The offer period ends on July 26.
Spohn said it now holds 16.68% of voting rights in the MDAX-listed cement maker, while parties affiliated with Spohn held 10.91% of voting rights. Subsidiaries of affiliated parties hold 3.83% of voting rights.
On June 12, Spohn announced a EUR 60/share or total EUR5.8bn bid for HeidelbergCement that is reportedly backed up by private investor Adolf Merckle.