In a solid waste facility, a transfer station or a material recovery facility, the tipping floors are where money is made or lost. If the floors are kept healthy and in good condition, the whole process will work properly.
By Jim Andrews
Tipping floors are subject to some of the most extreme and harsh conditions in solid waste facilities and transfer stations. They are exposed to a daily barrage of aggressive chemicals, impact loads, abrasive elements and damage from heavy processing equipment. Crucial to the successful operation of a transfer station is keeping these tipping floors in “top” shape while minimizing downtime and optimizing return-on-investment.
Tipping floors are normally composed of poured concrete. However, concrete does not hold up well under the heavy abuse of a high-volume transfer station and is prone to cracking and fracturing. In high-volume transfer stations, the surface of the tipping floor can lose from 1/4 to 1 inch of concrete every year depending on waste stream and equipment used. In these cases, the tipping floor may need repairing every two to three years. Not only is this costly, but a facility can also be out of operation for up to two weeks or more while the concrete floor is being repaired.
Right: Laser scanning tipping floor.
Photos courtesy of American Restore.
Alternatively, new installation technology and advances in material performance allow a better solution. High-performance, cement-based products provide improved durability with quick installation. This minimizes downtime impact to facility operations, as well as reduces the overall cost of floor maintenance. By increasing abrasion resistance, compressive strength and impact distribution along with low permeability, high-performance floor toppings are well suited to the tough working environment of tipping floors.
Tipping Floor Locations
Tipping floors are an intermediate position between a solid waste source, such as a dense suburban community and a landfill. Rather than have 15 or 20 small trucks making daily trips to the landfill, the trucks go to a central transfer station once they have finished their route. At the transfer station the trucks “tip-out” the garbage onto the floor—hence the name “tipping floor.”
The most efficiently designed transfer stations have a tunnel or drive-through area below the tipping floor. Larger waste transfer trucks are situated in the tunnel under a large hole at the end of the tipping floor. After the garbage is “tipped-out” onto the floor, heavy front-end loaders push the garbage into the hole where it falls into the larger trucks. Now, instead of 15 or 20 trucks going to a landfill, only three or four of the larger trucks are needed. This saves money on transportation costs and eliminates excessive truck traffic through a community.
Because of the constant pushing and scraping of the front-end loaders, tipping floors are exposed to continual stress. While some facilities might process only 500 to 1,000 tons-per-day, larger facilities might handle from 3,000 to 5,000 tons-per-day of solid waste. Not only does this refuse contain glass and metal pieces that gouge the floor, but it also contains chemicals and liquids that degrade the floor.
Tipping floors have also become integral to the recycling process at material recovery facilities (MRFs). As government regulations are enforced for recycling, products that can be reused back into the economy such as plastic, paper, glass and metal must be sorted. Since it is difficult to sort these materials at the landfill, the separation process is done at the MRFs. The floors at these facilities are also subject to deterioration from glass and metal particles.
Right: Wear indicator in tipping floor topping.
Tipping Floor Deterioration
Corrosive liquids are another threat to tipping floors and have become a critical point for waste station facilities. Government mandated clean water regulations have changed the way solid waste is transported from the local community to the waste stations. As solid waste is collected, waste liquids can leak out of the backs of the trucks as they drive though a community.
Environmental directives demand that these waste liquids be processed within the waste stream and not leaked out into the community. To contain the liquids, garbage trucks installed large rubber gaskets along the truck’s container edges. With this improvement, all the waste liquid is now transferred to the transfer station. While this is good for the environment, it is bad for the concrete tipping floor.
As the solid waste is dumped onto the tipping floor, so does this “soup” of acidic and caustic liquids. As it sits on the floor waiting to be processed and moved, these liquids chemically attack the floor and breakdown the cement. Along with the impact and abrasion damage that the tipping floors receive, corrosive liquids also aggressively weaken them causing accelerated wear.
Tipping Floor Wear
So now that we have established that tipping floors will deteriorate at some point, we need to understand how to determine when the floors need to be repaired. Most tipping floors start out as a concrete slab that is 8-inches to 12-inches thick. The floors will degrade at different times and under different conditions—depending on how much use the floor receives.
Monitoring floor wear is critical to budget planning and for scheduling repairs to avoid facility downtime and loss of income. With accurate floor monitoring, a facility manager can identify several years in advance when a floor repair is necessary, allowing time for budget considerations and downtime.
The process of evaluating, monitoring and specifying repair work on a tipping floor can be a complicated and daunting process. However, through simple methodology and selective maintenance the continued performance of a tipping floor can be ensured for the lifetime of a facility.
There are several methods available for determining floor wear. Visual inspection is, of course, a good indicator but not always technically reliable. Certain floor conditions such as cracks, gouges, ponding water and holes indicate that a tipping floor is losing some of its original surface but does not determine when the floor needs to be resurfaced.
I have often told groups when I speak on the subject that when I walk into a transfer station and see a cutting torch chained to a column or setting off to the side, I know that from time-to-time they are burning the rebar out of the floor, this is not a good sign.
There are more scientific methods offered that can provide a better indication of floor deterioration. One of these methods is called “scanning the floor.” A laser-scanning device measures the floor elevation when the floor is new or “healthy”. Over a specified period of time, such as every six to 12 months, another electronic measurement is taken. After a year or two of measurements an exact indication can be made of how much wear the floor is receiving. With these scientific calculations, it can be predicted when a floor will need repairs and exactly where the repairs will be needed. This precise indication of floor wear helps facility managers plan for repairs rather than being forced to shut down a facility for emergency repairs when the tipping floor becomes so compromised that it cannot be used.
Another method for determining floor wear is a “Wear Indicator”—a triangular-shaped piece of aluminum. Wear Indicators are embedded into the tipping floor at predetermined locations. As the concrete tipping floor begins to wear so does the top of the aluminum triangle. By measuring the exposed surface of the triangle face, it is possible to determine how much floor wear has occurred and when a floor repair should be scheduled.
Usually a tipping floor must have an indication of at least one-half-inch of wear before the floor can be assessed for possible repair. The facility manager should also be aware of the original design and construction of the floor since not all concrete is the same. Field analysis or floor sampling might be needed to determine wear characteristics and floor constitution.
It is also important to factor in how much use a facility receives and how much use is anticipated. Sometimes economic or environmental considerations enter into the equation along with budget requirements when determining floor repair needs. Facility managers should know if the waste stream will continue to be consistent or if there are indications that it will be increasing. For instance, if more housing or commercial development is planned for the community. Does the area have a lot of C&D, food waste and/or other organic streams?
Tipping Floor Repair
Once it has been determined that a tipping floor needs to be repaired, some facility managers might think it would be advantageous to “just pour more concrete on top of the damaged floor.” This solution, though, is neither cost-efficient nor practical. It has been established that concrete floors have a short life span—between two-to-three years depending on usage. Having to continually replace the floors in this short time frame is costly and can shut down a facility for up to two weeks while repairs are made.
Concrete floor replacement is time-consuming and labor-intensive—the damaged floor must be broken up and hauled off, totally removing and replacing concrete slabs, which can be risky in other ways that I will not go into at this time.
To facilitate an overlay, the surface must be prepared, and a bonding agent applied before the new concrete floor can be poured. A facility must interrupt tipping floor activity for one-to-two weeks while the concrete work is being done (and it can take up to seven days or more before the concrete reaches full strength). Between the loss of revenue and the continual costs for new concrete tipping floors, replacing concrete floors with more concrete might not be a viable budget option.
An Alternative to Concrete
A more valuable, cost-effective alternative for repairing tipping floors is now available in the form of high-performance cement-based toppings. These engineered toppings consist of a combination of recycled iron shavings and specialized cements and additives. They are made of a strong, chemical and impact-resistant cement materials specifically designed for tipping floors. This repair material is eight to 10 times better performing than the original concrete. These specialty toppings can be quickly installed over a weekend, eliminating the need for lengthy work interruption.
Iron aggregate flooring can last years longer than standard concrete mixes, making it much easier to fit tipping floor replacement into a budget. The low-porosity topping is also easier to keep clean than concrete flooring, since it does not absorb the fats and oils contained in the waste stream. As the engineered topping wears, it develops a “modeled” effect, which provides better traction for waste handling equipment, unlike concrete floors whose smooth surface provides no traction.
Tipping Floor Tips
Once a facility manager has determined that the tipping floor needs to be repaired, there are several important points to consider when choosing an engineered-topping floor repair system. Do research to find the repair company that will provide the best products for your investment. If possible, get recommendations from other users. Make sure that the repair company employs professional, well-trained repair technicians and uses the proper equipment. Get several references and check them out.
One of the challenges of tipping floor repair is scheduling for downtime. You do not want to shut down your facility while repair work is being done. Engineered toppings can be installed over a weekend, allowing a facility to be up-and-running on Monday morning. The existing concrete floor does not have to be torn-up. Once the damaged floor surface is cleaned and prepared the engineered topping is poured on top of the concrete floor. The new slab should be about 1-1/2-inches to 2-1/2-inches thick.
Another advantage of engineered toppings is that only a portion of a floor can be repaired if necessary. For example, a facility might have a 50,000 square foot tipping floor, but only a segment of the floor is damaged (5,000 square feet to 10,000 square feet). In this instance a “postage-stamp repair” can be made—negating the need to restore the entire floor. This not only saves money, but also allows waste station operations to continue while the damaged floor section is repaired.
Tipping Floor Maintenance
Once the new-engineered topping has been installed, a continued maintenance program should be instituted. As described earlier, “scanning the floor” can determine how much wear a tipping floor has received. After the floor has been repaired, “scanning the floor” will demonstrate how much material has been applied to the floor. With this information, the floor should be monitored approximately every six to 12 months to calculate when another repair would be necessary. This report will help a facility manager to plan budget and downtime for the next repair process.
Alternately, Wear Indicators can be installed in the floor surface to indicate when the floor is beginning to show wear on its surface. A reputable floor repair service should provide and set-up a measurement system for monitoring floor wear. They should continue to monitor floor wear with frequent visits to your facility or they can train facility personnel to perform and gauge the measurements.
Healthy Tipping Floors
In a solid waste facility, a transfer station or a material recovery facility, the tipping floors are where money is made or lost. If the floors are kept healthy and in good condition, the whole process will work properly. Badly damaged floors with cracks, gouges and holes will put stress on waste transfer equipment and front-end loaders and their tires. Uneven floor surfaces are unsafe for personnel, putting them at risk from slips and falls. Having to shut down a facility for two weeks or more, especially for an unscheduled floor repair, does not make good business sense.
An old garbageman once told me, “I have 250 trucks on my route, 15 transfer trailers and six front end loaders to push trash across my floor. But, I have only one tipping floor and I can’t afford to have any problems with it!”
Engineered floor toppings for tipping floor repair offer a long-lasting, impact and chemical-resistant alternative to plain concrete. They can be quickly installed providing a cost-efficient solution that will return a tipping floor to better-than-new condition. Along with a continual floor maintenance program, engineered floor toppings are a worthwhile business investment to consider. | WA
Jim Andrews is CEO of American Restore (Huntington Beach, CA) and Owner of Delta Pacific. He has been in the concrete repair business for more than 35 years. He and his team have restored hundreds of transfer station floors all over the U.S. Jim has helped develop materials used in the repair process of concrete and is constantly testing new technologies for both the waste and concrete industries. He can be reached at [email protected] or visit www.tippingfloors.com.