What Is Self Compact Concrete | What Is U Box Test | Equipment U-Box Test | Procedure U-Box Test

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) is focussed on high performance, better and more reliable, and uniform quality.

Also, read: What Is Self Compact Concrete | What IsWhat is CBR Test in Civil | Equipment V-Funnel Test | Procedure V-Funnel Test. | Procedure for V-funnel flow time at T5 mm

List of Test Methods for Workability Properties of Self Compacting Concrete (SCC).

• Slump flow by Abrams cone.
• T_{50 cm} Slump flow
• J-ring
• V-funnel
• V-funnel at T₅ minutes
• L-box
• U-box
• Fill-box
• GTM Screen Stability Test
• Ouimet

In this article, we are discussion & Procedure Slump Flow Test  

Also, read: Types of Plaster Finishes (List of Plaster Finishing)

What Is U Box Test?

The test was developed in Japan The test is used to measure the filling ability of self com, pacting concrete.

The apparatus consists of a vessel that is divided by a middle wall into two compartments shown by R1 and R2 in Show in Figure.

An opening with a sliding gate is filled between the two compartments.

Reinforcing bars with a nominal diameter of 13 mm is installed at the gate with the center to center distance of 50 mm.

This creates a clear spacing of 35 mm between the bars. The left-hand section is filled with about 20 liters of concrete.

The gate is then lifted and the concrete flows to the other section. The height of concrete in both sections is measured.

Also, read: Requirements of Good DPC | Prevention of Dampness: Use of DPC | Methods of Damp proofing

Equipment U-Box Test:

1. U-Box

U-box of a stiff non absorbing material

2. Trowel

This tool is used to place cement mortar.

3. Scoop

This use in QC department for the material.

4. Stopwatch

Use for time record

Also, read: What Is Plumbing | Systems of Plumbing | Difference Between One pipe, Two Pipe, Single Stack, and Single Stack Partially Ventilated | How to Choose of Plumbing System.

Procedure U-Box Test:

• About 20 litre of concrete is needed for this test.
• Ensure that sliding gate can open freely and then close it.
• Moisten the inside surface and remove any surplus water.
• Fill the one compartment of the apparatus with about 20 litre concrete.
• Leave it to stand for 1 minute.
• Lift the sliding gate and allow the concrete to flow to the other compartment.
• Once the concrete has come to rest, measure the height of the concrete in the second compartment in two places.
• Calculate the mean. Let it be H₂. The height of concrete in the 1st compartment be H₁.
• Calculate H₁ – H₂ the filling height. The whole test has to be completed within 5 minutes.

Also, read: What Is Self Compact Concrete | What Is J-ring Test | Equipment of J-ring Test | Procedure of the J-Ring Test

Calculations U-Box Test:

• Filling time, Express the measured filling time, TU (sec) = ______ sec
• Height in the pouring compartment (H₁) = _______
• Height in the other compartment (H₂) = ______
• Calculate (H₁– H₂) = ________

Results U-Box Test:

• The filling height of self compacting concrete is ______

Significance U-Box Test:

• If the concrete flows as freely as water, at rest it will be horizontal, so H₁– H₂ = 0.
• Therefore the nearer this test value, the ‘filling height’, is to zero, the better the flow and passing ability of the concrete.