Concrete slump test is to determine the workability or consistency of concrete mix prepared at the laboratory or the construction site during the progress of the work. Concrete slump test is carried out from batch to batch to check the uniform quality of concrete during construction.
In this post, we will learn about types of slump or type of slump. We included a video i.e. helpful to understand slump test video and will fetch slump test report after completing the slump test procedure. We will also know about slump test lab report, including slump test for workability of concrete. In we will take or start slump test discussion in the comment section if you need any guidance or query than you can post a comment. The slump test concrete and slump test conclusion in clearly explained in slump cone test video. You can pause the video and learn concrete slump test steps. We also shared a link to concrete slump test results which includes concrete slump test report, concrete slump test lab report prepared on concrete slump test which is the conclusion of slump test.
Definition for Concrete Slump Test
- The slump is a measurement of concrete’s workability or fluidity.
- It’s an indirect measurement of concrete consistency or stiffness.
A slump test is a method used to determine the consistency of concrete. The consistency, or stiffness, indicates how much water has been used in the mix. The stiffness of the concrete mix should be matched to the requirements for the finished product quality.
Concrete slump test procedure Video
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Standard Test Method for Slump of Hydraulic-Cement Concrete.
This is a test required to pass the American Concrete Institute (ACI) Field Technician Certification Program — “Concrete Field Testing Technician—Grade I.” A Concrete Field Testing Technician—Grade I is an individual who has demonstrated the knowledge and ability to properly perform and record the results of seven basic field tests on freshly mixed concrete.
Concrete Slump Test
The concrete slump test is used for the measurement of a property of fresh concrete. The test is an empirical test that measures the workability of fresh concrete. More specifically, it measures consistency between batches. The test is popular due to the simplicity of apparatus used and simple procedure.
Principle of Concrete Slump Test
The slump test result is a measure of the behavior of a compacted inverted cone of concrete under the action of gravity. It measures the consistency or the wetness of concrete.
Apparatus used in Concrete Slump Test
- Slump cone,
- Scale for measurement,
- Temping rod (steel)
The procedure of Concrete Slump test:
- The mold for the slump test at is a frustum of a cone, 300 mm (12 in) of height. The base is 200 mm (8in) in diameter and it has a smaller opening at the top of 100 mm (4 in).
- The base is placed on a smooth surface, and the container is filled with concrete in three layers, whose workability is to be tested.
- Each layer is tempted 25 times with a standard 16 mm (5/8 in) diameter steel rod, rounded at the end.
- When the mold is filled with concrete, the top surface is struck off (leveled with mold top opening) using screening and rolling motion of the tamping rod.
- The mold must be firmly held against its base during the entire operation so that it could not move due to the pouring of concrete and this can be done using handles or foot – rests brazed to the mold.
- Immediately after filling is completed and the concrete is leveled, the cone is slowly and carefully lifted vertically, an unsupported concrete will now slump.
- The decrease in the height of the center of the slumped concrete is called a slump.
- The slump is measured by placing the cone just beside the slumped concrete, and the temping rod is placed over the cone so that it should also come over the area of slumped concrete.
- The decrease in the height of concrete to that of mold is noted with scale. (usually measured to the nearest 5 mm (1/4 in).
Precautions in Concrete Slump Test
In order to reduce the influence on slump of the variation in the surface friction, the inside of the mould and its base should be moistened at the beginning of every test, and prior to lifting of the mould the area immediately around the base of the cone should be cleaned from concrete which may have dropped accidentally.
Types Of Slump
The slumped concrete takes various shapes, and according to the profile of slumped concrete, the slump is termed as;
- Collapse Slump
- Shear Slump
- True Slump
In a collapse slump, the concrete collapses completely. A collapse slump will mean that the mix is too wet or that it is a high workability mix, for which slump test is not appropriate.
In a shear slump, the top portion of the concrete shears off and slips sideways. OR
If one-half of the cone slides down an inclined plane, the slump is said to be a shear slump.
- If a shear or collapse slump is achieved, a fresh sample should be taken, and the test is repeated.
- If the shear slump persists, as may the case with harsh mixes, this is an indication of lack of cohesion of the mix.
In a true slump, the concrete simply subsides, keeping more or less to shape
- This is the only slump which is used in various tests.
- Mixes of stiff consistency , have a Zero slump so that in the rather dry range no variation can be detected between mixes of different workability.
However , in a lean mix with a tendency to harshness, a true slump can easily change to the shear slump type or even to collapse, and widely different values of slump can be obtained in different samples from the same mix; thus, the slump test is unreliable for lean mixes.