So today we were asked by a contractor to provide him a specification for Flowable Fill under some footings that were to have over excavation done below them. I’ve always assumed that Flowable Fill was just a general phrase used for a proprietary material.
Do any of you actually specify a design mix or do you just call out a minimum compressive strength?
Jeff: I would just call a local batch plant and ask for their specs for CDF (controlled density fill). These mixes are very flowable and should work well.
From my project notes:
TYPE OF CONST CEMENT MIN F’c MAX SIZE MAX AIR
TYPE AT 28 DAYS AGG SLUMP
(MPa) (in) (in) (%)
CLSM GUb 0.7 3/16 10 4-6
CLSM GUb 1 3/16 10 4-6
CLSM GUb 2 3/16 10 4-6
CLSM TRIAL MIX PROPORTIONS
MIN CEMENT 50 PCY
MIN FLY ASH (TYPE F) 150 PCY
FLYASH SHALL NOT HAVE A HIGH ALKALI (4.5% MAX), SULPHATE OR REACTIVE MATERIAL CONTENT
FINE AGGREGATE 2700 PCY TO ASTM C33
MAX WATER 290 PCY
CLSM SHALL BE FLOWABLE AND SHOULD NOT BE VIBRATED U/N
The tabular stuff has to be formatted using a non-proportional font.
Flowable fill is known by a variety of names. It’s official name is “Controlled Low Strength Material (CLSM)” and has both ACI and ASTM standards and recommendations.
Here is a link to a document put out by the National Ready Mix Concrete Association on the design of CLSM.