Botanical name: Paspalum dilatatum
Family name: Poaceae
Paspalum is a grass weed which has very short stout rhizomes, which join plants together to form dense clumps. In lawns, paspalum is one of the broadest leafed grasses likely to be found. As the shoots tend to grow quite flat to the soil surface under a mowing regime, they are able to survive constant mowing to a low cutting height. (Massey Uni Weeds Database).
Growing in a crack in the pathway, the tightly packed and well-trampled rhizomes spreading over the concrete. It will be a tough one to remove - I'll leave it for now.