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Re: Maximum Aggregate Size

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In fact, ACI 211.1-91 is not limiting the max. aggregate size related to the dimension between reinforcement and formwork.
ACI 318 sect. 3.3.2 also states nominal max. aggregate size.
"Clear spacing between reinforcement and formwork(Cover Depth)", is not applicable for determining the max. appregate size.   
In slab, formwork will be filled by vertical direction of placing, not by horizontal movement.
In vertical member, no one places concrete in between reinforcement and formwork.
Basically, max aggregate size depends on the narrowest member size and spacing of rebars.
In thin member, spacing of rebars between near face and far face could be critical.
Use of larger size as practical is always recommended so as to decrease the demend of cement content  

----- Original Message ----- 
From: Michael Bryson <mbryson(--nospam--at)>
To: <seaint(--nospam--at)>
Sent: Tuesday, June 17, 2003 4:30 AM
Subject: Maximum Aggregate Size

> ACI 211.1-91 gives the maximum aggregate size as 3/4 of the clear spacing between reinforcing bars and between reinforcement and formwork.
> California practice commonly uses 1" max aggregate size. This means you would need to space reinforcing bars and have clear cover of at least 1.33" (say 1.5"). Slabs typically require 3/4" minimum (or 1" minimum for a higher fire rating).
> Is there a problem with allowing a 1" max aggregate size but keeping a 3/4" cover? This seems to be the standard practice and I am not aware of any problems with it.
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