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The mineral carbonation (MC) curing of cement-based materials could be employed to obtain both CO 2 sequestration and accelerated strength gain. But there is still absence of understanding on the gas-solid reaction kinetics and mechanisms. This study aims to improve the understanding of gas-solid reaction between CO 2 and cement-based materials during the MC curing, and evaluate the feasibility of blending calcium silicate (CS) as intensified addition. Based on the accelerated carbonation experiments, the impact of different factors (pressure, temperature and water-to-binder rate) on the reaction rate and the CO 2 uptake were systematically investigated. The MC curing showed significant diffusion-controlled kinetics and the reaction gradually turned into the stable product-layer diffusion controlling process. The evolution process of kinetics indicated the increasingly dense structure of cement matrix, as verified by SEM analysis. The blended CS was found to significantly enhance the reaction rate and CO 2 uptake capacity, accompanied with the intensified carbonation conversion of cement components. The increased Klinkenberg permeability of blended CS paste after MC curing demonstrated the diluted effect of CS. In terms of the practical feasibility, MC curing also contributed remarkably to the compressive performance improvement of cement paste with blended CS. [ABSTRACT FROM AUTHOR]

Capturing CO 2 directly from the atmosphere using chemicals (air capture) is a strategic approach to mitigate global warming. Before the widespread deployment of air capture, technical challenges, such as the poor kinetics under ultra-low CO 2 concentrations, must be addressed. This work aims to characterize and optimize the mass transfer process of a novel moisture swing adsorption method for air capture. The phase inversion technique is employed to fabricate a heterogeneous structured sorbent. The modified shrinking core model and a revolving bed reactor are developed to evaluate the adsorption kinetics. The sorbents exhibit significant diffusion-controlled kinetics under most of the measurement conditions. The effects of ambient conditions on kinetics, such as temperature and relative humidity, were investigated. The diffusion and chemical reaction rate drop sharply as the temperature decreases from 20 to 0 °C. The relative humidity shows a more obvious effect on the chemical reaction than on the physical diffusion process due to the mechanisms of hydration water involved in the chemical reaction. On the other hand, reducing the size of the sorbent particles to several micrometers could effectively avoid the substantial reduction in the adsorption rate under lower temperatures. Using the determined kinetic parameters, suggestions for kinetics optimization are proposed for air capture under different weather conditions. [ABSTRACT FROM AUTHOR]