NEXCEL Project Paper 33
Release time: 2025/03/03 Publisher： original Views：
Effect of CO2-mixing dose and prolonged mixing time on fresh and hardened properties of cement pastes
Ph.D student Luo Shuang, Principal Investigator of NEXCEL 2023 PHD project titled 'Beneficial use of DPCR to prepare CO2-ready-mix cement-based materials', and her supervisor Prof. Ling Tung-Chai from Hunan University have published a paper entitled 'Effect of CO2-mixing dose and prolonged mixing time on fresh and hardened properties of cement pastes' in 'Journal of Zhejiang University-SCIENCE A' (SCI) recently.
This study aims to investigate the influence of CO2-mixing dose (mass fractions of 0.3%, 0.6%, and 0.9%) and prolonged mixing time on the fresh and hardened properties of cement pastes. The CO2-mixing can act as coagulant in fresh cement mixtures, resulting in a significant reduction in workability associated with the formation of a rich calcium carbonate network on the surface of cement particles. The CO2-mixing cement pastes were found to be much stiffer and more difficult to handle, place, and compact than the control mixture, which had a negative effect on the mechanical strength performance of the hardened pastes. However, prolonging the mixing time for 1 min (immediately after CO2-mixing) can effectively improve the workability (by ∼53%–85%) by breaking up the flocculation network of deposited calcium carbonates. As a result, the presence of detached calcium carbonate accelerated early cement hydration and densified the microstructure; this improved early-age compressive strength by ∼6%–32%, depending on the CO2-mixing dose used. Therefore, it seems that the CO2-mixing dose should be controlled at ⩽0.6% with the mixing time prolonged in order to attain satisfactory workability and mechanical strength.
Paper Details:
Journal of Zhejiang University-SCIENCE A 2023 24(10): 886-897
https://doi.org/10.1631/jzus.A2200571
