If all concrete cracks to some degree, then what number of cracks in a concrete floor is considered acceptable? That was a question recently posed to our technical expert Chris Sullivan. He says it boils down to three things:
floor size, the owner's perception and crack
severity. Minor surface cracks are generally better tolerated because they are easier to disguise than major structural cracks.

Read his response. 

If you're involved in the staining or polishing of concrete, be sure to attend the 2009  International Concrete Polishing & Staining Conference, to be held Oct. 1-4 in Atlanta, Ga. The event will feature equipment displays, demonstrations and  seminars, networking opportunities, and expert speakers. 

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Both control joints and expansion joints are critical to minimizing cracks in
concrete floors. Control joints are used to relieve the stress within a concrete slab by "coaxing" the crack to occur within the joint, where you can't see it. Expansion joints (also called isolation joints) are designed to allow an entire slab to expand and contract without coming into contact with an adjacent slab, wall or floor embedment, such as a column.

See Joints in Concrete Slabs.

The placement and number of joints are equally important. Even if you install plenty of joints, they won't do much good if they aren't where they should be in the slab.

See Be Active in Deciding Where Control Joints Will Be Placed.

If the concrete floor is a slab on grade, then the subbase supporting it must be sound, with no settlement or movement. An unstable subbase is likely to lead to major structural cracks that will be hard to remedy. Proper compaction is key to ensuring subbase stability.

See How to Build High-Quality Slabs on Grade.

Shrinkage is a main cause of cracking in concrete slabs. As the concrete hardens and dries, it shrinks due to the evaporation of excess mixing water. The wetter or soupier the concrete mix, the greater the shrinkage will be and the greater the likelihood for cracks to develop. Using concrete with a low water-cement ratio and not adding excess water at the jobsite will help to keep shrinkage in check.

Even if your floor does crack, there are a number of remedies available for repairing the damage. You can inject large cracks with a resin, such as an epoxy or polyurethane, or fill smaller cracks with a concrete caulk or patching compound. These materials are often available in a range of colors, so the repair is less visible.

Find crack repair products and suppliers.