Joined: 26 Jan 2003
|Posted: Mon Mar 12, 2012 12:05 pm Post subject: Summary of E-Conf -Final Days 13 & 14
|- - - - - - Conference on Durability of Concrete Ends.
Like every event , which has a beginning , has an end too and this conference is no exception.
After sincere & fruitful discussions by a galaxy of Experts , and brainstorming by participants
for last 14 days , the e -conf has come to an end.
For budding engineers - - - -some poetry
May, you take away some morning , from eve of my life
(Koi subah tum bhi ley lo , meri sham-e zindagi se)
Experiences of those who spent their life time devoting for knowledge and practice is always
utilized by generations next. The e- conference will go a long way in helping the participants
and viewers of sefi to retrospect and act in right direction on matters of concrete Durability
I am also presenting the last summary as the final chapter of conference of last two days ,
and before that, express my heartiest gratitude and thanks to all participants with special
compliments to Moderators of the e-conf Dr N Subramanian and Mr Vijay Kulkarni ,
and organizing brain behind e- conf Madam Alpa Sheth (Admin SEFI) and Mr Sanjeev
providing untiring support.
I also thank prominent experts Mr Aswath, Dr Narain Nayak ,Mr Alok Bhowmick ,
P Eng Mr Suraj Singh, Mr LK Jain, Mr Dipak Bhattacharya , Mr Jignesh , Mr Jayant
Kulkarni and all others (not possible to name all ) for their active participation for
knowledge sharing and guidance .
Also, last but not the least: - - - -
Misinterpretation , if any ,of discussions while summarizing is unintentional and
- - - - - - - - - - - - - Summary of posting(s) of last two days i.e. day s 13 & 14 .
This is probably longest summary due to heavy response to e- conference in last
two days and some delay from my end .
Er Bishwa keenly followed the proceedings of e conf and states that there is no reliable
means to estimate service life of structure to be constructed .How 100 yrs of maintenance
free life can be specified. The issue of Quality constructions is very much relevant in India
where more than 50% of cement is used in non/semi engineered constructions.
Dr Narayan Nayak expressed happiness over the response to the e conf and also the
deliberations taken and very nicely responded to pending queries . Regarding cover
blocks issue as very rightly highlighted by Er Jayant Kulkarni, the quality at most sites
is poor since importance of cover for durability is not appreciated . There is tendency to
provide gravel pieces ,mosaic tiles (as informed on e conf) , and wooden blocks are also
provided. In Gammons Reality , M60 grade conc prefabricated cover blocks are used.
PVC cover blocks have advantages of being pervious and sturdy but compatibility with
concrete is a problem and micro cracking can be a possibility.
Regarding use of Fly Ash in concrete , it must be processed- FA meeting IS Codal
requirements.FA must be tested at regular intervals. Use of micro silica is based on
certifications provided by suppliers. Indian produced FA is exported to other countries
and Dirk India alone exports to the tone of 400 tons/day. Delegates expressed concerns
over FA use for concrete but no concern is about the quality of aggregates especially
Fine Agg. Quality of river sand in Mumbai is poor and varies season to season and some
use creek sand too. Mr Nayak sincerely advised the use of processed FA based on his
his hard core experience at sites of carrying out testing including 180 days tests.
Regarding pond ash , his advice is to use it for FA bricks . Regarding addition of FA
at site , it is preferable if batching plant is computerized.
Regarding Fineness , BIS must give range of fineness for grades 53,43,33. As rightly
said by one delegate that the possibility of supplying wrong grade can not be ruled
in absence of fineness ranges.
Regarding RMC quality , it is a problem. Generally due precautions are taken at RMC
plants but when it comes to pouring point , the client is not satisfied. The main problem ,
after concrete leave from RMC plant are Lead time which may vary in metro like Mumbai
from half Hr to four Hrs and admixture effect go hay wire. Nobody adds admixtures in stages
Further temp variations between day and night is substantial leading to quality problems
and covering mixer with moist Hessian cloth is good practice. Waiting at site is also a
problem due to contractor not ready for immediate concreting.
Regarding performance based specifications ,Mr Nayak fully agrees with Mr Vijay Kulkarni
we must aim for it by starting in iconic projects. Appreciated suggestion of Madam Alpa
for inclusion of professors and researchers in codal committees but generally due to
funding problems , they do not attend.
Regarding participation of contractor in discussions as raised by Mr Bhowmick , Mr Nayak
cited himself as attending this conference with 35 yrs hard core construction experience apart from
teaching and design experience where he always looked for innovations ,improvements
and on- field applications.
On repairs and maintenance , he feels that it is must to have codes /guidelines for maintenance
He complimented all on e conf.
Dr N Subramanian , conf- Moderator , thanked Dr Nayak for excellent posting and practical issues
brought out in the e -conf . He also appreciated him for being co-author of book with Mr LK Jain
on 'HB on Advanced con Technology".
Er LK Jain touched very important points raised in conf. Regarding BIS committees , the top brains
from research and academics avoid committees and so is the case with consultants since
other works are more remunerative.For any important standard , not even a dozen of comments.
Regarding cements, the strength of 53 grade cement is far below the cement used world wide
and for that reason it is not exported to Europe. Grade 33 has no buyers. All, at user end , generate
demands for higher strength cements.Cement industry is definitely market -driven. There is
need to act collectively to save the profession.Cement manufacturer are holding upper limit
on grade. Even upper limit for blended cement is 33 grade but in market blended cement is sold
having strength above 43 or 53 . In case 53 grade is perceived as high strength cement, we must
introduce 63 and 73 grades to be at par with Developed world.Lack of understanding shall not rule in
concluding sessions of e- conf, as echoed by Er LK Jain.
Dr MR Kalgal agreed that Mr LK Jain commented rightly on code committees . BIS do not pay the
expenses of travel & stay .egarding performance based specifications , he feels that in India
it is better for some more time to stick to prescriptive specifications since majority of constructions
are handled by less trained/untrained.
Er Vinay Gupta states that application of water soluble silane compound on finished conc surface
all over after curing stage so that there is no further water absorption by concrete will enhance its
Consulting Er Jayant Kulkarni must be appreciated for active participation during conference and
yet another viewpoint from him regarding M/sand. Due to shortage of natural sand it has become
necessity to use crushed sand (m/sand). Natural sand is round in shape due to flow of water.
Crusher sand is not acceptable unless crushed through VSI crusher which provides gradation
and fines below 150 micron. Surface area of crushed sand is more and hence requires higher
water in mix for desired workability and fears reduction in strength due to higher w/c ratio.
Er LK Jain opined about Manufactured sand that replacement of natural sand by crushed stone
has effects like finer portion in crushed sand is higher than natural sand and hence better grading.
Difference in particles shape of two sands , the M/sand may need little more dose of plasticizes
to have particular workability.If mixes with two sands are seen wrt compressive strengths , the
M/sand is advantageous. But one of reason in M/sand is energy requirements in its production which
make it costly and not-green. Mr LK Jain questioned the basis of barring use of river sand by
environmentalists since taking out sand from river reduces silt transport to sea and also
taking out sand provides river waters higher section for flow adding to flood plains along
Er Vaishu has few queries regarding reasons for use of 43 grade for slip-form works.
Regarding 33 grade, it can be used for controlling cracking as alternative to early strength cement
Er Bijay Sarkar posted very real facts pressurizing Civil engineers on execution side citing
example of Thermal power plants. The civil engineers are LIFO (Last in - first out) in any kind of construction
of such magnitude in Industrial arena.Elect / Mech engineers plan all requirements and based on that
Civil engineers design and construct. But time left for project construction is always squeezed
forcing construction engineers to sacrifice quality since durability is considered as long
term issue and squeezed targets dates become the aim immediate.Quality give long term
benefit to some others but maintaining time schedule give immediate benefit to project manager
and most of engineers look for immediate. Other non technical issue is rampant corruption which is
root cause of sacrifice of quality , and even quantity. Third major point is lack of knowledge.
Very nicely brought out by Er Bijay Sarkar based on his experience of working in TPP's.
Er Jignesh agreed that Mr Bijay has raised valid concerns about non tech issues. The construction
schedules are crashed due to constuction management tools (IT,Standardization) & superior Erection
technologies. LIFO is a professional hazard. Though early construction schedule is prime motto,
stringent Quality is also demanded by clients.
Er Dipak Bhattacharya feels that as designer , he fully agrees with non -tech issues raised.
Constuction on foundation starts based on design which forsee all loadings and wait for
soil reports and pressurized to issue foundations next day. On construction , pvt clients
rarely employ competent engineers.Any thing wrong ,civil Er s are caught and designers are
forced to work on trouble shooting exercises.
Dr SM Kulkarni also posted his views on non tech issues.The root cause of all issues is
accpetannce of situation helplessly.LIFO is correct for civil engineers.Probably more
innovations in this field are due to this effect and whatever situation the reliability of structure
shall not be affected.All round corruption is also a factor, and is a crime.Detailed planning
can take care of time and cost . He thanked Er Bijay Sarkar for bringing to notice these
pertinent non tech issues.
Er Suraj Singh discussed about non technical issues enchroaching quality deliverables
as pointed by Er Bijay.
In another posting he appreciated the viewpoints of TPS61. stating that FA, GGBS and MS
are commonly used all over Middle East & Gulf. In fact nowhere OPC is used except
precast factories.UAE uses GGBS everywhere whereas Qutar use PFA. Combination of PFA
GGBS and MS is used in many projects . Use of GGBS provides better control over thermal
gradient. It is better if design engineer specifies its use and methods to control effect on form work
Er Jayant Kulkarni discussed regarding de-shuttering time in IS 456 , since cements scenario
has undergone change and conc give 50-60% strenth in three days and 80-85% in seven days.Whether
this can be revised looking to early strength gain. But E value at early stages is less than 28 days
and strain cannot be predicted though strength is higher ,thereby leading to higher crack widths
Dr N Subramanian , the conf Moderator, thanked Dr M Kalgal and fully agrees with him
regarding training of work force regarding developments in concrete technology. Even engineers are
not aware of problems of early strength gains and proper curing. Shortage of fine aggregates
and lime stone indicate dwindling natural resources. we must aim for 100 yrs durable structures .
Also cement companies may be asked to re -introduce Grade 33 .
Er BV Harsoda hailed the viewpoint of accuratetestlab regarding profit making rules over
quality in present days .
Er Alok Bhowmick reminded Mr Manu regarding presentation material uploaded in e conf
on 28 theFeb which may address issues raised by him.
Er Vaishu raised query earlier whether stone dust can be used in cc rods construction .
Dr NS also stated that this can be used referring to posting of Er Francis in econf.
Er LK Jain feels that stone dust is not a manufactured sand. Part replacement of 15-20%
sand may be attempted by trial tests .
Er Suraj Singh posted about Alkali aggregate reaction and alkali -silica reaction subnote.
Tests for durability like alkali -silica reaction and rapid chloride penetration tests
are mandated.Also using SCM's in concrete initial curing arrangement can prevent
cracks formation considerably. Citing example of sewage treatment works, the crack
formation was observed even using 30%P FA but later reducing spacing and dia of
reinf reduced crack formation .Reduction in panel length also gave favorable results.
Dr N Subramanian responds to Er Gautam regarding FBEC reinf and says that
this is extensively used in Bridges all over the world and surveys show no corrosion in
epoxy coated bars even after 35 yrs. Yes bond length needs to be increased and
ACI gives required equations. Care needs to be taken while transporting and bending
for any loss of coating and treating damaged spots by site applications of epoxy.
Mr TP Singh ,Director , Construction Research Center stated that posting regarding HVFAC
was not appearing on e conf portal.
I must express compliments to Mr TP Singh who posted a very enlightening/exhaustive
posting as (TPS61) and same has been highly acknowledged in summary of posting
of days 11 & 12.
Er B V Harsoda posted about RMC stating that Ready mixed conc Manufacturers
Association (RMCMA) is non profit industry organization of leading RMC producers of India.
Its mission is to promote RMC as most preferred concrete in India at par with Advanced World.
Quality Scheme is developed in two parts contained meticulously in Quality Manuals I & II
Part I involves extensive annual audit of RMC production facilities . Er Harsoda provided
links to down load both parts of Manuals.
Er Suraj Singh posted a performa for Project management monitoring performance
measurements which has been developed on his life time experience and not extracted
Er KS Raghuveer enquires about chemicals to be used to get durable & strong conc while using
manufactured sand.Er Mohan accepted the viewpoint since water absorption mainly depend upon
shape & texture of particles. The resulted product from M sand can never rbe same as that of natural
sand. Structural work maybe done with natural sand but extrnal finishes can be catered with exposed
work, cladding, adhesives etc.
Er Alok Bhowmick discussed about the service life design concept stating that considerable work is
going on at international level in this regard. Though in India , design life is concept at present ,but
if design /detailing is carried out by competent engineers followed by construction as per norms and
good engg practices ,concrete is cured well and routine maintenance carried pro-actively , the
purpose is fulfilled in respect of design life concept for the present. In another posting he thanked
Dr Narayan Nayak for summing up points of discussion along with viewpoint rating the posting
as best in ecof. Some of issues still not covered/debated are form client perspective on quality and
durability, conc properties with blended cements (since stress strain relationship is developed with
OPC), Prestressed conc structures where corrosion in PS steel have disastrous effects ,and detailing
of areas requiring Mech couplers.
ER Gautam Chattopadhyay feels that PS cables are covered by sheaths and further grouted, are they
really subject to corrosion.If sheaths are to be spliced , these are joined with thermal tapes.If grout
is not contaminated , cables may not subject to corrosion.The concreting at end block is cause
of problems in few cited instances. Responding, MR Bhowmick says that PS cable corrosion is common
in particularly aggressive environment and in cold countries.Problems in PS tendons are primarily
due to Quality of PS steel (brittle failure), Grout voids and segregation (Bleed corrosion), water /
chlorides penetrating tendons (corrosion) . Corrosion protection s improved with plastic ducts and
special grouts.In India problem is in coastal belt.
On Deshuttering time & durability , Er Gautam states that it may be 7 to 10 days for buildings and in
bridges 28 days is enough.At de-shutter , only self weight is there .A beam with slenderness ratio 12 may
not deflect excessively. In bridges SIDL comprising of wearing coat , kerbs/railing /crash barrier and
LL comes mush later. But use of HVFAC needs attention in bridges. FA retard setting time. The effect
on E value as pointed by Er Jayant also needs attention since Mod of elasticity not only affects
deflection , but MR as also crack width.
Er SM Kulkarni agrees that fineness requirements of various cement grades is same but even
soundness requirements are same .It is only the compressive strength at 72 hrs which distinguish.
Therefore cements is not to be judged by fineness only.
Er Chirag Baxi states that deterioration of any structure is due to its quality or surrounding conditions
Structure must be constructed with absolute quality control.Deterioration due to corrosion is matter
of concern .Adoption of protective measures has to be selective.
Er Jignesh talked about construction water quality since chlorides in water can directly attack.
Water for construction is arranged by owner at site after testing it. Further each storage is tested.
Dr NS hailed the viewpoint stating that Water for drinking is scarce and it is generally regarded
that potable water is good enough for concrete works.
Er Mohan thanked for e conf benefit engineering community. Commenting on Non - tech issues
he feels that top managers in charge -de - affairs must be civil engineers who has quality and
durability conscience /or otherwise listen to quality team.
Dr NS thanked Mr Prabhakar for his points .Commenting on Mr Prabhakar's view for
use of MS bars being corrosion resistant due to lower strength result in less cracking, he
says it may be not be the only reason. The concrete earlier was with OPC grade 33 and well cured.
The study indicate that if detailing rules are followed , cracking is within permissible levels.
Use of MS is not economical and good quality MS is not available now.
Er Mohan wants to know that is it possible to the constituents of cement mortar (after it sets) thru
some chemical analysis. Er BV Harsoda responded that it is possible to disintegrate constituents
of mortar by chemical analysis and advised him to contact nearby material testing lab and
also provided links
Mr R Nagendra , Tech Director , Civil -aid Technoclinic , Banglore provided his observations
on Manufactured sand stating that it is high time to use M sand due to scarcity of natural sand.
RMC palnts at big sites crush rock fines. Availability of M sand is limited and all crushing plants
do not have VSI crushers and even with it, needed gradation/shape is not achieved.M asnd
manufacturers do not wash it to remove fines passing 75micron seive. Sometimes
CRF (quarry dust) or bad quality sand(called as filtered sand) is used. Use of FA & GGBS is
on rise and with such quality of sand , the durability is a concern. Only lab based tests are
conducted for durability and In - situ tests are not done. Also compatibilty of admixtures with
wide variety of cements needs to be seen.
Er Bijay Sarkar highlighted the issues related to FA and FA concrete. Coal is received in size 350mm
down and crushed to 20mm down size in crusher house and again sent Mill in bunker building for
milling to dust form ,pulverized and thrown into boiler furnace. Ash is produced from burning of coal
and its particle size is too small. Quality of FA also depend on method of burning in boiler ie
chemical used and temp . Earlier all FA was released in air thru Chimney but with stringent enviro
norms , the ash is captured in ESP electrostatically and also in chimney hopper to some extent
and collected at remote located Silos. Bottom coarser ash is deposited in Ash pond for future
mine'filling/other use . Also the quality of coal varies. Indian coals have 30 to 46% ash whereas
in developed countries it is 5 to 20%. Out of total Ash , 80% is FA and other 20% is bottom ash.
Bott ash has large quantum of unburnt coal and stone dust but FA is telcom powder like..
Cenent companies are also planning to construct cement plants within TPP.
- - - - - -I think highly useful information about FA and Pond ash , must appreciate Mr Sarkar
Closing remarks from E conf Moderators Dr N subramanian and Mr Vijay Kulkarni
The 23 points noted are regarding RMC plant quality, need to review IS 456 provisions, FA
& other admixtures improve quality ,Need to educate about chemistry, Need to study effects
on FA concrete under high temp, shortage of good quality fine agg. and water lead to use of
Foundary sand and rock dust and IS456 needs to incorporate this.FA conc to be cured for
longer time as also form removal , Different grades of cement be made available by
manufacturers, Using FA the choice of right ingredient is important, W/C or W/CM ratio
is very important , certifications for all engaged in construction,a must, Tests on durability
lice RCP T etc shall be made mandatory, Engineers must update themselves following
seminars and tech literature, Modern cement contain high C3S content and curing must
start early, compatibility of super plasticizers and other chemical admixtures must be
studied carefully, Mix design is important for HVFA ans SCC, Temp for concreting
shall be maintained at 30deg C for general and 20deg C for special structures,
Performance based specifications needs to be developed and used for iconic projects,
Cover to reinf is very important and proper cover blocks to be used, Durable conc is a
team work of engineers, contractor,consultant , owners and maintenance team.In severe
conditions , the steel reinf must be protected using galvanization, fusion bonded epoxy
coating and In some cases surface coating of conc is also essential , Field experienced
engineers must represent codal committees.
Closing Remarks from Madam Alpa Sheth ,admin /SEFI , and the Organizer of e conf is highly encouraging .
Madam Alpa expressed that econf on concrete Durability received a record response breaking
all past records of e conferences held so far.Many important issues have been discussed
involving all stake holders of construction Industry . Cement and admixture industry was
little quiet. He attributed success of conference to Moderators Dr N Subramanian and Mr Vijay
Kulkarni and also recognized the summarising of postings as entrusted to me .She also
thanked Mr Sanjeev and his team behind the scenes providing support despite problems
faced due to heavy rush of posting and with no- funds situation with SEFI. She thanked all
participating the e conf.
Again expressing satisfaction over the thumping success of e- conference and Thanking all
Conf - raconteur
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