Q: What does it mean when somebody specifies a Class 5 concrete floor?

A: The short answer refers to a slab floor for an ordinary light industrial application, but some additional information can help put thatinto context. It's standard practice to talk about concrete floors based on their intended use. Table 2.1 in ACI 302.1R,"Guide for Concrete Floor and Slab Construction," presents the nine different classes identified by ACI and lists the anticipated traffic, use, special consideration, and final finish associated with each type.

Five classes are placed as monolithic concrete; three involve two course construction with either a bonded or unbonded overlay atop a base slab; and the ninth (superflat) can involve either a topping or monolithic placement.

floor with an exposed surface that will hold up under industrial vehicular traffic with pneumatic tires and"moderately soft solid wheels." The ACI table says these floors typically are in industries such as manufacturing, processing, and warehousing.

Under special considerations, the requirements are simple and straightforward. The slab should be built on good uniform subgrade and have good joint layout, abrasion resistance, and curing. A hard steeltroweled finish is recommended.

For anyone involved with concrete floors, spending some time with the ACI guide from time to time is a worthwhile investment. The electronic version can be particularly useful because many links embedded in the text automatically take you to other referenced sections within the text as well as to other documents.