01 Jul 97
Specifications for Bentonite Slurry
Supplied During Excavation
Not less than necessary to bore
Constant volume sample cup with lid connected to a balance
shaft and less than 70 lb/cu ft
gravity arm is filled with slurry so when placing the lid some
slurry is forced out of a hole in the lid. Tap the edge of the cup
to break up any entrained air or gas. Wipe excess slurry from
the cup and lid. Place the balance arm into the fulcrum and
move the rider on the balance arm to balance the assembly.
Read the specific gravity from the scale on the balance.
30 to 50 sec
Place a finger over the bottom chute of the funnel and fill the
funnel with slurry through a screen at the top of the funnel until
the slurry level reaches the bottom of the screen (1 quart
capacity). The slurry is allowed to flow from the funnel through
the chute and number of seconds required to drain the funnel
is recorded. Time measured is the viscosity.
0.03 psf to 0.2 psf (1.4 to 10
The initial strength is determined by filling a container about 3
inches in diameter to the bottom line on a scale with freely
agitated slurry. The scale is vertically mounted in the
container. A thin metal tube is lowered over the scale and
released. The tube is allowed to settle for 1 minute and the
shear strength recorded on the scale reading at the top of tube
. The 10-minute gel strength is determined in a similar
manner except that 10 minutes is allowed to pass before the
tube is lowered over the scale.
9.5 to 12
A pH electric meter of pH paper may be used.
2 % maximum by volume
A specified amount of slurry is mixed in a marked tube. The
content mixture is vigorously shaken, and all of it is then
poured through a No. 200 mesh screen so that sand
particles are retained on the screen. The sand particles are
washed into a marked tube by fitting the large end of a funnel
down over the top of the screen holder, then inverting the
screen and funnel assembly. The tip of the funnel is fitted into
the clear measuring tube and water sprayed from a wash
bottle on the screen. The percent volume of sand is read from
the marked measuring tube after the sand has settled.
Routine inspection with
(1) Routine inspection tests. The most common routine
nondestructive tests (NDT) using wave propagation shall be
NDT is to externally vibrate the drilled shaft by applying a
performed to check the quality of the installed drilled shafts.
sudden load as from a hammer or heavy weight dropped from a
Additional special tests as indicated in the following paragraphs
specified height. Signals from the wave are recorded by
are performed if defects are suspected in some drilled shafts.
Routine tests performed as part of the inspection procedure are
shaft or embedded in the concrete at some location in the
typically inexpensive and require little time. Special tests to
length of the shaft. Access tubes may also be installed in
determine defects, however, are often time consuming,
expensive, and performed only for unusual situations.
concrete between access tubes. Refer to FHWA-HI-88-042