Application of substitute building materials in geogrid reinforced soil structures and other civil engineering constructions

Abstract

Mineral waste has become not only the largest waste stream in many countries, but also a reliable source of material to replace primary raw materials. Much of this material is already being used successfully. However, the potential of many materials such as slag or ashes, is currently not fully unlocked as this kind of material is used only for backfilling, often referred to as downgrading. In this study, the use of recyclables in higher value applications was investigated. In several laboratory tests, the usability of substitute building materials (SBM) in green applications, such as green roofs, green facing elements or fill material in (geogrid) reinforced soil structures ((G)RSS), was tested. The study concept includes both, soil mechanical laboratory tests and greening tests on SBM. The greening tests showed that broken bricks are suitable when mixed with organic materials. Pure brick rubble material can only be insufficiently greened. Chemical and soil mechanics tests were carried out with the fill materials. Some materials such as Lignite fly ash were excluded from soil mechanical tests because of insufficient chemical properties. These materials are not suitable for building applications without a sealing layer. Many other materials, such as recycled concrete or different kinds of slags have equivalent or even better soil mechanical properties than primary materials. Many of these materials also have chemical properties that allow almost unlimited use in construction.Based on the laboratory results, the construction of an RSS with complete substitution of the primary building materials will be started as a large-scale pilot test in the next step.