By Richard First, BASF Corporation

Managing an industrial facility requires one to wear many hats. Everyone from the company president to the forklift operator regularly highlights areas where repairs or improvements are needed. Moreover, the facility manager is expected to be an expert on every facet of the building. Improvements are expected to be completed within an extremely short time frame, within a limited budget.

Unfortunately, “good, fast or cheap … pick any two” is usually the name of the game. Most often the two selected criteria are fast and cheap. While this no doubt solves an immediate need, it often leads to continual performance issues, repeated downtime and the spending of proverbial “good money after bad.”

It’s unrealistic to expect anyone to be an expert on everything. However, facility owners should have a solid understanding of the needs and requirements of a facility, an appreciation for the likely cause(s) of failures and an understanding of the options that will prevent repeated failures.

WHY IS MY FLOOR CRACKED?

It is commonly said, “There are two types of concrete: concrete that is cracked and concrete that is going to crack.” The reality is that cracks in concrete industrial floors are common and, in fact, expected. At a minimum, cracks on a warehouse floor can result in unattractive spalls and chips in the floor and excessive wear on forklift wheels. At the other end of the spectrum, cracks on a floor in a food production facility can lead to microbial growth that can result in a costly product recall or, in the case of a pharmaceutical research lab, delay the introduction of a revolutionary drug. Suffice it to say, cracking is a very important issue when considering industrial concrete floors and warrants serious discussion.

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Known as crazing cracks, these static cracks are generally not detrimental to the long-term performance of the concrete and their size will not increase over time.

BASF Corporation

Known as crazing cracks, these static cracks are generally not detrimental to the long-term performance of the concrete and their size will not increase over time.

When concrete cures, hardens and gains strength, it shrinks. If left on its own, a cast concrete slab will shrink in all directions. However, a poured concrete slab is subject to various restraints which restrict the concrete’s natural shrinkage. It is this restraint that results in cracking. The roughness of the base on which the concrete is poured, drains to which the slab is sloped and columns that support the roof are all examples of physical restraints that act upon a concrete slab. While ambient conditions during placement are the likely cause for much of the cracking observed on industrial concrete floors, flaws in design and attention to detail also account for cracking.

A Crack Is a Crack … Or Is It?

Cracking can range from fine, spider web-like networks that are only visible when the floor is wet, to wide cracks that span entire slabs. Some cracks get filled in with dirt and debris and never increase; others continue to spread. Understanding the various types of cracking and their likely causes allows a facility manager to make informed decisions as to the most appropriate solutions, as well as to effectively manage the various stakeholders’ expectations.

In general, cracks are treated differently depending on whether they are static or dynamic. As one might suspect, static means the crack is not changing. This means that the stress or restraint that originally led to the crack, is no longer present. Static cracks can be filled with a rigid filler, and many flooring systems can be successfully applied over them without concern of their recurrence.

A dynamic crack is the result of an external stress that is still present. A dynamic, alternately termed as “moving,” crack will persist and often get larger over time. Dynamic cracks cannot simply be filled and overlaid with a flooring system. The external stress that caused the dynamic crack must be acknowledged, and the continued movement must be allowed. Examples of both static and dynamic cracks follow.

While every scenario cannot be considered here, a brief look at typical examples of cracks will provide an adequate knowledge base for a facility manager to understand cracks in their own floors.

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Cracking can present in the opposite of settling. Instead of the base sinking as the concrete dries and shrinks, the edges curl upward off the base.

One crack scenario could include a finely spaced network of small cracks. These cracks were caused by the surface drying before a curing compound was applied during the concrete placement. Known as crazing cracks, these static cracks are generally not detrimental to the long-term performance of the concrete and their size will not increase over time. The presence of crazing cracks, however, may be indicative of poor wear resistance due to the poorly cured concrete surface. Any resinous flooring material, installed over the mechanically prepared substrate, should be able to bridge and seamlessly cover crazing cracks. Alternatively, liquid hardeners/densifiers can be effective for restoring the hardness of a poorly cured concrete slab.

Because concrete shrinks, it is recommended to cut regularly spaced joints into the concrete. Such joints are appropriately named “control joints,” as they control where the concrete will crack. By looking at the pattern of these cracks, one can quickly see that the concrete slab in this garage floor should have been cut into four quadrants. Once the concrete is fully cured and the initial drying shrinkage is complete (typically six months), these cracks can be filled with a semi-rigid joint filler without concern of recurrence.

Another example of a static crack would be where the base or substrate under a concrete slab settles and results in a crack. Once concrete has settled, it will no longer crack. However, cracking can present in the opposite of settling. Instead of the base sinking as the concrete dries and shrinks, the edges curl upward off the base. Once curled, there is a lack of support under the slab, resulting in cracking when heavy loads drive across these areas. This cracking, typically in a diamond-shaped pattern, usually occurs where two control joints cross. All static cracks, properly detailed, can be filled with either a semi-rigid joint filler or epoxy, or filled and overlaid with seamless, resinous flooring solutions. Curling cracks, however, often pose more complex repair scenarios and a flooring specialist should be consulted.

As described earlier, dynamic cracks are moving and the result of an external stress that will continue for the life of the structure. These stressors need to be isolated from the concrete so they do not induce cracking, hence the name “isolation joints.” Isolation joints need to account for continued movement and are typically filled with an elastomeric sealant.

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The coating, which is recommended for exposure to NaOH, has failed, resulting in dramatic deterioration of the concrete slab below.

Cracking can also result from a failure to isolate a structural column from the floor slab, which is a must. Re-entrant cracks are also quite common and are the result of pouring concrete around a corner wall, drain or other rigid corner. As the concrete cures and shrinks, a crack forms at the corners. These are often dynamic and should be acknowledged; however, the dynamic crack can be filled with a rigid filler, and a new joint can be cut and filled with a sealant for a more aesthetically pleasing solution.

It may take some time and experience before a facility manager is able to identify the types and causes of the cracks in his/her facility. It is always best to consult a flooring expert if one has questions regarding the type of crack and how to correct the issue.

WHY IS MY FLOOR SO BEAT UP?

Industrial floors, whether plain concrete or coated, get heavily abused. Forklift traffic in defined patterns, steel-wheeled carts, concentrated chemicals and steam cleaning practices can all cause damage to concrete floors and most coatings. Understanding the specific in-service conditions your floor experiences is critical to selecting the flooring solution that will provide the service life and durability desired. Physical, chemical and thermal stresses, though often related, should be considered individually, as flooring materials are often particularly suited to handle one of these better than the others.

Let’s Get Physical

Physical abuse refers to abrasion or impact. Abrasion is the result of a continued wearing or grinding of the floor surface. In its most innocuous form, abrasion can be in the form of foot traffic. At the other extreme, automatic guided vehicles (AGVs) that continuously move in defined traffic patterns in a manufacturing facility or warehouse, subject a floor to extreme abrasion.

As one might assume, impact is the result of an object hitting the floor. A hammer that is dropped causes an isolated impact that may result in chipping of the concrete or coating. Carts equipped with steel wheels, on the other hand, continuously impact joint edges and lead to severe deterioration at joints and drains.

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Surface defects can range from small pores or pinholes to bubbles and blisters that are coin-sized or larger.

Abrasion and impact, though seemingly separate issues, both require heavy-duty flooring systems, often applied at increased thicknesses to ensure long-term protection. High-strength concrete will not typically provide long-term performance against these mechanical stresses. While some concrete may have a very high compressive strength and exhibit good wear resistance, it also tends to be brittle and unable to absorb the impact.

Chemistry: It’s All How You React

In addition to the physical wear to which an industrial floor is subjected, most production facility floors are also exposed to a myriad of chemicals. This includes those used during manufacturing as well as those used to clean and/or sanitize. Unfortunately, while concrete does exhibit good wear resistance, it is not resistant to many chemicals. Chemical deterioration of a floor is not always due to exposure to a single chemical; rather, it is often the result of a “cocktail” that involves the combination of several different chemicals. Moreover, most chemical spills, if left unattended, will concentrate by evaporation, causing additional damage. Not only do chemicals cause direct damage, but chemicals on a floor tend to exacerbate existing flooring issues.

Consider an epoxy floor coating that has begun to disbond. As the area is continually subjected to chemical attack, the chemical will continue to etch its way along the bond between the concrete and the epoxy coating and lead to further physical and safety concerns.

Another complex scenario involves mixers handling sodium hydroxide (NaOH), which are regularly rinsed with water. The coating, which is recommended for exposure to NaOH, has failed, resulting in dramatic deterioration of the concrete slab below. What was not considered during the flooring selection was that NaOH, when put into a solution with water, generates significant heat. In this example, it was the thermal exposure that led to the coating failure, not the chemical exposure itself.

If You Can’t Stand the Heat

Thermal stresses are commonplace in certain operations, particularly in food and beverage production facilities. Hot water is used to clean production floors, live steam from process equipment is released directly onto the floor and walls, and floors are often subjected to high-pressure steam cleaning.

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Blisters are a unique example of surface defects that are the result of a pressurized force from under a floor coating. These defects are typically coin-sized but can be much larger.

The thermal stress leads to expansion of both the epoxy coating as well as the concrete substrate. Because epoxy expands at a rate of six times that of concrete when heated, it tends to disbond, or delaminate, from the concrete surface when subjected to temperatures above 140 degrees Fahrenheit. Urethane concrete flooring materials can handle these extreme temperature ranges because they behave similarly to concrete, thermally speaking.

Coolers also present an extreme example of thermal stresses and, similar to high-temperature environments, require specialized flooring systems. Metal substrates, flexible floors and significant thermal swings all pose concerns that only an experienced installer can adequately address.

BLISTERS, BUBBLES AND PINHOLES, OH MY!

There is another general category that warrants treatment in the scope of this article: surface defects. Surface defects can range from small pores or pinholes to bubbles and blisters that are coin-sized or larger.

Pinholes can result from multiple installation or material issues. Outgassing is a common cause of pinholes. When a pancake batter-consistency flooring material is installed over a porous concrete substrate, the material seeps into the pores of the concrete and displaces the air, and the displaced air rises to the surface of the flooring material (consider a glass of soda). If the material still has a relatively fluid consistency, the space occupied by the “popped” air bubble is filled with material and a smooth, level surface is maintained. If not, the bubble may or may not “pop,” and a pore may be evident on the floor surface. Bubbles that did not make it to the floor surface may also remain within the bulk of the floor coating, creating increased porosity.

Unsightly pinholes on a floor surface collect dirt and harbor bacteria. Such surfaces are difficult to clean and sanitize. An experienced installer will ensure the appropriate steps are followed for the selected flooring system to deliver the anticipated surface.

Blisters are a unique example of surface defects that are the result of a pressurized force from under a floor coating. These defects are typically coin-sized but can be much larger. Incomplete curing of a previous coat during the installation process may result in a blister due to the outgassing of the previous coat, as described earlier. The presence of oils or other bond-breaking materials on the substrate may also result in blisters. Blisters on a concrete floor are the direct result of closing the surface too early or hard troweling air-entrained concrete.

One example of the cause of blisters in a floor coating is moisture vapor transmission (MVT) through a slab. Moisture that is commonly present under a concrete slab tends to migrate through the slab in an attempt to equalize the humidity difference underneath the slab compared with the ambient space above the slab. This moisture is typically present as vapor instead of water, and builds pressure as it tries to equalize. This is the reason that a bag of drywall plaster will set up in the bag if stored in a basement for more than a month.

In an industrial setting, hydrostatic pressure associated with MVT builds under resinous coatings and often results in blisters and/or delaminations. (Note that soluble salts are also important for this to occur.) Various coating technologies have different tolerances for MVT. Several coatings/primers on the market are designed to mitigate significant pressures brought about by MVT, especially for those coating technologies that are sensitive to MVT.

Moisture-related issues present difficult and complex problems for a facility manager, and an experienced flooring contractor can provide invaluable experience in solving such issues. They can also identify the moisture levels within a slab to determine if a moisture mitigation solution is required before a protective coating is installed.

AN OUNCE OF PREVENTION

Ease of cleaning versus slip resistance is an age-old dilemma. Most facility managers want their floors to be easy to clean, but also want to ensure that slip resistance (that is, the coefficient of friction) is sufficient to help prevent slip-and-fall accidents. The following factors should be considered when trying to ensure the most appropriate surface texture is selected.

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Moisture-related issues present difficult and complex problems for a facility manager, and an experienced flooring contractor can provide invaluable experience in solving such issues. Here, a pH reading is conducted of the fluid found inside a blister.

Every facility’s environment is different, and it is often the environmental factors in a facility that most impact the slip resistance of the floor. Fatty acids in a food facility and leave-on sanitizers in a pharmaceutical facility, for example, can lead to dramatically slippery floors, regardless of whether the floor exhibits a textured surface. When considering a new flooring solution, a mock-up is instrumental in ensuring a facility’s needs will be met. Any desired slip-resistance testing should be completed on mock-ups that are subjected to the actual in-service conditions the floor will experience.

A thorough understanding of the chemicals or environmental factors to which a production floor will be exposed, will help determine the best protocol for cleaning and maintaining the floor. The wet and dry static coefficients of friction reported on a manufacturer’s data sheet can also provide some guidance as to the appropriate flooring solution for a facility. Again, an experienced contractor is often the best resource for guidance in this matter, as they help facility managers solve problems like these in similar facilities and can provide best-practice recommendations.

HOW DO I GET THERE FROM HERE?

With all the factors and considerations described here, a facility manager can quickly become overwhelmed and opt to blindly throw darts, hoping for a workable solution. This puts facility managers back where they started—in need of a solution. It takes a real effort to not merely call the convenient or low-cost flooring installer or to keep calling for warranty work on failed floors. There is always a cost and headache associated with callbacks.

Selecting a good contractor also plays a critical role in the flooring decision-making process. Many contractors specialize in certain industry sectors. This allows them to offer best practices that truly provide solutions for your facility. Such best practices allow one’s facility to remain operational without ongoing interruptions to production and can significantly reduce the long-term costs associated with oversold solutions and poor decision making.