Tests on concrete Concrete
This test is performed
to check the consistency of freshly made concrete. DeptThe slumpofCiviltest is
done to make sure a concrete mix is workable. The measured slump must be within
a set range, or tolerance, from the target slump.Workability of concrete is
mainly affected by consistency i.e. wetter mixes will be more workable than
drier mixes, but concrete of the same consistency may vary in workability.
It can also be defined as the
relative plasticity of freshly mixed concrete as indicative of its workability.
Tools and apparatus used for slump test
Standard slump cone (100 mm top diameter x 200 mm
bottom diameter x 300 mm high)
Bullet-nosed rod (600 mm long x 16 mm diameter)
Slump plate (500 mm x 500 mm)
Procedure of slump test for concrete:
v Clean the
cone. Dampen with water and place on the slump plate. The slump plate should be
clean, firm, level and non-absorbent. Collect a sample of concrete to perform
the slum test
firmly on the footpieces and fill 1/3 the volume of the cone with the sample.
Compact the concrete by 'rodding' 25 times. Rodding means to push a steel rod
in and out of the concrete to compact it into the cylinder, or slump cone.
Always rod in a definite pattern, working from outside into the middle.
v Now fill
to 2/3 and again rod 25 times, just into the top of the first layer.
v Fill to
overflowing, rodding again this time just into the top of the second layer. Top
up the cone till it overflows.
v Level off
the surface with the steel rod using a rolling action. Clean any concrete from
around the base and top of the cone, push down on the handles and step off the
lift the cone straight up making sure not to move the
sample. Turn the cone upside down and place the rod across the
Take several measurements and
report the average distance to the top of the sample.If the sample fails by
being outside the tolerance (ie the slump is too high or too low), another must
If this also fails the remainder of the batch should be
The compression test shows the
compressive strength of hardened concrete. The compression test shows the best
possible strength concrete can reach in perfect conditions. The compression
test measures concrete strength in the hardened state. Testing should always
be done carefully. Wrong test results
can be costly.
The testing is done in a
laboratory off-site. The only work done on-site is to make a concrete cylinder
for the compression test.
The strength is measured in Megapascals
(MPa) and is commonly specified as a characteristic strength of concrete
measured at 28 days after mixing. The compressive strength is a measure of the
to resist loads which tend to
Apparatus for compression test
Cylinders (100 mm diameter x 200
mm high or 150 mm diameter x 300 mm high) (The small cylinders are normally
used for most testing due to their lighter weight)
Bullet-nosed rod (600 mm x 16 mm)
Procedure for compression test of concrete
v Clean the
cylinder mould and coat the inside lightly with form oil, then place on a
clean, level and firm surface, ie the steel plate. Collect a sample.
v Fill 1/2
the volume of the mould with concrete then compact by rodding 25 times.
Cylinders may also be compacted by vibrating using a vibrating table.
v Fill the
cone to overflowing and rod 25 times into the top of the first layer, then top
up the mould till overflowing.
v Level off
the top with the steel float and clean any concrete from around the mould.
clearly tag the cylinder and put it in a cool dry place to set for at least 24
After the mould is removed the cylinder is sent
to the laboratory where it is cured and crushed to test compressive strength