Replies

1. 
   Fred_Matthews | Sep 08, 1999 10:01am | #1

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   If I recall, the authors of the article used a 7 sack mix, equivalent to a 4500 psi mix. I would doubt that you'd achieve a 2500 psi design strength from the redi-mix brands. The reason the authors used such a rich mix can be summed up in one word:
   b density.
   More cement, greater strength and a richer, denser mix (this relationship holds true only within a certain range, and provided that the cement particles are given a chance to fully hydrate (the chemical process in which concrete hardens and gains strength)). If you want to use a rich, dense mix, do what the authors did and order from a ready mix company or if inclined, batch your own w/ a mixer, clean water and good, clean, well graded aggregate. I would think a 3/8" pea gravel would work well.
   I definitely would
   b not
   recommend a fiber mesh mix...unless you like little nylon fibers sticking up on occasion.

2. 
   Guest_ | Sep 08, 1999 07:07pm | #2

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   Emile,

   The amount of concrete required is usually just a few cubic feet. It's an amount easily handled by a DIYer. As an added bonus, you'll be able to control not just the amount of cement in the mix, but the amount of water as well. Both ingredients are crucial to a well formed, strong slab.

   For an average countertop, a single 94 pound bag of portland cement will suffice. Add a few bags of sand. Go to a gravel pit or a landscaping business, most allow a customer to take a trunk full of pea gravel for $15 or so. A few pounds of colorant at $4 per pound, or acid stain. A bit of hardware cloth or rebar and you're set.

   For a grand total of $50-75 or so in materials you have all the fixin's. I totally agree with Fred regarding his advice to avoid the fibers. They are neither neccessary nor desired in a countertop. For the inexperienced, troweling a smooth surface can be tough. With a hairy slab, frustrating as well.

   Don't just build forms and start a pour. You may end up with a rather large and difficult to move paperweight. Do small samples, 12" square of so. Get used to working the mix. For a DIYer, integral color and inverted casting are much easier then dealing with acid washes, stains, and neutralizers. There are several other threads in the archives, do a search.

   Best of luck.

3. 
   Mccrane | Sep 10, 1999 11:12am | #3

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   The countertop story is an example of what is wrong with Fine Homebuilding. Someone with minimal experiance writes about their experiment with some new technique where no one cares about cost. To use a ready mix truck for the small quanity of concrete involved is absurd.

4. 
   Guest_ | Sep 12, 1999 10:26am | #4

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   What, no truck for the neighbors to see???

   In the article's defense, at least it presented a fairly thorough technique discussion instead of a breezy design piece -- like that twisted tower thing. Or designing around your overpriced furniture. Or the imbecilic: Draining gutter runoff? What up with that? These are the sorts of article that get me annoyed with FHB.

   Then there's that lunatic with the moldy house article.... Don't get me started.

5. 
   Emile_Husson | Sep 12, 1999 10:28am | #5

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   I've read the article on concrete countertops in the latest issue and I was wondering if any of the commercially packaged mixtures such as Quikrete's sand mix or fiber mix would be as good as trucking in the custom mix.

   Quikrete's help line says their fiber mix uses a gravel aggregate and I'm concerned about getting the smoothest finish possible.