From: Goedjn 
Newsgroups: alt.home.repair misc.consumers.house
Subject: Re: Concrete for planter.. what kind?
Date: Fri, 19 May 2006 11:25:20 -0400

>>I'm going to be making some large square planters out of concrete. Basically
>>3x3x3, with sides about 3" thick.  I'd like the finish to be as smooth as
>>possible.
>
>
>I agree with a light weight approach for this type of container.
>
>INGREDIENTS NEEDED: 
>
>Horticultural perlite
>Peat moss
>Portland cement


Well, it depends on why you want big-ass concrete planters.
If you're trying to stop drunk drivers hurtling off the corner
before they plow into your livingroom, skip the pearlite.

(or car bombers, or whatever.    note that a 3' high planter
isn't big enough to stop a tank.... :-) )