Resistance of concrete to magnesium sulfate attack under combined action of carbonation and dry-wet cycles

Deterioration of carbonized fly ash concrete (FAC), concrete with high volume mineral admixture (HVMAC), and high performance hybrid fibers reinforced expansive concrete (HPHFREC) exposed to 5% magnesium sulfate solution was investigated. Two corrosion regimes were employed: natural immersion and dry-wet cycle. Experiment results show that carbonation changes the chemical component of concrete surface and reduces the resistance of concrete to magnesium sulfate attack, though carbonation compacts the concrete surface to some extent. The dry-wet cycles accelerate the diffusion of magnesium sulfate and develop the micro-crack of concrete. Under combined action of carbonation and magnesium sulfate, HVMAC gets the best resistance to sulfate attack and is applicable to the atrocious environment, but FAC which has been broken up is not applicable to the concrete engineering in such environment. Under combined action of carbonation, dry-wet cycle, and magnesium sulfate, HPHFREC2, of which the reinforced effect of the fibers is obviously well, shows the better resistance of concrete to sulfate attack.