Epoxy Resin for the Slope Consolidation Intervention on the Tropea Sandstone Cliff (Southern Calabria, Italy)

The Tropea cliff (southern Calabria, Italy), affected by fast weathering processes and landslides, has needed various interventions of slope consolidation aimed at reducing hazard conditions. These interventions were performed with low environmental impact techniques in order to preserve the architecture and the landscape of the area. In 1998, a consolidant resin was tested on a limited portion of the Tropea sandstone cliff. The purpose of this test was checking the resin behavior against erosion processes. Previous researches showed a good resistance to erosion with only a slight opacification of the treated sandstone portion. This paper aims at studying the behavior of the consolidant resin after 17 years from its application. The research was performed by several laboratory tests. The Fourier transform infrared spectroscopy analysis has indicated that the consolidant product was an epoxy resin. The scanning electron microscopy analysis has shown that the resin has penetrated into the rock up to 2 mm. The chemical analysis further testified that the tested surface is characterized by higher content of soluble salts than the non-treated surface. The salt content is mainly related to the infiltration of water enriched in soluble salts, due to the marine aerosol. The soluble salts, crystallizing in the rock pores and between the mica sheets, produce an increase of physical stress that is responsible of the exfoliation processes of the resin. Therefore, the use of epoxy resin on the tested sandstone rocks increases the strength on the outer rock surface, with a consequent good resistance to erosion processes just in a restricted period. Overtime, water infiltration introduces dangerous soluble salts below the treated surface, causing salt crystallization with important exfoliation processes of the treated rock surface.