ABSTRACT
Pollutant gases are increasing day by day with increase in industrialization and traffic. Gases like SO2, NOx etc. attack mortar and concrete both by dry and wet 2 χ process. In wet process, the attack is by the acids formed in contact with water. Ca(OH)2 for example can form leachable salts with NOx, increasing the porosity of concrete, whereas SO2 forms expansive salts, causing cracking. Besides their individual effect, these gases have synergistic effect. The deterioration caused due to the synergism is much more than the damage caused by the individual gases. Mechanism of deterioration is discussed. Some of the laboratory tests and analysis of sample from bridges are reported.
