Preparing low-calcium carbonatable clinker using waste concrete powder and its negative CO2 emission feasibility

[Geoengineering News]

https://www.sciencedirect.com/science/article/abs/pii/S2352710226010181

Authors: Jiaxin Li, Wei Chen, Bo Li, Bo Yuan, Kuo Yang 

02 May 2026

https://doi.org/10.1016/j.jobe.2026.116197

Highlights

•Preparing carbonatable clinker with C2S–C3S2 as the main phase with low-calcium content.

•Net-negative carbon emission via CO2 sequestration.

•A circular economy strategy turning waste concrete into carbon-sink building materials.

Abstract

Innovative building materials represent an essential pathway for addressing the stockpiling of construction waste as well as achieving carbon emission reduction in the building materials industry. This study presents an experimental investigation on converting high-silica waste concrete powder (WCP) into a low-calcium carbonatable clinker. Based on the CaO-SiO2-Al2O3 ternary phase diagram, through compositional design, WCP was mixed with a supplementary calcium source (waste hydrated cement paste, HCP) to form a clinker comprising C2S and C3S2 at 1150°C. The synthesized clinker was subsequently carbonation-cured, achieving a compressive strength of 83.8 MPa at 7 days with CaCO3 as the main binding phase. Carbon footprint assessment reveals that maximum CO2 sequestration (340.06 kg CO2/ t clinker) exceeds CO2 emission (254.37 kg CO2/ t clinker), resulting in a net-negative carbon footprint. This work establishes a circular economy pathway transforming waste into carbon-sink building materials for sustainable construction.

Source: ScienceDirect