Slump Test – Definition, Standard, Measurement Of Workability and Method
Definition of slump test for concrete: Concrete slump test is conducted on-the-spot to find out the uniformity and workability of fresh concrete. This test is important to check the quality of concrete instantly in construction site in short span.
Concrete Slump Test International Standard: There are different types of international codes to provide definite testing standards for concrete slump test. These standards identify methods, equipment for finding out the uniformity of fresh concrete through slump test. It is necessary to conduct the slump test with adherence to these standards. The standards for concrete slump test are given below.
• American Society for Testing and Materials (ASTM): ASTM slump test standards are ASTM C 143, ASTM C143M.
• The American Association of State Highway and Transportation Officials (AASHTO): AASHTO slump test standards are AASHTO T119, AASHTO BS1881.
• British & European standard: British & European slump test standard is BS EN 12350-2.
• Indian standard: IS 1199 – 1959
Concrete Slump Test Equipment:
• Different types of equipments are used to conduct the slump test. The test equipment should abide by the above standards. The commonly used equipments are Mould, Base plate, Tamping rod, Tape measure etc.
Method of Concrete Slump Test:
• Initially, the inside surface of the mould should be cleansed properly. Oil can be used on the surface.
• After that, the mould is arranged on a clean, smooth, horizontal and non-porous base plate.
• The mould is then stuffed with fresh concrete in three layers. By applying a steel rod with dia 5/8 inches, each layer is tamped 25 times. The rod is rounded at the ends. The tamping should be performed consistently.
• As soon as the mould is filled, extra concrete should be eliminated and the surface should be leveled. Once the mould is filled with fresh concrete, the base of the mould is retained tightly with handles.
• After that the mould is upraised slowly in the vertical direction and then unsupported concrete will slump. The reduction in height at the centre point is calculated to nearest 5mm or 0.25 inch and it is called ‘slump’.
Measurement of workability from Slump Test: If shear slump or collapsing of slump happens, the test should be reiterated. The slump test should be perfect to obtain the accurate result. The result can be categorized based on the slump value.
1. Very low workability: slump value 0-25mm or 0-1 inch
2. Low workability: slump value 25-50mm or 1-2 inch
3. Medium workability: slump value 50-100mm or 2-4 inch
4. High workability: slump value 100-175mm or 4-7 inch
According to 'Fresh Concrete' by P. Bartos, slump results are categorized as follow :
1. No slump: slump value 0 mm or 0 inch
2. Very Low: sump value 5-10 mm or 0.25-0.5 inch
3. Low: sump value 15-30 mm or 0.75-1.25 inch
4. Medium: sump value 35-75 mm or 1.5-3 inch
5. High: sump value 80-155 mm or 3.25-6 inch
6. Very High: sump vaue180 mm or 6.25 inch to collapse
On the basis of European Standard ENV 206: 1992, workability is divided in 4 categories of S1, S2, S3 and S4. Slump ranges are:
• S1: 10-40 mm
• S2: 50-90 mm
• S3: 100-150 mm
• S4: more than 160 mm
The low slump value specifies less workability and high sump value specifies high workability.