Spray-Based Method for Protecting and Restoring Historic Adobe Walls Using Nanomontmorillonite Clay

[Image: see text] Restoring and protecting historic buildings worldwide are important because heritage buildings are records of the civilizations of various countries. Herein, nanotechnology was used to restore historic adobe walls. According to the Iran Patent and Trademark Office (IRPATENT) 102665, nanomontmorillonite clay has been selected as a natural and compatible material with adobe. Furthermore, it has been used as nanospray to be a minimally invasive method to fill cavities and cracks in the adobe surface. Various percentages of nanomontmorillonite clay (1–4%) in the ethanol solvent and the frequency of spraying on the wall surface were evaluated. Scanning electron microscopy and atomic force microscopy images, porosity tests, water capillary absorption, and compressive strength tests were used to evaluate the efficiency of the method, analyze cavity filling, and detect the optimal percentage of nanomontmorillonite clay. Results indicate that the double use of the 1% nanomontmorillonite clay solution exhibited the best results, filled the cavities, and reduced the pores on the surface of the adobe, increasing compressive strength and reducing water absorption and hydraulic conductivity. The use of a more dilute solution causes the nanomontmorillonite clay to penetrate deeply into the wall. This innovative method can help mitigate the existing disadvantages of historic adobe walls.