The slump in concrete refers to a measure of its consistency and workability. It is a test used to assess the flow and deformation of freshly mixed concrete. The slump test involves filling a cone-shaped mold with concrete, compacting it, and then removing the mold to see how much the concrete slumps or settles.
The measurement is typically done in millimeters and can help determine if the concrete mix has the desired workability for a particular construction application. Different slump values are suitable for various construction needs, with higher slumps indicating more fluid or workable concrete and lower slumps indicating a stiffer or less workable mix.
Here are some common slump values and their typical applications:
1. True Slump (0-25 mm or 0-1 inch): This is a low slump value and indicates a very stiff or dry mix. It is suitable for applications like road pavements and precast concrete products.
2. Shear Slump (25-50 mm or 1-2 inches): A moderate slump value, often used for various construction projects where a balance between workability and strength is required, such as columns and beams.
3. Collapse Slump (50-175 mm or 2-7 inches): A high slump value, indicating a very fluid and workable mix. It is commonly used for applications like pumped concrete and heavily reinforced structures.
Concrete slump test is carry out at construction site to know about workability of fresh concrete, define the consistency of concrete, must be ideal for pouring, this test is very much famous worldwide for easy Apparatus and their procedure. This is basic and essential knowledge for civil engineers of doing slump test of concrete at construction site
Concrete slump or slump cone test is widely used because of the simplicity of apparatus required and the test procedure, the slump test is to determine the consistency of freshly concrete mix prepared at the laboratory or the construction site during the the progress of the work, not shows directly workability.
What is the slump in concrete
Regarding this, “what is the slump in concrete”, the slump in concrete is a field method that it measures the workability and consistency of concrete on construction site. This test is performed to test to check the consistency of freshly mixed concrete in specific batch and this test does not give direct measures of workability.
Concrete slump test standards, their appartus, procedure, result and types
Regarding this, what is concrete slump test, the slump test is simple test procedure which is gives satisfactory results for the concrete mix of medium to high workability, it has been widely used for workability tests since 1922, due to low cost and provides immediate result.
Basic facts according to ASTM-C125-93 the property determining the effort required to manipulate a freshly mixed quantity of concrete with minimum loss of homogeneity and according to ACI-116R-90(ACI1990)-: the property of of freshly mixed concrete which determine the easy and homogineity with which it can be mixed placed consolidated and finished.
Here we going to two standard laboratory test which flows the specific guideline code book provide is ASTM C143 in the U.S.A, IS 1199 1959 in india and EN 12350-2 in Europe.
Apparatus for concrete slump test
Apparatus for concrete slump test are following:-
1. Slump cone or mould with top diameter 100mm, bottom diameter 200mm and height of 300mm
2. Standard tamping rod with diameter 16mm and length 60cm.
3. Nonporous base plate
4. Measuring scale
Procedure of concrete slump test
Procedure of concrete slump test- concrete slump test is very simple to procedure:-
1. First fill in the inner surface of the empty mould and then apply oil to it.
2. Set the mould on a horizontal non porous base plate
3. Fill the slump cone with concrete in 4 approx equal layer
4. Compact each layer with 25 stroke by standard temping road
5. Remove the the excess concrete and level the top
6. Clean the water leaved between base plate and mould
7. Raise the mould from concrete immediately and slowly remove it completely
8. Measures the difference between height of the slump cone and the height of the specimen being slump value.
Types of slump in concrete
Regarding this, types of slump in concrete test- initially slump cone raised, then its sample shape depend to water cement ratio, due to fact that slump of test considered collapse, shear type of slump, true slump and zero slump.
What is the true slump value?
Regarding this, what is the true slump value?, this type of slump represent medium workable concrete, concrete mix after the test when slumps evenly all around without desintegration is called the true slump, generally the true slump value of concrete slump test is lies between 25 – 50 mm or 1 – 2 inches.
What is a zero slump concrete?
Regarding this, “what is a zero slump concrete?, zero-slump concrete is the defined as concrete mix for very stiff or dry mixes consistency or workability which is performing no slump value after removal of the mould is known as zero slump concrete.
Zero slump concrete represent very low water cement ratio and low workable concrete, It is also known as no slump concrete, it is used for road construction.
What is shear slump?
Regarding this, what is shear slump?, shear slump is not good slump for work, it can be define as highly workable concrete mixe due to high ratio of water to cement that’s cause bleeding and segregation and it is undesirable and unsuitable for concrete work that provide less durability.
What is collapse slump?
Regarding this, what is collapse slump?, concrete mix is too wet and harse and clean generally caused due to compaction is not done properly, irregular stroke given by tamping rod to one side.
What is a good slump for concrete
Regarding this, what is a good slump for concrete?, consistency and workability of concrete mixtures is measured by slump, it is test on construction site and laboratory, good slump for concrete is suitable for concrete of medium to high workability have slump value 25 mm to 125 mm, as the value of slump increases, the wetter the concrete mix, slump value 100 mm (4inch) is good for pumping and normal weight concrete.
What is workability in concrete
Workability means workable concrete that can be easily placed, poured and compaction without segregation and bleeding, relatively its provides enough strength and long durability for concrete structure, workability is relevant to water cement ratio, workability increases as water cement ratio increases and strength decreases.
Factors affecting workability are following:-
1. Water content:- the higher the water content per cubic meter of concrete, the higher will be the workability.
2. Aggregate/cement ratio- higher the aggregate/cement ratio, the leaner the concrete and lower the workability, lower aggregate/cement ratio gives better workability.
3. Size of aggregate- the bigger the size of aggregate, higher will be the workability.
4. Shape of aggregate- rounded or cubical aggregate makes the strong concrete mix compared to angular, elongated or flaky aggregate.
5. Well graded aggregates with less wide content it gives higher workability
6. Admixures-admixtures may increases workability
Measurement of workability from slump test
Workability from slump test is measures by major scale, shear slump or collapse slump performance the test should be repeated, only true slump performed the result, classified result within some ranges according to the slump values.
● Very low workability:- their slump value is 0 – 25 mm
● Low workability:- their slump value is 25 – 50 mm
● Medium workability:- their slump value is 50 -100 mm
● High workability:- their slump value is 100 -175 mm
Concrete slump limit and their uses
Concrete slump limit is identified the low workability to high workability, in case of dry sample can be performed very low workability having slump range 0-25 mm (0-1 inch) are typically used in pavements or roads.
Low workability having slump range 25-50 mm are used in heavy mass construction, foundation with light reinforced.
Medium workability having slump range 50-100 mm (2-4 inch) are used in heavily reinforced section, beam, slab, column, pumped concrete, slip form work and high workability having slump range 100-150 mm(4-6 inch) are used in retaining walls and thin vertical member.
What is the purpose of a concrete slump test
What is the purpose of a concrete slump test? Concrete slump testing is most common method to determine the consistency or workability and widely used due to fact that the simplicity of apparatus reguired and the test procedure that can be performed in test on site and laboratories.
As the value of slump increases, the value of compacting factor also increases, identified the low to high slump value of concrete.
Advantages of slump in concrete test
Advantages of slump in concrete- concrete slump test as simple and easy field method than any other workability, this test can be performed at the construction site as well as in the laboratory.
Limitations of concrete slump test
Concrete slump test is limited to concrete with the the maximum size of aggregate less than 40 mm, perform only for medium or high workability, the slump test does not show any diffeince of concrete of different work abilities.
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Slump value for concrete
Slump value for concrete is the the gap between top of slump cone and and subsided concrete, it measures the difference between height of the slump cone and height of the specimen wing tested is slump value and slump test recommended values of slumps for different concrete mixes are follows:-
1) Heavy mass construction:- 25- 50 mm
2) Pavements : – 20- 30 mm
3) Bridge decks:- 25- 75 mm
4) lightly reinforced:- 25- 75 mm
5) floors:- 25- 75 mm
6) canal lining:- 25- 75 mm
7) strip footings:- 25- 75 mm
8) Heavily reinforced sections:- 50-100 mm
9) Beams:-50- 100 mm
10) slabs:- 50-100 mm
11) column:-50-100 mm
12) Pumped concrete:-50-100 mm
13) slip form work:-50-100 mm
14) retaining walls:-75-150 mm
15) Thin vertical member:- 75-150 mm
What is the ideal value of slump
What is the ideal value of slump? Slump value of concrete is suitable for medium to high workability having slump value 25 mm to 125 mm, we consider two sample dry case and wet case, ideal value of slump will be 25-50 mm (1-2 inch) in case of dry sample and 150-175 mm (6-7inch) in case of wet sample.