So far I tagged them as paving stones because the material resembles those (something like 'faux_bricks'). But now, I am very unsure this is correct and should correct my changes.

OSM wiki do 'surface' tag doesn't seem to address this material. They are large blocks, so I believe it might be better to tag as 'concrete:plates' (desc.: heavy-duty plates). Here is a firm that produces them from concrete to prove their concrete relatedness (it's just the finish that changes the perception of material): https://www.betonlucko.hr/betonska-galanterija-stepenice.html

On the flip side, this tagger seems to be tagging them as 'asphalt':
https://help.openstreetmap.org/questions/75153/tagging-of-surface

Any ideas or experience from other taggers on this issue?