[stadry]

itsounds like' chattahoochee', an occasionally applied covering/coat ing to/on concrete, most epoxies are 2 part resin & catalyst some are 3 part eg poly sulfidesusually a 2 part water based epoxy is mixed w/graded riverrock then troweled onto the primed concrete surface a surface coating of the same wtr-bas'd epoxy's then rolled onto the surface to seal it, single partwtr bas-d urethane works better impo -yours may be experiencing delamination in areas- not uncommon-visuallyacceptable repairs iffy w/o matching aggregate. you might get lucky & find an acceptable bag at either apron store- another reason epoxies are not recomended for exerior use. sadly -too late for yours sher wms has uv resistant to yellowing aforementioned urethane has acceptable
aggregate' driveways are correctly defined 'exposed aggregate' -a surface retarder is applied to the concrete after final finishing then, 'later'cement paste is pressure washed awayexposing the concrete's aggregate another method is broadcasting aggregate onto the surface &, using a bull float &embedding it into the fresh conc afterit has taken its 'initial set'no one can define later' as it depends on the desired aggregate exposure( mild or extreme)- then again no one can define when concrete is finished curing.the only 1 i know who can help you is me, there of coursetheremay be others but i don't know them my observation' is most are 'driveway painters,' not concrete artisans.
pressure washer 4,000 psi 4 gal per min- 15-30degree nozzle NEVER 0 degree tip