Degradation of mortar fully buried in saline soil containing sodium sulfate or magnesium sulfate.

• The saline soil does not change the internal degradation mechanism of mortar, and the degradation products are still mainly composed of gypsum and ettringite. • The degradation rate of saline soil containing sodium sulfate to mortar is faster than that of sodium sulfate solution. It is contrary for saline soil containing magnesium sulfate. • When the mortar is degraded by sulfate, an obvious movable corrosion interface is observed in mortar along corrosion direction. The sulfate attack of salt solution and saline soil on concrete structures is an essential factor threatening their durability. The degradation of saline soil to concrete structures has attracted more attention than the salt solution in recent years. Thus, the degradation of mortar buried in saline soil containing sulfate ions was investigated in this study. Combined with the macro and micro degradation results, the saline soil does not change the internal degradation mechanism of mortar because the degradation products are also mainly composed of gypsum and ettringite. The degradation rate of soil containing sodium sulfate to mortar is more vital than that of the corresponding salt solution. However, the results are contrary for soil containing magnesium sulfate and the corresponding salt solution. An evident and movable degradation interface in the eroded mortar is observed based on a color difference along the direction of degradation; The fly ash with a high replacement (60 wt%) is unfavorable to the resistance of the mortar under sulfate attack, because it contains a high aluminum phase to form ettringite. The slag can increase the resistance of the mortar under sulfate attack due to its smaller content of aluminum phase and higher activity. [ABSTRACT FROM AUTHOR]