You have a problem. The cracks * are * a risk.
The problem is, that if water penetrates - and it will, quickly or slowly, over months or decades, it will corrode the steel. Corroding steel expands with great force, forcing the concrete open, and exposing the steel to more water flow,and deeper.
Over time, you end up with this kind of problem if you are unlucky....... an entire building collapse because some part of the concrete structural elements don't have the needed strength, and steel and rust are degrading it constantly.
What to do
The problem you have is, stopping water ever getting into those cracks. But not many things guarantee that.
For example you can cover with waterproof cement/concrete, but the place they join will let water in. You can coat with tanking product or rubber/bitumen paint, but it is not likely to protect the work enough over time, and as the ground shifts over the years.
(Normally, water can penetrate concrete, but it doesn't matter. It has to travel through about 60-75mm of concrete to reach the steel. The cement in concrete is very alkaline, and when the water has to get through that thickness of concrete first, the alkali level and access to free water and oxygen effectively stops the steel+water+oxygen process (that causes corrosion), from ever happening. Cracks, however small, are like an opening in the defences, and can allow corrosion to happen instead.)
I had this problem once. The solution we reached was to sandblast or grind the surface of the concrete to get past any surface deposits and powder. Then use a building industry epoxy coating, which bonds to concrete "for the life of the building". We used Sika products. Sikadur 31, 32 and Combiflex (all "Normal") are all suitable Sika products. These are products specifically designed for concrete repair and protection, where there are cracks, degradation, exposed steel, or a risk of penetration+corrosion. We found the 31 a bit stiff,the 32 a bit runny, and the combiflex just right. Its sold as part of a combiflex system, but is also a valid epoxy in its own right, and has a good spreadable texture. Spread it on, and important, not just the crack but a good 60 or 70mm each side of every crack as well. Work it into cracks and into the surface where you can. When it sets, the next day, water won't be able to penetrate and reach the crack without traveling through 70mm+ of concrete, which is the protection the steel should have had. Once set, you can build on it exactly as you would build on the original concrete.
Not cheap, but a lot cheaper than digging and redoing, specialist concrete repair/waterproofing contractors, or finding out the hard way later.