The Engineering Within The Foundation

Last week all of the 65 concrete piers were drilled and filled with cement.  After they hardened and were set, the dirt was again leveled and most of the piers were covered.  They will be exposed again in due time, but for now there are other preparations to be completed before the final slab is poured.

On top of each pier will eventually sit a metal plate and screw mechanism embedded in the slab.  That screw can be adjusted to raise or lower the slab in that area.

In order to strengthen the slab over each pier a network of steel cables and rebar will be fixed.  

To strengthen the edges of the slab, a footing will be dug and L-shaped steel rebar added.  The tensioning cables will exit the edge of the slab and will eventually be tightened and clamped in place.  One of the unique properties of concrete is that it gains strength when it is compressed.  Thus, by adding tension to the embedded cables, encased in plastic sleeves, the slab is placed is a state of continual compression.  This helps prevent the slab from cracking and also causes the entire slab to moved as one piece.  If ever the ground under the slab swells or shrinks because of changes in moisture content, the foundation should not be affected.

Here is some of the steel rebar and cables laying ready to be placed next week.