2011-fall-floor

Shrinkage compensated slab on new distribution center dock.

Cold facility flooring often isn’t considered a key element in a successful operation, yet every building needs a firm foundation. Companies who overlook this soon realize how much of a headache it can become if problems arise. The truth is you get what you pay for.

Consider this. One refrigerated warehouse operator selected a conventional concrete floor for a new, 40-foot clear building. The owner installed racking up to 38 feet high. Soon, he noticed the floor showed faulting as well as cracking in the center of the aisle.

After some investigation, experts determined the slab and sub-grade were overloaded and the rebar – which would have restricted vertical faulting – was missing. Unfortunately, this building quickly cost the owner much more than the few dollars saved during construction.

Another example involves a large food distributor whose project included a multi-temp building intended to operate 24/7, 364 days of the year. This ESI project had freezer, cooler and dry storage (racked and floor stack) and many dock doors. Reliable flooring was needed because there is little downtime for joint or crack repairs.

ESI’s experienced architect and structural engineer recommended flooring that features shrinkage compensating (SC) concrete with trap rock. Meanwhile, ESI interviewed the client to fully understand the operation’s racking types and loads – as well as any possible future variations. ESI also investigated the site’s sub-grade ground to determine what kind of load it could take. This analysis considered variables such as settlement, sub-grade modulus, potential water sources, expansive soil potential, etc. ESI held a “pre-pour” meeting involving everyone – the specialty floor contractor, geotechnical firm, concrete testing firm and related contractors. ESI provided outline and placement parameters, a quality control test for SC expansion on every pour, as well as testing steps for strength and subgrade. ESI gave testing firms the authority to accept or reject work or conditions during the pour. ESI also had a consultant on site to test whether the finished floor was indeed flat and level. The end result was an excellent floor slab and a satisfied client.

ESI believes the advantage in SC concrete floors is a reduction of about 80 percent in floor joint length. This is accomplished by spreading the joints to about 100′ x 100′ – instead of the more common 20′ x 20′ spacing of conventional concrete mix. Conventional concrete joint spacing is limited by the shrinkage of the concrete after placement. SC concrete first expands – then it shrinks back just slightly smaller than it started. Thus it translates to less tension than conventional concrete. This facilitates increased joint spacing in SC projects.

Most owners have not heard of SC concrete because it is a specialty. And although they may have heard of hardened floors, they don’t understand SC concrete’s important benefits. These include reduced floor joint maintenance, reduced wheel maintenance on rolling stock and reduced wear on the floor. That’s because SC eliminates spalled concrete, which turns into a grinding compound embedded in a pallet jack’s plastic wheels.

One of the biggest areas of misunderstanding is that many owners think getting a floor hardened with trap rock is the same as SC concrete. In reality, SC and trap rock are simply different options. In any case, SC floors have special design and placement requirements that cannot be ignored.

ESI recommends owners pick a knowledgeable architect/engineer and floor contactor with a national reputation for SC trap rock floors.

By Steve King

Steve King is a regional vice president with more than 30 years of experience in the design and construction of millions of square feet of facilities for the foodservice industry.