Chemical composition and main physical-chemical characteristics (apparent density, electrical resistivity, thermal conductivity, compression strength) carbon cathode block samples of spent lining for aluminium electrolysis unit produced by OJSC "RUSAL Krasnoyarsk"; it is shown that to increase the bath service life it is necessary to form a crust to decrease alumina-cryolite melts penetration into electrolysis carbon cathode blocks which will reduce environmental impact.