Effects of general and saturated humidity on concrete performance deterioration under sulfur dioxide attack

Abstract

A large amount of SO2 is emitted with the rapid development of industrialization, and there are big differences in the deterioration of concrete subjected to SO2 attack between the environments of general humidity and saturated humidity. This paper conducted the simulation tests of concrete subjected to SO2 attack at general humidity (RH = 80 %) and saturated humidity (RH = 98 %), and the sulfuration depth, mass, and compressive strength were comparatively studied. The distributions of pore-solution pH and SO2- 4 concentration of concrete at different exposure times and depths were analyzed, and the deterioration mechanisms on concrete under SO2 attack in these environments were compared. The results indicated that the sulfuration depth and mass remained unchanged in the middle and later periods of the attack at 80 % RH, and the compressive strength at 20d was still larger than that before SO2 attack. However, the sulfuration depth and mass increased rapidly at 98 % RH, and the compressive strength loss rate was 18.80 % at 20d. The ions concentrations at 98 % RH changed greatly with increasing exposure time, and the pH and SO2-4 concentration of concrete at 1 mm at 20d were 2.41 times less and 3.86 times larger than those at 80 % RH, respectively. The initial product at 80 % RH was ettringite, which converted to gypsum with the progress of SO2 attack, and these expansive products decreased the porosity of concrete. A large amount gypsum was produced at 98 % RH, leading to the initiation and propagation of microcracks, and the porosity increased to 41.43 %.