*3.7. Chemical Attack Resistance*

Table 5 displays the percentage weight loss suffered by the granite and ASPU under chemical attack.


**Table 5.** Weight loss after chemical attack of granite and ASPU samples.

The norm NBR 13818 [25] proposed reagents are ammonia chloride and potassium hydroxide, used to make cleaning products, hydrochloric acid, which is found in floor, stone and tiles heavy cleaner products and citric acid, contained in several fruits, must be in constant contact with the specimens.

Through the obtained results it is possible to verify that the exposure to all the reagents provoked a weight loss in the stones. Although these losses could be considered insignificant, in the long term the constant use of these substances can compromise their performance and aesthetics.

Hydrochloric acid (HCl) was the most aggressive reagent for both granite and ASPU, with a 0.043 g weight loss, followed by potassium hydroxide (KOH), citric acid (C6H8O7) and ammonium chloride (NH4Cl). Hydrochloric acid is a strong and high degree of ionization acid manifesting the greatest weight loss. Therefore, cleaning materials containing this substance and potassium hydroxide should be especially avoided and it is recommended to clean with care using only a damp cloth with diluted neutral soap.
