WORKABILITY
Slump test is used to determine the workability of fresh concrete. Slump test as per IS: 1199 – 1959 is followed.The apparatus used for doing slump test are Slump cone and Tamping rod.
Procedure to determine workability of fresh concrete by slump test.
i) The internal surface of the mould is thoroughly cleaned and applied with a light coat of oil.
ii) The mould is placed on a smooth, horizontal, rigid and nonabsorbent surface.
iii) The mould is then filled in four layers with freshly mixed concrete, each approximately to one-fourth of the height of the mould.
iv) Each layer is tamped 25 times by the rounded end of the tamping rod (strokes are distributed evenly over the cross section).
v) After the top layer is rodded, the concrete is struck off the level with a trowel.
vi) The mould is removed from the concrete immediately by raising it slowly in the vertical direction.
vii) The difference in level between the height of the mould and that of the highest point of the subsided concrete is measured.
viii) This difference in height in mm is the slump of the concrete.
Reporting of Results
The slump measured should be recorded in mm of subsidence of the specimen during the test. Any slump specimen, which collapses or shears off laterally gives incorrect result and if this occurs, the test should be repeated with another sample. If, in the repeat test also, the specimen shears, the slump should be measured and the fact that the specimen sheared, should be recorded.
Typical Questions
Ques 1. What is the ideal value of slump?
Answer 1 In case of a dry sample, slump will be in the range of 25-50 mm that is 1-2 inches. But in case of a wet concrete, the slump may vary from 150-175 mm or say 6-7 inches. So the value of slump is specifically mentioned along the mix design and thus it should be checked as per your location.
Slump depends on many factors like properties of concrete ingredients – aggregates etc. Also temperature has its effect on slump value. So all these parameters should be kept in mind when deciding the ideal slump
Ques 2. How does a superplasticizer effect the slump of concrete?
Answer 2 Value of Slump can be increased by the addition of chemical admixtures like mid-range or high-range water reducing agents (super-plasticizers) without changing the water/cement ratio.
Ques 3. How much time one should take to raise the cone?
Answer 3 Once the cone is filled and topped off [ excessive concrete from top is cleared ] raise the cone within 5-10 seconds.
Ques 4. What are the dimensions of the cone used in Slump Test?
Answer 3 The dimensions are
Top Diameter – 10cm
Bottom Diameter – 20cm
Height – 30cm
If you have a query, you can ask a question here.
what is the relationship between slump test & structural engineer
well if the concrete is too dry (not easy to vibrate).. add up to 19 litres OR 38 litres of water into the mixer truck (full 5 m3).
1. when to start curing the sample?
2. what is the relationship between a slump and water cement ratio?
3. what are the ratios of materials needed to do slump test in a typical mould?
i have to do a paper presentation about this topic can any one help me & give tips
what are the factors influencing workability of fresh concrete?
a)what is the equipment used in the slump test and compaction factor test?
b)what is the steps taken in preparing the test materials of slump test and compaction factor test?
c)what is the factor in determining the workability of slump test and compaction factor test?
slump means workability but workability means ? i.e. how much time we can keep our concrete at site before using?
what is the best water cemment ratio for the mix ratio 1:2:4..with 3kg cemment???
How much slump should maintain for the following grade of concrete
M15 :…….
M20 :…….
M25 :…….
M30 :…….
M35 :…….
M40 :…….
M50 :…….
whats the ideal range for slump of 36 cubic meters of concrete of floor with thickness of slab 30cm?
how i can design under ground septic tank (7.2m width and 10m length with 3.1m high)and furface of tank flush with surface level? please if there is any specific procedure thanks for advance
1-what is the best slump 10-30mm or slump 30-60 for workability?and why?
2-what is the best cement for concrete?why?
3-best zone of aggregate?why?
conclusion of workability of fresh concrete.
why is the test done and the frequency at which is done at site
a)why is the slump test suitable for site use?
b)wat r the limitation of slump test?
c)sketch the 3 main form of slump test?
d)will the addition of the measure water to a ready concrete mix gave the desired water/cement ratio??/
why is the slump test done and the frequency at which it is done at site?
How much slump should maintain for the following grade of concrete
M15 :…….
M20 :…….
M25 :…….
M30 :…….
M35 :…….
M40 :…….
M50 :…….
what is metarial test of murrum?
What are relationship among+slump, compaction factor and vb test in terms of results obtained.
The slump test is intended to get an idea of the flow behaviour, or rheology, of the mix. It is an empirical test, and doesn’t tell a lot about the state of the mix, though is useful for an indication of batch-to-batch variations. I would recommend using a purpose-designed workability test such as the CTPT” which is designed to measure the rheological behaviour of the mix. A probe of “standard” geometry is rotated in a sample of the mix at a range of controlled speeds, and the torque generated at each speed is recorded. A plot of speed vs torque gives a line characteristic of the flow properties.
Cement and Concrete mixes generally behave as “Bingham Fluids”, this is to say that they do not start to flow until a yield stress has been overcome, and then the torque is linearly related to speed; this allows the flow to be characterised by the slope of the line and the yield torque.
Work has shown that these parameters vary with water content, aggregate type and content, sand:cement ratio and so on.
Hope this helps
Roy