Use of zinc stearate to produce highly-hydrophobic adobe materials with extended durability to water and acid-rain

Abstract This paper presents a novel solution to increase the durability of adobe materials using zinc stearate at doses ranging from 0.25% to 2.00% w/w. Shrinkage, apparent density and ultrasonic propagation speed measurements were performed on the cured samples. In addition, water absorption and durability features were determined by capillary tests, Karsten tube measurements, immersion in water, hydrochloric acid (5% w/w) and sulphuric acid (5% w/w) solutions. The durability study was complemented by rain erosion and acid-rain erosion tests. The capillary water absorption was comparable to that of hydrophobic cement renders and the acid-rain erosion was negligible in samples containing 1.00–2.00% w/w zinc stearate. Besides, SEM examination confirmed the protective action of zinc stearate in front of acid-rain. To conclude, zinc stearate was found to be was an excellent choice to increase the durability of adobe materials.