More tensioning weights for railway cables

Spotted from the train on the way to Cologne. 13 discs. Say diameter 15 cm and depth 4cm. Volume would be about 700 cubic cm. A search suggested a density of 2.4 grams per cubic centimetre for hardened concrete. That means each block would be 1.7 kg. The total stack would be 22 kg. That would be a force of about 200N. Is that enough? I need to look at the size of the wires next time. I think the blocks are concrete. If they were steel, the force would be nearly 4 times bigger.