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[SEAOC] RE: [SEAOC] under water concrete

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As important as the mix design is, you first need to establish placement 
techniques.  For instance if the concrete is pumped, the mix will be 
different than a mix that is placed using toggle bags or buckets.  Placement 
technique will vary relative to water depth, flow, proximity to batch site, 
and volume and size of placement.

Place the concrete so that fresh concrete is displaced by additional fresh 
concrete.  If using a tremie pipe keep the end submerged in the fresh 
concrete.  Start at the lowest elevation and work up maintaining a head of 
concrete.

In general the slump should not exceed 5", use 1 1/2" aggregate (unless it 
is pumped), use rounded aggregate, adjust the fines to obtain the desired 
slump, and use about 10% more air entraining than normal above water 
concrete.

Design the mix the same as you would for other sea water or fresh water as 
applicable.  If sea water, use Type V Sulfate resistant cement, drop the w/c 
ratio to about 0.40.  If it is reinforced consider an admixture like Armatec 
by Sika, cathodic protection, rebar coatings, carbon fiber rebar, and/or 
fiberglass fiber reinforcing to control micro cracks.

Review the Concrete Manual by the US Dept. of Interior and Design and 
Control of Concrete Mixes by the PCA.

Harold Sprague
sprague(--nospam--at)bv.com
 ----------
From: seaoc
To: seaoc
Subject: [SEAOC] under water concrete
Date: Tuesday, October 01, 1996 4:58PM

Hello,

I have a question about under water concrete. What properties does such a
concrete need?  And how to obtain these properties?  Is it important that 
the
water where the concrete is poured, is sea water?

Many thanks in advance


Filip Van Rickstal

Dep. of civil engineering
KULeuven
de Croylaan 2
B-3001  Heverlee
tel.++32(0)16/32.16.80
E-mail: Filip.VanRickstal(--nospam--at)bwk.kuleuven.ac.be

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