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Summary of E-Conf -Days 6

 
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
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vikram.jeet
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PostPosted: Sun Mar 04, 2012 1:13 am    Post subject: Summary of E-Conf -Days 6 Reply with quote

CURING for Durability  - - - Most important activity post- Pouring


We are nearing  the midst of e-conference on Concrete Durability and response from
experts/engineers is thumping. Most views while discussing important issues related
to Durability  have never forgot to mention  the crucial & most  important activity
after concrete pouring ,   and that is Proper Curing of Concrete  for stipulated period
without  which all  prior efforts of ideal mix design, tested ingredients , careful mixing
and placing by the construction team and pains taken by   Concrete Technologists
may go in vain . We can easily  say that ' Curing is for   Enduring ' the Concrete to
to possess  its strength and longevity. Curing must be addressed adequately in
specifications and checks must be incorporated in the contracts, to see the curing
being done properly  at sites . It is so important  but still  very neglected activity and
is mostly left to  labor only,  without any records and without much  supervision from
engineers.


On Day 6 of the e- Conference  , we have very educative  postings - - - - - -

Madam Alpa Sheth referred to the paper by Prof P K Mehta  wherein the  cause of
deterioration of early- days coarser  portland cements  was not due to cracking  but due
to leaching etc and  modern  age high strength cements being finer , the cracking
is more pronounced.Cracking is a cause of deterioration , though no direct
relation ship has been established.Madam Alpa  requests for opinion from experts
on HVFA concrete, self compacting concrete with viscosity controlling admixture.
Madam Alpa also refers to the posting from  the overseas participant  Er  Moruf
and requests opinion on Self compacting concrete vs flyash based concrete
in terms of durability.

Er Alok Bhowmick discussed about his experiences of Konkan Railway project
and induction  of third party QA  Agency comprising of team of Quality  engineers and
their reporting the matters directly to top management  resulted in effective QC
on long 760 Km stretch.

Er Dipak Bhattacharya states his findings very emphatically that Use of fly ash
has nothing to do with Durability enhancement qualities. Introduction of Flyash
was primarily to economize the  Cement but it has not happened.Vested interests
have publicised the puzzolona cements with grades 33, 43 & 53 with increased
pricing and suddenly 33 grade was removed from market.He  feels that durability
is achieved by protection of concrete and protection of reinforcement. TMT bars
use as reinforcement serves the purpose of reinf protection but for concretes
SRC is the solution but very costly proposition .Thus to have a durable concrete
approach shall be to have impermeable concrete  to possible extent, and use
of super- plasticizers help very much in this direction  but again add to cost. Better
Mix design using same  qualities of aggregates and cement ,denser will be
MIx ,better will be impermeability and better strength  - - not easy to achieve but
approach must be sincere.The substance of posting is very emphatic &
excellent for other participants to  respond.

Er Jignesh appended a note regarding effect of high temp and high pressure on
concrete and concluded that concrete with  Fly ash based cement shall be
avoided for machine foundations as it will have detrimental effects on concrete
at high temp and high pressures.

Conf - Moderator  Mr Viay Kulkarni has discussed about the other issues pertinent
to durability of concrete in addition to those posted earlier.The  Use of advanced
software for QA/QC . Complaints in RMC namely In-adequate slump,Lower 7 days
and 28 days strength and surface cracking . RMC  suppliers with certification can
assure   the adequacy &  capability of RMCM of  having necessary infrastructure
for Quality concrete production.QA can be achieved thru robust QA -plan by
continuous monitoring of properties of ingredients, Process control, properties of
fresh and hardened conc and statistical analysis for strength and durability.Some
early warning systems like cumulative summation technique are adopted  abroad
and few  RMC manufacturers  in India. Short-listing RMCM shall be based on technical
skills.Other issues are Non structural cracks due to plastic shrinkage/plastic
settlement and thermal shrinkage or combine which become matter of dispute with
clients.These cracks are harmless structurally but affect durability by providing
direct access to chlorides , sulphates and CO2.Specifying pour temp shall be
essential , and  increased use of SCM's  enhances durability and
sustainability. Mr kulkarni also responded to query of  Er Jignesh regarding FA
concrete subject to high temp . I must appreciate  Mr Vijay  Kulkarni  for his  
enlightening posting on pertinent Issues for concrete durability  ,
- - -truly a  living legend of this field  as also Moderator of this e -Conf.

Er Jignesh appreciated Mr Kulkarni's views for touching the aspect of  temp of
fresh conc at placement.He feels that limit of temp below 30 degree for general
works may be reduced for critical structures sensitive to low strains and  for
these , it may be less  than 20 deg.

Er Bhowmick likes to get to thread of original paper by R W Burrows in reference to
posting from Er Moruf and expects views from experts  Mr Rajmane and Mr Kulkarni
who have life long experience on CT.

Er Jayant Kulkarni informed that lot of research has been reported for Service life
Assessment based on mathematical modelling.Most important parameter is rate of
chloride penetration leading to initiation of corrosion of reinf. It is very important for
cold countries using deicing salts /or structures in marine environment. While  Listing
various parameters involved for formulating  guidelines  for service life , he feels that
it may provide some indicator .

Er As Parulekar informed that there are very effective durabilty tests like RCPT but
these are lab based on test specimen cubes etc. The NDT in form of UPSV can be
used on structural component's  like beams ,columns ( after prior testing on  known
results- lab- specimens tested by RCPT )

Er Jignesh reminded that FA based cements achieve strength slowly and forms
are to be removed later than OPC based concrete work. PPC should be cheaper
since Fly ash % is as high as 35% ,but in market there is not much difference in
rates.Also availability of OPC is getting difficult. Can HVFA be used in lieu .In another
posting he gave reference to a paper on experimental work done on FA conc
subject to high temp.There is reduction in compressive , tensile capacity as well
as reduction in modulus of Elasticity. He needs some literature on Aggregates
in various parts in India and its effects on ASR.   His participation in econf  is
highly encouraging and  appreciative.

Dr N Subramanian , conf- Moderator, appreciated the views of Er Bhowmick 's listing
of reasons for poor quality in India and added humor in the e-conf  in his post .Dr NS
response, as usual on sefi, is always clear cut and straightforward as evident from
various postings from him on  the subject topic of e-conf  .

Er Bhowmick , acknowledge that FA based concrete have extended setting  time
and slow strength gain and delays construction. FA Concrete is more prone to surface
scaling under exposure to deicing chemicals .In India this problem is not there.
Fly ash percentage must be adjusted in mix to reap maximum benefits, but pricing
is due to nexus of many involved in trade.Regarding HVFA , greater QC is needed
and presently industry is  not geared for this.


Regards to all participating in the e- conference or viewing it from their desk-tops/laptops and expecting more response in coming days

vikramjeet
Conf-Raconteur

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nagesh_shankarnarayan
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Joined: 10 Jul 2011
Posts: 2

PostPosted: Sun Mar 04, 2012 11:10 am    Post subject: Summary of E-Conf -Days 6 Reply with quote

Sir,
 
We have an article published by Mr. John Gneadinger of Con-cure Corporation (USA) who mentions the importance of mix and maintaining the proper curing, the possible places of strength reductions in the open areas of form work, how to have the best mix design with the temperature monitored etc. Please go through the article published in the latest edition of NBM & CW magazine or read the same at the URL given below and please revert back to us for any clarification. The URL is: http://www.nbmcw.com/articles/concrete/concrete-strength-test/28073-in-place-concrete-strength-and-temperature-the-science-of-maturity.html

Regards,
B.S. NAGESH. 
PROPRIETOR
SAMHITHA INNOVATIONS
(Distributors for Maverick Ultrasound,Con-cure Concrete Maturity Monitoring Instruments & dealers in Proceq NDT instruments). 
No.7/1, 14th Cross, Margosa Road, Malleshwaram,
Bangalore-560 003. Karnataka. India.
Ph: 080 23463943.
Mob:+91 98860 00953.
Email: sales@samhithainnovations.com (sales@samhithainnovations.com)
Website: www.samhithainnovations.com

************************************************************************DISCLAIMER***********************************************************************
Information contained and transmitted by this e-mail is confidential and proprietary to Samhitha Innovations and is intended for use only by the addressee. If you are not the intended recipient, you are notified that any dissemination or copying of this e-mail is strictly prohibited and you are requested to delete this e-mail immediately and notify the originator. Samhitha Innovations does not enter into any binding agreement with any party by e-mail. Any view expressed by an individual do not necessarily reflect the view of Samhitha Innovations & is not responsible for any consequences.




On Sun, Mar 4, 2012 at 6:44 AM, vikram.jeet <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
  CURING for Durability - - - Most important activity post- Pouring


We are nearing the midst of e-conference on Concrete Durability and response from
experts/engineers is thumping. Most views while discussing important issues related
to Durability have never forgot to mention the crucial & most important activity
after concrete pouring , and that is Proper Curing of Concrete for stipulated period
without which all prior efforts of ideal mix design, tested ingredients , careful mixing
and placing by the construction team and pains taken by Concrete Technologists
may go in vain . We can easily say that ' Curing is for Enduring ' the Concrete to
to possess its strength and longevity. Curing must be addressed adequately in
specifications and checks must be incorporated in the contracts, to see the curing
being done properly at sites . It is so important but still very neglected activity and
is mostly left to labor only, without any records and without much supervision from
engineers.


On Day 6 of the e- Conference , we have very educative postings - - - - - -

Madam Alpa Sheth referred to the paper by Prof P K Mehta wherein the cause of
deterioration of early- days coarser portland cements was not due to cracking but due
to leaching etc and modern age high strength cements being finer , the cracking
is more pronounced.Cracking is a cause of deterioration , though no direct
relation ship has been established.Madam Alpa requests for opinion from experts
on HVFA concrete, self compacting concrete with viscosity controlling admixture.
Madam Alpa also refers to the posting from the overseas participant Er Moruf
and requests opinion on Self compacting concrete vs flyash based concrete
in terms of durability.

Er Alok Bhowmick discussed about his experiences of Konkan Railway project
and induction of third party QA Agency comprising of team of Quality engineers and
their reporting the matters directly to top management resulted in effective QC
on long 760 Km stretch.

Er Dipak Bhattacharya states his findings very emphatically that Use of fly ash
has nothing to do with Durability enhancement qualities. Introduction of Flyash
was primarily to economize the Cement but it has not happened.Vested interests
have publicised the puzzolona cements with grades 33, 43 & 53 with increased
pricing and suddenly 33 grade was removed from market.He feels that durability
is achieved by protection of concrete and protection of reinforcement. TMT bars
use as reinforcement serves the purpose of reinf protection but for concretes
SRC is the solution but very costly proposition .Thus to have a durable concrete
approach shall be to have impermeable concrete to possible extent, and use
of super- plasticizers help very much in this direction but again add to cost. Better
Mix design using same qualities of aggregates and cement ,denser will be
MIx ,better will be impermeability and better strength - - not easy to achieve but
approach must be sincere.The substance of posting is very emphatic &
excellent for other participants to respond.

Er Jignesh appended a note regarding effect of high temp and high pressure on
concrete and concluded that concrete with Fly ash based cement shall be
avoided for machine foundations as it will have detrimental effects on concrete
at high temp and high pressures.

Conf - Moderator Mr Viay Kulkarni has discussed about the other issues pertinent
to durability of concrete in addition to those posted earlier.The Use of advanced
software for QA/QC . Complaints in RMC namely In-adequate slump,Lower 7 days
and 28 days strength and surface cracking . RMC suppliers with certification can
assure the adequacy & capability of RMCM of having necessary infrastructure
for Quality concrete production.QA can be achieved thru robust QA -plan by
continuous monitoring of properties of ingredients, Process control, properties of
fresh and hardened conc and statistical analysis for strength and durability.Some
early warning systems like cumulative summation technique are adopted abroad
and few RMC manufacturers in India. Short-listing RMCM shall be based on technical
skills.Other issues are Non structural cracks due to plastic shrinkage/plastic
settlement and thermal shrinkage or combine which become matter of dispute with
clients.These cracks are harmless structurally but affect durability by providing
direct access to chlorides , sulphates and CO2.Specifying pour temp shall be
essential , and increased use of SCM's enhances durability and
sustainability. Mr kulkarni also responded to query of Er Jignesh regarding FA
concrete subject to high temp . I must appreciate Mr Vijay Kulkarni for his
enlightening posting on pertinent Issues for concrete durability ,
- - -truly a living legend of this field as also Moderator of this e -Conf.

Er Jignesh appreciated Mr Kulkarni's views for touching the aspect of temp of
fresh conc at placement.He feels that limit of temp below 30 degree for general
works may be reduced for critical structures sensitive to low strains and for
these , it may be less than 20 deg.

Er Bhowmick likes to get to thread of original paper by R W Burrows in reference to
posting from Er Moruf and expects views from experts Mr Rajmane and Mr Kulkarni
who have life long experience on CT.

Er Jayant Kulkarni informed that lot of research has been reported for Service life
Assessment based on mathematical modelling.Most important parameter is rate of
chloride penetration leading to initiation of corrosion of reinf. It is very important for
cold countries using deicing salts /or structures in marine environment. While Listing
various parameters involved for formulating guidelines for service life , he feels that
it may provide some indicator .

Er As Parulekar informed that there are very effective durabilty tests like RCPT but
these are lab based on test specimen cubes etc. The NDT in form of UPSV can be
used on structural component's like beams ,columns ( after prior testing on known
results- lab- specimens tested by RCPT )

Er Jignesh reminded that FA based cements achieve strength slowly and forms
are to be removed later than OPC based concrete work. PPC should be cheaper
since Fly ash % is as high as 35% ,but in market there is not much difference in
rates.Also availability of OPC is getting difficult. Can HVFA be used in lieu .In another
posting he gave reference to a paper on experimental work done on FA conc
subject to high temp.There is reduction in compressive , tensile capacity as well
as reduction in modulus of Elasticity. He needs some literature on Aggregates
in various parts in India and its effects on ASR. His participation in econf is
highly encouraging and appreciative.

Dr N Subramanian , conf- Moderator, appreciated the views of Er Bhowmick 's listing
of reasons for poor quality in India and added humor in the e-conf in his post .Dr NS
response, as usual on sefi, is always clear cut and straightforward as evident from
various postings from him on the subject topic of e-conf .

Er Bhowmick , acknowledge that FA based concrete have extended setting time
and slow strength gain and delays construction. FA Concrete is more prone to surface
scaling under exposure to deicing chemicals .In India this problem is not there.
Fly ash percentage must be adjusted in mix to reap maximum benefits, but pricing
is due to nexus of many involved in trade.Regarding HVFA , greater QC is needed
and presently industry is not geared for this.


Regards to all participating in the e- conference or viewing it from their desk-tops/laptops and expecting more response in coming days

vikramjeet
Conf-Raconteur








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