The slump test of concrete helps determine the workability of new concrete. It is one of the most traditional methods applied to determine how easy it is to use concrete. The slump test of concrete method has been widely used since 1922 and is referred to as the slump cone test.
Revolutionizing slump testing with new technology
The workability of the freshly made concrete should be checked using the slump test of concrete test so that constructors can do placement easily. Apart from that, the slump test concrete indicates the ratio of water-cement and the properties of materials and mixture. Slump testing helps evaluate flowability of the concrete mixture. Larger the slump value means greater flowability of the concrete.
Slump tests can be conducted easily on-site to check whether the concrete mix has expected fluid properties. Slump test concrete can be used to measure the consistency of individual batches. Slump test of concrete is a simple and low-cost test prepared on-site during work.
Source: Pinterest
known about :Micro Concrete: All you need to know to build a house
Slump test: Factors that affect the slump test concrete
- Air content of concrete
- Mixing, batching, and transporting concrete
- Size of aggregate
- Temperature of concrete
- Techniques and sampling of concrete slump testing
- W/c ratio of concrete
- Cleanliness of aggregates
- Fineness of materials
- The moisture content of aggregates
See also: Types of concrete
Slump test: Various shapes of concrete slump
There are four types of concrete slump:
- Zero slump: The first one would be the zero slump that is formed if the shape of the concrete is exactly as that of the shape of the mould, and this would indicate a rigid and consistent shape that would not be possible to work.
- True slump: The second one would be a true slump which is formed when the concrete settles down very quickly, taking the shape of a mould. This type of slump is preferred.
- Shear slump: When a shear slump is formed, half of the cone slides down the inclined plane. If the concrete is shear, it indicates that the mix lacks cohesiveness. A shear slump might develop in case of a harsh mix. So one should take a fresh sample and repeat the test.
- Collapse slump: Finally, the collapse slump indicates a high water-cement ratio. If the mix is too wet or has high workability, it would indicate a collapse slump.
Slump test: Apparatus used
The following are the pieces of equipment used for the slump test concrete:
Source: Pinterest
- A slump cone with a diameter of 20 cm at the base, 10 cm at the top, and a height of 30 cm.
- A base plate with clamps is used to attach the foot parts.
- The base plate with a lifting handle for convenient transporting.
- A graded steel road with a diameter of 16 mm and 600 mm length is also available that is rounded at one end and graduated in mm.
See also: Types of building materials
Understanding the science behind slump testing in construction
- One should acquire a sample of the concrete mix if the slump test concrete is to be conducted on the ground.
- Concretes containing aggregates that have a maximum size of 38 mm or larger are required for wet sieving.
- It should be ensured that the mould’s inner surface is cleaned thoroughly and is clear of excess moisture and set concrete.
- The mould should be placed on a metal plate that is flat, levelled, horizontal, stiff, and non-absorbent. It should be ensured that the mould is firmly in its place while it’s filled with the material that would be used.
- All the layers should not be filled in the mould. Only one-fourth of the height mould should be filled.
- There should be at least twenty-five strokes of the tamping rod on each layer.
- To form an extent across the whole cross-section that would be uniform, the second and subsequent layers must penetrate through all three layers. After this, the layer must be tamped down to the bottom.
- As far as the top layer is concerned, the concrete must be levelled with a towel or taping rod to ensure that the mould is filled.
- The tamping rod is screed and rolled to remove the concrete surface only after the upper surface has been rodded.
- If you notice spilling between the base and the mould, then you need to wipe this out immediately.
- While removing the mould, it should be raised vertically, gently and cautiously.
- If you measure the difference between the mould’s height as well as the test specimen’s peak height, then you can assess the concrete.
- The area where the sample would be taken should be free of vibration or stress.
Slump test: Size of slump cone
The top, as well as bottom ends of the cone are open. The cone’s base diameter is generally larger than the top diameter. If we speak about the standard size, then the internal top diameter of the cone is 3.9 inches, around 100 mm, and the bottom diameter of the cone is 7.9 inches, around 200 mm.
The height of the cone is around 12 inches, around 305mm. The metal tamping road has a diameter of 16 mm and a length of 600 mm long with a bullet nose. The surface of the whole apparatus should be dry and clean.
All about :Why is compaction factor test vital for construction?
Improving concrete quality with accurate slump testing
- The slump test concrete is used to ensure the uniformity of the different batches of similar concrete under field conditions and to ascertain the effects of plasticisers.
- The slump test concrete is used to know the day-to-day or hour-to-hour variations of the materials being fed to the mixer.
- An increase in the slump would also mean an unexpected increase in aggregate moisture content.
- If the slump is too high or low, it gives an immediate warning and enables the mixer operator to remedy the situation.
- As the slump test concrete has varied applicability and is extremely simple, it is widely used.
FAQs
Why is a slump cone test done?
A slump cone test is done to check the workability of the freshly created concrete and the ease with which the concrete flows.
What are the constraints of the slump test?
Some of the limitations of the slump test are listed below: There is no correlation between workability and slump value. Only plastic mixes can cause a slump, and dry mixes cannot cause a slump. Aggregates that have a larger size than 40 mm are not suited for concrete. There is a wide range of possibilities, and it is tough to determine the value that would be the proper one.
