Site Visit #5: Slab-On-Grade

When I arrived on site there were two stages of concrete construction that I was able to observe. There were two buildings that had only had their slabs poured at this point so i was able to see thise along with the various protrusions for plubming and other utilities. The other stage I was able to see was the pouring of a concrete pad/footer for where the dumpster was to be.

The floor slab for whole building is done in one pour using concrete block as permanent formwork and temporary wood in some places, such as door openings. The same day concrete is poured, the control joints are cut and the next day sealant is sprayed. Some cracking was still observed, however the super said it wouldn’t matter. The porch slabs were poured separately. Plumbing is Integral with the slab.

Something I found especially interesting about thw concrete work was that there was no rebar or welded wire fabric used in the slabs. The concrete has reinforcing fibers made of glass instead. (See detailed photo) the dumpster slab that I watched being poured DID have WWF.

Under the slabs are footers which, in some cases, are up to 20 feet wide. 

In pouring the slab and footer, especially on the largest, 16- unit building they encountered issues in digging through VERY rocky soil. This was not expected and ended up costing an additional 100,000. This was either a problem with bad estimating or poor soil analysis.