What Is Self Compact Concrete?
Making concrete structures without vibration has been done in the past. For example, the placement of concrete under-water is done by the use of tremie without vibration.
Shaft concrete and mass concrete may be successfully placed without vibration. But the above examples of concrete are normally of lower strength and difficult to obtain consistent quality. Modern application of SCC (self-compacting concrete)Â is focussed on high performance, better and more reliable, and uniform quality.
List of Test Methods for Workability Properties of Self Compacting Concrete (SCC).
- Slump flow by Abrams cone.
- T50 cm Slump flow
- J-ring
- V-funnel
- V-funnel at T5Â minutes
- L-box
- U-box
- Fill-box
- GTM Screen Stability Test
- Ouimet
In this article, we are discussion & Procedure Slump Flow Test Â
Slump Flow Test.
What Is Slump Flow Test?
The slump flow test is done to assess horizontal flow of concrete at the absence of obstructions. It is the most commonly used test and gives a good assessment of filling ability. It may be used at the site. The test also indicates the resistance to segregation.
Equipment for Slump Flow Test
Slump ConeÂ
The usual slump cone having a base diameter of 200 mm, top dia. 100mm, and height 300mm are used.
Base Plate For Slump Flow test
A stiff base plate square in shape is having at least a 700 mm side. Concentric circles are marked around the center point where the slump cone is to place. A firm circle is drawn at 500 mm diameter
A trowel
This tool is used to place cement mortar.
Scoop
This use in QC department for the material.
Measuring tape
To measure the length.
Stopwatch
Use for time record
Procedure of Slump Flow Test
- About 6 liters of concrete is needed for this test.
- Place the baseplate on level ground.
- Keep the slump cone centrally on the base plate.
- Fill the cone with the scoop.
- Do not tamp.
- Simply strike off the concrete level with the trowel.
- Remove the surplus concrete lying on-base place.
- Raise the cone vertically and allow the concrete to flow freely.
- Measure the final diameter of the concrete in two perpendicular directions and calculate the average of the two diameters.
- This is the slump flow in mm.
- Note that there is no water or cement paste or mortar without coarse aggregate is seen at the edge of the spread concrete.
Calculations of Slump Flow Test
Largest diameter of slump flow (dm) = _______ mm
Diameter perpendicular to largest diameter (dr) = _______ mm
Slump flow = (dm+dr) /1
Results of Slump Flow Test
The slump flow of Self compacting concrete is _______ mm
Interpretation of Slump Flow Test
The higher the flow value, the greater its ability to fill formwork under its own weight.
A value of at least 650 mm is required for SCC (Self Compact Concrete). In case of severe segregation, most coarse aggregate will remain in the center of the pool of concrete and mortar and paste at the periphery of concrete.
T50 Slump Flow Test
The procedure for this test is same as for slump flow test. When the slump cone is lifted, start the stopwatch and find the time taken for the concrete to reach a 500 mm mark.
This time is called T50 time. This is an indication of the rate of spread of concrete. A lower time indicates greater flowability. It is suggested that T50 time may be 2 to 5 secs.
FAQs about Self-Compacting Concrete (SCC)
What is self-compacting concrete (SCC)?
Self-compacting concrete (SCC) is a highly flowable type of concrete that spreads into place, fills formwork, and encapsulates reinforcement without the need for mechanical vibration.
What are the advantages of using SCC?
SCC offers several advantages, including improved workability, reduced labor costs (due to elimination of vibration), better surface finishes, and enhanced structural integrity due to reduced segregation.
How is the workability of SCC tested?
The workability of SCC is primarily assessed using tests such as the slump flow test, T50 time test, J-ring test, V-funnel test, L-box test, and others. These tests evaluate the flowability, passing ability, and resistance to segregation of SCC.
What is the slump flow test and how is it conducted?
The slump flow test measures the horizontal flow of SCC when it spreads under its own weight. It involves filling a slump cone with SCC, allowing it to flow freely, and measuring the diameter of the concrete spread. A higher value indicates better flowability.
What is the significance of T50 time in SCC testing?
T50 time refers to the time taken for the SCC to spread to a diameter of 500 mm after the slump cone is lifted. A lower T50 time indicates faster flowability and better performance of SCC in filling formwork.
What are the typical results of the slump flow test for SCC?
A slump flow of at least 650 mm is generally desirable for SCC, indicating its ability to flow and fill formwork effectively without segregation.
How does SCC prevent segregation during placement?
SCC contains special additives that enhance cohesion and reduce bleeding, ensuring that coarse aggregates remain uniformly distributed throughout the concrete mixture without settling or separating.
Can SCC be used in all types of concrete applications?
SCC is suitable for a wide range of applications, including heavily reinforced structures, precast elements, and structures with complex geometries where traditional concrete placement methods may be challenging.
What are the key considerations when using SCC on construction sites?
It is essential to ensure proper mix design, quality control of materials, and adherence to testing protocols to achieve the desired performance and durability of SCC in various construction applications.
How does SCC contribute to sustainable construction practices?
SCC can contribute to sustainable practices by reducing noise pollution (due to elimination of vibration), optimizing material usage, and improving construction efficiency, thereby lowering overall environmental impact.
