Several
test methods have been developed and together with visual inspection
are often
utilised to verify the performance of fresh SCC. However,
none of these
methods are standardised as yet, either nationally or
internationally.
Some
of these test methods include the Slump-flow test, Funnel test, U
Type
& Box Type tests, T50 Test, J-Ring
test, the Orimet test
and the GTM Screen Stability Test
Some
of these tests are described below:
a.The
Slump Flow Test:This
is
a test method for evaluating the flowability of SCC, where the
slump flow of
SCC with coarse aggregates having the maximum size of less than 40 mm
is
measured . The basic equipment is the same as for the
conventional slump
test. However, the concrete placed into the mold is not rodded. When
the slump
cone has been lifted and the sample has collapsed, the diameter of the
spread
is measured rather than the vertical distance of the collapse.
Slump
Flow Test. A
technician lifts the slump
cone and measures the diameter of the SCC
Spread: (Source: Vic roads: Geo Pave)
Slump
flows for an SCC mix
can range from 18 to more than 30 inches. Observations of the flow
should look
for no separation of grout from the mix, no fringe of water at the edge
or on
the surface, and an even distribution of aggregate in the
patty . The greater the slump flow, the higher the level of
"flowability" of the concrete.
b. Funnel
Test:A
test method for evaluating the material segregation resistance of SCC,
using a
funnel where the efflux time of SCC with coarse aggregates having the
maximum
size of less than 25 mm is measured.
V-Flow/funnel
test is the concrete
equivalent to the Marsh Funnel for grout testing. A V- shaped
box is made with a narrow opening at the bottom. (See photo on right
:Source-Concrete Monthly : March’04 issue) A
gate is fixed, at the bottom of
the box. The box is filled with concrete. The gate is opened and the
time for
the concrete to flow out of the box is measured. Low flow times
indicate a
lower plastic viscosity of the mix. This test provides a qualitative
assessment
of the SCC mix viscosity.
c.U-Type
and Box-Type Tests: These
are methods for testing flowability of SCC through an obstacle
with coarse aggregates having the maximum size of less than 25 mm. A
U-Box is a U-shaped box divided into two sections that are
separated by a door. (See
photo on right
:Source-Concrete Monthly : March’04 issue) One
side is filled with concrete
with the door in place. The other side has rebar placed in it of a
given size
and spacing. The door is removed and the concrete flows through the
rebar,
reaching an equilibrium height on the other side of the U-box. The
height of
the concrete is measured. This test measures the ability of the
concrete to
flow through rebar and fill a form. The higher the concrete flows on
the other
side of the U-box, the greater the ability of the concrete to flow
through
dense rebar and around corners in a form
Box
Type Filling Unit and
Flow Obstacle
d.T50
Test:A
test method for evaluating the material segregation resistance of SCC,
where
the 500-mm flow reach time is measured in the slump flow test above,
that is,
the time for the flow to reach 500 mm is measured in the slump flow
test. SCC
should give T50 = 2 - 5 seconds.
Concrete-Techgroup
expresses its gratitude to Mr
Larry Storer for permitting the use
of article “Self-compacting concrete: powerful tool for
complicated pours”
(written by Tim Avery in March’04 issue of CONCRETE
Monthly). Other
References: 1.“Development
of High-Strength Self-Compacting Concrete with reduced segregation
potential” by
Dr. R. Sri Ravindrarajah, D. Siladyi and
B. Adamopoulos 2.“Ultra
High Performance Self Compacting Concrete”
by
Jianxin Ma1 & Jorg Dietz1 3.Vic
roads: GEO PAVE : Technical Note on Self Compacting Concrete 4.
“Self-Compacting Concrete : Development, Applications and
Investigations” by
Masahiro Ouchi 5.
“Applications of Self-Compacting Concrete in Japan, Europe and the United States”: US
FHWA
