BUZZI UNICEM S.P.A. launched a voluntary offer to all holders of Germany's DYCKERHOFF preference shares to exchange their preference shares for savings shares of Buzzi Unicem S.p.A. The Casale, Italy-based cement producer is following through on earlier statements that it would face the responsibility attendant upon its new role as major shareholder of Dyckerhoff. An exchange rate of 2.4-to-1 (for six weeks) was cited by company officials, affecting 90% of voting shares.