Towards net-zero reinforced concrete: A critical review

This paper reviews the efficiency of approximately 150 net-zero strategies for reinforced concrete, based on around 180 references. These strategies cover raw materials, manufacturing, transportation, construction, carbon calculation, standards, and projects/applications. The results show that CO₂ emissions from cement can be reduced by 6 % to 70 % by developing low-carbon cement, such as geopolymer cement and calcined clay-limestone cement. A significant amount of CO₂ can be sequestered in the final cement pastes and aggregates through CO₂ curing. In some specific applications, CO₂ emissions from steel reinforcement can be reduced by approximately 90 % by using fibre-reinforced polymer bars. Optimising energy sources and processes during manufacturing and transportation can reduce CO₂ emissions by up to 90 %, while employing 3D printing technology can cut CO₂ emissions by up to 25 % compared to traditional cast-in-situ construction. Therefore, achieving the net-zero target is nearly feasible separately for cement and steel reinforcement with the use of specific technologies. Further work should explore the feasibility of coupling these net-zero strategies in reinforced concrete, considering its long-term mechanical properties and durability.