Cracks in your concrete floor are usually only minor aesthetic problems. In some cases however, they can be indications of major structural issues. Small hairline to 1/16th of an inch cracks are typically found on slabs located on all types of floors from residential structures to multi story commercial towers.
Most small cracks are as a result of; the curing process causing the concrete to shrink slightly or created from a point of pressure on the slab from a load-bearing wall. If the concrete is a different height on either side of the crack, this is known as heaving. In a residential garage, this typically would happen when a portion of the slab has sunk away from the rest of the slab. Cracks like this are not common however they do require more of an in-depth analysis and sometimes the pumping up of the slab portion that has sunk.
If the cracks are smaller, they can often be filled with DIY products from your local hardware supply store. Some products sold locally are generally weaker and not very long lasting, they will also not look very nice due to the techniques used to install them.
When repairing cracks in previously finished concrete floors, epoxy injection is sometimes the best route because the crack can then be repaired from below the surface thereby having minimal negative effects on the appearance of the floor itself.
Cracks that appear prior to having a concrete floor decoratively finished should be addressed by an experienced and professional concrete tradesman. The technique used by professionals with the right tools includes chasing the crack (cutting it open further to remove loose concrete and debris) in order to allow for better adhesion and penetration of the crack repair material.
If the floor were then going to be decoratively finished, the crack repair would be smoothed down and honed to the level of the existing floor in order to minimize its appearance.
Crack repair products are available in an array of specialty and standard colours that can be customized at the manufacturer. In some cases clear crack filing products used by professionals can be colour matched on site to your floor.
It is important to repair all cracks as soon as possible, especially in wet areas or areas subject to hard wheeled traffic such as, steel wheels on dollies, carts and especially in areas subject to fork lift traffic.
If cracks are not repaired in a timely manner, this type of traffic or wet environments can cause contamination or further erosion leading to larger cracking and further damage.