Terrified that me and my sister were exposed to asbestos as kids

In our backyard, we had a little outdoor shed with a concrete floor. It was old, and no one used it. The concrete was white and breaking apart, and my sister and I, as kids, would take pieces of it and use them as ‘chalk’ to draw pictures and letters. Now that I’m older, I’m worried we were actually drawing with pieces of asbestos.

I don’t recall ever seeing any fibers, but I’m still anxious about it. Is it possible the concrete contained asbestos, or is that unlikely?