Practice Test Geeks(ACI) American Concrete Institute Concrete Finisher Practice Test
← All ACI Flashcard Decks

Floor Flatness & Levelness (FF/FL Numbers) Flashcards

7 cards from real ACI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Floor Flatness & Levelness (FF/FL Numbers) flashcards as text

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

    Answer: ACI 360R

    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.

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

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

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

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

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

    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.

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

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

    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.

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

    Answer: 34 elevation differences

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

  6. What construction condition is most likely to produce low FF numbers (poor flatness) in freshly placed concrete?

    Answer: Inconsistent screed strikes causing ridges and low spots during placement

    Inconsistent screed strikes that leave ridges, valleys, or uneven surfaces during placement directly result in low FF numbers, as these local deviations are captured by the profiler.

  7. When a floor FF specification is written as 'FF 50 / FL 35,' what do these two numbers represent?

    Answer: Minimum FF of 50 for flatness and minimum FL of 35 for levelness that the floor must achieve

    The specification 'FF 50 / FL 35' means the floor must achieve a minimum floor flatness number of 50 and a minimum floor levelness number of 35 as measured per ASTM E1155.