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RE: Construction Joint for massive Foundation Slab

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This is an interesting question.  I don't know a lot about dam construction,
but an adjacent placement is cast after the forms are stripped and the
surface is prepared by wet sand blasting and water cleaning.  The heat of
hydration is more of an issue in controlling the thermal gradient.  

You can control the heat of hydration by minimizing the cement, lowering the
initial mix temperature, and using fly ash as a partial cement replacement.

A well graded aggregate mix and the use of as large a maximum aggregate as
possible will also drop the amount of cement required and help minimize

Harold Sprague
The Neenan Company

-----Original Message-----
From: Kho Poh Teck [mailto:ptkho(--nospam--at)]
Sent: Friday, May 21, 1999 9:26 PM
To: 'seaint(--nospam--at)'
Subject: Construction Joint for massive Foundation Slab

Can anyone give some advice on the appropriate time lapse prior to
casting a 2nd half pour of a massive foundation slab? Size 50m x 50m x
3m. Is it acceptable to cast the adjoining piece at the peak temperature
of hydration of the first slab provided adequate reinforcement is
provided to prevent thermal cracks. Personally I don't think the young
concrete is able give sufficient bond strength for making tthe rebars
effective to limit the crack width. What is the normal practice in Dam

KHO Poh Teck