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Re: Concrete Mix for low permeability

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> > Ron Martin wrote:
> >
> > . > I can put waterproofing on the deck, but I was wondering if there was any
> > . > additive or concrete mix design  that would offer less permeability
> > . > should the waterproofing fail.  The client is doing some of his own
> > . > waterproofing work and therefore, I want to attempt to "adjust" for his
> > . > learning curve.
> >
> > . > Thanks again.
> >
> > . > Ron Martin
> > . > Tuscaloosa, AL
> >
> > Ron,
> >
> > Since the owner wants to do something him/herself, I would strongly recommend
> > to the owner that roofing be applied and remind him/her that concrete, in and
> > of itself, is not impermeable.  I am sure that the owner would hear you say,
> > "impermeable," when you actually say, "less permeable."  Probably best to
> > say, "All concrete leaks."  (If the client brings up "dams," you can explain
> > that is why dams have drainage galleries.)

Couldn't be more true !!

> > In an event, I would avoid any concrete additives that contain calcium
> > chloride.  One additive that I am aware of that is touted by its manufacturer
> > as being a waterproofing agent for concrete has calcium chloride as its major
> > ingredient.

I could add that sloping the top surface of the concrete so that no ponding will
occur along with good drainage is a must.
Also, take into consideration the following:
1. True that higher cement content concrete gives higher strength concrete and
thus in a way leads to more durable concrete, but it also causes more shrinkage
cracks and thus affects permeability. So adding superplasitcizer and reducing the
cement content could help here.
2. Weather conditions during casting can have a huge effect on shrinkage
cracking, especially in the few hours following final set, when curing cannot be
applied to protect the concrete. Waiting for ideal conditions can be worth it,
and by ideal I mean high relative humidity, no wind and mild temperatures.

Moni Serhal