Geomechanical characterization of volcanic aggregates for paving construction applications and correlation with the rock properties

In volcanic terrains and in particular island regions, the aggregates come from the mechanical crushing of lava rocks and pyroclastic deposits. This study offers an experimental database of the geomechanical characteristics of different volcanic rock lithotypes and the aggregates obtained from these rocks. For this purpose, 971 aggregate samples and 643 rock samples of 11 different common volcanic lithotypes (including basalts, trachybasalts, trachytes, phonolites, ignimbrites and pyroclasts) were tested. These represent the majority of stone materials found in volcanic islands. Furthermore, correlations between the different properties of the aggregates (volumetric, geometric and mechanical properties) have been established, as well as between certain aggregate properties and the source rock. This allows an estimation of the foreseeable characteristics of the aggregates based on their origin. The results show that the aggregates from massive lithotypes provide superior resistance, partly due to their high density. These generally comply with the standard specifications although the particle shape may present an excessive flakiness index. However, the most abundant volcanic aggregates come from very porous rocks with a vesicular or scoriaceous structure, non-cubic particles, low resistance and high absorption, though they provide good drainage capacity. The high statistic dispersion of the geomechanical properties is due to the different viscosity of the magmas, degrees of explosiveness of the volcanic eruption and random spatial distribution. Even the abundant vesicular and scoriaceous volcanic aggregates, generally considered as marginal materials, may offer adequate quality and properties for certain construction applications. In this sense, the use of these aggregates might contribute to the development of infrastructures in these regions and thus a sustainable utilization of this natural material.