Concrete Floors: Understanding the terminology

A few terms associated with concrete floors may be unfamiliar to readers. This brief glossary of terms—taken from Concrete Sawing and Drilling Association (CSDA) ST 11, Measuring Concrete Micro Surface Texture—is intended to help.

Roughness average value (Ra) from averaging and digital readout instruments: The readout device shall display the average deviation from the filtered mean line in λin (λm.). This quantity is the roughness average Ra, formerly known as arithmetic average (AA) and centreline average (CLA). For uniform interpretation of readings from contact-type instruments of the averaging type, it should be understood the reading that is considered significant is the mean reading around which the value tends to dwell or fluctuate with a small amplitude.

Nominal surface: This refers to the intended surface boundary (exclusive of any intended surface roughness)—the shape and extent of which is usually shown and dimensioned on a drawing or descriptive specification.

Real surface: This is the actual boundary of an object; its deviations from the nominal surface stem from the processes that produce the surface.

Measured surface: This is a representation of the real surface obtained by the use of a measuring instrument.

Waviness: The more widely spaced component of the surface texture, waviness may be caused by such factors as machine or workpiece deflections, vibration, and chatter. Roughness may be considered as superimposed on a wavy surface.

Lay: The predominant direction of the surface pattern, the ‘lay’ is ordinarily determined by the production method used.

Error of form: This term refers to widely spaced deviations of the real surface from the nominal surface, which are not included in surface texture. The term is applied to deviations caused by such factors as errors in machine tool ways, guides, or spindles, insecure clamping, or incorrect alignment of the working surface, or uneven wear. Out-of-flatness is a typical example.

Flaws: Unintentional, unexpected, and unwanted interruptions in the topography typical of a surface, such topographical interruptions are only ‘flaws’ when agreed on in advance by buyer and seller.

To read the article, “Concrete Floors: Does ‘sealed’ mean the same thing as ‘polished?'” click here.

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