Investigation of mechanical properties and damage characterization of cement pastes prepared by coupled carbonation-hydration curing

To achieve carbon reduction, a coupled carbonation-hydration curing approach has been developed. This study employs the acoustic emission (AE) technique to analyze the mechanical properties and damage characterization of cement paste under this curing method. Microscopic techniques clarify the evolution of products, microstructures and micromechanical parameters, highlighting their impact on mechanical behavior. Results indicate that the carbonation-hydration equilibrium is achieved when the ratio of CaCO₃ to amorphous content is less than 2. In this system, C-S-H gels are predominantly formed, while the CaCO₃ content remains minimal. At the balance system, the compressive strength increases by 4.16 %–16.25 %, while the pore volume in the range of 1–200 nm decreases by 13.19 %–19.54 % compared to standard curing. Conversely, the ratio greater than 2 results in over-carbonation, with CaCO₃ as the dominant product and few C-S-H gels. In the over-carbonation system, the compressive strength and pore volume in the range of 1–200 nm decrease by 13.21 %–34.62 % and 21.55 %–40.85 %, respectively, compared to standard curing. Under coupled carbonation-hydration curing, cement pastes exhibit significant stress instability, with damage primarily from tensile cracks in the balanced systems and mixed shear-tensile or tensile cracks in the over-carbonated systems.