Abstract: Soluble salts is a critical disease for Yungang grottoes of Datong city in Shanxi province, which leading to the surface weathering strengthen reduction and structure damage. An experiment of deterioration simulation with sodium sulfate has been carried out for the sandstone taken from the sculptures distribution layers. The deformations of samples have been real time monitored and the mass loss, strength decrease and pore character change, and etc. have been tested during the salt crystallization cycles. Following conclusions have been obtained. Firstly, the injury of the soluble salts is the main reason for the powdered form on the sand rock surface, which cause the historical value is fading away. Secondly, the inner structure has been changed and the glue materials have been destroyed by the crystalline of the salts inside the rock, the consequence is the porosity ratio increase and stiffness and strength decrease. Lastly, in the dry season, the deterioration effect of soluble salt on rock should higher than other time from the comparative of two phases simulation tests, thenardite (Na2SO4) and mirabilite (Na2SO4•10H2O). For long term prediction of the deterioration action of salts, a logarithm model has been used for porosity increase and an exponent model for strength decrease.

Key words: soluble salt, Yungang grottoes, deterioration model