Environmentally sustainable use of recycled crushed concrete aggregate in earthworks

Recently, new environmental concerns regarding earthwork constructions have emerged. Such concerns are considerably wide, ranging from water economy to carbon dioxide emissions and waste control in construction phases. To decrease the use of non-renewable natural resources as well as environmental effects of earthworks, natural aggregate materials can be replaced with recycled materials such as recycled crushed concrete aggregate. The effect of crushed concrete to sustainability is manifold: high deformation modulus produces savings in layer thickness, the aggregate is approximately 10 % lighter, and its “urban” availability produces savings in transport and less waste to landfills, it allows savings in transport and in natural aggregates, and produces stiffer base and subbase layers and thereby less maintenance, etc. One of the largest contributors of the greenhouse gas emission is the production of cement for use in concrete. However, concrete is well-known for its carbon dioxide (CO2) uptake by carbonation. The uptake rate becomes higher in a recycling process because the reacting surface area is increased by crushing processes. The use of recycled crushed concrete aggregate therefore benefits environment by reducing greenhouse gas emissions and energy consumption, and by conserving natural aggregate sources.