Laboratory Investigations of the Properties of Volcanic Ash Seals

Summary An essential part of understanding seals includes studying the physical and mechanical behaviors of seals upon chemical interaction with fluids in the subsurface and, specifically, how chemical cementation and fluids being potentially aggressive impact the mechanical behavior of the bonded fabric. In this paper we focus on the chemistry of the cementation process of volcanic ash, the resulting formation of fibrous minerals and their impact on strength, and the role of CO2 in undermining such a cementation process. Intriguingly, volcanic ash and many of the fluids present in the subsurface (i.e., lime, alkalis, and sulfur) have been used to produce ancient mortars and still used in modern cementitious binders. This intertwining of the cementation of ash-based mortars and ash beds in the subsurface is an opportunity for cross-fertilizing knowledge across the Geosciences and Engineering, which is crucial to understand how fluid chemistry controls or undermines the cementation and strength of seals in the subsurface.