Question: I have cracks in my concrete basement floor from which I believe radon gas is creeping in. What is the best way to seal those cracks?
Answer: Before you do anything about that cracked floor, test for radon first. Better yet, have a professional make the test for you.
The reason for contacting a professional: You might need to install a system to exhaust the vapors if the radon is present in a dangerous concentration. The concentration of radon should be checked both before and after the concrete is sealed.
Sealing the cracks in the floor of your basement might be all that you need to do. Then again, maybe more work will be needed.