Texture of nopal treated adobe: restoring Nuestra Señora del Pilar mission

Materials eroded, non-eroded, and treated with the local nopal mucilage adobe, from the Nuestra Señora del Pilar mission located in Sonora Mexico, are compared. The treatment of adobe bricks with an alcohol–water solution prior to the nopal application is proposed in order to increase their resistance to erosion. Using X-ray diffraction, small angle X-ray scattering, scanning electron microscopy and nitrogen adsorption techniques, we compared the structural and textural properties of eroded and non-eroded adobe materials. In the samples treated with nopal it is shown how the nopal coats the adobe small particles. The nopal impregnated material is stable up to 200 °C. A non-conventional distinction among these materials is made through fractal geometry and nitrogen adsorption. We also show through XRD measurements that erosion is homogeneous and not selective.