A number of R&D projects have been carried related to the use of expanded clay lightweight aggregate (expanded clay LWA) in Civil Engineering applications and particularly in Geotechnics. Expanded clay LWA is used as frost insulation material in road pavements, light weight fill for stability improvement, reduction of settlement and reduction of earth pressure, and as drainage material in backfills and drainage ditches. The research projects have focused on verification of material properties and structural behaviour through laboratory and field tests. The projects have verified that expanded clay LWA has physical, mechanical and environmental properties to be largely used as lightweight fill material in roads, railways and other geotechnical construction works.