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.
if the workbility is increase what effect come on mix design.
plz give me ans
if the increase of workalibity was because of adding water, the stregnth will affected . But if the workabilty increase by adding concrete additive such superplasticizer. generally no effect on the strength and also the mix design
Hi,
Either the cement quantity is increase in the ratio or the compresive strength of concrete is week in nature.
Rgds,
MAnoj
when increase the workability,the amount of water containing is increase.so that case,we can’t use that mould..if ane location need a more percentage of water,so we can use increased workability mould.
what are the factor that influence concrete slump test???
what does concrete consistency mean and why is it so important in determining workability???
what is the advantages and disadvantages of slump test????
what is the exact dry volume of mix proportion for slump test?
do the slum give result to us diffrent for diffrent grade
normally concrete grade not related to slump with latest technology…we still can get a same grade concreet with diffrent slump/flow…as long as the concrete remain homogeneoes
Which is the latest IS code for Slump test And when published ?
How we can measure the Slump of MSA 80mm ?
normally for msa 80..its very difficult to meausre the slump…normally use VB test ..
Hi,
After takeout slump mould during test, just put concrete mould inverted very near to the green concrete and measure the diference is call slump of concrete.
Rgds,
MAnoj
why we just stroke 25 times , not more than 25 , reason for that?
If we stroke more than 25 then, may be occurring bleeding of cement slurry. By 16 dia ms round bar and as per the concrete surface area in slump mould. The no’s of stroke 25 is enough for testing work ability of concrete.
if the value of slump is 65mm what is the nature of concrete , is it plastic or semi plastic?
At the time of test we get slump value 10 mm. pl. define it….. is it good for commerical Building const ….. or not.
The slump is to low. So the workability become difficult. So avoid this.
Dear Sir, I am the student od Maldives National University, i’m doing Civil engineering, and its my first year. and i have few qs.
1-What are the consequences of inadequate compaction of concrete?
2-In your opinion, what could be the possible sources of errors while compacting
aggregate by these methods?
can you please help.
thanks.
Procedure and theory somewhat well, but missing most of the important parameters. Here some of the important parameters as per my view.
1. Initially at what ratio of Cement, Fine aggregate, Course aggregate and water we will start the test.
2. Up to which ration we will repeat the test frequently.
3. What are the desirable and acceptable value of slump test.
4. I think water quality is drinkable we need to use.(should not be more alkaline or acidic).
5. Mixing of concrete for test, it is small quantity that we need to carry out manually, so first we need to dry the course and fine aggregate to avoid optimum moisture content, After drying bring back to room temperature at least one to two hours and then only we will start mixing. First measure the ratio by weight which we need to carry out for test. Mix thoroughly fine and coarse aggregate. And mix with cement evenly in which cement should properly mixed. And finally add water which is calculated as per cement used (i.e: 40%, 50%, 60% etc.. of cement).
Finally come out with result with its interpretation.
By: Yadav Lal Bhattarai
Civil Engineering, Sharda University
as par IS1199 what is the exact value of workability
hello…
i just want to ask… as you have mentioned in this test procedure,,, what specific type of oil or grease can we use to apply at the walls of the mould??? will the application of grease affect the fresh concrete mixture basically with the outcome of slump test???
thanks.
sir i m sdo in defence housing authority karachi pakistan i want to know wall slabs & foundation actual slump.
what should be requirement of slump value for mass concrete.
can we use concrete after 3 hr by adding admixture in concrete to get workability?
Pls enlight me more on s/t.
What slump value of fresh concrete in slab,column and piers.?
if we knock the mixture with metal rod more than 25 times , then the mixture becomes stuff… slump will not collapse even for 0.9 % of w/c ….personal experiènce…:-D