Nowadays, the cement industry still constitutes an important pollutant industrial sector. Then, the strategies to reduce its environmental impact are a popular topic of research. One of these strategies consists of replacing partially clinker with other materials, such as volcanic powder. Here, it has been analyzed the effects at 1500 hardening days of the addition of volcanic powder on the microstructure and durability properties of mortars that incorporate 10% and 20% of this addition as clinker replacement. Reference mortars prepared with ordinary Portland cement without additions were also studied. The volcanic powder has been obtained from the last eruption of the Calbuco volcano (41 ° 20 ′ S, 72 ° 37 ′ W, 2003 m.a.s.l.). This volcano is placed in the southern Andes, between the cities of Ensenada and Puerto Montt in Chile, and its last subplinian eruption occurred on April 2015.

The mortars were kept in an optimum condition (20ºC and 100% relative humidity) until the testing age. Their microstructure has been characterized using mercury intrusion porosimetry, impedance spectroscopy, differential thermal analysis and scanning electron microscopy. As durability parameters, among others, the steady-state chloride diffusion coefficient and the absorption after immersion have been determined. According to the results obtained, mortars with volcanic powder showed similar porosities and more refined microstructure compared to reference mortars. Furthermore, the durability properties at 1500 hardening days of mortars which incorporate volcanic powder were similar or even better than those noted for reference ones without additions, with the added value of contributing to sustainability.