The basement floor has concrete! Everyday the Kravis Center looks closer to what we’re used to seeing in a parking garage. In this blog, we’re going to learn about the work that goes into that concrete on the ground, known as “slab on grade” or S.O.G.
Once the underground electrical and plumbing work was completed, the sub-grade was prepped with 2” of sand and a 15 millimeters vapor barrier. This Stego Wrap is covered by another 2” of sand. In order to have electricity to the building, some electrical conduit is run from underground, through the sand, vapor barrier and concrete.
Once the sub-grade is done, rebar is laid. There is one layer of rebar which is designed in a cross pattern about 18” apart. The slab also has fiber mesh, which are strands of plastic mixed in the concrete at the batch plant. The rebar serves to strengthen the concrete, as we’ve mentioned in the blog before. The fiber mesh helps prevent cracking. The slab poured in our basement is 5” thick.
The first pour was 15,000 square feet (s.f.) and 330 cubic yards (c.y.); the second pour was 20,000 s.f. and 420 c.y. of concrete. The videos below show concrete being poured. You’ll see there is a self-propelled laser screed machine being used in the video. This is necessary to vibrate the concrete in order to ensure the concrete consolidates around the rebar. The screed also levels the concrete (you will see is moving across the surface of the poured concrete).
Finally, the slab was finished with a swirl pattern in order to provide traction to vehicles. Otherwise, if this weren’t done, it would become slippery when wet.
