Physical salt attack on concrete incorporating nano-silica

The damage induced by crystallization of salts (physical salt attack, PSA) has been often misidentified as chemical attack. Under certain environmental conditions, PSA may cause notable surface damage of concrete partially embedded in salt-rich soils. The process is similar to salt weathering of natural rocks. The current study investigated the effect of refining the microstructure of concrete by nano-silica additions on its resistance to PSA in an accelerated procedure. Specimens were partially immersed in a high-concentration sodium sulphate solution and simultaneously exposed to cyclic temperature and relative humidity. Specimens’ deterioration was monitored for more than 100 cycles of exposure. Also, an effort was made to analyse the relationships between specimen damage, characteristics of pore structure and absorption capacity. Finally, the immersed and drying portions of specimens were tested by X-ray diffraction and Rietveld analysis and scanning electron microscopy to identify the root cause of damage.