     



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JVCSNL
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PostPosted: Fri Mar 02, 2012 6:19 pm    Post subject: Reply with quote

Dear Members,

To best of my knowledge, FA based concrete achieves strength slowly compared to portland cements.  Hence, the formworks are removed later than that of OPC based concretes.

Also, Mr. Deepak Bhattacharya has touched a very sensitive point.  The PPC should have been cheaper as it uses as high as 35% of trash material (Fly ash, which is still a pain to manage).  There is not much difference in PPC and OPC prices.  

Recently I was informed that it is difficult to procure OPC in large quantities compared to PPC.  

The question again arises that shall we use HVFA based concrete in all applications.  

Experts of concrete technology can enlighten us as we take decision based on limited information provided to us by cement producers, contractors and developers- who may have their own interest.  

Regards,

Jignesh V Chokshi
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bsec
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PostPosted: Sat Mar 03, 2012 4:46 am    Post subject: Alternatives to early strength cements for controlling Cr Reply with quote

Dear Members,

It is well known that fly ash concrete typically has extended setting time and slow strength gain, leading to low early-age strengths and delays in rate of construction.

In addition, concretes containing fly ash are often reported to be more susceptible to surface scaling when exposed to de-icing chemicals than portland cement concrete (This is not our problem in India fortunately!).  

It is therefore important to know how to adjust the amount of fly ash to minimize the drawbacks, while maximizing the benefits.  

IRC code limits the proportion of fly ash in concrete to a maximum limit of 35% by mass of cement (IRC:SP:70-2005).  

Pricing of PPC versus OPC – Well it is the nexus between politicians and cement lobby that is the root cause. However, leave aside the cost, the eco-friendliness of PPC should be good enough reason for us to promote flyash concrete.  

Regarding use of HVFA, I think the industry is still not geared to take this plunge. It requires much greater degree of quality control at site than what is practiced.

Best Wishes

Alok Bhowmick


From: JVCSNL [mailto:forum@sefindia.org]
Sent: Friday, March 02, 2012 11:49 PM
To: econf@sefindia.org
Subject: [ECONF] Re: Alternatives to early strength cements for controlling Cr



Dear Members,

To best of my knowledge, FA based concrete achieves strength slowly compared to portland cements. Hence, the formworks are removed later than that of OPC based concretes.

Also, Mr. Deepak Bhattacharya has touched a very sensitive point. The PPC should have been cheaper as it uses as high as 35% of trash material (Fly ash, which is still a pain to manage). There is not much difference in PPC and OPC prices.

Recently I was informed that it is difficult to procure OPC in large quantities compared to PPC.

The question again arises that shall we use HVFA based concrete in all applications.

Experts of concrete technology can enlighten us as we take decision based on limited information provided to us by cement producers, contractors and developers- who may have their own interest.

Regards,

Jignesh V Chokshi

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abhio
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PostPosted: Sat Mar 03, 2012 6:10 am    Post subject: Reply with quote

Please correct me if I am mistaken, but as far as I know, IS: 269, IS: 8112 and IS: 12269 specify only the MINIMUM fineness of cement. This allows cement manufacturers to pack the same cement as 33, 43 or 53 grade as per their discretion and demand. This is particularly unfortunate for projects where large concrete pours are required for massive structures where we would like to have slow setting times with gradual evolution of heat of hydration.
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mohannaikleo
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PostPosted: Sat Mar 03, 2012 5:16 pm    Post subject: Alternatives to early strength cements for controlling Cr Reply with quote

Dear members,

     High volume fly ash concrete is still in research level. Some RMC plants are still using only 53 grade OPC, they are procuring in bulk quantity. it is true that the concept of design mix will contribute to durability, more than that its a minimum and combined responsibility of consultant and contractor to achieve durability of concrete by achieving quality.That is what we can call Professional Ethics?

Thanks,
Mohan Naik   

On Sat, Mar 3, 2012 at 10:31 AM, bsec <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear Members,

It is well known that fly ash concrete typically has extended setting time and slow strength gain, leading to low early-age strengths and delays in rate of construction.

In addition, concretes containing fly ash are often reported to be more susceptible to surface scaling when exposed to de-icing chemicals than portland cement concrete (This is not our problem in India fortunately!).

It is therefore important to know how to adjust the amount of fly ash to minimize the drawbacks, while maximizing the benefits.

IRC code limits the proportion of fly ash in concrete to a maximum limit of 35% by mass of cement (IRC:SP:70-2005).

Pricing of PPC versus OPC – Well it is the nexus between politicians and cement lobby that is the root cause. However, leave aside the cost, the eco-friendliness of PPC should be good enough reason for us to promote flyash concrete.

Regarding use of HVFA, I think the industry is still not geared to take this plunge. It requires much greater degree of quality control at site than what is practiced.

Best Wishes

Alok Bhowmick


From: JVCSNL [mailto:forum@sefindia.org (forum@sefindia.org)]
Sent: Friday, March 02, 2012 11:49 PM
To: econf@sefindia.org (econf@sefindia.org)
Subject: [ECONF] Re: Alternatives to early strength cements for controlling Cr



Dear Members,

To best of my knowledge, FA based concrete achieves strength slowly compared to portland cements. Hence, the formworks are removed later than that of OPC based concretes.

Also, Mr. Deepak Bhattacharya has touched a very sensitive point. The PPC should have been cheaper as it uses as high as 35% of trash material (Fly ash, which is still a pain to manage). There is not much difference in PPC and OPC prices.

Recently I was informed that it is difficult to procure OPC in large quantities compared to PPC.

The question again arises that shall we use HVFA based concrete in all applications.

Experts of concrete technology can enlighten us as we take decision based on limited information provided to us by cement producers, contractors and developers- who may have their own interest.

Regards,

Jignesh V Chokshi
     





     



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PostPosted: Mon Mar 05, 2012 3:15 am    Post subject: Re: Alternatives to early strength cements for controlling Reply with quote

Referring to Prof Mehta's paper, Ms Alpa Seth has rightly pointed that one of the major factors responsible for the problem of durability pertains to the changing characteristics of Portland cement. Over years, there has been a large increase in the C3S content and the fineness of cement, both of which contribute to speeding up the hydration reaction, thereby providing high early strength and the accompanying side effect of higher heat of hydration.   I have collected data on the changing contents of C3S and C2S for cements from the USA and the same is given below.




                * Source: Gonnerman and Lerch, PCA, USA, 1952.
                # Source: Johansen, Taylor and Tennis, PCA, USA, 2005.

In view of these changes in the cement characteristics, design strengths could be achieved with low cement content and higher w/b ratio. This fact was vividly brought out by Prof R N Swamy with data from U.K. He reported how the cement content and the w/b ratio for a typical M35 grade concrete changed in that country over the 1960-85 period:





                Source:  Swamy, R.N. The Indian Concrete Journal, Dec 2007, pp. 7-15.

Similar data from the Indian side is unfortunately is not available. However, our data cannot defy the world trend. Possibly, there is a time lag and the difference could be the year of occurrence. I still remember the time when 53 grade cement was introduced in the BIS code. There were few voices who resisted it. However, slowly they were silenced by the market forces! Presently, as everyone is aware, 33-grade cement has vanished from the market and whatever is sold under 43-grade is very closely matching with 53-grade. The European cement code EN 197-1 specifies both the lower and upper strength limits for their 32.5, 42.5 and 53.5 grades. In our OPC codes, the upper limit was conspicuously absent. Last year, the CED Committee 2.2 approved the amendment to introduce the upper limits. However, I understand that the final approval to the amendments is still pending.

With today's cements, it's not a big deal to achieve M20, M25 and M30 in our country. With little knowledge of mix design one can easily achieve the strengths but not the durability.

Many times, the cement industry is accused of dancing to the tune of builders, many of whom are keen to remove the forms the very next day! We can certainly debate on how much faster our construction should be. However, let's accept the fact that higher speed of construction has become a dire necessity and that we have to bear with the available cements.

It is in this context that we have to look at the role of SCMs, which can mitigate many negative effects of what of Burrows term as "crack-prone cement" in the ACI Monograph 11 The Visible and Invisible Cracking of Concrete. The use of SCM with modern-day cement not only reduces the heat of hydration but also reduces the increase in the peak temperature and its early occurrence. Further, as many researchers have pointed out, the resulting microstructure with SCM is far superior to that of pure OPC concrete.

I agree that one should be careful in using SCMs and that is why my insistence on choosing a "knowledgeable" RMC producer. My suggestions of incorporating the provisions of upper limit on concrete pour temperature and shrinkage limit made under my submission on March 2nd on "Other pertinent issue on concrete durability" may kindly be looked from the perspective of reducing the cracking tendency of present-day concrete and to improve its long-term durability.

Under HVFA concrete, when we are replacing a large portion of OPC by fly ash, we

are constrained to adopt low w/b ratio to achieve the specified early-age strength. The lower w/b ratio and the pozzolanic reaction of OPC+ fly ash are the best guarantees for achieving lower permeability — the crux of durability. Further the bogey of the reduction of concrete pH is not correct as some researchers have proved that the pH of pore solution in fly ash concrete does not get reduced.

Vijay Kulkarni





     
     
     
alpa_sheth wrote:
Dear All:  

In one of Prof P K Mehta’s papers, http://icjonline.com/views/2001_01_Mehta.pdf, he has mentioned that in earlier times (pre-1930s) when there was coarser ground portland cements with lesser C3S, deterioration in concrete was due to factors other than cracking (leaching etc.). In recent times due to demand of early strength cements, the cements have gotten finer. This has lead to increased cracking and while the relationship between cracking and deterioration in concrete is not mathematically established, it is indisputable that cracking causes deterioration. He further laments the undue importance given to the strength – durability relationship which in his opinion sidetracks the issue.  

Dr. Mehta panacea to the durability pains is use of lesser water content, use of coarser Portland cements and use of HVFA. I am aware Prof Dr Mehta has expanded much on this since


<if>a) <endif> I would like the opinion of cement experts on the validity of this stand, 10 years after the paper was published. Are all conc. technologists on the same page with Prof Mehta or there are other equally valid theories?  
<if>b) <endif>If there is concensus, why has HVFA concrete not taken on as it should have?  
<if>c) <endif>What is better for durability, self compacting concrete or HVFA concrete?  
<if>d) <endif>Is there any chance that expensive self-compacting concrete/viscosity-controlling admixtures will become more affordable and thus more prevalent as a more durable alternative?  




Best regards,
Alpa

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PostPosted: Mon Mar 05, 2012 2:31 pm    Post subject: Reply with quote

Dear All,

It is very interesting to note the Worldwide as well  Indian trend in the production of cement. Most of us, who are the in the design and construction field are not aware of the Chemistry of cement, nor is it taught in the universities.



From the above Table provided by Er Kulkarni we may observe that the C3S (Alite) content has gone up by 2.67 times and C2S(Belite) content has gone down by about 2.82 times.

We only other major components in Cement are C3A and C4AF.  though the C3S content reduced and C2S increased, the total C3S +C2S contents remained about 70-72%. More over, the current day cements are finely ground. These modifications in the composition of cement are done mainly to obtain high early strength.

I request Er Vijay Kulkarni and others to inform whether these changes are pertaining to Grade 53 cement or other cements also.

Expt. results show that fineness or C3S content does indeed show a large increase in heat of hydration, shrinkage, etc. Woods, Steinour and Starke,1933 developed a statistical relation between heat of hydration and calculated compound composition (using the Bogue equations):

Total Heat (J/g) = 136 (%C3S) + 62 (%C2S) + 200(%C3A) + 30(%C4AF).

Fineness of cement also increases the heat generation, as it provides a larger surface area to be wetted, thus generating more heat at early ages. Compressive strength at early ages (7 days) will increase with an increase in C3S content for well-cured concretes. At 28 days, however, C3S has little influence on the strength of concrete (over a C3S range from 35% to 65% C3S) [Kelham and Moir, 1992]. It has also been found such an effect is there in concretes made with ground granulated blast furnace slag (ggbfs) replacements in addition to the high C3S content. A 50% ggbfs blend gave the same strengths at 91 and 365 days,
but 28-day strengths increased with an increase in cement C3S content from 35% to 65%. For 70% ggbfs blends, all three strengths increased with the same increase in cement C3S content.

Osbourne and Hardcastle, 1997 reported that a high C3S content in cement (67%
compared to 33.5%) adversely affects concrete durability, resulting in increased ingress of chlorides from sea water at greater depths (21 mm) into the concrete member. They go on to conclude that long term durability is achieved with well cured concretes made with low C3S cement. on the other hand, Kelham and Moir, 1992 found that the durability of concrete, in the case of poorly cured
concrete, is improved with an increase in the cement C3S content (from 35% to 65%). They also reported improved resistance to freeze/thaw damage and reduced permeability to oxygen with increases in C3S content. They concluded that, in poorly cured concrete, the high C3S content in cement resulted in faster hydration, which improved the durability such that it was more comparable to well cured concrete. This kind of mixed results confuses designers. But in any case increased amount of C3S and fineness are sure to develop high heat of hydration during early days- which once again shows the importance of curing.


Internal Curing  of concrete has been used in 16 highway  bridge decks over the last couple years in New York State as part of a Federal study and the results look good, reports Mr Ron Vaughn, Senior Sales Engineer at Northeast Solite Corporation, New York in another ASCE discussion Forum.   We should do research and encourage this practice oin India at least in bigger projects.

Very long-term strength development, however, may be detrimentally affected by
increased fineness and C3S content. In a study conducted by Withey and Wendt 1943 at the University of Wisconsin, 50-year test results revealed that concrete with a cement fineness of 231 m2/kg and C3S content of 30% was still gaining strength after 50 years, while concrete with a cement fineness of 380 m2/kg and C3S content of 57% did not gain strength after a period of 10 years.


ASTM has no upper limit on the proportion of C3S or fineness for Type II cements(High-Early Strength Portland Cement).AASHTO, on the other hand, does impose limits on both properties for Type II cements; a maximum 58% C3S content and a maximum average Wagner Turbidimeter fineness limit of 220 m2/kg (with no single value above 230 m2/kg). The maximum Blaine fineness limit is 400 m2/kg, with no single value to be above 420 m2/kg. These fineness limits also apply to Types I, IV, and V portland cements.

Best wishes
Subramanian
References

  • Kelham, S. and Moir, G. K., “The Effect of Cement C3S Level on Concrete Properties,” 9th International Congress on the Chemistry of Cement, New Delhi, India, 1992.
  • Woods, H.; Steinour, H. H.; and Starke, H. R., “Heat Evolved by Cement in Relation to Strength,” Engineering News Record, Vol. 110, April 6, 1933,
  • Osborne, G. J. and Hardcastle, J. L., “Changes in Properties of Portland Cement and Their Effects on Concrete Durability,” 4th CANMET/ACI International Conference on the Durability of Concrete, Sydney, Australia, Vol. 2, 1997, pages 1411 to 1432.
  • Withey, M.O. and Wendt, K.F., “Some Long Time Tests of Concrete,” Journal of the American Concrete Institute, Vol. 14, No. 4, February 1943, page 221 to 238.
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Dr. N. Subramanian
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PostPosted: Mon Mar 05, 2012 4:37 pm    Post subject: Re: Alternatives to early strength cements for controlling C Reply with quote

Dear Er Mohan Naik,

Substantial work has been done in serveral parts of the world on HVFA concrete. Initial impedus to this work was provided by Prof. V.M. Malhotra of CANMAT Canada and Prof. P.K. Mehta of USA

See the following:
1. Malhotra, V.M., and P.K. Mehta., “High-Performance, High-Volume Fly Ash Concrete for Building Sustainable & Durable Structures, Third Edition,” Supplementary Cementing Materials for Sustainable Development Inc., Ottawa, Canada, 142pp, 2008.
2. International workshop on Sustainable Development & Concrete Technology, China, 2004 (http://publications.iowa.gov/2941/1/SustainableConcreteWorkshop.pdf)
3. http://www.ce.berkeley.edu/~paulmont/CE60New/Concrete%20and%20the%20Environment.pdf
4. http://www.intrans.iastate.edu/pubs/sustainable/mehtasustainable.pdf
5. Special issue on HVFA concrete, The Indian Concrete Journal Nov. 2004(editorial by Malhotra and Mehta-http://www.asocem.org.pe/bivi/dsi/Diseminacion_industria/indian_concrete_11_2004.pdf)
6. http://www.ijest.info/docs/IJEST10-02-09-88.pdf
7. http://wisdotresearch.wi.gov/wp-content/uploads/tlsflyash.pdf
www.flyash.com
8. http://www.ce.berkeley.edu/~paulmont/165/Powerpoint_07/Group%2017.pdf
9. http://www.ecosmartconcrete.com/kbase/filedocs/csrleveltonhighrise.pdf
10. http://www4.uwm.edu/cbu/Papers/1998%20CBU%20Reports/REP-346.pdf
11. http://www.nrmca.org/research/rac%20hvfa%20concrete%20upadhyaya%20goulias%20obla.pdf
12. http://www.ce.berkeley.edu/~paulmont/165/Mehta2.pdf

13. www.flyash.com
Work done at NIST
Dr D.P. Benz working at NIST, Gaithersburg, MD, USA, has done commendable work on cement & concrete. His paper on Thermal properties of high-volume fly ash mortars and concretes, may be found at http://concrete.nist.gov/~bentz/FAThermalprop.pdf
Also see another paper by him:
http://concrete.nist.gov/~bentz/RheologyandSettingHVFA.pdf

Dr Benz has also developed the Award winning Virtual Cement and Concrete Testing Laboratory, which I had mentioned in one of my earlier posting a few months ago. For ready reference I am giving he link here:http://www.nist.gov/el/building_materials/inorganic/vcctl.cfm/

NIST has a wealth of info on Internal curing also: http://ciks.cbt.nist.gov/~bentz/lwagg.html

COST (Concrete Optimization Software Tool) is an online design/analysis system, developed by Scientist at NIST to assist concrete producers, engineers and researchers in determining optimal mixture proportions for concrete (http://ciks.cbt.nist.gov/cost/).

Regards
Subramanian
mohannaikleo wrote:
Dear members,

     High volume fly ash concrete is still in research level. Some RMC plants are still using only 53 grade OPC, they are procuring in bulk quantity. it is true that the concept of design mix will contribute to durability, more than that its a minimum and combined responsibility of consultant and contractor to achieve durability of concrete by achieving quality.That is what we can call Professional Ethics?

Thanks,
Mohan Naik    

On Sat, Mar 3, 2012 at 10:31 AM, bsec <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
             Dear Members,

It is well known that fly ash concrete typically has extended setting time and slow strength gain, leading to low early-age strengths and delays in rate of construction.

In addition, concretes containing fly ash are often reported to be more susceptible to surface scaling when exposed to de-icing chemicals than portland cement concrete (This is not our problem in India fortunately!).

It is therefore important to know how to adjust the amount of fly ash to minimize the drawbacks, while maximizing the benefits.

IRC code limits the proportion of fly ash in concrete to a maximum limit of 35% by mass of cement (IRC:SP:70-2005).

Pricing of PPC versus OPC – Well it is the nexus between politicians and cement lobby that is the root cause. However, leave aside the cost, the eco-friendliness of PPC should be good enough reason for us to promote flyash concrete.

Regarding use of HVFA, I think the industry is still not geared to take this plunge. It requires much greater degree of quality control at site than what is practiced.

Best Wishes

Alok Bhowmick


From: JVCSNL [mailto:forum@sefindia.org (forum@sefindia.org)]
Sent: Friday, March 02, 2012 11:49 PM
To: econf@sefindia.org (econf@sefindia.org)
Subject: [ECONF] Re: Alternatives to early strength cements for controlling Cr



Dear Members,

To best of my knowledge, FA based concrete achieves strength slowly compared to portland cements. Hence, the formworks are removed later than that of OPC based concretes.

Also, Mr. Deepak Bhattacharya has touched a very sensitive point. The PPC should have been cheaper as it uses as high as 35% of trash material (Fly ash, which is still a pain to manage). There is not much difference in PPC and OPC prices.

Recently I was informed that it is difficult to procure OPC in large quantities compared to PPC.

The question again arises that shall we use HVFA based concrete in all applications.

Experts of concrete technology can enlighten us as we take decision based on limited information provided to us by cement producers, contractors and developers- who may have their own interest.

Regards,

Jignesh V Chokshi
     





     



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PostPosted: Mon Mar 05, 2012 6:15 pm    Post subject: Alternatives to early strength cements for controlling Cr Reply with quote

Dear Mr. Choksi,

I'm thankful to you because you've understood my statements in depth.


I shall raise a still more serious and fundamental question!


We're blindly discussing the role of Flyash without going into the details of the composition of the Flyash. 


What is Flyash? Can anybody define it in terms of its composition?Has it been standardized? It is similar to discussion of usefulness of milk, without mentioning whether it is single-toned, double-toned, Full cream or skimmed milk.


Flyash is a naturally available material coal, fully burnt, half-burnt and is as varying as naturally available coal in its variable mineral content,apart from the other  ingredients which cannot be burnt.Metallurgists call it Ash Content, which is primarily inert and have no role in any function of Flyash except adulterating it.Though our country is blessed with sufficient stock of non-coking (thermal coal), the Ash Content is so high, we often import even non-coking coal for many important processes.


When cement is produced with such high quality control, norms and disciplines, how can we afford to mix / blend and make experiment  with Fly Ash whose mineral content is neither standardized  nor in anybody's control.


Can Dr. Subramanium or any other learned person throw some light on it? 


Thanks,


Dipak Bhattacharya
--
On 5 March 2012 22:07, Dr N. Subramanian <forum@sefindia.org (forum@sefindia.org)> wrote:[quote]            Dear Er Mohan Naik,

Substantial work has been done in serveral parts of the world on HVFA concrete. Initial impedus to this work was provided by Prof. V.M. Malhotra of CANMAT Canada and Prof. P.K. Mehta of USA

See the following:
1. Malhotra, V.M., and P.K. Mehta., “High-Performance, High-Volume Fly Ash Concrete for Building Sustainable & Durable Structures, Third Edition,” Supplementary Cementing Materials for Sustainable Development Inc., Ottawa, Canada, 142pp, 2008.
2. International workshop on Sustainable Development & Concrete Technology, China, 2004 (http://publications.iowa.gov/2941/1/SustainableConcreteWorkshop.pdf)
3. http://www.ce.berkeley.edu/~paulmont/CE60New/Concrete%20and%20the%20Environment.pdf
4. http://www.intrans.iastate.edu/pubs/sustainable/mehtasustainable.pdf
5. Special issue on HVFA concrete, The Indian Concrete Journal Nov. 2004(editorial by Malhotra and Mehta-http://www.asocem.org.pe/bivi/dsi/Diseminacion_industria/indian_concrete_11_2004.pdf)
6. http://www.ijest.info/docs/IJEST10-02-09-88.pdf
7. http://wisdotresearch.wi.gov/wp-content/uploads/tlsflyash.pdf
www.flyash.com
8. http://www.ce.berkeley.edu/~paulmont/165/Powerpoint_07/Group%2017.pdf
9. http://www.ecosmartconcrete.com/kbase/filedocs/csrleveltonhighrise.pdf
10. http://www4.uwm.edu/cbu/Papers/1998%20CBU%20Reports/REP-346.pdf
11. http://www.nrmca.org/research/rac%20hvfa%20concrete%20upadhyaya%20goulias%20obla.pdf
12. http://www.ce.berkeley.edu/~paulmont/165/Mehta2.pdf

13. www.flyash.com
Work done at NIST
Dr D.P. Benz working at NIST, Gaithersburg, MD, USA, has done commendable work on cement & concrete. His paper on Thermal properties of high-volume fly ash mortars and concretes, may be found at http://concrete.nist.gov/~bentz/FAThermalprop.pdf
Also see another paper by him:
http://concrete.nist.gov/~bentz/RheologyandSettingHVFA.pdf

Dr Benz has also developed the Award winning Virtual Cement and Concrete Testing Laboratory, which I had mentioned in one of my earlier posting a few months ago. For ready reference I am giving he link here:http://www.nist.gov/el/building_materials/inorganic/vcctl.cfm/

NIST has a wealth of info on Internal curing also: http://ciks.cbt.nist.gov/~bentz/lwagg.html

COST (Concrete Optimization Software Tool) is an online design/analysis system, developed by Scientist at NIST to assist concrete producers, engineers and researchers in determining optimal mixture proportions for concrete (http://ciks.cbt.nist.gov/cost/).

Regards
Subramanian
      mohannaikleo wrote:                Dear members,

     High volume fly ash concrete is still in research level. Some RMC plants are still using only 53 grade OPC, they are procuring in bulk quantity. it is true that the concept of design mix will contribute to durability, more than that its a minimum and combined responsibility of consultant and contractor to achieve durability of concrete by achieving quality.That is what we can call Professional Ethics?

Thanks,
Mohan Naik

On Sat, Mar 3, 2012 at 10:31 AM, bsec forum@sefindia.org (forum@sefindia.org))> wrote:
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