www.sefindia.org

STRUCTURAL ENGINEERING FORUM OF INDIA [SEFI]

 Forum SubscriptionsSubscriptions DigestDigest Preferences   FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups  RegisterRegister FAQSecurity Tips FAQDonate
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log in to websiteLog in to websiteLog in to websiteLog in to forum 
Warning: Make sure you scan the downloaded attachment with updated antivirus tools  before opening them. They may contain viruses.
Use online scanners
here and here to upload downloaded attachment to check for safety.

Welcome note for Econference on Concrete Durability from the

 
This forum is locked: you cannot post, reply to, or edit topics.This topic is locked: you cannot edit posts or make replies. Thank Post    www.sefindia.org Forum Index -> E-conference on Durability of Concrete - Feb 27 to March 11 - 2012
View previous topic :: View next topic  
Author Message
Dr. N. Subramanian
General Sponsor
General Sponsor


Joined: 21 Feb 2008
Posts: 5300
Location: Gaithersburg, MD, U.S.A.

PostPosted: Mon Feb 27, 2012 12:12 am    Post subject: Welcome note for Econference on Concrete Durability from the Reply with quote

Dear Delegates,

We use Concrete everywhere- buildings, bridges, roads, dams, sidewalks, airport runways, even in canoes. Concrete is next only to water in terms of consumption-It is estimated that 40 tons of concrete is consumed by every person alive on Earth, with another ton added each year. Yet very few of us know how to make it durable.

Robert Courland in his new book "Concrete Planet: The Strange and Fascinating Story of the World's Most Common Man-Made Material says that "In a way, the story of concrete is also the story of civilization: its roots reach back to prehistoric times and even predate agriculture and the wheel. Our ancient ancestors were actually experimenting with limestone and kilns more than 2000 years before the dawn of agriculture. Kilning limestone represented humankind's first use of complex chemistry. It was also the earliest known industrial process. Archeologists have discovered floors of dwellings in Turkey and Iran that are extraordinarily hard and date back to 7000 B.C. The earliest use of concrete dates back to before 5600 BC: a 250-mm floor slab from this period, which was made using a red lime, sand and gravel mix, has been discovered on the banks of the Danube in Yugoslavia. Thus the use of concrete as a building material evolved over the centuries”.

As you might expect this is an ongoing process of trial and error and the availability of raw materials.  Volcanic ash was a key ingredient in the Roman cement that was so popular during the days of the Roman Empire. Meanwhile, a growing number of scholars now believe that many of the pyramids in Egypt were constructed with some kind of concrete. More impressive is the construction of the Pantheon in Rome in 126 A.D. This structure is the world's largest unreinforced concrete dome with a diameter of 43.3 m and is in use even today. It is the greatest example of the durability of concrete. Several other concrete structures built by Romans still exist.

But it is surprising that few of today’s concrete structures are lasting one-tenth as long, largely because of the steel used to reinforce them begins to deteriorate at a rapid rate after just a few decades. Is it because, the secrets of concrete manufacturing is lost with the fall of the Roman Empire?

Even though a number of modern concrete buildings are showing distress, several outstanding buildings and bridges have been built using RCC and are believed to last more than 100 years. Tremendous developments have taken place in the technology of concrete itself and a number of new materials, such as self compacting concrete, have been developed. The Indian code IS 456 was revised in 2000 and most of the major revisions were pertaining to durability. In addition, the analysis and design methods have also improved. Only a handful of structures are being analyzed and detailed today, without computer software, meaning we use more accurate and rigorous calculation methods. But still can we say that our concrete structures are durable and will last long for 100 years?

What is the problem? Is Concrete is treated as engineered material? Present day concrete has several ingredients compared to the concretes made by Romans- mineral and chemical admixtures in addition to the traditional course and fine aggregates, cement, and water (Several replacements are being proposed for aggregates as quality aggregates are no longer available in several parts of the country). Are our concretes properly mixed, placed, vibrated, cured and maintained? Each phase is important and the care taken during them enhances durability. Of course, the environment in which the concrete structures stand has changed considerably- we have more Co2 and other chemicals in the atmosphere now than Roman times-the manufacture of concrete itself is responsible for 5-8% of the emission of CO2. But the codes contain provisions to increase the cover in different environments- Are these provisions enough to protect our structures? Please read the uploaded articles about the possible recommendations to revise the codal provisions.

Can we improve the cover of concrete structures using special formwork? Or is it necessary to replace the steel reinforcement, which is considered responsible for most of the failures of concrete structures? Is the limit states method, which allows more stress in reinforcement to be taken in the calculation, thus increasing the crack width is to blame? Some blame mineral admixtures for corrosion of steel bars but in several laboratory as well actual constructions, they are found to decrease the permeability of concrete and thus prolong the life of structures. Let us discuss about all these and more in the next two weeks.

As usual this is a free discussion forum. The moderators will intervene only when the discussions go out of control or when they want to make a comment. Our raconteur, Er Vikramjeet will summarize the proceedings every couple of days.

Hope all of you will enthusiastically take part in the deliberations and make our concrete structures last for ever like the Pantheon in Rome!

Dr N Subramanian

Posted via Email
Back to top
View user's profile Send private message
arunkashikar
General Sponsor
General Sponsor


Joined: 14 Oct 2008
Posts: 91

PostPosted: Mon Feb 27, 2012 5:40 am    Post subject: Welcome note for Econference on Concrete Durability from the Reply with quote

I have come across structures made up of load bearing shear walls consisting of EPS concrete ( Alleviated expanded polystyrene concrete) and steel reinforcement. EPS concrete here is light weight and also low strength. Compressive strength is as low as 6MPa

These structures, though cannot meet the criteria of IS:456, are being validated by reputed institutes in India ( including some IITs) based on load tests and comparing them with load bearing masonry structures.

How correct it is to use concrete as low as M6, in case of load bearing wall? is it correct to compare these structures with reinforced masonry structures? Though these structures are not common yet here, many foreign companies have started promoting these,( especially for low cost, low rise structures) and reputed educational institutes are willing to validate them based on the tests. Municipal authorities also may accept these if they are validated by educational institutes of repute.

Though structures may pass load tests, fire resistance, permeability tests etc. how correct it is to use concrete as low as M6, from durability perspective?

Regards,
Arun Kashikar



From: Dr N. Subramanian [mailto:forum@sefindia.org]
Sent: 27 February 2012 05:48
To: econf@sefindia.org
Subject: [ECONF] Welcome note for Econference on Concrete Durability from the Moderators



Dear Delegates,

We use Concrete everywhere- buildings, bridges, roads, dams, sidewalks, airport runways, even in canoes. Concrete is next only to water in terms of consumption-It is estimated that 40 tons of concrete is consumed by every person alive on Earth, with another ton added each year. Yet very few of us know how to make it durable.

Robert Courland in his new book "Concrete Planet: The Strange and Fascinating Story of the World's Most Common Man-Made Material says that "In a way, the story of concrete is also the story of civilization: its roots reach back to prehistoric times and even predate agriculture and the wheel. Our ancient ancestors were actually experimenting with limestone and kilns more than 2000 years before the dawn of agriculture. Kilning limestone represented humankind's first use of complex chemistry. It was also the earliest known industrial process. Archeologists have discovered floors of dwellings in Turkey and Iran that are extraordinarily hard and date back to 7000 B.C. The earliest use of concrete dates back to before 5600 BC: a 250-mm floor slab from this period, which was made using a red lime, sand and gravel mix, has been discovered on the banks of the Danube in Yugoslavia. Thus the use of concrete as a building material evolved over the centuries”.

As you might expect this is an ongoing process of trial and error and the availability of raw materials. Volcanic ash was a key ingredient in the Roman cement that was so popular during the days of the Roman Empire. Meanwhile, a growing number of scholars now believe that many of the pyramids in Egypt were constructed with some kind of concrete. More impressive is the construction of the Pantheon in Rome in 126 A.D. This structure is the world's largest unreinforced concrete dome with a diameter of 43.3 m and is in use even today. It is the greatest example of the durability of concrete. Several other concrete structures built by Romans still exist.

But it is surprising that few of today’s concrete structures are lasting one-tenth as long, largely because of the steel used to reinforce them begins to deteriorate at a rapid rate after just a few decades. Is it because, the secrets of concrete manufacturing is lost with the fall of the Roman Empire?

Even though a number of modern concrete buildings are showing distress, several outstanding buildings and bridges have been built using RCC and are believed to last more than 100 years. Tremendous developments have taken place in the technology of concrete itself and a number of new materials, such as self compacting concrete, have been developed. The Indian code IS 456 was revised in 2000 and most of the major revisions were pertaining to durability. In addition, the analysis and design methods have also improved. Only a handful of structures are being analyzed and detailed today, without computer software, meaning we use more accurate and rigorous calculation methods. But still can we say that our concrete structures are durable and will last long for 100 years?

What is the problem? Is Concrete is treated as engineered material? Present day concrete has several ingredients compared to the concretes made by Romans- mineral and chemical admixtures in addition to the traditional course and fine aggregates, cement, and water (Several replacements are being proposed for aggregates as quality aggregates are no longer available in several parts of the country). Are our concretes properly mixed, placed, vibrated, cured and maintained? Each phase is important and the care taken during them enhances durability. Of course, the environment in which the concrete structures stand has changed considerably- we have more Co2 and other chemicals in the atmosphere now than Roman times-the manufacture of concrete itself is responsible for 5-8% of the emission of CO2. But the codes contain provisions to increase the cover in different environments- Are these provisions enough to protect our structures? Please read the uploaded articles about the possible recommendations to revise the codal provisions.

Can we improve the cover of concrete structures using special formwork? Or is it necessary to replace the steel reinforcement, which is considered responsible for most of the failures of concrete structures? Is the limit states method, which allows more stress in reinforcement to be taken in the calculation, thus increasing the crack width is to blame? Some blame mineral admixtures for corrosion of steel bars but in several laboratory as well actual constructions, they are found to decrease the permeability of concrete and thus prolong the life of structures. Let us discuss about all these and more in the next two weeks.

As usual this is a free discussion forum. The moderators will intervene only when the discussions go out of control or when they want to make a comment. Our raconteur, Er Vikramjeet will summarize the proceedings every couple of days.

Hope all of you will enthusiastically take part in the deliberations and make our concrete structures last for ever like the Pantheon in Rome!

Dr N Subramanian  







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.

Posted via Email



~WRD000.jpg
 Description:
 Filesize:  823 Bytes
 Viewed:  588 Time(s)

~WRD000.jpg


Back to top
View user's profile Send private message
vijay.kulkarni
E-Conference Moderator


Joined: 27 Feb 2012
Posts: 6

PostPosted: Mon Feb 27, 2012 3:13 pm    Post subject: Re: Welcome note for Econference on Concrete Durability from Reply with quote

EPS concrete, besides being lightweight, has excellent thermal insulation and sound insulation properties. Further, fire resistance is also better, but will depend upon the thickness of the wall. The use of EPS will reduce the energy requirements in buildings (reduced cost of air-conditioning) and will reduce the sizes of structural elements in view of the lighter weight. In addition, EPS is a waste product, which is now generated in appreciable volume in India. Thus EPS concrete has a lot of potential as an eco-friendly material. However, in my opinion, the application of EPS concrete needs to be limited to non-load bearing walls only. With just 5-6 MPa strength, the material cannot possibly be used as a structural element”.

You may appropriately take cognizance of the above remarks in your summery.

Thanks once again.

Vijay
arunkashikar wrote:
I have come across structures made up of load bearing shear walls consisting of EPS concrete ( Alleviated expanded polystyrene concrete) and steel reinforcement. EPS concrete here is light weight and also low strength. Compressive strength is as low as 6MPa

These structures, though cannot meet the criteria of IS:456, are being validated by reputed institutes in India ( including some IITs) based on load tests and comparing them with load bearing masonry structures.

How correct it is to use concrete as low as M6, in case of load bearing wall? is it correct to compare these structures with reinforced masonry structures? Though these structures are not common yet here, many foreign companies have started promoting these,( especially for low cost, low rise structures) and reputed educational institutes are willing to validate them based on the tests. Municipal authorities also may accept these if they are validated by educational institutes of repute.

Though structures may pass load tests, fire resistance, permeability tests etc. how correct it is to use concrete as low as M6, from durability perspective?

Regards,
Arun Kashikar



From: Dr N. Subramanian [mailto:forum@sefindia.org]
Sent: 27 February 2012 05:48
To: econf@sefindia.org
Subject: [ECONF] Welcome note for Econference on Concrete Durability from the Moderators



Dear Delegates,

We use Concrete everywhere- buildings, bridges, roads, dams, sidewalks, airport runways, even in canoes. Concrete is next only to water in terms of consumption-It is estimated that 40 tons of concrete is consumed by every person alive on Earth, with another ton added each year. Yet very few of us know how to make it durable.

Robert Courland in his new book "Concrete Planet: The Strange and Fascinating Story of the World's Most Common Man-Made Material says that "In a way, the story of concrete is also the story of civilization: its roots reach back to prehistoric times and even predate agriculture and the wheel. Our ancient ancestors were actually experimenting with limestone and kilns more than 2000 years before the dawn of agriculture. Kilning limestone represented humankind's first use of complex chemistry. It was also the earliest known industrial process. Archeologists have discovered floors of dwellings in Turkey and Iran that are extraordinarily hard and date back to 7000 B.C. The earliest use of concrete dates back to before 5600 BC: a 250-mm floor slab from this period, which was made using a red lime, sand and gravel mix, has been discovered on the banks of the Danube in Yugoslavia. Thus the use of concrete as a building material evolved over the centuries”.

As you might expect this is an ongoing process of trial and error and the availability of raw materials. Volcanic ash was a key ingredient in the Roman cement that was so popular during the days of the Roman Empire. Meanwhile, a growing number of scholars now believe that many of the pyramids in Egypt were constructed with some kind of concrete. More impressive is the construction of the Pantheon in Rome in 126 A.D. This structure is the world's largest unreinforced concrete dome with a diameter of 43.3 m and is in use even today. It is the greatest example of the durability of concrete. Several other concrete structures built by Romans still exist.

But it is surprising that few of today’s concrete structures are lasting one-tenth as long, largely because of the steel used to reinforce them begins to deteriorate at a rapid rate after just a few decades. Is it because, the secrets of concrete manufacturing is lost with the fall of the Roman Empire?

Even though a number of modern concrete buildings are showing distress, several outstanding buildings and bridges have been built using RCC and are believed to last more than 100 years. Tremendous developments have taken place in the technology of concrete itself and a number of new materials, such as self compacting concrete, have been developed. The Indian code IS 456 was revised in 2000 and most of the major revisions were pertaining to durability. In addition, the analysis and design methods have also improved. Only a handful of structures are being analyzed and detailed today, without computer software, meaning we use more accurate and rigorous calculation methods. But still can we say that our concrete structures are durable and will last long for 100 years?

What is the problem? Is Concrete is treated as engineered material? Present day concrete has several ingredients compared to the concretes made by Romans- mineral and chemical admixtures in addition to the traditional course and fine aggregates, cement, and water (Several replacements are being proposed for aggregates as quality aggregates are no longer available in several parts of the country). Are our concretes properly mixed, placed, vibrated, cured and maintained? Each phase is important and the care taken during them enhances durability. Of course, the environment in which the concrete structures stand has changed considerably- we have more Co2 and other chemicals in the atmosphere now than Roman times-the manufacture of concrete itself is responsible for 5-8% of the emission of CO2. But the codes contain provisions to increase the cover in different environments- Are these provisions enough to protect our structures? Please read the uploaded articles about the possible recommendations to revise the codal provisions.

Can we improve the cover of concrete structures using special formwork? Or is it necessary to replace the steel reinforcement, which is considered responsible for most of the failures of concrete structures? Is the limit states method, which allows more stress in reinforcement to be taken in the calculation, thus increasing the crack width is to blame? Some blame mineral admixtures for corrosion of steel bars but in several laboratory as well actual constructions, they are found to decrease the permeability of concrete and thus prolong the life of structures. Let us discuss about all these and more in the next two weeks.

As usual this is a free discussion forum. The moderators will intervene only when the discussions go out of control or when they want to make a comment. Our raconteur, Er Vikramjeet will summarize the proceedings every couple of days.

Hope all of you will enthusiastically take part in the deliberations and make our concrete structures last for ever like the Pantheon in Rome!

Dr N Subramanian  







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.

Posted via Email
Back to top
View user's profile Send private message
naresh7918
SEFI Member
SEFI Member


Joined: 23 Sep 2011
Posts: 7

PostPosted: Mon Feb 27, 2012 3:55 pm    Post subject: Welcome note for Econference on Concrete Durability from the 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 5:47 AM, Dr N. Subramanian <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear Delegates,

We use Concrete everywhere- buildings, bridges, roads, dams, sidewalks, airport runways, even in canoes. Concrete is next only to water in terms of consumption-It is estimated that 40 tons of concrete is consumed by every person alive on Earth, with another ton added each year. Yet very few of us know how to make it durable.

Robert Courland in his new book "Concrete Planet: The Strange and Fascinating Story of the World's Most Common Man-Made Material says that "In a way, the story of concrete is also the story of civilization: its roots reach back to prehistoric times and even predate agriculture and the wheel. Our ancient ancestors were actually experimenting with limestone and kilns more than 2000 years before the dawn of agriculture. Kilning limestone represented humankind's first use of complex chemistry. It was also the earliest known industrial process. Archeologists have discovered floors of dwellings in Turkey and Iran that are extraordinarily hard and date back to 7000 B.C. The earliest use of concrete dates back to before 5600 BC: a 250-mm floor slab from this period, which was made using a red lime, sand and gravel mix, has been discovered on the banks of the Danube in Yugoslavia. Thus the use of concrete as a building material evolved over the centuries”.

As you might expect this is an ongoing process of trial and error and the availability of raw materials. Volcanic ash was a key ingredient in the Roman cement that was so popular during the days of the Roman Empire. Meanwhile, a growing number of scholars now believe that many of the pyramids in Egypt were constructed with some kind of concrete. More impressive is the construction of the Pantheon in Rome in 126 A.D. This structure is the world's largest unreinforced concrete dome with a diameter of 43.3 m and is in use even today. It is the greatest example of the durability of concrete. Several other concrete structures built by Romans still exist.

But it is surprising that few of today’s concrete structures are lasting one-tenth as long, largely because of the steel used to reinforce them begins to deteriorate at a rapid rate after just a few decades. Is it because, the secrets of concrete manufacturing is lost with the fall of the Roman Empire?

Even though a number of modern concrete buildings are showing distress, several outstanding buildings and bridges have been built using RCC and are believed to last more than 100 years. Tremendous developments have taken place in the technology of concrete itself and a number of new materials, such as self compacting concrete, have been developed. The Indian code IS 456 was revised in 2000 and most of the major revisions were pertaining to durability. In addition, the analysis and design methods have also improved. Only a handful of structures are being analyzed and detailed today, without computer software, meaning we use more accurate and rigorous calculation methods. But still can we say that our concrete structures are durable and will last long for 100 years?

What is the problem? Is Concrete is treated as engineered material? Present day concrete has several ingredients compared to the concretes made by Romans- mineral and chemical admixtures in addition to the traditional course and fine aggregates, cement, and water (Several replacements are being proposed for aggregates as quality aggregates are no longer available in several parts of the country). Are our concretes properly mixed, placed, vibrated, cured and maintained? Each phase is important and the care taken during them enhances durability. Of course, the environment in which the concrete structures stand has changed considerably- we have more Co2 and other chemicals in the atmosphere now than Roman times-the manufacture of concrete itself is responsible for 5-8% of the emission of CO2. But the codes contain provisions to increase the cover in different environments- Are these provisions enough to protect our structures? Please read the uploaded articles about the possible recommendations to revise the codal provisions.

Can we improve the cover of concrete structures using special formwork? Or is it necessary to replace the steel reinforcement, which is considered responsible for most of the failures of concrete structures? Is the limit states method, which allows more stress in reinforcement to be taken in the calculation, thus increasing the crack width is to blame? Some blame mineral admixtures for corrosion of steel bars but in several laboratory as well actual constructions, they are found to decrease the permeability of concrete and thus prolong the life of structures. Let us discuss about all these and more in the next two weeks.

As usual this is a free discussion forum. The moderators will intervene only when the discussions go out of control or when they want to make a comment. Our raconteur, Er Vikramjeet will summarize the proceedings every couple of days.

Hope all of you will enthusiastically take part in the deliberations and make our concrete structures last for ever like the Pantheon in Rome!

Dr N Subramanian
     



     



Posted via Email
Back to top
View user's profile Send private message
Dr. N. Subramanian
General Sponsor
General Sponsor


Joined: 21 Feb 2008
Posts: 5300
Location: Gaithersburg, MD, U.S.A.

PostPosted: Mon Feb 27, 2012 9:34 pm    Post subject: Re: Welcome note for Econference on Concrete Durability from Reply with quote

Dear Er Arun,

Thank you for the info. May be its use in Europe & USA is restricted they have come to India! Read the following from

http://lightweightconcreteco.com/products/foamlite/recycl/
"Foam Lite and Eps Concrete – Part of the solution to a big     problem
Styropor®/Styrofoam®, which is an expanded polystyrene (eps), and extruded polystyrene (xps) are not biodegradable. It is estimated that on a volume basis, post consumer and post manufacturer expanded and extruded polystyrene, constitute 7% of the waste being placed in landfills in the US.
In Europe, these products are being totally banned from landfills, with the originating manufacturer being responsible for their collection, recycling, or disposal. Many landfills in the US now ban the waste of eps and xps manufacturers. The environmental movement in the US was instrumental in having fast-food companies such as McDonald’s discontinue the use of eps containers because the items are not biodegradable.

Yet because of their desirability as a lightweight protective packaging material and their insulation qualities, eps and xps use continues to grow. That in turn results in a continuing increase in the availability of eps waste. Eps manufacturers, aware of the jaundiced eye cast by landfills, and the public, on the litter problem of eps in particular, have established an industry organization to alleviate the problem.

Unfortunately, the organization provides little or no informative or useful information to the general public or its members on methods to recycle expanded polystyrene.

Where landfill restrictions combined with the lack of alternative recycling programs exist, eps manufacturers may actually be willing to pay eps concrete companies or individuals for accepting their waste."

Anyhow any concrete with strengths less than 20MPa should not be used as structural purposes as per IS 456.

Regards
Subramanian

  

arunkashikar wrote:
I have come across structures made up of load bearing shear walls consisting of EPS concrete ( Alleviated expanded polystyrene concrete) and steel reinforcement. EPS concrete here is light weight and also low strength. Compressive strength is as low as 6MPa

These structures, though cannot meet the criteria of IS:456, are being validated by reputed institutes in India ( including some IITs) based on load tests and comparing them with load bearing masonry structures.

How correct it is to use concrete as low as M6, in case of load bearing wall? is it correct to compare these structures with reinforced masonry structures? Though these structures are not common yet here, many foreign companies have started promoting these,( especially for low cost, low rise structures) and reputed educational institutes are willing to validate them based on the tests. Municipal authorities also may accept these if they are validated by educational institutes of repute.

Though structures may pass load tests, fire resistance, permeability tests etc. how correct it is to use concrete as low as M6, from durability perspective?

Regards,
Arun Kashikar



From: Dr N. Subramanian [mailto:forum@sefindia.org]
Sent: 27 February 2012 05:48
To: econf@sefindia.org
Subject: [ECONF] Welcome note for Econference on Concrete Durability from the Moderators



Dear Delegates,

We use Concrete everywhere- buildings, bridges, roads, dams, sidewalks, airport runways, even in canoes. Concrete is next only to water in terms of consumption-It is estimated that 40 tons of concrete is consumed by every person alive on Earth, with another ton added each year. Yet very few of us know how to make it durable.

Robert Courland in his new book "Concrete Planet: The Strange and Fascinating Story of the World's Most Common Man-Made Material says that "In a way, the story of concrete is also the story of civilization: its roots reach back to prehistoric times and even predate agriculture and the wheel. Our ancient ancestors were actually experimenting with limestone and kilns more than 2000 years before the dawn of agriculture. Kilning limestone represented humankind's first use of complex chemistry. It was also the earliest known industrial process. Archeologists have discovered floors of dwellings in Turkey and Iran that are extraordinarily hard and date back to 7000 B.C. The earliest use of concrete dates back to before 5600 BC: a 250-mm floor slab from this period, which was made using a red lime, sand and gravel mix, has been discovered on the banks of the Danube in Yugoslavia. Thus the use of concrete as a building material evolved over the centuries”.

As you might expect this is an ongoing process of trial and error and the availability of raw materials. Volcanic ash was a key ingredient in the Roman cement that was so popular during the days of the Roman Empire. Meanwhile, a growing number of scholars now believe that many of the pyramids in Egypt were constructed with some kind of concrete. More impressive is the construction of the Pantheon in Rome in 126 A.D. This structure is the world's largest unreinforced concrete dome with a diameter of 43.3 m and is in use even today. It is the greatest example of the durability of concrete. Several other concrete structures built by Romans still exist.

But it is surprising that few of today’s concrete structures are lasting one-tenth as long, largely because of the steel used to reinforce them begins to deteriorate at a rapid rate after just a few decades. Is it because, the secrets of concrete manufacturing is lost with the fall of the Roman Empire?

Even though a number of modern concrete buildings are showing distress, several outstanding buildings and bridges have been built using RCC and are believed to last more than 100 years. Tremendous developments have taken place in the technology of concrete itself and a number of new materials, such as self compacting concrete, have been developed. The Indian code IS 456 was revised in 2000 and most of the major revisions were pertaining to durability. In addition, the analysis and design methods have also improved. Only a handful of structures are being analyzed and detailed today, without computer software, meaning we use more accurate and rigorous calculation methods. But still can we say that our concrete structures are durable and will last long for 100 years?

What is the problem? Is Concrete is treated as engineered material? Present day concrete has several ingredients compared to the concretes made by Romans- mineral and chemical admixtures in addition to the traditional course and fine aggregates, cement, and water (Several replacements are being proposed for aggregates as quality aggregates are no longer available in several parts of the country). Are our concretes properly mixed, placed, vibrated, cured and maintained? Each phase is important and the care taken during them enhances durability. Of course, the environment in which the concrete structures stand has changed considerably- we have more Co2 and other chemicals in the atmosphere now than Roman times-the manufacture of concrete itself is responsible for 5-8% of the emission of CO2. But the codes contain provisions to increase the cover in different environments- Are these provisions enough to protect our structures? Please read the uploaded articles about the possible recommendations to revise the codal provisions.

Can we improve the cover of concrete structures using special formwork? Or is it necessary to replace the steel reinforcement, which is considered responsible for most of the failures of concrete structures? Is the limit states method, which allows more stress in reinforcement to be taken in the calculation, thus increasing the crack width is to blame? Some blame mineral admixtures for corrosion of steel bars but in several laboratory as well actual constructions, they are found to decrease the permeability of concrete and thus prolong the life of structures. Let us discuss about all these and more in the next two weeks.

As usual this is a free discussion forum. The moderators will intervene only when the discussions go out of control or when they want to make a comment. Our raconteur, Er Vikramjeet will summarize the proceedings every couple of days.

Hope all of you will enthusiastically take part in the deliberations and make our concrete structures last for ever like the Pantheon in Rome!

Dr N Subramanian  







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.

Posted via Email
Back to top
View user's profile Send private message
milapsingh
SEFI Member
SEFI Member


Joined: 02 Sep 2011
Posts: 2

PostPosted: Tue Feb 28, 2012 5:03 am    Post subject: Welcome note for Econference on Concrete Durability from the Reply with quote

It is extremely informative for all members interested in knowing about newer materials. This also opens possibility to use various materials , first with engineering imagination and then actually prototyping and putting to test for actual reliability.


Warm Regards

Milap Singh Jadaun

From: vijay.kulkarni [mailto:forum@sefindia.org]
Sent: Monday, February 27, 2012 8:43 PM
To: econf@sefindia.org
Subject: [ECONF] Re: Welcome note for Econference on Concrete Durability from the



EPS concrete, besides being lightweight, has excellent thermal insulation and sound insulation properties. Further, fire resistance is also better, but will depend upon the thickness of the wall. The use of EPS will reduce the energy requirements in buildings (reduced cost of air-conditioning) and will reduce the sizes of structural elements in view of the lighter weight. In addition, EPS is a waste product, which is now generated in appreciable volume in India. Thus EPS concrete has a lot of potential as an eco-friendly material. However, in my opinion, the application of EPS concrete needs to be limited to non-load bearing walls only. With just 5-6 MPa strength, the material cannot possibly be used as a structural element”.

You may appropriately take cognizance of the above remarks in your summery.

Thanks once again.

Vijay
arunkashikar wrote:
I have come across structures made up of load bearing shear walls consisting of EPS concrete ( Alleviated expanded polystyrene concrete) and steel reinforcement. EPS concrete here is light weight and also low strength. Compressive strength is as low as 6MPa

These structures, though cannot meet the criteria of IS:456, are being validated by reputed institutes in India ( including some IITs) based on load tests and comparing them with load bearing masonry structures.

How correct it is to use concrete as low as M6, in case of load bearing wall? is it correct to compare these structures with reinforced masonry structures? Though these structures are not common yet here, many foreign companies have started promoting these,( especially for low cost, low rise structures) and reputed educational institutes are willing to validate them based on the tests. Municipal authorities also may accept these if they are validated by educational institutes of repute.

Though structures may pass load tests, fire resistance, permeability tests etc. how correct it is to use concrete as low as M6, from durability perspective?

Regards,
Arun Kashikar



From: Dr N. Subramanian [mailto:forum@sefindia.org]
Sent: 27 February 2012 05:48
To: econf@sefindia.org (econf@sefindia.org)
Subject: [ECONF] Welcome note for Econference on Concrete Durability from the Moderators



Dear Delegates,

We use Concrete everywhere- buildings, bridges, roads, dams, sidewalks, airport runways, even in canoes. Concrete is next only to water in terms of consumption-It is estimated that 40 tons of concrete is consumed by every person alive on Earth, with another ton added each year. Yet very few of us know how to make it durable.

Robert Courland in his new book "Concrete Planet: The Strange and Fascinating Story of the World's Most Common Man-Made Material says that "In a way, the story of concrete is also the story of civilization: its roots reach back to prehistoric times and even predate agriculture and the wheel. Our ancient ancestors were actually experimenting with limestone and kilns more than 2000 years before the dawn of agriculture. Kilning limestone represented humankind's first use of complex chemistry. It was also the earliest known industrial process. Archeologists have discovered floors of dwellings in Turkey and Iran that are extraordinarily hard and date back to 7000 B.C. The earliest use of concrete dates back to before 5600 BC: a 250-mm floor slab from this period, which was made using a red lime, sand and gravel mix, has been discovered on the banks of the Danube in Yugoslavia. Thus the use of concrete as a building material evolved over the centuries”.

As you might expect this is an ongoing process of trial and error and the availability of raw materials. Volcanic ash was a key ingredient in the Roman cement that was so popular during the days of the Roman Empire. Meanwhile, a growing number of scholars now believe that many of the pyramids in Egypt were constructed with some kind of concrete. More impressive is the construction of the Pantheon in Rome in 126 A.D. This structure is the world's largest unreinforced concrete dome with a diameter of 43.3 m and is in use even today. It is the greatest example of the durability of concrete. Several other concrete structures built by Romans still exist.

But it is surprising that few of today’s concrete structures are lasting one-tenth as long, largely because of the steel used to reinforce them begins to deteriorate at a rapid rate after just a few decades. Is it because, the secrets of concrete manufacturing is lost with the fall of the Roman Empire?

Even though a number of modern concrete buildings are showing distress, several outstanding buildings and bridges have been built using RCC and are believed to last more than 100 years. Tremendous developments have taken place in the technology of concrete itself and a number of new materials, such as self compacting concrete, have been developed. The Indian code IS 456 was revised in 2000 and most of the major revisions were pertaining to durability. In addition, the analysis and design methods have also improved. Only a handful of structures are being analyzed and detailed today, without computer software, meaning we use more accurate and rigorous calculation methods. But still can we say that our concrete structures are durable and will last long for 100 years?

What is the problem? Is Concrete is treated as engineered material? Present day concrete has several ingredients compared to the concretes made by Romans- mineral and chemical admixtures in addition to the traditional course and fine aggregates, cement, and water (Several replacements are being proposed for aggregates as quality aggregates are no longer available in several parts of the country). Are our concretes properly mixed, placed, vibrated, cured and maintained? Each phase is important and the care taken during them enhances durability. Of course, the environment in which the concrete structures stand has changed considerably- we have more Co2 and other chemicals in the atmosphere now than Roman times-the manufacture of concrete itself is responsible for 5-8% of the emission of CO2. But the codes contain provisions to increase the cover in different environments- Are these provisions enough to protect our structures? Please read the uploaded articles about the possible recommendations to revise the codal provisions.

Can we improve the cover of concrete structures using special formwork? Or is it necessary to replace the steel reinforcement, which is considered responsible for most of the failures of concrete structures? Is the limit states method, which allows more stress in reinforcement to be taken in the calculation, thus increasing the crack width is to blame? Some blame mineral admixtures for corrosion of steel bars but in several laboratory as well actual constructions, they are found to decrease the permeability of concrete and thus prolong the life of structures. Let us discuss about all these and more in the next two weeks.

As usual this is a free discussion forum. The moderators will intervene only when the discussions go out of control or when they want to make a comment. Our raconteur, Er Vikramjeet will summarize the proceedings every couple of days.

Hope all of you will enthusiastically take part in the deliberations and make our concrete structures last for ever like the Pantheon in Rome!

Dr N Subramanian







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.

Posted via Email
Back to top
View user's profile Send private message
Display posts from previous:   
This forum is locked: you cannot post, reply to, or edit topics.This topic is locked: you cannot edit posts or make replies. Thank Post    www.sefindia.org Forum Index -> E-conference on Durability of Concrete - Feb 27 to March 11 - 2012 All times are GMT
Page 1 of 1

 

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


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