Strength of Concrete MCQ with answer and solution

Concept

The split tensile test determines the indirect tensile strength of concrete by applying a compressive line load along the generator of a cylindrical specimen.

Formula

f_t = 2P / (π × l × d)

Step-by-step solution

1. Understand the standard procedure of the split tensile test (IS 5816). 2. Place a cylindrical concrete specimen horizontally in the compression testing machine. 3. Apply a compressive load uniformly along the length (generator) of the cylinder, which is perpendicular to its cylindrical axis. 4. Due to Poisson's effect, this compressive line load creates a relatively uniform tensile stress perpendicular to the loaded diametral plane, splitting the cylinder.

Explanation

In the split tensile strength test (Brazilian test), a cylindrical concrete specimen is placed horizontally between the loading surfaces of a testing machine. The compressive load is applied linearly and uniformly along the length of the cylinder (perpendicular to its longitudinal axis), which induces transverse tensile stress across the diametral plane, causing it to split along the vertical diameter.

Why the other options are wrong

A: Axially along a cube is incorrect because split tensile tests use cylinders, not cubes. C: Parallel to the cylindrical axis would cause direct compression, not splitting tension. D: Along the diagonal of a cube is used for different setups or not standard for split tension.

Shortcut

Remember 'Split tensile = Perpendicular to axis'. Compression is applied along the line, causing tension across the diameter.

Common mistake

Confusing the direction of applied load with the direction of induced tensile stress; the load is compressive and applied perpendicular to the axis, while the induced stress is tensile.