SLUMP TEST Introduction The slump test is perhaps the most widely used because of the simplicity of the apparatus required and the test procedure. The slump test indicates the behavior of a compacted concrete cone under the action of gravitational forces. The slump test is a practical means of measuring the workability. Changes in the value of slump obtained during a job may indicate changes in materials, in the water content or in the proportions of the mix, so it is useful in controlling the quality of the concrete produced. The test carried out with a mould called the slump cone. The slump cone is placed on a horizontal and non- absorbent surface and filled in three equal layers of fresh concrete, each layer being tamped 25 times with a standard tamping rod. The top layer is struck off level and the mould is lifted vertically without disturbing the concrete cone. The subsidence of concrete in millimeters is termed the slump. After the test, slumps evenly all around is called true slump. In the case of very lean concrete, one half of the cone may slide down the other which called a shear slump or it may collapse in case of very wet concretes. The slump test
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SLUMP TEST
Introduction
The slump test is perhaps the most widely used because of the simplicity
of the apparatus required and the test procedure. The slump test indicates the
behavior of a compacted concrete cone under the action of gravitational forces.
The slump test is a practical means of measuring the workability. Changes in the
value of slump obtained during a job may indicate changes in materials, in the
water content or in the proportions of the mix, so it is useful in controlling the
quality of the concrete produced.
The test carried out with a mould called the slump cone. The slump cone
is placed on a horizontal and non-absorbent surface and filled in three equal
layers of fresh concrete, each layer being tamped 25 times with a standard
tamping rod. The top layer is struck off level and the mould is lifted vertically
without disturbing the concrete cone. The subsidence of concrete in millimeters is
termed the slump. After the test, slumps evenly all around is called true slump.
In the case of very lean concrete, one half of the cone may slide down the
other which called a shear slump or it may collapse in case of very wet
concretes. The slump test is essentially a measure of consistency or the wetness
of the mix.
Objective
To find a workability of the specimen.
To find a consistence of the specimen.
Apparatus
1. Tamping rod - straight bar of circular cross section, 16 mm diameter,
600mm long with both end hemispherical.
2. Inspection Scale - Machine steel, 0-10 cm slump measurement, 1 cm
increment.
3. Base Plate - Steel sheet, carrying handle, 600 x 600 x 5 mm
4. Sampling tray - 1.2 x 1.2 x 50mm deep made from minimum 1.6mm thick
non-corrodible metal.
5. Scoop - Cast alumunium approximately 100mm wide.
6. Trowel - Pointed type
7. Brush - Steel wire
8. Specimen
9. Cone - Made of metal not readily attacked by
cement paste with the following internal
dimensions:
diameter of base 200 ± 2mm
diameter of top: 100 ± 2mm
height 300 ± 2mm
Cone Tamping rod
Procedure
1. Filled mold in three equal layers.
2. Each layer is rodded 25 times to settle the concrete, before the next layer
is added.
3. Full mold is ready to be pulled off to measure slump.
4. Remove the cone from the concrete by raising it vertically, slowly and
carefully, in 5 to 10 seconds.
5. Partial mix being revealed by removal of mold.
6. Immediately after the cone is removed, measure the slump to the nearest
5mm by using the rule to determine the height of the cone and of the
highest point of the specimen being tested
Result
Quantities Cement (kg) Water(kg or litres)
Fine aggregate
(kg)
Coarse aggregate
(kg) – 20 mm size
Per trial mix of 0.0135 m³
4.8 2.8 9.4 15.4
The result of slump test by using the above amount of cement, water, fine
aggregate and coarse aggregate was 10.5 cm collapse slump.
Discussion
We must reduce water content in the concrete for avoid shear failure.
However, the slump test has been found to be useful in ensuring the uniformity
among different batches of supposedly similar concrete under field conditions.
Conclusion
Slump result was 105mm but shear failure which mean collapse. Hence the
concrete is non-acceptable. This happened because there a lot of water content
in the concrete and look wetly during the test. It seems that it is because of one
of our member mistake, which put the water, more than 2.8 liters.
Water content in the concrete, mean higher the workability but lower the
strength. If the cement content higher, the workability also become higher. The
good mix particles, particle shape and size are cubical or rounded, the workability
also become high. We concluded that our specimen is a high workability but
shear failure which mean lateral collapse.
COMPRESSIVE STRENGTH OF CONCRETE CORES
Introduction
There are some methods to assess the quality of hardened concrete from
properties of concrete at early age. The compressive strength testing technique
is one of the available methods to evaluate the properties. It is a destructive test
on sample and a easy technique compared with some other test. The accuracy
and prediction of this technique has been satisfactory.
Objectives
The aim of this work was to establish a general and direct relationship
between the compressive strength and its property behaviour regardless of the
differences in mix proportions and age of concretes.
This method describes the procedure for making and curing compression
test specimens from fresh concrete and for determining the compressive
strength of the specimens.
Apparatus
1) Molds – 150mm X 150mm X 150mm. Molds shall be water tight and
the base plate or bottom
2) Tamping Rod - a round straight steel rod 16 mm in diameter and 600 mm
in length.
3) Sampling Equipment - scoop or shovel, trowel,
4) Curing Equipment - a moist storage cabinet or room capable of
maintaining specimens at a temperature within ± 1 degrees of 23 ◦C
5) Compression testing machine complying with BS 1881: Part 115.
Sampling Equipment Compression testing machine Molds – 150mm X 150mm X 150mm
Procedure
1) Place the mold on a firm, level surface.
2) Form the test sample by placing concrete in the mold in three layers of
approximately equal volume.
3) Move the scoop around the top edge of the mold to ensure a symmetrical
distribution of the concrete within the mold.
4) Rod each layer with 25 strokes of the tamping rod. For layers 2 and 3, the
rod shall penetrate about 25 mm into the underlying layer.
5) Distribute the strokes uniformly over the cross-section of the mold.
6) Close the voids left by the tamping rod by lightly tapping the sides of the
mold.
7) After the top layer has been rodded, the surface will be struck off with a
trowel and covered with saran wrap to prevent evaporation.
8) Store the specimen undisturbed for 24 hours in such a way as to prevent
moisture loss and to maintain the specimen within a temperature range of
15oC to 27oC.
9) Remove the test specimen from the mold between 20 and 48 hours and
transfer carefully to the place of curing and testing. If molds are being
shipped it is permissible to leave specimen in cardboard mold during