Slab on Ground Concrete

The 5” thick slab on ground for the Yuma Federal Courthouse expansion posed a considerable number of construction issues for the engineers, designers, concrete supplier, and contractors.  For a variety of reasons, measures to reduce shrinkage and the resulting cracking were paramount in many construction areas.  With day-time temperatures reaching 100 degrees F in windy conditions, pours were adjusted to a night-time schedule requiring three all-night placements.  

The slab also contained myriad areas of cut-outs, slab protrusions for water and electrical conduits, and many slab interruptions for walls, small rooms, and offices.  The 3,500 psi concrete design was also optimized to reduce the tendency for shrinkage by increasing coarse aggregate size and using a relatively low cement content, thereby maintaining a low W/C ratio.  One of the key shrinkage-reducing measures was the use of a high dosage of macrosynthetic fiber reinforcement in lieu of conventional temperature-steel reinforcement, which offered a uniform three-dimensional non-corrosive way to reduce cracking.  

FORTA-FERRO® macro fiber was used at a dosage of 7.0 lbs/cu yd in approximately 30,000 square feet of floorslab, requiring over 450 cubic yards of concrete.  In addition, FORTA-FERRO® was used successfully in 1,300 square feet of slab on metal deck construction, and dramatically reduced cracking found in other similar deck placements that had been placed previously.  Even at the high dosages, the macro fiber mixed, distributed, pumped and finished extremely well throughout, offering a cost-effective and labor-free alternate to conventional temperature reinforcement.  

Project Details:

Owner:  United States Federal Courthouse, Yuma, AZ

Design & Construction Manager:  General Services Administration, Design and Construction Division, Region 9, San Francisco, CA

Project Manager:  Abacus Project Management, Inc., Phoenix, AZ

Structural Engineer:  Caruso Turley Scott Inc., Tempe, AZ

Design/Build Contractor:  Sundt Construction, Tempe, AZ

Concrete Consultant:  Structural Services LLC, Atlanta, GA

Mix Design Consultant:  Geotechnical Testing Services Inc., Yuma, AZ

Ready-Mix Supplier:  BLT Ready Mix, Yuma, AZ

Pumping Contractor:  BLT Ready Mix, Yuma, AZ

Fiber:  FORTA-FERRO® macro-synthetic 2 ¼” @ 7.0 lbs/cu yd

For more information, please visit: www.forta-ferro.com