ACI Floor Flatness & Levelness (FF/FL Numbers) 3

Question 1

Which ACI document specifically covers design and construction of slabs-on-ground, including flatness and F-number considerations?

Accepted Answer

ACI 360R

Answer

ACI 360R, 'Guide to Design and Construction of Slabs on Ground,' covers flatness, levelness, F-number requirements, and related considerations for slab-on-ground construction.

Question 2

What effect does slab curling (warping from differential drying shrinkage) have on FL numbers measured long after placement?

Accepted Answer

Curling can decrease FL numbers as slab edges lift relative to the center

Answer

As slabs dry differentially through their depth, edges and corners can curl upward, reducing FL (levelness) readings compared to measurements taken shortly after placement.

Question 3

How are F-numbers statistically calculated from dipstick profiler elevation difference measurements?

Accepted Answer

From the statistical variance of sequential elevation differences, converted to an F-number using a standard formula

Answer

F-numbers are derived from the statistical variance (standard deviation) of sequential elevation differences, providing an objective and repeatable measure of surface waviness and slope.

Question 4

What does it mean when the FL specification for a concrete floor is listed as 'unspecified' or not applicable?

Accepted Answer

No levelness tolerance is required; only flatness (FF) is enforced

Answer

When FL is unspecified or not applicable, the project only enforces flatness (FF), which is common for intentionally sloped floors or areas where absolute levelness is not required.

Question 5

Per ASTM E1155, what is the minimum number of elevation differences required to produce a statistically valid F-number for a floor section?

Accepted Answer

34 elevation differences

Answer

ASTM E1155 requires a minimum of 34 elevation differences to produce statistically reliable F-number results for a measured floor section.

(ACI) American Concrete Institute Concrete Finisher Practice Test

(ACI) American Concrete Institute Concrete Finisher Practice Test

ACI Floor Flatness & Levelness (FF/FL Numbers) 3