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Re: Flowable Fill

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Title: Re: Flowable Fill

I just looked at the list for the first time in a while, so this may be old news, but up in Washington it is known as "CDF" for controlled density fill.  The Washington DOT specified mix design is:

Portland Cement 70 to 95 #/CY
Fine aggregate 3300 #/CY (3500 #/CY if Class C fly-ash used)
Air Entrainment: Manufacturer's maximum recommended dosage
Fly Ash Class F 300 #/CY (or 150#/CY Class C)
Water As required to produce a flowable consistency (10" maximum slump); not to exceed 300#/CY

We have used it in many places where the contractor would otherwise have to shore an excavation; it provides instant “compacted structural fill”.  The product can be excavated quite easily with a backhoe or Bobcat.  It can be trimmed with a shovel to a vertical edge where it is going to be used as one side of a form for concrete foundation.  We have used it in one project so support and stabilize an old half-rotted stone foundation under 35’ of 21” URM wall as excavation proceeded, and then came back later to dig it out and place the finished structure.

Bill Sherman:  2500 PSI as lean concrete?   I’m only 58, and I still remember when F’c = 2500 psi was the standard mix, 3000 was for significant horizontal spans, and 4000 was extra-high strength!


Kris P. Hamilton, PE
Geiger Engineers
114 W. Magnolia Street
Suite 505
Bellingham, WA  98225

Ph: 360 734 7194
Fx: 360 734 7399