I have a tibia bone fracture, I am with cast from 3 months. I would like to know how many days will it take to heal. Why is there a delay in recovery?

Bone. Takes approximately 5-8 weeks to heal. Smoking or low vitamin d levels can cause delay in bone healin as could motion between the bony fragments. Questions specific to your case should be directed to the doctor who is looking at your xrays as they are the only one who knows what is going on.