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RE: Water-cement ratio in type V concrete

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See below for responses.

Harold Sprague
Krawinkler, Luth & Assoc.
4412 W. Eisenhower Blvd.
Loveland, CO 80537
Voice: 970 667-2426
Fax: 970 667-2493
Email: hsprague(--nospam--at)klaalov.com



-----Original Message-----
From:	LtTang [SMTP:LtTang(--nospam--at)aol.com]
Sent:	Wednesday, March 25, 1998 11:59 PM
To:	seaoc(--nospam--at)seaoc.org
Subject:	Water-cement ratio in type V concrete

Hello all,

With the recent talk about Type V concrete, I would like to post the following
questions for our panel.

1. How important is the water cement ratio in mixing Type V concrete?
For proper sulfate resistance the recommended w/c ratio is very important.  As the w/c ratio increases the sulfate resistance is lessened.  I don't have the exact proportions, but I would not vary from the ACI recommendations.

2.  Does higher ratio (greater than 0.45 per UBC) in anyway diminish concrete 
     strength or reduce concrete capacity in protecting foundations from sulfate 
     deterioration.
Depending on how high you go it will have an adverse effect on both strength and sulfate resistance.  Look at the Bureau of Reclamation "Concrete Manual".

3.  Since the UBC specify the 0.45 ratio, how can this be maintained in the
field?     
     I've seen on numerous occasions pumping contractors hosing water to keep
the concrete from hardening.  
If they are adding water in the field to keep the concrete from hardening, you've got some real problems.  If they are adding water to increase workability its not good, but it is not as bad as trying to retard a set by adding water.

4.  Will your standard slump test determine what ratio the concrete is at when
it's ready for pumping?
No.  The slump test will only be an indication of probable w/c ratio.  It is used more to give an indication as to workability.  If you have doubts about the w/c ratio check the delivery ticket.  If you still have doubts, require independent verification at the batch plant.


5. Should engineers begin an observation program to check for this ratio?
Thoroughly read what is in ACI 301 and in 318 regarding quality control.  You can require independent verification.  If you get a wide discrepancy of your field tests vs. the mix design submittals, it is time to hire an independent inspector at the batch plant.

The reason why I am asking this is that there is a recent lawsuit, still
pending, that involves this.  The lawyers are speculating that since the party
involved does not specify the 0.45 ratio on plans, he/she should be held
liable for complete foundation repair cost.  From the mix tickets, the water
cement ratio was noted to be 0.6 when the trucks left the mixing plant.  
If it not specified either explicitly in the specs or implicitly by a performance spec, you are at the mercy of the supplier.  Verification of the mix with the delivery tickets is essential on the inspection side.

They contended that because of the high ratio, concrete is more poruos which allows
sulfate to seep into the concrete faster, damaging it before adequate strength
was reached.  
The high w/c ratio will increase the porosity, but more so in the hardened concrete as the paste portion of the matrix shrinks.  Before it is set, the concrete is not porous. Consider placing concrete underwater, you displace the water with the concrete placed with a tremie.


It's interesting how lawyers can dig through anything to build
their case.  Anyway, your reply would be greatly appreciated.
I don't know if I have helped or have caused sleep deprivation.  I hope I've helped.

Respectfully,

Long T. Tang

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