Preliminary assessment of the efficacy of nano–MgO–based dispersion for the consolidation of artificial weathered sandstone

Abstract The consolidation of weathered sandstone has been an important subject in cultural heritage conservation. Due to the loss of cementing materials, the structure of sandstone becomes loose, thus mechanical strength decreases dramatically. To restore cohesion between sand grains, a novel nano‐MgO‐based consolidant (MMH dispersion) is studied. In this paper, the MMH dispersions with different concentrations and number of applications are applied on artificial weathered sandstone specimen with trickling infiltration treatment to select the optimal consolidation method. The consolidation products that formed in the pores between sand grains are characterized through XRD analysis and SEM observation. The effectiveness of consolidation treatment is evaluated in terms of mechanical properties (i.e., compressive strength and surface hardness) and compatibility (i.e., color variation and capillary water absorption). Due to the formation of 5 Mg(OH) 2 ·MgCl 2 ·8H 2 O, sand grains are more effectively bonded. Therefore, the treated specimens experience a significant improvement in mechanical strength. Finally, the specimens are subjected to a salt crystallization test, the results of which show that the MMH consolidant increased the durability of the specimens. After treatment, the intermediate concentration of MMH consolidant with five applications reveals the best potential to act as a promising consolidation method for the conservation of the weathered sandstone.