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Crucial issues in respect of durability of Concrete
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vijay.kulkarni
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PostPosted: Mon Feb 27, 2012 12:37 am    Post subject: Crucial issues in respect of durability of Concrete Reply with quote

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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JVCSNL
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Joined: 26 Jan 2003
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PostPosted: Mon Feb 27, 2012 5:12 am    Post subject: Crucial issues in respect of durability of Concrete Reply with quote

Dear All,

With an extremely informative and through provoking opening remarks by Dr. NS and Mr. Vijay Kulkarni, I am sure the ECONF would be interesting and a great platform for sharing knowledge on concrete durability.

I have my views on this subject as follows:

Good concrete (if I can say in simplistic terms) is an outcome of right selection of material like coarse aggregate, fine aggregates, cement, water, admixtures. Each of these materials having their own role to play and the role when they become together. In fact, it is more of a team effort than an individual effort. Any weak link will ensure bad concrete.  

While we select right material, we also need an effective integrator. The concrete mix designer who ensures that the mix of these ingredients is right and most optimum. The concrete mix designer is a leader who will ensure that the team of ingredients plays effectively, knowing the fact that more is not better. The mix designer will have to take into account of the effective relationship of cement and water as well as based on the knowledge of properties of each of these materials under laboratory conditions.  

To ensure best concrete, these ingredients shall be mixed with right tools and right people, under right ambient and physical surrounding conditions.  

Since these ingredients are handled by differently at different times, the assurance of best outcome is jeopardized.  

Lot of information is shared about the marvels that have stood centuries. I have always wondered that how it had been possible. When I think and try to figure out the potential causes of the same, I feel that such marvels were more of the objective than a routine process.  

The people who built such marvels were undoubtedly great engineers possessing design and construction knowledge. They selected the right materials (may be after a great search) and best materials. They also selected the best of the available talent for construction. They also supervised the work at every phase. And probably, there was no time pressure as well as fund limitation. I guess, when best of the minds work with commonly devised objective, I think best outcome is ensured. Also, an extremely stringent quality control was in place when working with the conditions.  

Today, as I have perceived, the designer needs to specify grade of concrete. RMC or concrete contractor will supply the concrete. The bar bender and the carpenter will do their role separately, the quality control will see that samples were taken and its reports were made and signed off. Each of these divided roles have cost and profit within and probably the common objective is not seen by all the participants of the whole building construction story. The designer sitting in office seldom worried about the quality of concrete at site. Many of the forum members would have seen the condition of reinforcement at site during monsoon. The mud from reinforcement is cleaned with small cloth and allowed to take all the task.

Let me clarify here that I do not deal with designing, making, pouring, curing, testing of concrete every day. With limited site exposure and having spend almost two decades in engineering, these are my views.  

The materials stored in the batching plant areas are tested under ideal conditions. I know a case where the site was near the salt farms and with high speed winds that would carry small salt particles and deposit on the open yards of coarse and fine aggregate will certainly deteriorate quality of concrete. The batching plant contractor was not bothered of it as he wanted to follow the mix design given. Certainly may be the case of water and other ingredients.  

Mostly people associated with the entire process are most bothered about their work as their money is involved. Also, most projects are developed under tremendous time pressures and due to this, most of them do not think about seasonal effects on the materials. Many times, the projects developed by people who seldom know the requirement and since developer holds power, many times compromises happen.  

Considering sudden industrial growth and need for huge amount of concrete and looking to lack of talent in the civil engineering (post IT boom) we are certainly facing problems pertaining to durability of concrete.  

In summary, the concrete durability can be ensured only by right material selection, mixing, transportation, placement, curing, protecting etc. by right people under supervision of right people. The monitoring of physical and ambient conditions every day will help concrete perform its purpose under given conditions. If concreting remains as a routine process among many stakeholders, the durability of concrete will be difficult to ensure.  

Regards,

Jignesh V Chokshi


From: vijay.kulkarni [mailto:forum@sefindia.org]
Sent: Monday, February 27, 2012 6:07 AM
To: econf@sefindia.org
Subject: [ECONF] Crucial issues in respect of durability of Concrete



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.

<![if !supportLists]>1. <![endif]>
India is fortunate as it is not facing what Prof. P K Mehta says the "epidemic of concrete deterioration."  
<![if !supportLists]>2. <![endif]>
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.
<![if !supportLists]>3. <![endif]>
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.
<![if !supportLists]>4. <![endif]>
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.  
<![if !supportLists]>5. <![endif]>
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.
<![if !supportLists]>6. <![endif]>
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.
<![if !supportLists]>7. <![endif]>
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.
<![if !supportLists]>8. <![endif]>
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.  
<![if !supportLists]>9. <![endif]>
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.  
<![if !supportLists]>10. <![endif]>
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.
<![if !supportLists]>11. <![endif]>
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.  
<![if !supportLists]>12. <![endif]>
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.
<![if !supportLists]>13. <![endif]>
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.  
<![if !supportLists]>14. <![endif]>
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.
<![if !supportLists]>15. <![endif]>
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

Posted via Email
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goanengineer
SEFI Member
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Joined: 22 Feb 2012
Posts: 1

PostPosted: Mon Feb 27, 2012 9:42 am    Post subject: Crucial issues in respect of durability of Concrete Reply with quote

Dear All,

Though RMC is considered to be advanced but RMC is the main culprit and we will realise this after 15-20 yrs or so. Cutting edge competion is pricing, no transperency (Like use of word 'Cementatious', poor quality of GGBS or Fly ash, Manipulations of test results (Confrontation on third party test results) apart quantity manipulations, use of substandard Cement, too much use of fines in the name of pumpability.


Parameters like permeability should be seriously thought about.


Degradation of IS 456 2000 or other latest codes are also responsible for poor quality of conrete. Diluted Acceptance criteria is RMC manufacturer's gain.




Goa Engineers.

On Mon, Feb 27, 2012 at 1:44 PM, JVCSNL <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear All,

With an extremely informative and through provoking opening remarks by Dr. NS and Mr. Vijay Kulkarni, I am sure the ECONF would be interesting and a great platform for sharing knowledge on concrete durability.

I have my views on this subject as follows:

Good concrete (if I can say in simplistic terms) is an outcome of right selection of material like coarse aggregate, fine aggregates, cement, water, admixtures. Each of these materials having their own role to play and the role when they become together. In fact, it is more of a team effort than an individual effort. Any weak link will ensure bad concrete.

While we select right material, we also need an effective integrator. The concrete mix designer who ensures that the mix of these ingredients is right and most optimum. The concrete mix designer is a leader who will ensure that the team of ingredients plays effectively, knowing the fact that more is not better. The mix designer will have to take into account of the effective relationship of cement and water as well as based on the knowledge of properties of each of these materials under laboratory conditions.

To ensure best concrete, these ingredients shall be mixed with right tools and right people, under right ambient and physical surrounding conditions.

Since these ingredients are handled by differently at different times, the assurance of best outcome is jeopardized.

Lot of information is shared about the marvels that have stood centuries. I have always wondered that how it had been possible. When I think and try to figure out the potential causes of the same, I feel that such marvels were more of the objective than a routine process.

The people who built such marvels were undoubtedly great engineers possessing design and construction knowledge. They selected the right materials (may be after a great search) and best materials. They also selected the best of the available talent for construction. They also supervised the work at every phase. And probably, there was no time pressure as well as fund limitation. I guess, when best of the minds work with commonly devised objective, I think best outcome is ensured. Also, an extremely stringent quality control was in place when working with the conditions.

Today, as I have perceived, the designer needs to specify grade of concrete. RMC or concrete contractor will supply the concrete. The bar bender and the carpenter will do their role separately, the quality control will see that samples were taken and its reports were made and signed off. Each of these divided roles have cost and profit within and probably the common objective is not seen by all the participants of the whole building construction story. The designer sitting in office seldom worried about the quality of concrete at site. Many of the forum members would have seen the condition of reinforcement at site during monsoon. The mud from reinforcement is cleaned with small cloth and allowed to take all the task.

Let me clarify here that I do not deal with designing, making, pouring, curing, testing of concrete every day. With limited site exposure and having spend almost two decades in engineering, these are my views.

The materials stored in the batching plant areas are tested under ideal conditions. I know a case where the site was near the salt farms and with high speed winds that would carry small salt particles and deposit on the open yards of coarse and fine aggregate will certainly deteriorate quality of concrete. The batching plant contractor was not bothered of it as he wanted to follow the mix design given. Certainly may be the case of water and other ingredients.

Mostly people associated with the entire process are most bothered about their work as their money is involved. Also, most projects are developed under tremendous time pressures and due to this, most of them do not think about seasonal effects on the materials. Many times, the projects developed by people who seldom know the requirement and since developer holds power, many times compromises happen.

Considering sudden industrial growth and need for huge amount of concrete and looking to lack of talent in the civil engineering (post IT boom) we are certainly facing problems pertaining to durability of concrete.

In summary, the concrete durability can be ensured only by right material selection, mixing, transportation, placement, curing, protecting etc. by right people under supervision of right people. The monitoring of physical and ambient conditions every day will help concrete perform its purpose under given conditions. If concreting remains as a routine process among many stakeholders, the durability of concrete will be difficult to ensure.

Regards,

Jignesh V Chokshi


From: vijay.kulkarni [mailto:forum@sefindia.org (forum@sefindia.org)]
Sent: Monday, February 27, 2012 6:07 AM
To: econf@sefindia.org (econf@sefindia.org)
Subject: [ECONF] Crucial issues in respect of durability of Concrete



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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naresh7918
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Joined: 23 Sep 2011
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PostPosted: Mon Feb 27, 2012 3:59 pm    Post subject: Crucial issues in respect of durability of Concrete Reply with quote

Dear All,

It is very inspiring to read such wonderful articles which are related to construction.

However, of late, in most of the presentations/conferences related to Civil Engineering I find a lot of content related to "Ancient Structures" (which undoubtedly leave us in wonder and awe) in spite of having no clear evidence about their construction methodologies. And as Civil Engineers, though we try to seek answers in ancient structures, for our present problems, I feel we are doing so in vain. As for ancient structures like Pyramids, Sphinx, or any Megalithic structure for that matter are believed to be constructed by entities from other parts of universe (aliens is the right word), which leave us in dark about the materials that were used and the methods they adopted. This belief is due to the simple fact that, in spite of present day technology and understanding abilities we have, it is nearly impossible to duplicate these ancient structures. So, somehow I feel, as Civil Engineers, looking back at ancient structures to find answers or inspiration, in trying to understand present day construction problems may take us nowhere. Instead I would encourage the present construction engineers to seek innovative ideas w.r.t construction materials and methodologies, that will give us durable structures.
Lastly, the ancient structures are not only significant from construction point of view but various other aspects as well. For example, the great Pyramids consists of underground tunnels which were made to tap the magnetic energy (significant for electrical engineers). Also some researchers claim that Pyramids are created on magnetic null zones. Mysteriously if we imagine a line drawn from Pyramids around the glob, many ancient structures with astonishing similarities are located along the straight line. So, only Civil Engineers taking the credit for such ancient structures is unfair.

I would like to conclude saying, let us not try to find for answers in ancient structures (to make concrete more durable), but think of some innovative solutions.


Regards,
Naresh Reddy.

On Mon, Feb 27, 2012 at 1:44 PM, JVCSNL <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear All,

With an extremely informative and through provoking opening remarks by Dr. NS and Mr. Vijay Kulkarni, I am sure the ECONF would be interesting and a great platform for sharing knowledge on concrete durability.

I have my views on this subject as follows:

Good concrete (if I can say in simplistic terms) is an outcome of right selection of material like coarse aggregate, fine aggregates, cement, water, admixtures. Each of these materials having their own role to play and the role when they become together. In fact, it is more of a team effort than an individual effort. Any weak link will ensure bad concrete.

While we select right material, we also need an effective integrator. The concrete mix designer who ensures that the mix of these ingredients is right and most optimum. The concrete mix designer is a leader who will ensure that the team of ingredients plays effectively, knowing the fact that more is not better. The mix designer will have to take into account of the effective relationship of cement and water as well as based on the knowledge of properties of each of these materials under laboratory conditions.

To ensure best concrete, these ingredients shall be mixed with right tools and right people, under right ambient and physical surrounding conditions.

Since these ingredients are handled by differently at different times, the assurance of best outcome is jeopardized.

Lot of information is shared about the marvels that have stood centuries. I have always wondered that how it had been possible. When I think and try to figure out the potential causes of the same, I feel that such marvels were more of the objective than a routine process.

The people who built such marvels were undoubtedly great engineers possessing design and construction knowledge. They selected the right materials (may be after a great search) and best materials. They also selected the best of the available talent for construction. They also supervised the work at every phase. And probably, there was no time pressure as well as fund limitation. I guess, when best of the minds work with commonly devised objective, I think best outcome is ensured. Also, an extremely stringent quality control was in place when working with the conditions.

Today, as I have perceived, the designer needs to specify grade of concrete. RMC or concrete contractor will supply the concrete. The bar bender and the carpenter will do their role separately, the quality control will see that samples were taken and its reports were made and signed off. Each of these divided roles have cost and profit within and probably the common objective is not seen by all the participants of the whole building construction story. The designer sitting in office seldom worried about the quality of concrete at site. Many of the forum members would have seen the condition of reinforcement at site during monsoon. The mud from reinforcement is cleaned with small cloth and allowed to take all the task.

Let me clarify here that I do not deal with designing, making, pouring, curing, testing of concrete every day. With limited site exposure and having spend almost two decades in engineering, these are my views.

The materials stored in the batching plant areas are tested under ideal conditions. I know a case where the site was near the salt farms and with high speed winds that would carry small salt particles and deposit on the open yards of coarse and fine aggregate will certainly deteriorate quality of concrete. The batching plant contractor was not bothered of it as he wanted to follow the mix design given. Certainly may be the case of water and other ingredients.

Mostly people associated with the entire process are most bothered about their work as their money is involved. Also, most projects are developed under tremendous time pressures and due to this, most of them do not think about seasonal effects on the materials. Many times, the projects developed by people who seldom know the requirement and since developer holds power, many times compromises happen.

Considering sudden industrial growth and need for huge amount of concrete and looking to lack of talent in the civil engineering (post IT boom) we are certainly facing problems pertaining to durability of concrete.

In summary, the concrete durability can be ensured only by right material selection, mixing, transportation, placement, curing, protecting etc. by right people under supervision of right people. The monitoring of physical and ambient conditions every day will help concrete perform its purpose under given conditions. If concreting remains as a routine process among many stakeholders, the durability of concrete will be difficult to ensure.

Regards,

Jignesh V Chokshi


From: vijay.kulkarni [mailto:forum@sefindia.org (forum@sefindia.org)]
Sent: Monday, February 27, 2012 6:07 AM
To: econf@sefindia.org (econf@sefindia.org)
Subject: [ECONF] Crucial issues in respect of durability of Concrete



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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PostPosted: Mon Feb 27, 2012 5:27 pm    Post subject: Crucial issues in respect of durability of Concrete Reply with quote

Dear All,
 
At the outset I thank the organizers of this E-Conference on choosing a subject matter for the conference, which is topical and apt for the moment, looking at the current demand for infrastructural growth ahead.
 
My views on the subject are as follows :


1.0  If we go back to history, durability became a major issue of concern in 80’s for concrete structures when serious deteriorations were observed in bridges & structures in cold countries in Europe, America & UK due to corrosion of reinforcement & prestressing steel. The problem became more acute for bridge decks due to use of de-icing salts.


2.0     Major problems were also seen in Middle East around the same time, when chloride induced corrosion was observed.


3.0     Subsequent developments globally in codes and standards in fighting the problems of carbonation and chloride induced corrosion of reinforcement and ensuring the longevity of concrete structure were primarily the outcome of the above.


4.0    Since the maximum damage caused in RCC structures (worldwide) is perceived to be primarily due to corrosion of reinforcement, the environmental classification in IS 456 as well as IRC codes are based on specific mechanism of duration (i,e. corrosion only).


5.0    90% of the geographical area of our country (leaving aside the 10% of the coastal belt & the cold areas of Jammu & Kashmir) do not have any serious problem of chloride induced corrosion or carbonation as witnessed in the European countries, UK, USA. 


6.0   In spite of this advantage, our structures, built in the recent past, suffer from serious durability problems and they are found to be in distress well before their expected service life of say 50 years (for buildings) and 100 years (for bridges & other important structures).  As a bridge Engineer, I have quite often noted that bridges built in 60’s are still in sound condition while bridges built in 90’s are in distress.  There is a need for introspection here.


7.0  Durability of concrete therefore is a problem which can be attributed to the following reasons :
 
a)  Service Environment - Aggressive external / internal conditions
b)           Poor Material Selection
c)           Poor Design & Detailing  
d)           Poor Workmanship
 
Though all the above stated factors contribute in reducing the design life of the structure, If I am asked to give % contribution of each of the above causes in durability of structures in our country, I will give only 10% to item a) and b) each, 20% to item c) and balance 60% to item d).




 
8.0        In other words, major cause of durability problem in our structures is “poor workmanship” rather than “aggressive external / internal condition”. PLEASE NOTE – THE PERCENTAGES GIVEN ARE NOT BASED ON ANY SURVEY, BUT BASED ON MY OWN ENGINEERING JUDGEMENT.
 
9.0        In my view therefore, if we want to address the durability issue of concrete, we must address the larger issue of poor workmanship & poor design / detailing rather than the issue of aggressive environment. This is not to say that the aggressive environment can be ignored.
 
10.0     What is the reason for poor workmanship ? Is it  :
 
a)           large scale corruption in the construction industry ?
b)           Lack of knowledge ?
c)           Lack of accountability ?
d)           Deficiency in training in our education system ?
e)           No encouragement for good quality work ?
f)            Combination of all above ?
 
We need to ponder & address.  
 
 
With best wishes
 
 
Alok Bhowmick
Quote:


     



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PostPosted: Mon Feb 27, 2012 9:17 pm    Post subject: Re: Crucial issues in respect of durability of Concrete Reply with quote

Dear Er Jignesh,

I appreciate your inputs.  Concrete is an engineered material. As you say, the ingredients of concrete have to be properly selected for the intended use, mixed , placed and vibrated and cured properly in order to get the desired life and properties. If any of the old structures are displaying these characteristics that means that the concrete with which they were built were properly designed and constructed.

Even without mineral admixtures we can have good reliable concretes. Many structures (I guess it will be 70 -80%) are constructed by people who do not have enough exposure to concrete as a material. They think that if it is mixed and poured it will stay there forever. They fail to realize that mix design plays an imp. role. For example, if one uses 1:2:4 mix, they will get about M 20 strength. Though the comp. strength is an important measure, it alone can  not guarantee long life!

Thanks again for your input!

Designers have so many responsibilities. They can only check reinforcements. they can not sit throughout the concreting process. Is it not the responsibility of the builder to produce good quality concrete by engaging proper people and labs for proportioning the mix and testing it for quality? I think we should specify additional tests for permeability also to obtain quality concrete.

Regards
NS

[quote="JVCSNL"]Dear All,

With an extremely informative and through provoking opening remarks by Dr. NS and Mr. Vijay Kulkarni, I am sure the ECONF would be interesting and a great platform for sharing knowledge on concrete durability.

I have my views on this subject as follows:

Good concrete (if I can say in simplistic terms) is an outcome of right selection of material like coarse aggregate, fine aggregates, cement, water, admixtures. Each of these materials having their own role to play and the role when they become together. In fact, it is more of a team effort than an individual effort. Any weak link will ensure bad concrete.  

While we select right material, we also need an effective integrator. The concrete mix designer who ensures that the mix of these ingredients is right and most optimum. The concrete mix designer is a leader who will ensure that the team of ingredients plays effectively, knowing the fact that more is not better. The mix designer will have to take into account of the effective relationship of cement and water as well as based on the knowledge of properties of each of these materials under laboratory conditions.  

To ensure best concrete, these ingredients shall be mixed with right tools and right people, under right ambient and physical surrounding conditions.  

Since these ingredients are handled by differently at different times, the assurance of best outcome is jeopardized.  

Lot of information is shared about the marvels that have stood centuries. I have always wondered that how it had been possible. When I think and try to figure out the potential causes of the same, I feel that such marvels were more of the objective than a routine process.  

The people who built such marvels were undoubtedly great engineers possessing design and construction knowledge. They selected the right materials (may be after a great search) and best materials. They also selected the best of the available talent for construction. They also supervised the work at every phase. And probably, there was no time pressure as well as fund limitation. I guess, when best of the minds work with commonly devised objective, I think best outcome is ensured. Also, an extremely stringent quality control was in place when working with the conditions.  

Today, as I have perceived, the designer needs to specify grade of concrete. RMC or concrete contractor will supply the concrete. The bar bender and the carpenter will do their role separately, the quality control will see that samples were taken and its reports were made and signed off. Each of these divided roles have cost and profit within and probably the common objective is not seen by all the participants of the whole building construction story. The designer sitting in office seldom worried about the quality of concrete at site. Many of the forum members would have seen the condition of reinforcement at site during monsoon. The mud from reinforcement is cleaned with small cloth and allowed to take all the task.

Let me clarify here that I do not deal with designing, making, pouring, curing, testing of concrete every day. With limited site exposure and having spend almost two decades in engineering, these are my views.  

The materials stored in the batching plant areas are tested under ideal conditions. I know a case where the site was near the salt farms and with high speed winds that would carry small salt particles and deposit on the open yards of coarse and fine aggregate will certainly deteriorate quality of concrete. The batching plant contractor was not bothered of it as he wanted to follow the mix design given. Certainly may be the case of water and other ingredients.  

Mostly people associated with the entire process are most bothered about their work as their money is involved. Also, most projects are developed under tremendous time pressures and due to this, most of them do not think about seasonal effects on the materials. Many times, the projects developed by people who seldom know the requirement and since developer holds power, many times compromises happen.  

Considering sudden industrial growth and need for huge amount of concrete and looking to lack of talent in the civil engineering (post IT boom) we are certainly facing problems pertaining to durability of concrete.  

In summary, the concrete durability can be ensured only by right material selection, mixing, transportation, placement, curing, protecting etc. by right people under supervision of right people. The monitoring of physical and ambient conditions every day will help concrete perform its purpose under given conditions. If concreting remains as a routine process among many stakeholders, the durability of concrete will be difficult to ensure.  

Regards,

Jignesh V Chokshi
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PostPosted: Mon Feb 27, 2012 9:41 pm    Post subject: Re: Crucial issues in respect of durability of Concrete Reply with quote

Dear Er
Alok Bhowmick ,

Thank you for your input on concreting of Bridges. If in your assessment 60% of the problems in Bridges is due to poor workmenship, think about the concreting in ordinary buildings! Bridges are often built by bigger companies which have good and experienced technicians who do the concreting. Whereas 70-80% of buildings are build by Masons, who are not trained.

As expressed by the other moderator Er Kulkarni it is important to train Masons and others in the construction industry. I quote the following from his posting
"
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."

Once again as mentioned by him even RMC plants should
have audit-based quality scheme. Anyhow the use of RMC is only about 10-14% of the total concrete consumed in India.

Curing which is very important for the quality of concrete is either ignored or not paid for!

Regards
Subramanian

       

Quote:

bsec wrote:
Dear All,
  
At the outset I thank the organizers of this E-Conference on choosing a subject matter for the conference, which is topical and apt for the moment, looking at the current demand for infrastructural growth ahead.
  
My views on the subject are as follows :


1.0  If we go back to history, durability became a major issue of concern in 80’s for concrete structures when serious deteriorations were observed in bridges & structures in cold countries in Europe, America & UK due to corrosion of reinforcement & prestressing steel. The problem became more acute for bridge decks due to use of de-icing salts.


2.0     Major problems were also seen in Middle East around the same time, when chloride induced corrosion was observed.


3.0     Subsequent developments globally in codes and standards in fighting the problems of carbonation and chloride induced corrosion of reinforcement and ensuring the longevity of concrete structure were primarily the outcome of the above.


4.0    Since the maximum damage caused in RCC structures (worldwide) is perceived to be primarily due to corrosion of reinforcement, the environmental classification in IS 456 as well as IRC codes are based on specific mechanism of duration (i,e. corrosion only).


5.0    90% of the geographical area of our country (leaving aside the 10% of the coastal belt & the cold areas of Jammu & Kashmir) do not have any serious problem of chloride induced corrosion or carbonation as witnessed in the European countries, UK, USA.


6.0   In spite of this advantage, our structures, built in the recent past, suffer from serious durability problems and they are found to be in distress well before their expected service life of say 50 years (for buildings) and 100 years (for bridges & other important structures).  As a bridge Engineer, I have quite often noted that bridges built in 60’s are still in sound condition while bridges built in 90’s are in distress.  There is a need for introspection here.


7.0  Durability of concrete therefore is a problem which can be attributed to the following reasons :
  
a)  Service Environment - Aggressive external / internal conditions
b)           Poor Material Selection
c)           Poor Design & Detailing  
d)           Poor Workmanship
  
Though all the above stated factors contribute in reducing the design life of the structure, If I am asked to give % contribution of each of the above causes in durability of structures in our country, I will give only 10% to item a) and b) each, 20% to item c) and balance 60% to item d).




  
8.0        In other words, major cause of durability problem in our structures is “poor workmanship” rather than “aggressive external / internal condition”. PLEASE NOTE – THE PERCENTAGES GIVEN ARE NOT BASED ON ANY SURVEY, BUT BASED ON MY OWN ENGINEERING JUDGEMENT.
  
9.0        In my view therefore, if we want to address the durability issue of concrete, we must address the larger issue of poor workmanship & poor design / detailing rather than the issue of aggressive environment. This is not to say that the aggressive environment can be ignored.
  
10.0     What is the reason for poor workmanship ? Is it  :
  
a)           large scale corruption in the construction industry ?
b)           Lack of knowledge ?
c)           Lack of accountability ?
d)           Deficiency in training in our education system ?
e)           No encouragement for good quality work ?
f)            Combination of all above ?
  
We need to ponder & address.  
  
  
With best wishes
  
  
Alok Bhowmick
Quote:


     



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PostPosted: Tue Feb 28, 2012 4:01 am    Post subject: Crucial issues in respect of durability of Concrete Reply with quote

Dear Sir,

What you have said is absolutely true. Proper mix and pouring are essential ingredients. But the regular testing of samples which are being poured in is very very important.

Best wishes  and thanks for the interaction.

Iyer


 
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On Tue, Feb 28, 2012 at 2:47 AM, Dr N. Subramanian <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear Er Jignesh,

I appreciate your inputs. Concrete is an engineered material. As you say, the ingredients of concrete have to be properly selected for the intended use, mixed , placed and vibrated and cured properly in order to get the desired life and properties. If any of the old structures are displaying these characteristics that means that the concrete with which they were built were properly designed and constructed.

Even without mineral admixtures we can have good reliable concretes. Many structures (I guess it will be 70 -80%) are constructed by people who do not have enough exposure to concrete as a material. They think that if it is mixed and poured it will stay there forever. They fail to realize that mix design plays an imp. role. For example, if one uses 1:2:4 mix, they will get about M 20 strength. Though the comp. strength is an important measure, it alone can not guarantee long life!

Thanks again for your input!

Designers have so many responsibilities. They can only check reinforcements. they can not sit throughout the concreting process. Is it not the responsibility of the builder to produce good quality concrete by engaging proper people and labs for proportioning the mix and testing it for quality? I think we should specify additional tests for permeability also to obtain quality concrete.

Regards
NS

[quote="JVCSNL"]Dear All,

With an extremely informative and through provoking opening remarks by Dr. NS and Mr. Vijay Kulkarni, I am sure the ECONF would be interesting and a great platform for sharing knowledge on concrete durability.

I have my views on this subject as follows:

Good concrete (if I can say in simplistic terms) is an outcome of right selection of material like coarse aggregate, fine aggregates, cement, water, admixtures. Each of these materials having their own role to play and the role when they become together. In fact, it is more of a team effort than an individual effort. Any weak link will ensure bad concrete.

While we select right material, we also need an effective integrator. The concrete mix designer who ensures that the mix of these ingredients is right and most optimum. The concrete mix designer is a leader who will ensure that the team of ingredients plays effectively, knowing the fact that more is not better. The mix designer will have to take into account of the effective relationship of cement and water as well as based on the knowledge of properties of each of these materials under laboratory conditions.

To ensure best concrete, these ingredients shall be mixed with right tools and right people, under right ambient and physical surrounding conditions.

Since these ingredients are handled by differently at different times, the assurance of best outcome is jeopardized.

Lot of information is shared about the marvels that have stood centuries. I have always wondered that how it had been possible. When I think and try to figure out the potential causes of the same, I feel that such marvels were more of the objective than a routine process.

The people who built such marvels were undoubtedly great engineers possessing design and construction knowledge. They selected the right materials (may be after a great search) and best materials. They also selected the best of the available talent for construction. They also supervised the work at every phase. And probably, there was no time pressure as well as fund limitation. I guess, when best of the minds work with commonly devised objective, I think best outcome is ensured. Also, an extremely stringent quality control was in place when working with the conditions.

Today, as I have perceived, the designer needs to specify grade of concrete. RMC or concrete contractor will supply the concrete. The bar bender and the carpenter will do their role separately, the quality control will see that samples were taken and its reports were made and signed off. Each of these divided roles have cost and profit within and probably the common objective is not seen by all the participants of the whole building construction story. The designer sitting in office seldom worried about the quality of concrete at site. Many of the forum members would have seen the condition of reinforcement at site during monsoon. The mud from reinforcement is cleaned with small cloth and allowed to take all the task.

Let me clarify here that I do not deal with designing, making, pouring, curing, testing of concrete every day. With limited site exposure and having spend almost two decades in engineering, these are my views.

The materials stored in the batching plant areas are tested under ideal conditions. I know a case where the site was near the salt farms and with high speed winds that would carry small salt particles and deposit on the open yards of coarse and fine aggregate will certainly deteriorate quality of concrete. The batching plant contractor was not bothered of it as he wanted to follow the mix design given. Certainly may be the case of water and other ingredients.

Mostly people associated with the entire process are most bothered about their work as their money is involved. Also, most projects are developed under tremendous time pressures and due to this, most of them do not think about seasonal effects on the materials. Many times, the projects developed by people who seldom know the requirement and since developer holds power, many times compromises happen.

Considering sudden industrial growth and need for huge amount of concrete and looking to lack of talent in the civil engineering (post IT boom) we are certainly facing problems pertaining to durability of concrete.

In summary, the concrete durability can be ensured only by right material selection, mixing, transportation, placement, curing, protecting etc. by right people under supervision of right people. The monitoring of physical and ambient conditions every day will help concrete perform its purpose under given conditions. If concreting remains as a routine process among many stakeholders, the durability of concrete will be difficult to ensure.

Regards,

Jignesh V Chokshi

     



     


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PostPosted: Tue Feb 28, 2012 10:18 am    Post subject: Crucial issues in respect of durability of Concrete Reply with quote

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 10:59 am    Post subject: Crucial issues in respect of durability of Concrete Reply with 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

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