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Location of Construction joints in continuous RCC Slab.
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es_jayakumar
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PostPosted: Sat Jul 07, 2012 10:39 am    Post subject: Reply with quote

Dear Engineers,

Suppose construction joint was provided to a beam at 1/3 to 1/4 span and the extension of the beam is carried out after one year only ( remaining 2/3 to 3/4 portion). Then how much bond will be achieved between old and new concrete ? What is the mechanism by which the bonding is achieved ? Will not there be a tendency for the joint to rift apart, the presence of reinforcement notwithstanding, even if the CJ is provided in the minimum BM / SF region as told above? What is the exact theory behind this ?

Regards,

E S Jayakumar
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thirumalaichettiar
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PostPosted: Sat Jul 07, 2012 10:42 am    Post subject: Reply with quote

Er.Jeyakumar,
Pl.browse the link below in which I attached files clearing your doubt.

T.RangaRajan.
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vikram.jeet
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PostPosted: Sat Jul 07, 2012 11:37 am    Post subject: Location of Construction joints in continuous RCC Slab. Reply with quote

We may have to distinguish between construction joint and stage construction

construction joint is the joint when concrete is still in its green stage and its treatment
before laying fresh concrete is prescribed in the IS codes.The time gap shall not be more
than 12-24 hrs or so ,i think.

Stage construction : This is generally terminated at support and dowel bars for taking
support BM as well as shear force are left in position for casting future slab in future.

If some seating is left on supporting wall/beam for future slab , then dowels for  
shear can be relieved. Otherwise dowels need to be left for both BM and shear
At time of future construction , old hardened concrete is roughened /brushed
and epoxy is applied prior to concreting , but shear as well as moment  
transfer is achieved thru dowels.


best regds

vikramjeet



Dear Engineers, Suppose construction joint was provided to a beam at 1/3 to 1/4 span and the extension of the beam is carried out after one year only ( remaining 2/3 to 3/4 portion). Then how much bond will be achieved between old and new concrete ? What is the mechanism by which the bonding is achieved ? Will not there be a tendency for the joint to rift apart, the presence of reinforcement notwithstanding, even if the CJ is provided in the minimum BM / SF region as told above? What is the exact theory behind this ? Regards, E S Jayakumar
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ajayapc
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Joined: 14 Jul 2008
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PostPosted: Sun Jul 08, 2012 4:45 am    Post subject: Location of Construction joints in continuous RCC Slab. Reply with quote

Dear Sefians,In continuation to earlier comments, the joints shall be along perpendicular direction to the main reinforcement in slab and shall be located at 0.24 - 0.33 L (where L= span of slab in short direction), the location where SF ~ 0.
Regds



Ajay C



On Sat, 7/7/12, vikram.jeet <forum@sefindia.org> wrote:
Quote:

From: vikram.jeet <forum@sefindia.org>
Subject: [SEFI] Re: Location of Construction joints in continuous RCC Slab.
To: general@sefindia.org
Date: Saturday, 7 July, 2012, 7:17 PM

           We may have to distinguish between construction joint and stage construction

construction joint is the joint when concrete is still in its green stage and its treatment
before laying fresh concrete is prescribed in the IS codes.The time gap shall not be more
than 12-24 hrs or so ,i think.

Stage construction : This is generally terminated at support and dowel bars for taking
support BM as well as shear force are left in position for casting future slab in future.

If some seating is left on supporting wall/beam for future slab , then dowels for
shear can be relieved. Otherwise dowels need to be left for both BM and shear
At time of future construction , old hardened concrete is roughened /brushed
and epoxy is applied prior to concreting , but shear as well as moment
transfer is achieved thru dowels.


best regds

vikramjeet



Dear Engineers, Suppose construction joint was provided to a beam at 1/3 to 1/4 span and the extension of the beam is carried out after one year only ( remaining 2/3 to 3/4 portion). Then how much bond will be achieved between old and new concrete ? What is the mechanism by which the bonding is achieved ? Will not there be a tendency for the joint to rift apart, the presence of reinforcement notwithstanding, even if the CJ is provided in the minimum BM / SF region as told above? What is the exact theory behind this ? Regards, E S Jayakumar
-- ญญ
     



     




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aslrah
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Joined: 01 Oct 2008
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PostPosted: Wed Mar 16, 2016 5:43 am    Post subject: construction joint Reply with quote

Should the main bars be terminated at construction joint or they can continue as per the design for whole slab. Thanks for the reply.
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sknsrinivasan
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PostPosted: Wed Mar 16, 2016 6:16 am    Post subject: Re: construction joint Reply with quote

Dear aslrah

  The main Bar should continue at construction joint. Why we are providing construction joint we cant pouring the concrete at same time since incompletion of shuttering work and steel fabrication. you should provide construction joint 1/3 of span from the support This is as far as my knowledge

  In PT area Not like this because the Tendon  stressing portion will be at construction joint area. we have to provide additional reinforcement in construction joint area. i dont know how that reinforcement given by PT vendor  

Regards
N.Srinivasan
  

aslrah wrote:
Should the main bars be terminated at construction joint or they can continue as per the design for whole slab. Thanks for the reply.
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mishelwilson28
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Joined: 26 Jun 2020
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PostPosted: Fri Jun 26, 2020 6:13 pm    Post subject: Reply with quote

Hello there,

Can you please tell me which is company provides good contraction services? Because I'm purchasing a new home but I don't have an idea where to go to find good contraction group company you have any idea so please discuss to me.
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