Two different approaches to reduce the CO₂ emission of rock mass grouting

The Norwegian research project “Sustainable value chain and use of materials in road construction” aims to find novel ways of reducing environmental impacts of road infrastructure through recycling and reuse of waste materials. Heavy tunnel infrastructure consumes the most materials of all road constructions, thus finding solutions for reducing resource consumption and CO₂ emissions from tunnel infrastructure is a priority. This paper presents a study of two different approaches to reduce the CO₂ emission of grout for rock mass grouting: 1) up to 30 % reduction of cement content, using Silica Greenstone, a product derived from waste, as cement replacer; and 2) grout without cement clinker, using alkali-activated binder and mining tailings. Laboratory results for setting-time, viscosity and bleeding were found to be comparable to traditional cement-based recipes. The two approaches are also analyzed using life cycle assessment (LCA) to understand the potential CO₂ emissions reductions compared to standard grout.