Study on carbon-neutral ground improvement using recycled concrete fines

Reducing carbon dioxide (CO₂) emissions is an important aspect of global climate change. In Japan, CO₂ emissions from cement production account for approximately 5% of total CO₂ emissions. A technology system for the substantial reduction of CO₂ emissions was developed. In this system, high-slag cement with a slag content of over 60% was newly developed. Carbonate-demolished recycled concrete fine powders (RCFs) have also been developed. RCFs contain cement hydrates, that react with CO₂ and transforms into calcium carbonate. They can be used as carbon capture and utilization (CCU) materials. New cement and carbonate RCFs have been used for soil stabilization. The new cement has a reduction performance of 70% and 40% compared whit Ordinary Portland Cement (OPC) and conventional Blast furnace cement type B (BB cement). The RCFs were carbonated under dry conditions to form a CCU material that could fix 10% CO₂ by mass. This study presents the properties of RCFs and carbonate RCFs. Subsequently, in laboratory tests, the fluidity before hardening and the compressive strength of soil stabilization were investigated. The fluidity decreased when carbonate RCFs were used, requiring the use of a chemical admixture. The compressive strength of mixtures containing carbonated RCFs was found to be 1.1 to 1.5 times higher than those without it. Based on these findings, we conclude that these new materials can be applied as environmentally friendly ground improvement solutions.