I have an older home, circa 1957. The builder made window wells for
the basement windows out of cinder blocks stacked & cemented on top of
each other. The tops of some of the blocks has worn away and
occasionally lets rain water get up over the worn/broken edges.
I'd like to repair the tops of these blocks or at least just cover and
level off the entire multi-block surface with cement or similar.

The blocks, being old, are a fairly dark gray color so I suppose I
could go with a mix of portland cement / sand / gravel.

Any thoughts on the correct materials to use and ratios of those
materials?

Thanks!
Walt