Q.: Were the ACI tolerances for cast-in-place concrete (published in your October 1980 issue, beginning on page 743) adopted by the American Concrete Institute?

A.: The standard has been adopted but several changes in tolerances were made before adoption. As a result, in the CONCRETE CONSTRUCTION article to which you refer, three changes should be entered:


Page 745, end of column 2 (above the footnote), add "Elevation control points for slabs on grade

"In any 10 ft.± specified slab surface tolerance

"In any bay or 20 ft.

± 3/8 inch

"Maximum for total length of the structure

± 3/4 inch"


Page 747, column 2, third line below the second diagram, change:

"Class A" to "Class AA"


Page 752, under "Slipformed Construction Tolerances," make the following changes in lines 3 and 4, respectively:

"width dimensions" to "dimension" "adjacent" to "opposite"

In addition to the information published in the October 1980 issue of Concrete Construction, the complete standard includes tolerances for precast concrete, masonry construction, and reinforcing bar fabrication.The standard as adopted is known as ACI 117-81, "Standard Tolerances for Concrete Construction and Materials." The 9-page document is available from American Concrete Institute, Box 19150, Detroit, Michigan 48219, for $3.90 (ACI members, $2.80) plus $1 shipping and handling in the U.S. or $2 elsewhere.