TOXIC GAMES

The Split Tensile Strength Test is used to measure the tensile strength of concrete, which is important because concrete is weak in tension. Instead of pulling the concrete apart (which is hard to do directly), this test applies a compressive load across the side of a cylindrical specimen, causing it to split along its diameter.

Purpose:
• To find out the tensile strength of concrete.
• To help in understanding concrete’s behavior under tension.

Apparatus:
• Compression Testing Machine (CTM)
• Concrete cylinder (usually 150 mm diameter × 300 mm height)
• Plywood strips (to distribute load evenly)

Procedure:
1. Prepare a concrete cylinder and cure it for 28 days (or as needed).
2. Place the cylinder horizontally between the plates of the testing machine.
3. Place thin strips of plywood (about 3 mm thick) along the top and bottom between the cylinder and plates.
4. Apply the load gradually at a constant rate until the cylinder splits along its vertical diameter.
5. Record the maximum load applied at failure.

Calculation:

The split tensile strength (T) is calculated by:

T = \frac{2P}{\pi LD}

Where:
• T = Split tensile strength (in MPa)
• P = Maximum load at failure (in Newtons)
• L = Length of the cylinder (in mm)
• D = Diameter of the cylinder (in mm)

Typical Values:
• Split tensile strength is about 8–12% of the concrete’s compressive strength.

Notes:
• Test should be done carefully to avoid eccentric loading.
• Surface cracks at failure should be along the vertical diameter.

The Vee Bee Consistometer Test is used to determine the workability of dry or stiff concrete mixtures, which can’t be accurately measured by the traditional slump test. It’s especially useful for concrete with low water-cement ratios, like those used in road construction and precast elements.

Apparatus
• Vee Bee Consistometer (includes a vibrating table, a slump cone, and a cylindrical container)
• Tamping rod
• Stopwatch

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Procedure
1. Place the slump cone inside the cylindrical container of the Vee Bee apparatus.
2. Fill the cone with fresh concrete in 4 layers, each layer tamped 25 times with the rod.
3. Lift the cone vertically, just like in the slump test.
4. Start the vibration of the table and the stopwatch at the same time.
5. Observe the concrete as it flows and settles.
6. Stop the stopwatch when the concrete’s surface becomes completely horizontal and glazed (uniform surface, no slump shape).

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Result
• The Vee Bee time (in seconds) is the time it takes to fully remold the concrete into a cylindrical shape.
• Lower time = higher workability, and higher time = stiffer mix.

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Typical Values
• 2–5 seconds: Highly workable
• 5–10 seconds: Medium workability
• 10–20+ seconds: Low workability