Flow Cone Testing: ASTM C 939

[KBVT]

I am editing a specification section for Auger Cast Piles. I am unsure what flow cone test parameters I should be issuing to the contractor. The subsurface soils on the site are very poor, basically extremely soft silt & clays to a depth of 65-70 feet. We are using 16" diameter ACIP piles with 4000 psi grout, with depths in excess of 100 feet.

The base spec indicates a 21 second minimum requirement for the flow cone test, but the specialty subcontractor has already asked to relax the requirement to 16 sec. I am also unsure if the standard test is applicable or if the flow cone can be modified by removal of the 1/2" orifice allowing grout to pass through the 3/4" hole in the bottom of the cone. It would seem that the removal of the 1/2" orifice would allow the grout to flow out of the cone faster, decreasing the test time. I would appreciate any help. Thanks.

 

[vandede427]

you can't tamper/alter with the apparatus that the ASTM specifies.

 

[KBVT]

The 3/4" orifice does not appear directly in the standard but it is noted within the base UFGS 31 63 16 specification. Researching on the web also reveals that this is a common configuration. I can't tell when one configuration is more appropriate than the other.