23 Feb Atlanta Hartsfield Airport Entryway Project
In 2013 Concrete By Design was approached to aid in the process of beautifying the entryways of the Atlanta Airport. Because the airport sees an average of 260,000 people per day, the amount of foot traffic at each entrance is significant and the wear and tear on the concrete is a direct result. The concrete products that would be needed would have to be impressively durable while also creating a look that would be inviting. As well as the amount of foot traffic, these areas also bear the weight of massive concrete planters that serve dual purposes; to look nice and to create a safety barrier between motor vehicles and the interior of airport itself.
In addition to the specifications for the concrete, a further obstacle to overcome was the hours that the work could be done and the timeline for completion. The airport doesn’t close and doesn’t like to inconvenience its patrons, because of this, working hours were from 10pm until 5am and each entryway had to be completed in 3 days time. Lastly, in order to continue to keep safety a priority, each member of our team had to undergo background checks and obtain security clearance before working on this project.
Once we knew all of the challenges, we had to create a system to be used on each entryway so that we could maximize efficiency in the removal of the current concrete product, the preparation of the surface to accept a new concrete system and the application of the new product. Concrete By Design also had to do a significant amount of research on the innovative concrete product that would be used. The job was done in the heat of the summer so keeping with the specifications of how fast the concrete would set was something to be considered and addressed. Often times, the product sets faster due to increased temperatures.
The initial step to be completed was the removal of the existing surface. When removing concrete surfaces, there are challenges that must be overcome especially when working in agreement with OSHA standards. The reason for the extensive standards is that concrete particulates in the air contain silica dust, which is a dangerous particulate if inhaled. The safety of both employees and airport patrons was a priority to say the least. Before any actual work could begin, the area needed to be identified and secured from civilian traffic and extra lighting had to be brought in and set up due to the late hours and lack of sunlight. The planters mentioned above also had to be removed so the surface had no obstacles. The work could now get under way. The machine we used to remove the surface is an Edco diamond bit Grinder with a high powered concrete pulsating vacuum system made by CDC Larue.
The existing resurfacing coating was an old Kooldeck product commonly used on driveways, pool decks, and walkways. We used a series of the metal bonded diamond attachments on the Edco to achieve the proper concrete surface profile, aka CSP. Multiple passes with these different attachments over the existing surface had to be made to ensure it was fully removed, level, and uniform.
We started off with a PCD, or polycrystalline diamond to remove the heaviest layer of the coating and worked our way to a 16 grit diamond for the lower layer which was required from the manufacturer of the new product, SureCrete, to place their product. The vacuum was constantly emptied to keep the level of dust and concrete particulates out of the air during each stage of grinding. This bare concrete was now prepared for the next step in the process.
Subsequently, this raw surface had to be prepared so that it could accept a new product and guarantee adherence for the required durability. First, any cracks, imperfections, or fractures in the concrete had to be repaired using a liquid epoxy filler. In order to properly repair cracks, we used a “V” crack chaser blade on a hand grinder to prepare the crack and remove any loose concrete chips that could pose a threat to the integrity of the epoxy. We use liquid epoxy to fill, instead of concrete, because the process with the liquid is three fold and stands up better than a standard mortar based concrete crack filler. The liquid epoxy is poured into the crack, then the crack is filled with silica sand to reduce voids and achieve a level surface, the more liquid epoxy is poured on top to lock everything together, adding more tensile strength.
This surface is then ground again to level out with the surrounding concrete and is ready for pressure washing. Next, the surface had to be pressure washed using a high powered, 4000 psi pressure washer. Next, the concrete had to be acid etched which means pouring properly diluted muriatic acid over the surface to open the pores of the concrete enabling it to accept its next treatment. Once the acid was applied and had ample time to react, it needed to be neutralized with a baking soda and water solution.
Following neutralization, the surface was well rinsed again and all the liquid removed using an industrial sized shop vac. The prepared surface was ready for the application of new concrete overlay product.
Lastly, the new product was applied with the following method. This new product was manufactured by SureCrete of Florida and was pre-approved by the airport commercial construction committees for use. For this step, we applied a bond coat to fill any unseen imperfections that could still exist in the concrete and also to give a good surface to bond the final texture to the concrete.
The bond coat was mixed using a drill and paddle method after the proper amount of liquid was added. This bond coat only required water as opposed to other products that require water and resin. This single component product reduces the chance for product failure by reducing user errors and ensures consistency. Liquid color pigment was added to this coat to make certain that if any chips in the concrete existed, the top layer of product would be applied to an integrally colored surface instead of a white surface.
Finally the bond coat was ready for application using a squeegee and hand brushes for the edges. A nice, clean surface now existed for the application of the non-slip, final texture to be applied. Using the same material, with same color, but at a slightly thicker consistency, this final material was placed in a Graco texture sprayer. This sprayer created an orange peel texture to the surface and as the product began to dry, it was flattened with a steel trowel to create the tradition knockdown finish that the airport was requesting.
Once the proper cure times were met for the concrete, the overlay surface was ready for colored, protective, concrete sealer. To ensure that we met OSHA standards for slip resistance, we added a 30/40 mesh silica sand in between the two coats of sealer. This sealer completed the process, a required 8 hour time period had to be met before the surface was ready for foot traffic, or a 24 hour time period for heavier traffic.
This job was a success, though it posed many challenges along the way. Concrete By Design was grateful for the opportunity to work in a high profile location and we are willing and able to work for the Atlanta Airport should they ever need our services again.