I think I know the answer to this already but its worth a punt.
I laid a 4mx3m shed floor (clearly badly), with about 10 cm of hardcore and 7.5cm of cement, that whilst in the middle appears fine, on the outside has some very crumbly sections.
The floor doesn't need to last decades, it has a summerhouse(office) on it, so a few years use would be nice rather than it just collapsing when the winter arrives. Is there anything I can do to it to make it a bit more hardy in the short term other than knock it down and start again.?