Every year millions of tonnes of concrete rubble is generated in world due to various reasons, what is the best way to recycle this waste concrete?

The concrete rubble can be crushed using the appropriate machinery keeping in mind the subsequent proposed usage; either just crushing it for use as sub base for road construction; crushing, making it free from contamination such as sand , cement, dust & mixing it with virgin aggregate and using it for new constructions; using crushed material as back fill. However using it as back-fill is the least desired use. One should consider the recycling keeping in view cost effectiveness and the specifications of works where you want to use recycled material. 

Crush to the desired sizes to reuse in different type of construction.

Lightning are more likely to travel from water to solid in  extremely short duration and will travel through part of list resistance example boundary of aggregates (gravel, stones) and sand particles, in this way tear and separate the particles

Clean the rubble from all other building materials and rebar, crush it in the desired sizes for concrete and reuse it. You can us up to15 % in concrete without changing the quality of the concrete. Use more then15 % needs to be accompanied by a certificate of the aggregate/rubble. Normally you have to prove the quality by testing the material and you need to see that the material is consistent.

You can also reuse it on roads and pavements

this is a very good question,

and i will need to have an answer for it too .