Multi-storey car parks in the United States date back to 1918 when what is believed to have been the first was built at the Hotel La Salle at 215 West Washington Street in the West Loop area of downtown Chicago, Illinois.
Today, there are thousands and most are either prestressed concrete double-tee floor systems or post-tensioned cast-in-place concrete floor systems. The design loads for car parks are often less than the office building (50 psf versus 80 psf). Once in use, safety inspections are mostly up to the owners and operators.
This case study concerns a car park in downtown Denver, Colorado, which is over 15 years old. Its 26,000 square foot roof deck parking had suffered over the years, not just from the traffic loads, but also from the corrosive effects of corrosive road salts in winter and wide temperature fluctuations in summer.
The roof deck coating was failing rapidly and was allowing water to percolate between the concrete slabs to the floor below. Hidden from sight is the steel rebar which gives the structure enormous strength to support the basic load of the building but also those imposed by the automobile traffic.
Most especially, the leaks had to be stopped effectively to protect the rebar from further exposure to salts which can rapidly cause the steel rebar to rust. The rusting process can creep deep into the slabs creating enormous pressures which can flake and even fracture concrete, thus reducing load capacity. The discolored water leaks were also dripping onto parked cars, a cause of frequent complaint from customers.
The client wanted a coating solution that was high performance and with zero toxicity eg no VOCs or anything that could degrade and pollute water runoff. The coating had to be able to permanently seal gaps, adhere for decades and not be affected by micro movements of the structure.
VOC-free, zero toxicity Ecodur was chosen as it also has exceptional adhesion strength on concrete. On steel, the pull off strength is rated at 1,000 pounds per square inch making it ideal for rebar protection. Ecodur also permanently retains its flexibility and also its repairability indefinitely. New Ecodur can be applied to old Ecodur surfaces, no matter what age they are as long as they are clean and dry, and will make a perfect bond. It is also certified for potable water contact, mking it ideal to help reduced run-off pollution.
Ecodur takes an average of 30 minutes to become tack free allowing plenty of time for it to seep deep into cracks and slab gaps, providing an absolute plug against further ingress of corrosive liquids.
The original coating which had been failing, creating flakes which broke off damaging the yellow parking stall lines, was cleaned and removed with the surface left dry. An average of 30 to 50 mils of Ecodur was manually applied by the Preferred Painting.
A standard yellow line coat for stall markings was applied. Significantly, the Ecodur acts as the perfect primer base for the markings and it has already been demonstrated to extend the life of the lines because the yellow coat adheres exceptionally well. The final part of the process was a clear polyaspartic over coating which gives the job its ‘showroom’ effect.Polyaspartic chemistry was first introduced in the early 1990s making it a relatively new class of coating. Polyaspartic is actually an aliphatic polyurea and provides enhanced chemical and abrasion resistance making it an excellent choice for car parks.