tanenbaum served as chairman of warren, which, until its merger with lafarge north america, was canada's largest asphalt paving and aggregate company with operations serving approximately 54 communities. warren's activities also included major commercial aggregates operations, liquid asphalt trading and distribution and road maintenance. in december 2000 warren was merged into lafarge north america inc., north america's largest diversified construction materials company and supplier of cement, aggregates and concrete, and other materials for residential, commercial, institutional and public works construction in the united states and canada. as a result of this merger, kilmer became a significant shareholder in lafarge na, and tanenbaum served on the board and chaired its finance committee until the 2006 buyout by lafarge sa.