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concreting bottom slab of a large reservoir

 
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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Bubalan
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Joined: 04 Aug 2011
Posts: 84
Location: Tokyo, Japan

PostPosted: Mon Mar 05, 2012 4:07 pm    Post subject: concreting bottom slab of a large reservoir Reply with quote

Dear Sir,

In site we encounter a problem of constructing a large reservoir of
size 120m x 120m which is divided into two compartments.

this tank is 5 m in height of which 3 m below ground. the strata is
rocky and has no water table.The problem is:

For casting bottom slab, as per code max panel size of 7.5m2 is
allowed, after which it has to be provided with a joint. but my site
people say , it will not be 100% water tight, so go for one casting of
200tck slab with two expansion joint. also we have columns of 7.5m c/c
with roof slab.

solutions welcome!

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suraj
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Joined: 17 Apr 2008
Posts: 1980
Location: NCR Faridabad, E mail suraj_engineer@yahoo.co.uk

PostPosted: Wed Mar 07, 2012 6:18 am    Post subject: Reservoir Base Slab Pouring Reply with quote

Dear Eng Bubalan
Plastic Shrinkage Cracks/Form Removal

  1. It is really surprising that drawings do not give clear directions to cast this slab.
  2. How shall site team decide about what panel size should be cast in one go?
  3. It is job of structural design engineer to specify on drawings, all locations of CJ & EJ with provision of waterbars.
  4. Such slabs my be considerably thick that may also require concrete in 2 layers & also might be having certain sloping portions where, double forms with opening windows on top for pouring, would be required.
  5. Based on practice in field, such slabs should be cast in columns spacing bays with alternate pourings.
  6. In case, double layer pouring is to be done, overlapping on both bays, would be reqiored as well.
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gpsarathyy
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Joined: 28 Jun 2010
Posts: 484
Location: chennai

PostPosted: Wed Mar 07, 2012 7:23 am    Post subject: Reply with quote

Dear Sefian,

It should be shown in the design drawing if not site has to revert back to design office asking for the construction joint and the expansion joint details and locations.

For larger slabs like this, the usual way of concreting is doing the alternate panels both in x and z directions and finally the second concreting to be done to the remaining panels.
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JVCSNL
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Joined: 26 Jan 2003
Posts: 158

PostPosted: Wed Mar 07, 2012 7:53 am    Post subject: Reply with quote

The concern in your post appears to be the water tightness of the strucutre.  If we see from client's perspective, it is right also.  

The expansion joints can be at 36 m and other joints at 7.5 m.  The contraction joints at 7.5 m limit such pours and site get worried.

We can limit expansion joints at 30/36 m and provide a groove at top surface of the raft to act as a contraction joint at every 7.5 m.  This will allow site to pour large chunk of concrete.  Such details are available in ACI and can be used.  The groove shall be then filled with joint filler.

In all these, the engineering drawing shall clearly indicate construction joints, expansion joints, contraction joints in base raft as well as in wall plan and section.  Also, necessary details to ensure water tightness needs to be furnished alongwith specification for the joint fillers, water bars etc.

Regards,

Jignesh V Chokshi
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Bubalan
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Joined: 04 Aug 2011
Posts: 84
Location: Tokyo, Japan

PostPosted: Wed Mar 07, 2012 4:03 pm    Post subject: Reply with quote

The concern in your post appears to be the water tightness of the strucutre.  If we see from client's perspective, it is right also.  

The expansion joints can be at 36 m and other joints at 7.5 m.  The contraction joints at 7.5 m limit such pours and site get worried.

We can limit expansion joints at 30/36 m and provide a groove at top surface of the raft to act as a contraction joint at every 7.5 m.  This will allow site to pour large chunk of concrete.  Such details are available in ACI and can be used.  The groove shall be then filled with joint filler.

In all these, the engineering drawing shall clearly indicate construction joints, expansion joints, contraction joints in base raft as well as in wall plan and section.  Also, necessary details to ensure water tightness needs to be furnished alongwith specification for the joint fillers, water bars etc.

Regards,

Jignesh V Chokshi[/quote]



dear jignesh,

u r right, my doubt is regarding the water tightness of the structure. if possible can u send me the material.

my id : sbubalan@gmail.com
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