IN-SITU IR STUDY ON THE INITIAL SULPHITION AND CARBONATION OF CA(OH)(2) AND CAO BY SO2 POLLUTED AIR

Absorptions of SO2 and CO2 to fresh and aged forms of CaO arid Ca(OH)( 2) are investigated at dry and humid conditions. Sulphite formation on Ca(OH)2 is found to be fairly independent of the relative humidity, w hile surface water is found to be a necessary condition for the corres ponding carbonation reaction. Results supportive of Ca(OH)(2) sulphiti on to be strongly preferred before carbonation at humid conditions are produced. Marked improvements in SO2 adsorption are seen for the fres h substrates. The observations are put in perspective of an on-going e ffort to understand the roles of SO2 in the deterioration of calcareou s stone monuments, and are relevant to the chemistry of building mater ials. Copyright (C) 1996 Elsevier Science