Slump test of concrete for workability Complete procedure step by step – types, equipment reports, values with results

OBJECTIVES:

To calculate the value of slump test of concrete, and to know more about the workability, and fresh concrete.

INTRODUCTION:

The slump test of concrete is used vary often in concrete work. It is easily performed at a job site and is useful in detecting variations in mixes of given properties.

The slump test cone is placed on a smooth, level surface with the smaller opening at the top. It is filled in three layers of equal volume, each of, which is compacted 25 times with a standard rod having a hemispherical tip. The rod is then struck off, and the cone is slowly lifted and set beside the unsupported concrete. The rod is laid across the cone and a measure of the distance from the bottom of the rod to the average top of the concrete is taken. A vary stiff mix will have near zero slump. Lean mixes tend to be harsh and slumps can vary from true to shear in different sample of the same mixes.

The same slump can be recorded for concrete of different workability, depending on the aggregate Used. The slump test is not a true determination of workability, but it is a useful for on-site checks of variations in material or mixing
condition.

There are three main type of slump:

1. True slump.

2. Shear slump.

3. Collapse

 

 

STANDARDS

ASTM: C143

B.S: 1882 part 2

 

APPRATUS

            1. Slump mould.

2. Temping rod.

3. A several type of aggregate.

4. A Portland cements.

5. A clean water.

6. Trowel.

MATERIAL:

Cement, sand, aggregates, water

 Or mixed cement concrete (1:2:4)

PROCEDURE:

1.     Take cement, sand and coarse aggregate in required quantity. Mix it dry and add water measured quantity then mix concrete properly.

2.     Place cone on a steel plate (base plate) and prepared concrete is filled in 4 equal layers, each layer compacted by 25 blows of tamping rod.

3.     Top of cone is levelled by trowel.

4.     Remove cone with the help of stand carefully in vertically direction.

5.     Measure the settlement of concrete occurred and this is the slump.

OBSERVATION & CALCULATION

Cement concrete ratio =1:2:4

Water cement ratio= (0.5, 0.6, 0.7, 0.8)

Weight of cement =3kg

Weight of sand =6kg

Weight of coarse aggregate =12kg

Water=0.5×3=1.5 litres

 

WATER CEMENT RATIO	SLUMP VALUE
0.5 0.6 0.7 0.8	– – – –

 

 

RECOMMENDED SLUMP VALUE

S.NO	NAME OF WORKS	SLUMP VALUE IN mm
1	Concrete for roads and mass concrete	25 to 50
2	Concrete for RCC slabs and beams	50 to 100
3	Column and retaining wall	75 to 125
4	Mass concrete in foundation	25 to 50

 

PRECAUTION

1.      Clean the apparatus before use.

2.      The inside of mold should be free from moisture.

3.      Remove the mold in vertical direction, so that the concrete cone is not disturbed.