Concrete screws are part of the membrane mechanical fastening system for flat roofs when the roof base is concrete.
They require pre-drilling with a 5.00 mm or 5.5 mm drill depending on the condition of the concrete.
They have a special anti-corrosion coating that provides the highest degree of protection according to DIN 50018 S2.0L-15 Kesternich cycle. This cycle simulates an SO2-saturated atmosphere producing acid rain.
While the Kesternich test system requires relatively sophisticated equipment, a "home" test can use automotive battery acid. A zinc-coated screw placed in it "boils" and rusts before your eyes, and a specially coated screw will start to form rust spots after 3-4 days.