Modification of Composition and Microstructure of Portland Cement Pastes as a Result of Natural and Supercritical Carbonation Procedures

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• 作者：Carlos A. Garcí ; a-Gonzá ; lez ; Ana Hidalgo ; Carmen Andrade ; M. Cruz Alonso ; Julio Fraile ; Ana M. Ló ; pez-Periago ; and Concepció ; n Domingo
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2006
• 出版时间：July 5, 2006
• 年：2006
• 卷：45
• 期：14
• 页码：4985 - 4992
• 全文大小：398K
• 年卷期：v.45,no.14(July 5, 2006)
• ISSN：1520-5045

文摘

This study aims to analyze the effects of supercritical carbonation (CO₂ at 20 MPa and 318 K) on thephysicochemical properties of ordinary Portland cement pastes. The evolution of the main crystalline phasesof the cement pastes during carbonation was determined by means of X-ray diffraction and thermogravimetricanalysis. The pore structure was analyzed by low-temperature N₂ adsorption-desorption and mercury intrusionporosimetry techniques. Finally, the microstructure of the samples was observed by using scanning electronmicroscopy coupled with energy-dispersive X-ray detection for chemical analysis. For a natural carbonationprocess, diffusion of CO₂ into the pores of the cement paste is considered as the rate-controlling step. Instead,the accelerated reaction kinetics of calcium carbonate precipitation in the supercritical process was chemicallycontrolled by the detachment of calcium ions from solid portlandite or CSH gel. The total pore volume of thestudied cement pastes decreased with carbonation, which was associated with the deposition of the formedCaCO₃. Samples carbonated under the supercritical conditions developed a higher volume of gel pores thanthose obtained by natural carbonation.