Mix Design-Driven Control of Carbonation and Hydration in CO<sub>2</sub>-Mixed Cement Pastes: Effects of Water, Slag, and Surfactant

Mix Design-Driven Control of Carbonation and Hydration in CO<sub>2</sub>-Mixed Cement Pastes: Effects of Water, Slag, and Surfactant

This study systematically investigates the influence of mix proportion on and the early-age properties and CO<sub>2</sub> uptake of CO<sub>2</sub>-mixed cement paste, focusing on variations in the water-to-binder (w/b) ratio, slag content, and air-entraining agent (AEA) dosag...

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Bibliographic Details
Main Authors: Jingliang Xia, Chunjin Li, Haoyuan Ma, Qiang Ren
Format: Article
Language:English
Published: MDPI AG 2025-06-01
Series:Buildings
Subjects:
CO<sub>2</sub> mixing
CO<sub>2</sub> sequestration
mix proportion
carbonation
properties
Online Access:https://www.mdpi.com/2075-5309/15/12/2116
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Summary:This study systematically investigates the influence of mix proportion on and the early-age properties and CO<sub>2</sub> uptake of CO<sub>2</sub>-mixed cement paste, focusing on variations in the water-to-binder (w/b) ratio, slag content, and air-entraining agent (AEA) dosage. Mineralogical characteristics were analyzed using X-ray diffraction (XRD) and thermogravimetric analysis (TGA), while pore structures were assessed via nitrogen adsorption. CO<sub>2</sub> uptake was quantified immediately after mixing. Results indicate that a low w/b ratio limits CO<sub>2</sub> dissolution and transport, favors hydration over carbonation, and leads to a coarser pore structure. At moderate w/b ratios, excess free water facilitates concurrent carbonation and hydration; however, thinner water films ultimately hinder CaCO<sub>3</sub> precipitation and C-S-H nucleation. Slag contents up to 30% slightly suppress early carbonation and hydration, while higher dosages significantly delay both reactions and increase capillary porosity. An increasing AEA dosage stabilizes CO<sub>2</sub> bubbles, suppressing immediate CO<sub>2</sub> dissolution and reducing the early formation of carbonation and hydration products; excessive AEAs promotes bubble coalescence and results in an interconnected pore network. An optimized mix design, moderate water content, slag below 30%, and limited AEA dosage enhance the synergy between carbonation and hydration, improving early pore refinement and reaction kinetics.
ISSN:2075-5309

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