Why we are used 150X150X150 mm Cube size for Concrete strength checking
When i was in college i use to wonder that all construction site have the cube Cube Size
of 150mm x 150mm x 150mm.
of 150mm x 150mm x 150mm.
I checked in the IS code but in that also they never say that to use 150mm cubes, you can use any size cube for testing of compressive stregnth.
Max construction site have the cube testing machine of capacity 100 ton / 1000kn. and our compressive strength calculation is load / area i.e.- N/mm2
If the loading area increases the load for crushing or load at which it fails also increases.
If you are checking M30 concrete and you requires min. comp strength of 20N/mm2 and the Cube Size is 150mm then the load required to get this much strength is 742.5 Kn. if you use cube of size 300mm the load require becomes 2970 kn, this is practically not possible as to crush the cube u require 3000kn/300 ton capacity machine. When the applied load is much more the additional safety factors need to be increase because when cube fails under such loads may hit anything in room with bullet speed.
is 150mm then the load required to get this much strength is 742.5 Kn. if you use cube of size 300mm the load require becomes 2970 kn, this is practically not possible as to crush the cube u require 3000kn/300 ton capacity machine. When the applied load is much more the additional safety factors need to be increase because when cube fails under such loads may hit anything in room with bullet speed.
Also casting of this size cube and handling is not easy.
For feasibility, safety and ease of work we use 150mm size cubes.
If you have a machine with less capacity and load to crush the cube is more than the capacity of machine you can reduce the size of cube further to 100mm.
This you can do when you go for high grade concretes M50 and above and your machine capacity is 100 ton.
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