Concrete Mould & Slamp Cone

Size use for testing concrete cube on construction site will be 150mm x 150mm x 150mm.

There is no specification for cube size for testing concrete in IS code. You can use any size of cube for testing compressive strength of designed concrete mix. Even 150 mm size also not specified in IS code.

We consider 150 mm cube size as a standard size because, in our material testing lab and site testing equipment have maximum capacity of 100 ton/1000 kN. Compressive strength = load/area. From that, as increase in area of loading, increase in crushing load or load at which specimen fails also increase.

If you are testing M30 concrete, you require 33 N/mm2 compressive strength and and size of cube ia 150 mm than you requires maximum 742.5 kN load for testing this cube. If we increase cube size of 300 mm than load required will be about 2970 kN and that is not possible to test in our conditions. 300 mm cube size requires 3000kN /300 ton capacity testing machine.
Another reasons may be

• cube size more than 150 mm, not easy to cast and handle.
• We use 150 mm size of cube for feasibility and safety reasons.

(Safety in terms of, if we use higher dimension for cube for testing than it requires higher load to crush of fail the cube. When cube fails the load hit in the testing room with very high impact so it may create damage.)