Durable concrete floors begin with quality materials, good design, and proper workmanship. Beyond these essentials, measures can be taken to ensure your concrete floor is protected. If deterioration occurs, understanding its cause can help with the repair and prevention.
Many concrete slab surface defects (delamination, dusting, etc) and problems with floor flatness can be attributed to the quality of the material and/or the placing and finishing techniques. Retaining an expert installer who knows their locally available concrete material can be an important step in achieving good quality concrete floors. As an installer, having the right concrete mixture for the job and sufficient labor and equipment to properly place, consolidate, and finish the fresh concrete is crucial.
Beyond quality floor construction, implementation of surface or penetrating sealers can improve the wear resistance or protect concrete from chemical attack. There are a variety of surface sealers for use on concrete slabs. If your application is to protect a stained interior residential floor or prevent excessive wear and abrasion on an industrial slab, the appropriate surface treatment will vary. A discussion of the available sealers is given below.
When slab defects do arise, understanding their cause can help in repairing and preventing them in the future. These defects may be scaling, random cracking, crazing, or a delamination.
For more information on concrete durability, click here or see Effects of Substances and Guide to Protective Treatments, IS001.
Avoiding Slab Delaminations
Delaminations are separations in a slab, parallel to and generally near the upper surface, that result from bleed water and air being trapped below the prematurely closed (densified) mortar surface. The primary cause is finishing the surface before bleeding has occurred.
Delaminations are more likely to occur when factors that extend the bleeding time of concrete, such as:
- a cold subgrade
- a vapor retarder directly under the slab
- thick slabs
- a high water content
- entrained are air combined with factors that accelerate setting of the concrete surface, such as:
- high wind velocity
- low relative humidity
- rising air temperature
- exposure to direct sunlight
To avoid delaminations, consider the following:
- Do not use concrete with a high slump, excessively high air content, or excess fines.
- Use appropriate cement contents in the range of 515 to 565 lb/cubic yard.
- In cold weather, warm the subgrade before placing the concrete.
- Avoid placing a slab directly on the vapor retarder (see above).
- Avoid overworking the concrete, especially with vibrating screeds, jitterbugs, or bullfloats.
- Do not attempt to seal (finish) the surface too soon. Use a wood bullfloat on non-air-entrained concrete to avoid early sealing. Magnesium or aluminum tools should be used on air-entrained concrete.
- Reduce evaporation over the slab by using a fog spray or slab cover.
- Avoid using air contents over 3 percent for interior slabs.
Protecting Floors from Chemical Attack
Although portland cement concrete is durable in most natural environments, it is sometimes used in areas such as chemical processing plants where it is exposed to substances that can attack and deteriorate it.
Various surface protection options are available to protect concrete in even the most aggressive environments. Here are the advantages and disadvantages of several options:
PCA's Effects of Substances and Guide to Protective Treatments, IS001, is a comprehensive source for information on chemical attack and protection options.