HeidelbergCement AG shareholder Adolf Merckle, who is making a takeover offer to other shareholders, already owns a 31.45 per cent stake, according to the detailed conditions of the offering published Tuesday.  Merckle holds 31.45 per cent in HeidelbergCement voting rights, both directly - through his control of Spohn Cement GmbH - and indirectly.  Spohn Cement said two weeks ago it will offer HeidelbergCement shareholders Euro 60 a share for their stakes, valuing the company around EUR6.5bn.  Shareholders have until July 26 to decide whether they will accept the offer.