Curling Had an Effect on F-number Measurements

Concrete Curling is quantify whenever floor flatness and levelness are measured making use of F-number concept, timing of measurements is critical because curling of slabs upon the ground rise with time. The result is diminished F-numbers that could not meet specific values. Changes in F-numbers may provide difficulties for the floor covering contractor that has an expectation of exactly how flat and level the floor should be. The bigger the initial FF number, the greater the unfavorable effect of curling. For this reason, the Standard Tolerances for Concrete Construction and Materials under Section 4.8.4.1 of ACI 117-06 requires that floor test surfaces has to be documented and measuredjust under 72 hours right after slab concrete finishing procedures is completed and before the elimination of any supporting shores.


The required time limit applies to both gap under-straightedge as well as F-number measurements made prior to ACI 117-06; but it really wasn’t always the situation. Contractors really should look at to ensure what ACI document the project specs demand. Although ACI 117-06 is circulated, 80 % of the projects remain using ACI 117-90 and some continue to employ ACI 117-81.


The ACI 117-81 had mentioned that floor tolerance measurements has to be achieved a day following a concrete floor is finished and previous to shoring is removed, as a way to get rid of any results of deflection curling, and shrinkage.


When ACI 117-90 however, was written and published, it was included in the Section 4.5 the different specifications for the ideal time of the measurements. It will require that FL levelness tolerances should be measured within just 72 hours following slab concrete placement. Then, Floor finish tolerances as assessed using a 10-foot straightedge has to be finished in just 72 hours immediately after slab concrete placement. And then, there was no time requirement on gauging FF floor flatness. The explanation for this is because of the notion that nor curling or deflection will substantially modify a floor’s FF value. Therefore, tthere shouldn't be time limit around the measurement of this kind of characteristic.


The affirmation in the commentary indicating that nor curling or even deflection will considerably modify a floor’s FF value has since been shown to be wrong. For the most part, contractors perceived that curling had an impact on F-number measurements. F-number measurements accomplished 6 to 9 months after the concrete slab had been placed often showed that the floor had really changed, as these F-numbers were lower than F-numbers measured inside of 72 hours of placement. This is why ACI 117-06 needed that all dimensions such as FF, FL and the gap within a straightedge need to be accomplished inside of 72 hours. Even so, you cannot assume all specifiers and contractors understand this difference.


In order that F-number measurements reveal merely the floor flatness and levelness resulting from the concrete contractor’s initiatives, these measurements has to be done within 72 hours after conclusion of slab concrete finishing procedures. Or else, low F-numbers may very well be the effect of curling. Thus as soon as the floor covering contractor comes, disputes within the floor flatness and levelness may arise. The charge for grinding or patching a floor which has curled ought to be layed out before construction


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