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Crucial issues in respect of durability of Concrete
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PostPosted: Tue Feb 28, 2012 1:41 pm    Post subject: Certainly a very "Bleak Picture" of Concrete Const Reply with quote

Dear Ms Alpa-Seth,
What you have written about quality of Concrete Construction in India is, to say the least " A VERY BLEAK PICTURE". Scary in terms of Public-Safety. We have to introduce strong "Liability" laws. May be such laws are in place but not enforced. I was thinking of one project delivery system which has become very common in USA in last few years. Let us see if this will help solve this problem of Poor Concrete Construction in India.

From Council of American Structural Engineer (CASE) document:
CASE DOCUMENT 962-D.  


8. PROJECT DELIVERY SYSTEMS:  There  are many  methods do this. In this Design-Built, one company is responsible for both Design and Construction.


DESIGN-BUILD

Over the past twenty years, design-build projects have become more common. Typically, the owner hires a general contractor to design and build the project. Some owners prefer this method because there are a single source of contact and a single contract on the project. To provide this type of project delivery system, some contractors have in-house design teams to handle the projects; however, many go to the design community to contract for the design of the facility. Design-build contracts have many variations. One of the simplest contracts involves owner’s selection of a design-build contractor. The contractor then subcontracts for design services, as needed, to complete the project. At the other end of the spectrum, the owner develops a limited set of criteria and invites design-build contractors to bid the project. In the latter scenario, the owner must analyze and compare the proposals to determine exactly what is being proposed. This can be a formidable task. The design professional may work under the direction of the contractor on a design-build project. Generally, the contractor is an integral part of the design process and often dictates methods and materials to be used in the construction. The contractor usually dictates what information is required and at what time. Often, major portions of the design must be done early to provide pricing information to the owner. For projects in which several contractors are competing, information provided by the designers must be accurate enough for the contractor to develop a construction cost to which he will be bound for the life of the project. The designer has to balance the time required to provide accurate data for pricing with the cost of the design time. Also, the contractor and designer should have an agreement on the requirements for contingency, based on pricing an incomplete design.


Regards.


Vasudeo Pandya
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SATISH MADHAVRAO KULKARNI
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PostPosted: Tue Feb 28, 2012 4:04 pm    Post subject: Crucial issues in respect of durability of Concrete Reply with quote

Dear All,Concrete suggestions from Er. Jignesh V Chokshi. It is expeceted that Shri V.R. Kulkarni
and concerned would certainly initiate such e-minars in due course.

On Tue, Feb 28, 2012 at 6:25 PM, JVCSNL <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear Members,

It appears that most of the posts are related to our practices, deficiency of concrete knowledge etc., which is more general/ legal/engineering practice type.

We all probably know ourselves, our legal systems, our contractors, skill level of labour, our clients etc.. We can begin discussions where really, what best we can do from today.

I suggest that some concrete expert begin the topics with a specific subject like temperature control, concrete under severe conditions, concrete as fire protection, concrete that is subjected to sustained high temperature, concrete subjected to chemical attack, concrete for water tightness…, with some notes and some open points for further discussion.

We can also discuss the effect of such exposure on mechanical properties of concrete and how the same can be considered in our design and specifications.

Such discussion will help the community to incrementally increase the awareness and the same will result in potential implementation.

Regards,

Jignesh V Chokshi
     



     



Dr. Satish M. Kulkarni

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Dr. N. Subramanian
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PostPosted: Tue Feb 28, 2012 4:19 pm    Post subject: Re: Crucial issues in respect of durability of Concrete Reply with quote

Dear Er Alpa,

Thanks for the info! It is disturbing to note that even the concrete supplied by RMC plants is not reliable and do not attain even the required strength. Some of my friend in Chennai also expressed similar views.

In fact in steel code, we allow a greater partial safety factor, if the structure is welded in the factory than at site, assuming a better quality control in factory! If the quality of concrete made in RMC plants itself is nor reliable, then we are really in a bad shape-eventhough concrete made in RMC plants account for only 10-14% of the total vol. concrete made in India. But at certain locations, for example, crowded locations, RMC is the only solution- it is also faster.

When the RMC plant is at greater distance also the quality of concrete may suffer.

There is no harm in substituting other materials like foundry sand or rock dust for fine aggregate, but the quality of that concrete should be substantiated by actual tests. Whenever people think of money(profit) before work, the quality suffers! Your message should sound an alarm to others to use  concrete   only from standard RMC plants.

Reg. 28 day-strength, I think BIS should change the standard saying that the Std. for concrete with flyash and other similar materials should be 56 days, as they gain strength slowly. Hence 56-days strength should be used for such concretes- it will be higher than 28 day strength of conventional concrete.  

If we are relaying on 56 day strength or even 28 day strength- by that time we could have finished considerable work- what measures are you taking to know whether the concrete placed is of good quality. Are you using 3 day strength and extrapolating it? In 1978 code, there was a factor called age factor-which was useful to do such extrapolation, It has been removed now in 2000 version of the code.

Regards
Subramanian
alpa_sheth wrote:
Dear All:  

I think India is balanced on a unique cusp where the bullock-cart meets our latest rocket launch; where we build the Baha’i Temple and proudly predict a life >500 years and where buildings built less than five years ago are cracking crazily with corrosion.  

I speak here as any harried consultant who is required by statutory authorities to certify the stability of a building over who’s construction she has had no control. Let’s start with concrete as that is the subject of the econference- what really do we know of what we put in our buildings? True, we have ready mix concrete available in our cities which will purportedly give us concrete prepared under more quality control, but what are the systems and procedures that control the RMC producers? I know of many builders who have become ready mix concrete suppliers. There is no culture of record keeping, strict quality standards or even integrity. We are not able to check the silt content in the RMC. When there is no sand available in the entire city of Mumbai, from where do the RMC manufacturers (smaller ones) get it? What are the controls over the stone dust they use instead? What are the compatibility studies of the plasticiser used with the cement? What is the workability of the concrete? We may reject the ready mix concrete which fails the slump test at our site but I can assure that the rejected concrete finds its way to a smaller site which does not have any tests for acceptance of concrete.  

Many of us have experienced concrete not achieving its target strength even 48 days after casting. (This would be okay if we were made aware of such a possibility. During negotiations, they assure you of achieving strength in less than 28 days). Sometimes the strength is never achieved. Sites conceal such crucial information from designers in the fear that our interventions to correct the situation would delay the project. On the other hand, there are those sincere RMC engineers who will tell you that they were pulled up by their RMC companies as the concrete they supplied you gave strength 15% greater than the required. (Their bosses felt they had been uneconomical in their design mix and wasted the company’s resources. The strength should be exactly what was promised and not a percent more).

Yes, we have indeed come a long way from the 1970s when cities like Mumbai had dust in lieu of cement (that period will go down in history as Antulay cement era) and repairs and retrofit to those buildings built in the 70s was a very big business in the last decade. One had expected that with the invasion, as it were, of multinationals in the Indian scenario in the last ten years in concrete (esp. Cement), things would improve. But alas, they were possibly given such a bad picture of the situation prevalent in India (a country which they were made to believe is rife with corruption, nepotism and low quality standards) that they diluted even the existing standards we had in the country. The cements available in smaller towns in India will give you a good insight into the present mindset of the cement industry.  

We have good concrete technologists (some luminaries like Mr V R Kulkarni are with us as we discuss), we also have clients who are ready to invest, so where are we going wrong? What is the missing link? Alok suggested that poor workmanship is a serious problem compromising concrete durability. We do not have adequately trained engineers who understand concrete durability. We have poorly trained masons. Poor compaction leads to surface cracks in slabs. Seismic demands cause beam-column joints, shear walls and beams to be so very heavily reinforced (due to small member sizes) that vibration is not possible. This causes slow settlement of the concrete causing cracks at the reinforcement location. I could go on and on.  

But perhaps it is more than that. We live in an era of plenty. A contractor would rather do ten mediocre or poor quality projects than one excellent quality project. It takes too much time, effort and resources to go from 60% to 95%. So we are happy at 60%. It’s still first class, no?  

I think the problem of concrete durability is not one of lack of knowledge. It one of an attitude, of the lack of motivation to do it right, especially when there is no special reward for it or no punishment for lack thereof. It is a national ailment that plagues us in almost every sphere but we, at least, should do our bit to remedy it at our own small level.  

Perhaps I paint too bleak a picture and I would be happy for someone to make me see a more rosy picture.  

Best regards,

Alpa Sheth

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PostPosted: Tue Feb 28, 2012 4:23 pm    Post subject: Owners' responsibility Reply with quote

Well it is difficult topic but most of the time it is owners' responsibility to see that the quality is not compromised for gaining more profit. Frankly, how many owners are quality minded and are insisting of quality. Unless, we look at construction as an industry like car, steel, etc and come out with all regulations to safeguard, promote as well as encourage professional work environment, the situation would not improve. There is very less an engineer can do on small jobs (and even on big jobs!) apart from his/her professional duties. In my experience, government regulations along with aware owners have a bigger role to play. Such forums can help to form pressure groups to achieve that.
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PostPosted: Tue Feb 28, 2012 6:16 pm    Post subject: Re: Crucial issues in respect of durability of Concrete Reply with quote

Dear Er Jignesh V Chokshi,

Concrete technology is a very vast topic. I remember the series of interesting articles written by Prof. Neville in Concrete International. ACI. He also published this collection as a separate book-http://www.booksurge.com/Neville-on-Concrete-An-Examination-of/A/1419652079.htm

Regards
NS
JVCSNL wrote:
Dear Members,

It appears that most of the posts are related to our practices, deficiency of concrete knowledge etc., which is more general/ legal/engineering practice type.  

We all probably know ourselves, our legal systems, our contractors, skill level of labour, our clients etc.. We can begin discussions where really, what best we can do from today.

I suggest that some concrete expert begin the topics with a specific subject like temperature control, concrete under severe conditions, concrete as fire protection, concrete that is subjected to sustained high temperature, concrete subjected to chemical attack, concrete for water tightness…, with some notes and some open points for further discussion.  

We can also discuss the effect of such exposure on mechanical properties of concrete and how the same can be considered in our design and specifications.  

Such discussion will help the community to incrementally increase the awareness and the same will result in potential implementation.

Regards,

Jignesh V Chokshi

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arunkashikar
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PostPosted: Wed Feb 29, 2012 5:37 am    Post subject: Crucial issues in respect of durability of Concrete Reply with quote

I personally have experienced following issues with prominent RMC suppliers around Mumbai

1) Due to unavailability of river sand, crushed sand is always used. Most of the times crushed sand is not from VSI crusher and grading does not meet zone 2 or even zone 1. Concrete purchaser should ensure by seeing the authentic tests reports that the sand used is Zone II VSI sand.  
2) RMC produces use the same mix for all three exposure condition (always designed only for severe exposure condition), making it expensive for the mild exposure condition. If you ask for the mix design from them, you will always find very high target mean strength used in mix design. Excuse given for this is standard deviation of their concrete is more than even 5. How we can ensure the quality with such high standard deviation.
3) Temperature of concrete is not at all controlled, if you ask for placing temperature to be controlled to even 32 degree, RMC supplier ask for extra premium.

In my opinion, It is necessary to see tests reports of all materials including compatibility tests of admixtures used, and visit the RMC facility, before accepting RMC for any project. If the concrete fails to achieve strength at 28 days, RMC suppliers liability is usually limited to replacing the same quantity of concrete, but for a developer or contractor the loss is much more ( formwork, shuttering, reinforcement, NDT, and cost of demolition and casting again, if it comes to that!). It is also necessary to use IS code for RMC while specifying RMC as part of contract.

Regards,
Arun Kashikar




From: alpa_sheth [mailto:forum@sefindia.org]
Sent: 28 February 2012 15:59
To: econf@sefindia.org
Subject: [ECONF] Re: Crucial issues in respect of durability of Concrete



Dear All:

I think India is balanced on a unique cusp where the bullock-cart meets our latest rocket launch; where we build the Baha’i Temple and proudly predict a life >500 years and where buildings built less than five years ago are cracking crazily with corrosion.

I speak here as any harried consultant who is required by statutory authorities to certify the stability of a building over who’s construction she has had no control. Let’s start with concrete as that is the subject of the econference- what really do we know of what we put in our buildings? True, we have ready mix concrete available in our cities which will purportedly give us concrete prepared under more quality control, but what are the systems and procedures that control the RMC producers? I know of many builders who have become ready mix concrete suppliers. There is no culture of record keeping, strict quality standards or even integrity. We are not able to check the silt content in the RMC. When there is no sand available in the entire city of Mumbai, from where do the RMC manufacturers (smaller ones) get it? What are the controls over the stone dust they use instead? What are the compatibility studies of the plasticiser used with the cement? What is the workability of the concrete? We may reject the ready mix concrete which fails the slump test at our site but I can assure that the rejected concrete finds its way to a smaller site which does not have any tests for acceptance of concrete.

Many of us have experienced concrete not achieving its target strength even 48 days after casting. (This would be okay if we were made aware of such a possibility. During negotiations, they assure you of achieving strength in less than 28 days). Sometimes the strength is never achieved. Sites conceal such crucial information from designers in the fear that our interventions to correct the situation would delay the project. On the other hand, there are those sincere RMC engineers who will tell you that they were pulled up by their RMC companies as the concrete they supplied you gave strength 15% greater than the required. (Their bosses felt they had been uneconomical in their design mix and wasted the company’s resources. The strength should be exactly what was promised and not a percent more).

Yes, we have indeed come a long way from the 1970s when cities like Mumbai had dust in lieu of cement (that period will go down in history as Antulay cement era) and repairs and retrofit to those buildings built in the 70s was a very big business in the last decade. One had expected that with the invasion, as it were, of multinationals in the Indian scenario in the last ten years in concrete (esp. Cement), things would improve. But alas, they were possibly given such a bad picture of the situation prevalent in India (a country which they were made to believe is rife with corruption, nepotism and low quality standards) that they diluted even the existing standards we had in the country. The cements available in smaller towns in India will give you a good insight into the present mindset of the cement industry.

We have good concrete technologists (some luminaries like Mr V R Kulkarni are with us as we discuss), we also have clients who are ready to invest, so where are we going wrong? What is the missing link? Alok suggested that poor workmanship is a serious problem compromising concrete durability. We do not have adequately trained engineers who understand concrete durability. We have poorly trained masons. Poor compaction leads to surface cracks in slabs. Seismic demands cause beam-column joints, shear walls and beams to be so very heavily reinforced (due to small member sizes) that vibration is not possible. This causes slow settlement of the concrete causing cracks at the reinforcement location. I could go on and on.

But perhaps it is more than that. We live in an era of plenty. A contractor would rather do ten mediocre or poor quality projects than one excellent quality project. It takes too much time, effort and resources to go from 60% to 95%. So we are happy at 60%. It’s still first class, no?

I think the problem of concrete durability is not one of lack of knowledge. It one of an attitude, of the lack of motivation to do it right, especially when there is no special reward for it or no punishment for lack thereof. It is a national ailment that plagues us in almost every sphere but we, at least, should do our bit to remedy it at our own small level.

Perhaps I paint too bleak a picture and I would be happy for someone to make me see a more rosy picture.

Best regards,

Alpa Sheth  







Disclaimer: The Information contained and transmitted by this E-mail along with attachments, if any, may contain privileged, proprietary, and confidential material and is intended solely for the use of the individual or entity to which it is addressed. If you have erroneously received this message, please delete it immediately and notify the sender. If you are not the intended recipient, you are further notified that any use, distribution, transmission, printing, copying or dissemination of this information in any manner is strictly prohibited. The opinion expressed in this mail are those of the sender, and not necessarily reflect those of TATA HOUSING DEVELOPMENT COMPANY LTD.

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gattanianil
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PostPosted: Wed Feb 29, 2012 8:48 am    Post subject: Crucial issues in respect of durability of Concrete Reply with quote

I fully agree with Shri arun Kashikar.

I feel:


1. Why Govt. does not prescribe the quality standard for RMC plant. Why it is that Engineer have to see whether the concrete coming from RMC plant is of the desired quality.


2. Why Govt cannot ensure there should be no re rolling of steel and Quality of steel should be adequate .


3. Why in issuing stability certificate structural engineer has to approve the standard of material used and workmanship , when he has practically no hold over these things.


Regards


anil gattani


Subject: [ECONF] Re: Crucial issues in respect of durability of Concrete
From: forum@sefindia.org
Date: Wed, 29 Feb 2012 13:01:04 +0530
To: econf@sefindia.org

--             I personally have experienced following issues with prominent RMC suppliers around Mumbai

1) Due to unavailability of river sand, crushed sand is always used. Most of the times crushed sand is not from VSI crusher and grading does not meet zone 2 or even zone 1. Concrete purchaser should ensure by seeing the authentic tests reports that the sand used is Zone II VSI sand.
2) RMC produces use the same mix for all three exposure condition (always designed only for severe exposure condition), making it expensive for the mild exposure condition. If you ask for the mix design from them, you will always find very high target mean strength used in mix design. Excuse given for this is standard deviation of their concrete is more than even 5. How we can ensure the quality with such high standard deviation.
3) Temperature of concrete is not at all controlled, if you ask for placing temperature to be controlled to even 32 degree, RMC supplier ask for extra premium.

In my opinion, It is necessary to see tests reports of all materials including compatibility tests of admixtures used, and visit the RMC facility, before accepting RMC for any project. If the concrete fails to achieve strength at 28 days, RMC suppliers liability is usually limited to replacing the same quantity of concrete, but for a developer or contractor the loss is much more ( formwork, shuttering, reinforcement, NDT, and cost of demolition and casting again, if it comes to that!). It is also necessary to use IS code for RMC while specifying RMC as part of contract.

Regards,
Arun Kashikar




From: alpa_sheth [mailto:forum@sefindia.org]
Sent: 28 February 2012 15:59
To: econf@sefindia.org (econf@sefindia.org)
Subject: [ECONF] Re: Crucial issues in respect of durability of Concrete



Dear All:

I think India is balanced on a unique cusp where the bullock-cart meets our latest rocket launch; where we build the Baha’i Temple and proudly predict a life >500 years and where buildings built less than five years ago are cracking crazily with corrosion.

I speak here as any harried consultant who is required by statutory authorities to certify the stability of a building over who’s construction she has had no control. Let’s start with concrete as that is the subject of the econference- what really do we know of what we put in our buildings? True, we have ready mix concrete available in our cities which will purportedly give us concrete prepared under more quality control, but what are the systems and procedures that control the RMC producers? I know of many builders who have become ready mix concrete suppliers. There is no culture of record keeping, strict quality standards or even integrity. We are not able to check the silt content in the RMC. When there is no sand available in the entire city of Mumbai, from where do the RMC manufacturers (smaller ones) get it? What are the controls over the stone dust they use instead? What are the compatibility studies of the plasticiser used with the cement? What is the workability of the concrete? We may reject the ready mix concrete which fails the slump test at our site but I can assure that the rejected concrete finds its way to a smaller site which does not have any tests for acceptance of concrete.

Many of us have experienced concrete not achieving its target strength even 48 days after casting. (This would be okay if we were made aware of such a possibility. During negotiations, they assure you of achieving strength in less than 28 days). Sometimes the strength is never achieved. Sites conceal such crucial information from designers in the fear that our interventions to correct the situation would delay the project. On the other hand, there are those sincere RMC engineers who will tell you that they were pulled up by their RMC companies as the concrete they supplied you gave strength 15% greater than the required. (Their bosses felt they had been uneconomical in their design mix and wasted the company’s resources. The strength should be exactly what was promised and not a percent more).

Yes, we have indeed come a long way from the 1970s when cities like Mumbai had dust in lieu of cement (that period will go down in history as Antulay cement era) and repairs and retrofit to those buildings built in the 70s was a very big business in the last decade. One had expected that with the invasion, as it were, of multinationals in the Indian scenario in the last ten years in concrete (esp. Cement), things would improve. But alas, they were possibly given such a bad picture of the situation prevalent in India (a country which they were made to believe is rife with corruption, nepotism and low quality standards) that they diluted even the existing standards we had in the country. The cements available in smaller towns in India will give you a good insight into the present mindset of the cement industry.

We have good concrete technologists (some luminaries like Mr V R Kulkarni are with us as we discuss), we also have clients who are ready to invest, so where are we going wrong? What is the missing link? Alok suggested that poor workmanship is a serious problem compromising concrete durability. We do not have adequately trained engineers who understand concrete durability. We have poorly trained masons. Poor compaction leads to surface cracks in slabs. Seismic demands cause beam-column joints, shear walls and beams to be so very heavily reinforced (due to small member sizes) that vibration is not possible. This causes slow settlement of the concrete causing cracks at the reinforcement location. I could go on and on.

But perhaps it is more than that. We live in an era of plenty. A contractor would rather do ten mediocre or poor quality projects than one excellent quality project. It takes too much time, effort and resources to go from 60% to 95%. So we are happy at 60%. It’s still first class, no?

I think the problem of concrete durability is not one of lack of knowledge. It one of an attitude, of the lack of motivation to do it right, especially when there is no special reward for it or no punishment for lack thereof. It is a national ailment that plagues us in almost every sphere but we, at least, should do our bit to remedy it at our own small level.

Perhaps I paint too bleak a picture and I would be happy for someone to make me see a more rosy picture.

Best regards,

Alpa Sheth







Disclaimer: The Information contained and transmitted by this E-mail along with attachments, if any, may contain privileged, proprietary, and confidential material and is intended solely for the use of the individual or entity to which it is addressed. If you have erroneously received this message, please delete it immediately and notify the sender. If you are not the intended recipient, you are further notified that any use, distribution, transmission, printing, copying or dissemination of this information in any manner is strictly prohibited. The opinion expressed in this mail are those of the sender, and not necessarily reflect those of TATA HOUSING DEVELOPMENT COMPANY LTD.
     



     
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PostPosted: Wed Feb 29, 2012 9:07 am    Post subject: Implementation of quality standards and practices must. Reply with quote

Recently Association of Consulting Civil Engineers (India) Bangalore Centre conducted a three day National Seminar and Exhibition on Recent Developments in Repair, Rehabilitation and Retrofitting.  Eminent consultants shared their experiences with the civil engineering community. It was very clear that due to fast track construction, new materials, design deficiencies, negligence, unskilled manpower, lack of will power to implement quality construction practices and standards, many of the structures have durability issues. The problems connected with durability of structures are increasing as we claim that we are progressing. In this context the efforts by SEFI, having an e-conference on ‘Crucial issues in respect of durability of Concrete’ moderated by  Dr N Subramanian and Mr. Vijay Kulkarni will be very useful in understanding the behaviour of concrete and to handle concrete in a better way.

Civil construction works are visible process and looks simple. We see concrete making materials viz., cement, sand, aggregates and water everywhere unlike IC’s, Chips, Software codes. Everyone, the designers, architects, constructors, contractors, the field workers etc. including the clients feel and think that they know everything about these materials and concrete. Many a times we fail to give importance for the selection of right ingredient materials and preparation of concrete. Concrete Technology is one of the major subjects for all civil engineering students in all the engineering colleges but the way the subject is thought needs focus on the quality issues of concrete and it is very important to understand the behaviour of concrete during its service life.

We keep hearing about training of the work force for good construction including the engineers in various occasions. We do have bodies like Construction Industry Development Council (CIDC) to provide the impetus and the organizational infrastructure to raise quality levels across the industry. One of the focus areas is training manpower at skilled worker level and construction management level but the concerted efforts in this direction are missing. However the efforts of such organizations including BMTPC, ICI, ACCE (I), INSTRUCT etc should be appreciated.

The way concrete is prepared has changed from hand mix to Ready Mixed Concrete. Many projects have their own batching plants. In the last few years I have interacted with many civil and structural engineering consultants, visited many RMC plants and interacted with the RMC plant workforce only to get surprises. Be it, Concrete ingredient material selection, testing of materials, preparation of concrete, transportation, handling the delays, use of admixtures and placing of concrete, all are taken very casually. In my view this casual attitude is the main cause for quality and durability issues of concrete.

I would like to stress here on quality of Ready Mixed Concrete since use of RMC has increased many folds. The number of RMC plants (other than site based batching/mixing plants) are increasing and the kind of infrastructure, trained human resource and quality systems in many of these plants are not up to the mark and there is no regulatory body to check all this. Many of these plants are surviving on the ignorance and the casual attitudes of the stake holders towards concrete.

I must congratulate the efforts made by associations like Ready-Mixed Concrete Manufacturers Association (RMCMA) who have taken enormous efforts in evolving a quality scheme* for RMC. The scheme follows the best practices from advanced countries, with Indian character and is based on the different provisions contained in the relevant specifications of BIS. The efforts of Mr. Kulkarni in this direction will go a long way in improving the quality and durability of concrete.
*( Download the Quality Manuals from :
QC Manual Part I:http://www.rmcmaindia.org/CHECK%20LIST.pdf<xml><o></o>  
QC Manual Part II: http://www.rmcmaindia.org/Guidelines%20Final.pdf

Some state governments also have task forces for quality in construction but struggling to implement the quality standards.  I fail to understand why such task forces and authorities like PWD are not making it mandatory to follow the standards and quality principles. If we are serious to have durable structures, implementation of the quality standards at all levels must be made mandatory. There are no shortcuts.



Dr.Aswath M.U.
Immediate Past Secretary General
Association of Consulting Civil Engineers (I)
Editor-in -Chief: ACCE (I) Bulletin
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Sama Srinivas
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PostPosted: Wed Feb 29, 2012 9:43 am    Post subject: Crucial issues in respect of durability of Concrete Reply with quote

Simply they need power and Money without responsibility. God bless them.


Best Regards
Sama



From: gattanianil [mailto:forum@sefindia.org]
Sent: Wednesday, February 29, 2012 1:32 PM
To: econf@sefindia.org
Subject: [ECONF] Re: Crucial issues in respect of durability of Concrete



I fully agree with Shri arun Kashikar.

I feel:


1. Why Govt. does not prescribe the quality standard for RMC plant. Why it is that Engineer have to see whether the concrete coming from RMC plant is of the desired quality.


2. Why Govt cannot ensure there should be no re rolling of steel and Quality of steel should be adequate .


3. Why in issuing stability certificate structural engineer has to approve the standard of material used and workmanship , when he has practically no hold over these things.


Regards


anil gattani


Subject: [ECONF] Re: Crucial issues in respect of durability of Concrete
From: forum@sefindia.org (forum@sefindia.org)
Date: Wed, 29 Feb 2012 13:01:04 +0530
To: econf@sefindia.org (econf@sefindia.org)

-- I personally have experienced following issues with prominent RMC suppliers around Mumbai

1) Due to unavailability of river sand, crushed sand is always used. Most of the times crushed sand is not from VSI crusher and grading does not meet zone 2 or even zone 1. Concrete purchaser should ensure by seeing the authentic tests reports that the sand used is Zone II VSI sand.
2) RMC produces use the same mix for all three exposure condition (always designed only for severe exposure condition), making it expensive for the mild exposure condition. If you ask for the mix design from them, you will always find very high target mean strength used in mix design. Excuse given for this is standard deviation of their concrete is more than even 5. How we can ensure the quality with such high standard deviation.
3) Temperature of concrete is not at all controlled, if you ask for placing temperature to be controlled to even 32 degree, RMC supplier ask for extra premium.

In my opinion, It is necessary to see tests reports of all materials including compatibility tests of admixtures used, and visit the RMC facility, before accepting RMC for any project. If the concrete fails to achieve strength at 28 days, RMC suppliers liability is usually limited to replacing the same quantity of concrete, but for a developer or contractor the loss is much more ( formwork, shuttering, reinforcement, NDT, and cost of demolition and casting again, if it comes to that!). It is also necessary to use IS code for RMC while specifying RMC as part of contract.

Regards,
Arun Kashikar




From: alpa_sheth [mailto:forum@sefindia.org]
Sent: 28 February 2012 15:59
To: econf@sefindia.org (econf@sefindia.org) (econf@sefindia.org (econf@sefindia.org))
Subject: [ECONF] Re: Crucial issues in respect of durability of Concrete



Dear All:

I think India is balanced on a unique cusp where the bullock-cart meets our latest rocket launch; where we build the Baha’i Temple and proudly predict a life >500 years and where buildings built less than five years ago are cracking crazily with corrosion.

I speak here as any harried consultant who is required by statutory authorities to certify the stability of a building over who’s construction she has had no control. Let’s start with concrete as that is the subject of the econference- what really do we know of what we put in our buildings? True, we have ready mix concrete available in our cities which will purportedly give us concrete prepared under more quality control, but what are the systems and procedures that control the RMC producers? I know of many builders who have become ready mix concrete suppliers. There is no culture of record keeping, strict quality standards or even integrity. We are not able to check the silt content in the RMC. When there is no sand available in the entire city of Mumbai, from where do the RMC manufacturers (smaller ones) get it? What are the controls over the stone dust they use instead? What are the compatibility studies of the plasticiser used with the cement? What is the workability of the concrete? We may reject the ready mix concrete which fails the slump test at our site but I can assure that the rejected concrete finds its way to a smaller site which does not have any tests for acceptance of concrete.

Many of us have experienced concrete not achieving its target strength even 48 days after casting. (This would be okay if we were made aware of such a possibility. During negotiations, they assure you of achieving strength in less than 28 days). Sometimes the strength is never achieved. Sites conceal such crucial information from designers in the fear that our interventions to correct the situation would delay the project. On the other hand, there are those sincere RMC engineers who will tell you that they were pulled up by their RMC companies as the concrete they supplied you gave strength 15% greater than the required. (Their bosses felt they had been uneconomical in their design mix and wasted the company’s resources. The strength should be exactly what was promised and not a percent more).

Yes, we have indeed come a long way from the 1970s when cities like Mumbai had dust in lieu of cement (that period will go down in history as Antulay cement era) and repairs and retrofit to those buildings built in the 70s was a very big business in the last decade. One had expected that with the invasion, as it were, of multinationals in the Indian scenario in the last ten years in concrete (esp. Cement), things would improve. But alas, they were possibly given such a bad picture of the situation prevalent in India (a country which they were made to believe is rife with corruption, nepotism and low quality standards) that they diluted even the existing standards we had in the country. The cements available in smaller towns in India will give you a good insight into the present mindset of the cement industry.

We have good concrete technologists (some luminaries like Mr V R Kulkarni are with us as we discuss), we also have clients who are ready to invest, so where are we going wrong? What is the missing link? Alok suggested that poor workmanship is a serious problem compromising concrete durability. We do not have adequately trained engineers who understand concrete durability. We have poorly trained masons. Poor compaction leads to surface cracks in slabs. Seismic demands cause beam-column joints, shear walls and beams to be so very heavily reinforced (due to small member sizes) that vibration is not possible. This causes slow settlement of the concrete causing cracks at the reinforcement location. I could go on and on.

But perhaps it is more than that. We live in an era of plenty. A contractor would rather do ten mediocre or poor quality projects than one excellent quality project. It takes too much time, effort and resources to go from 60% to 95%. So we are happy at 60%. It’s still first class, no?

I think the problem of concrete durability is not one of lack of knowledge. It one of an attitude, of the lack of motivation to do it right, especially when there is no special reward for it or no punishment for lack thereof. It is a national ailment that plagues us in almost every sphere but we, at least, should do our bit to remedy it at our own small level.

Perhaps I paint too bleak a picture and I would be happy for someone to make me see a more rosy picture.

Best regards,

Alpa Sheth







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Jayant Kulkarni
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PostPosted: Wed Feb 29, 2012 3:25 pm    Post subject: Re: Crucial issues in respect of durability of Concrete Reply with quote

Dear All,

The following are few more important issues related to durability of concrete from RMC suppliers in urban context:

1.      Raw Material:

Commercial use of RMC has apparently eliminated certain problems like a) Monitoring quality of Raw Materials at every truck-load level. B) In adequate mixing time & control of water-cement ratio for every batch of concrete. However, the problem is not eliminated but shifted at higher volume level & at different locations.

Manufacturing of aggregate is not done by organized sectors today. There is hardly any Technical Expertise deployed at the point of manufacturing plant (crusher). There is a strong need for developing trade courses under expert guidance for ‘Crusher Operator’ and ‘Product Quality Control Manager’. The RMC plant operators do not have adequate choice to select Raw Material. Many a times they also face local problems. They have to select whatever is available. In short, the problem is shifted from smaller level to higher level. However, the root cause - Manufacturing Good Quality Raw Material is not addressed by the Industry in general.

2.      Cold Joints:
Continuous supply of RMC – sequencing of transit mixers is many times not achieved for various reasons. There is a time gap between arrival and departure of transit mixers. This results into unplanned & un-designed cold joints. Since the same cannot be anticipated, there is no arrangement in shuttering for planned construction joint. Normally the edge of the ‘Pour of Concrete’ remains un-vibrated & un-compacted. <o></o>

3.      Water Cement Ratio:

Sometimes extra water is added by Transit Mixer Driver, which is beyond the designed water cement ratio. Most of the time it is done to keep concrete in workable condition. This is because of unplanned delays like traffic jams, accidents etc. What is needed at this point of time is intervention of Expert Concrete Technologist. Any addition of extra water may affect final strength of concrete.
4.      Compatibility:

Cement-Admixture compatibility, this is very well discussed, well known difficulty. It is not addressed (probably) as a regular feature at RMC plant. This may result into delay in setting of concrete. We have witnessed a very difficult situation where the entire partially set  concrete was required to be removed from pile cap. Removing the concrete & cleaning the  reinforcement bars was extremely difficult & laborious task.

5.      Anticipation of Pour Time:

Anticipation of time required for pouring the entire mixer load goes wrong. This happens especially when the pour is for smaller / thinner elements like columns, pardis etc. The overall time required for completing a pour becomes more than 3 hrs.

6.      Need of Concrete Technologist :
The overall consumption of RMC has increased substantially over last one decade. In turn there is a increase in number of plants, run by reputed manufacturers as well as new mushroom manufacturers. Individually all plants (or at least group of 3/4 plants) need one full time Expert Concrete Technologist. There is great scarcity of this expertise in market. All the issues related to Mix Design, Cement & Admixture are better handled if there is a presence of Concrete Technologist. This issue needs to be taken up seriously by various institutions as well as RMC manufactures.



Jayant Kulkarni
Practising Structural Engineer


vijay.kulkarni wrote:
I am listing below some of the crucial issues confronting India in respect of durability of concrete. May be these could serve as starting points for comments from fellow engineers.




  1. India is fortunate as it is not facing what Prof. P K Mehta says the "epidemic of concrete deterioration."  

  2. No data on the extent of country-wide deterioration of the stock of concrete structures is available. However, we observe that many traces of the so-called "epidemic of deterioration" are evident in our coastal and industrial belts. These get vividly manifested on many occasions in cities like Mumbai, and other coastal cities where the repair of repairs business is notoriously flourishing.

  3. While old concrete structures (like the Gateway of India, Marine Drive, Mumbai Central Railway station building in Mumbai; Dum Dum and Coronation Bridges in West Bengal, Power Station in Ahmedabad - to cite only a few examples) are in good condition even after a long life span of more than 70-80 years, some new structures constructed recently have shown severe signs of premature deterioration.

  4. The spread of commercial RMC and use of captive batching/mixing plants in the urban and semi-urban areas can certainly considered to be advancements over the age-old labor-oriented practice of site-mixed concrete. This has helped in increasing the speed of construction; however, the culture of putting in serious efforts for enforcing improvement in quality is still lacking.

  5. Four years back, an audit-based quality scheme for RMC was launched and is presently being implemented throughout the country. However, only a few organized players in the commercial RMC segment adopted the scheme voluntarily. A vast majority of commercial RMC players and captive plant operators unfortunately refrained from adopting the scheme. Mere use of batching and mixing plant in production will not ensure quality. A sturdy enforcement mechanism is essential.

  6. Long-term durability is also dependent upon correct precautions taken in transporting, handling, laying, consolidating and curing of concrete. There is much to be desired in all these areas which fall under the purview of contractors. Negligence in these areas may result in a variety of defects such as cracking, voids, honeycombing, sand streaking, bleeding, dusting, crazing -- some which often lead to durability problems at later ages.

  7. Training and education of site supervisors will go a long way in mitigating the above problems. However, very little has been done in the country in this area. The Indian Concrete Institute (ICI) and the Building Materials and Technology Promotion Council (BMTPC) just made a small beginning in launching a pilot program in Training and Certification of Field and Lab supervisors in concrete. This is however a tip of an iceberg. A lot needs to be done in this area. Having skilled and certified technicians and supervisors on site is one of the essential pre-requisites in improving the quality and durability of concrete.

  8. A restricted survey conducted recently by the present writer revealed that the dominant grades of concrete supplied through commercial RMCs in metropolitan cities have gone up from M20 to M25 in Bangalore, Pune, Ahmedabad and Delhi; from M20 to M30 in Chennai and Kolkata and M35 in Mumbai. These are welcome trends. Further, some of the tall buildings in Mumbai, NCR and Kolkata have commenced adopting high-strength and high-performance concretes (grades of M60 and above). However, this trend is confined to niche areas.

  9. In an overwhelming majority of our construction contracts, concrete is still specified merely in terms of its 28-day strength and workability (slump) at pour site. On many occasions, adherence to durability provisions  as specified in IS 456: 2000 ( minimum cementitious material, maximum free water-binder ratio, clear cover to reinforcement) is either not specified or specified in ambiguous terms.

  10. Although there is a separate IS specification for RMC, many clients still use IS 456 in their material specification even while using RMC. This creates problems in sampling and frequency of testing of concrete and its ingredients.

  11. Durability provisions in IS 456:2000 were based on the state-of-the-art-knowledge prevailing in the 1980s and early 90s. In the last two decades, tremendous advancements have occurred in the state-of-the-art which unfortunately have not been reflected in our codes.  

  12. Take, for example, the definition of exposure classes. Almost all advanced countries have made the definition of exposure classes more rational by aligning them to the anticipated degradation mechanisms. In India, we still follow the arbitrary definitions, which many times is confusing.

  13. A plethora of R&D work done all over the world including India has proved beyond doubt that the partial replacement of ordinary Portland cement by supplementary cementitious materials like fly ash, ground granulated blast furnace slag, silica fume, high-reactive metakaolin helps in improving a variety of properties of concrete, mainly its long-term durability. However, there is still a strong resistance to use these materials in actual practice.

  14. Some enlightened clients have commenced adopting durability tests like water penetration test (DIN 1048), rapid chloride ion permeability test (RCPT), initial surface absorption test (ISAT) while qualifying concrete mixes. This is certainly a welcome development which should be encouraged.

  15. Durability is closely linked with service life and sustainability. The urgent need to adopt sustainability approach in concrete design and construction need not be overemphasized. World-over the current trend is to design concrete structures for longer service life. There are examples of recent structures which have been designed to last 100 years! Unfortunately, our codes do not even specify service life of structures. Further, considerable work has already been done in evolving and using mathematical models in predicting service life of structures and using the same in practice. There is also a perceptible shift from prescriptive specifications to performance specifications of concrete. India, being the second largest concrete producing country in the world, need to pick up and adopt many of these new trends.



    Vijay Kulkarni

    Principal Consultant, RMCMA,

    Immediate Past President, ICI

    Former Editor, ICJ
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