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Old 05-10-2008, 03:12 PM   #31
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Rebar Placement in a 3x3 concrete pad. Top, bottom or middle?


The original poster stated that he liked his mud on the dry side rather than the wet side (less rather than more slump). We are talking about sack mix here which is typically Type 2 concrete with a higher specified water to cement ratio to begin with (it's the wettest and least strong by design). Reducing water in this instance will definitely hamper hydration of the cement paste, and the photos bore out the additional problem of poor consolidation.

As far as the concerns re: excessive cracking, yes excessive water can and usually will lead to plastic shrinkage cracking, but we're talking about 9 sf of mud here, not 9,000. WRT the rusting steel and carbonic acid issues, again this is a tiny slab and evaporation is going to occur very rapidly (and pretty evenly given it's size). You'd need ALOT of water before those issues are a concern.

You are wise to follow your structural's specifications to the letter as you are building an engineered footing designed to distribute load over the entire surface area of the pad (hence the #4 bars each direction). I wouldn't confuse the structural engineer's requirements for the engineered spread footing with the little project outlined here in this thread.


Last edited by MacRoadie; 05-10-2008 at 03:24 PM.
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Old 05-10-2008, 06:13 PM   #32
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Rebar Placement in a 3x3 concrete pad. Top, bottom or middle?


Quote:
Originally Posted by MacRoadie View Post
TI wouldn't confuse the structural engineer's requirements for the engineered spread footing with the little project outlined here in this thread.
Absolutely. I only commented in case someone with a structural case such as mine relied on the internet rather than a structural engineer for their planning. In my case the footings will be supporting lally columns and a steel i-beam to support a load-bearing wall above.

Thanks for your clarifying comments.
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Old 05-11-2008, 08:44 AM   #33
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Rebar Placement in a 3x3 concrete pad. Top, bottom or middle?


usually 2 mats of #4 tied rebar's spec'd here


Last edited by yes.itsconcrete; 05-11-2008 at 08:48 AM.
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