Painted patio chalking
it sounds like they used the wrong material. adding an aggregate to the paint material will not cause the material to get chalky.
they could have primed with KILZ and interior primer - that causes the top coat to chalk. or they used an interior product for the finish coat.
there isn't much you can do to stop it. If you know what products they used I can tell you how to fix it.
from the brief description you gave, my recommendation would be to pressure wash it to remove the chalk and see how long it takes to chalk over again.
If you plan on re-coating it, without knowing what products they used, I think you are going to have to strip the existing coating down to the bare substrate. The easiest way to do that would be to hire a company to shot-blast it. in Cleveland you would be looking at $0.75 to $1.50 per square foot depending on the material thickness, size and condition.