OPERATING INSTRUCTIONS
FOR
SLUMP TEST APPARATUS
CONTENTS :
EQUIPMENT
INTRODUCTION
DESCRIPTION
SAMPLING
a) FIELD
I From Mixers
II From concrete at the time and place of
deposition
III Mixing the composite sample
b)
LABORATORY
I Mixing
Concretes.
II Machine Mixing
III Hand Mixing
SETTING UP AND TEST PROCEDURE
MAINTENANCE
EQUIPMENTS : The
equipment comprises the following :-
1.
One Slump Cone
complete with two foot pieces and two lifting handles.
2.
One Base plate consisting of a plate with four cleats
two clamps with wing nuts and one swivel arm.
3.
One Tamping Rod.
4.
One copy of operating instructions.
INTRODUCTION : Slump Test
Apparatus is made according to IS : 1199-1959 and is for the determination of
the consistency of concrete where the nominal maximum size of the aggregate
does not exceed 38mm. The test can be
carried out either in the laboratory or during the progress of work in the
field.
DESCRIPTION : The
apparatus consists of the following:-
1.
SLUMP CONE : The Slump Cone is in the form of a
frustum of cone with two lifting handles to facilitate lifting the cone from
the moulded concrete test specimen. It
has two foot pieces.
2.
BASE PLATE : The base
plate has four cleats. One of the cleats
has a hole through which the tamping rod passes.
There are two
clamp with wing nuts to clamp the Slump Cone to the base. A swivel arm is fixed
to the base. It acts both as the handle
to carry the entire assembly and in raised position as datum from which point
the slump of concrete is measured.
3.
TAMPING ROD : Tamping
rod has one
end. It is graduated at 1cm
interval.
SAMPLING : FIELD - Take a truly representative
sample from the batch of the composite sample obtained from the freshly mixed
concrete making it 0.02m3 in column. When the continuous mixers are
used a batch shall be regarded as the discharge during one minute. In the case of concrete containing aggregate
of maximum size more than 38mm concrete shall be wet sieved through 40mm screen
to exclude aggregate particles bigger then 38mm.
i.
FROM MIXERS :
Take at least three approximately equal sample increment making 0.02m3
in the column from a batch during its discharge, by passing a clean and dry
receptacle, with retaining sides, across the stream of concrete. The receptacle is to be constructed of
non-absorbent material preferably of metal and is such that the sample retained
is not segregated. If only three sample
increments are desired, take them at about the time when one quarter, one half
and three quarters of the concrete have been discharges from the mixer and if
more than three are required, take them at correspondingly shorter but equally
spaced intervals.
ii.
FROM CONCRETE AT THE TIME AND PLACE OF DEPOSITON : Collect the sample from not less than five
well distributed positions, avoiding the edge of the mass where segregation
might have occurred, while a batch of concrete is being discharges or
immediately after it has been discharges, on the site.
iii.
MIXING THE COMPOSITE SAMPLE : Mix the
sample obtained by either of the methods described above on a non-absorbent
base either with a shovel or other suitable implement in such a manner as to
ensure as to ensure uniformly.
SAMPLING : LABORATORY - As the
accurate control of the quantities of material and test conditions is possible,
this test may preferably be carried out
in the laboratory. Take the
representative samples of all the concrete materials. Test sample of aggregate shall be taken from larger lots by
quartering.
i.
MIXING CONCRETE : Mix all the concrete materials either
by hand or in a laboratory batch mixer, in such a manner as to avoid loss of
water or other materials.
ii.
MACHINE MIXING : Where the mixing drum is charged by a
power loader, introduce water before the solid materials are added. Load the skip with about on-half of the
coarse aggregate, then with the fine aggregate, then with the cement and
finally with the remaining coarse aggregate on top. (If all in aggregate is
used, load the skip, first with the remaining aggregate on top). If the mixing drum is hand loaded it shall be
charged with dry materials in a similar manner and the drum and shall be
continued until the resulting concrete is uniform in appearance. When using pan mixer, the concrete shall be
heaped together before sampling.
iii.
HAND MIXING : Mix the concrete batch on a
non-absorbent platform, with a shawl, trowel or similar suitable implement
using the following procedure :-
a. Mix the
dry cement and dry fine aggregate until the mixture is thoroughly blended and
uniform colour.
b. Then add
the coarse aggregate and mix with cement and find aggregate until the coarse
aggregate is uniformly distributed throughout the batch.
c. Then add
water and mix the entire batch until the concrete appears to be homogenous.
Protect the
sample from the weather.
SETTING UP AND TEST PROCEDURE : Clean the
internal surface of the mould free from superfluous moisture and any set
concrete. Apply a thin coating of grease
to the internal surface of the slump cone base plate. Position the slump cone on the base plate
which is positioned on a level surface.
Clamp the slump cone to the base and
fill it with concrete in four equal layers, each layer being given 25 well
distributed strokes with the tamping rod.
While tamping the first layer, the rounded end of the tamping rod shall
reach the bottom and for the rest of the layers, it shall reach the preceding
layer. Level off the surface unclamp the
slump cone and immediately and slowly remove the cone vertically. The concrete subsides. Raise the swivel arm resetting against the
stop. Introduce the tamping rod
graduated end through the swivel a ram and tough the highest point on the
specimen. Take the reading on the
tamping rod which gives the slump in centimeters. This test shall be carried out at a place
free from vibration or shock and within a period of 2 minutes after sampling.
Any slump specimen which collapses or
shears off laterally will give an
incorrect result and if this occurs, the test shall be reported with another
sample. If with the repeat test the same
thing happens record it as such.
Some indication of the cohesiveness and
workability of the mix can be obtained, after the slump measurement has been
complete, the side of the concrete is tamped gently with the tamping rod, e.g.
a well proportioned concrete which has an appreciable slump will gradually
slump further, but if the mix has been badly proportioned it is likely to fall
apart.
MAINTENANCE : Soon after the test the inner surface of the
slump cone is to be thoroughly cleaned.
If any amount of concrete sticks to the inner surface it affects the
further tests.
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