Effects of porosity on leaching of Ca from hardened ordinary Portland cement paste

Haga, Kazuko; Sutou, Shunkichi; Hironaga, Michihiko; Tanaka, Satoru; Nagasaki, Shinya

doi:10.1016/j.cemconres.2004.06.034

Cited by 223 publications

(112 citation statements)

References 11 publications

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“…The effect of degradation on the properties of cementitious materials has been reported in several studies in the literature (Adenot and Buil 1992;Carde et al 1996;Faucon et al 1996Faucon et al , 1998Haga et al 2005;Maltais et al 2004). In these studies leaching of calcium from cementitious materials have been accomplished both through immersion of the solid cementitious specimens in water (Faucon et al 1996;Haga et al 2005;Mainguy et al 2000) and through immersion of the specimens in chemical agents in order to accelerate the leaching process (Adenot and Buil 1992;Faucon et al 1996Faucon et al , 1998Haga et al 2005;Heukamp et al 2001;Mainguy et al 2000;Maltais et al 2004;Revertegat et al 1992;Ryu et al 2002;Saito et al 1992;Wittmann 1997).…”

Section: Introductionmentioning

confidence: 99%

“…In these studies leaching of calcium from cementitious materials have been accomplished both through immersion of the solid cementitious specimens in water (Faucon et al 1996;Haga et al 2005;Mainguy et al 2000) and through immersion of the specimens in chemical agents in order to accelerate the leaching process (Adenot and Buil 1992;Faucon et al 1996Faucon et al , 1998Haga et al 2005;Heukamp et al 2001;Mainguy et al 2000;Maltais et al 2004;Revertegat et al 1992;Ryu et al 2002;Saito et al 1992;Wittmann 1997). The results in these studies indicate that a layered structure is developed in the leached samples comprising an unaltered core delineated by total dissolution of Portlandite followed by different zones separated by dissolution/precipitation fronts and progressive decalcification of the CSH gel (Adenot and Buil 1992).…”

Section: Introductionmentioning

confidence: 99%

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Physical and Mechanical Properties of Cementitious Specimens Exposed to an Electrochemically Derived Accelerated Leaching of Calcium

Babaahmadi

Tang

Abbas

et al. 2015

International Journal of Concrete Structures and Materials

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Simulating natural leaching process for cementitious materials is essential to perform long-term safety assessments of repositories for nuclear waste. However, the current test methods in literature are time consuming, limited to crushed material and often produce small size samples which are not suitable for further testing. This paper presents the results from the study of the physical (gas permeability as well as chloride diffusion coefficient) and mechanical properties (tensile and compressive strength and elastic modulus) of solid cementitious specimens which have been depleted in calcium by the use of a newly developed method for accelerated calcium leaching of solid specimens of flexible size. The results show that up to 4 times increase in capillary water absorption, 10 times higher gas permeability and at least 3 times higher chloride diffusion rate, is expected due to complete leaching of the Portlandite. This coincides with a 70 % decrease in mechanical strength and more than 40 % decrease in elastic modulus.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Physical and Mechanical Properties of Cementitious Specimens Exposed to an Electrochemically Derived Accelerated Leaching of Calcium

Babaahmadi

Tang

Abbas

et al. 2015

International Journal of Concrete Structures and Materials

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“…Based on XMT images, the approximate degradation depth by CO2 saturated water is~3.5 mm for a cement column with water-to-cement ratio of 0.33 after a 5-month reaction (Figure 3.12), while~1 mm for a cement column with water-to-cement ratio of 0.38 after an 1-month reaction (Figure 3.5). Slower degradation rates (0.7 mm per month) for cement columns with water-to-cement ratio of 0.33 after a 5-month reaction than for cement columns (1 mm per month) with water-to-cement ratio of 0.38 after a 1-month reaction is attributed to slower Ca and carbonate diffusion through the pores of cement matrix with lower water-to-cement ratio (Haga et al 2005), as well as slower degradation rates with increasing reaction times due to the change of cement pore structure (Kutchko et al 2008).…”

Section: Cement-co2 Reaction For 5 Monthsmentioning

confidence: 96%

Effective Permeability Change in Wellbore Cement with Carbon Dioxide Reaction

Um¹,

Jung²,

Martin³

et al. 2011

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SummaryPortland cement, a common sealing material used in wellbores for geological carbon sequestration, was reacted with carbon dioxide (CO2) in supercritical, gaseous, and aqueous phases at various pressure and temperature conditions to simulate cement-CO 2 reaction along the wellbore from carbon injection depth to the near surface. Hydrated Portland cement columns (14 mm diameter × 90 mm long; water-tocement ratio = 0.33), including additives such as steel coupons and Wallula basalt fragments, were reacted with CO2 in the wet supercritical (the top half) and dissolved (the bottom half) phases under carbon sequestration conditions with high pressure (10 MPa) and temperature (50°C) for 5 months. In parallel, small-sized hydrated Portland cement columns (7 mm diameter × 20 mm long; water-to-cement ratio = 0.38) were reacted with CO 2 in a dissolved phase at high pressure (10 MPa) and temperature (50°C) for 1 month or with wet CO2 in gaseous phase at low pressure (0.1 MPa) and temperature (20°C) for 3 months. X-ray microtomography images reveal the cement that reacted with CO 2 saturated groundwater had degradation depth of~1 mm for 1 month and~3.5 mm for 5 months, whereas the degradation was minor with cement exposure to supercritical CO 2 . Scanning electron microscopy-energy dispersive spectroscopy analysis showed the carbonated cement was comprised of three distinct zones: the innermost less degraded zone with Ca atom % > C atom %, the inner degraded zone with Ca atom % ≈C atom % due to precipitation of calcite, the outer degraded zone with C atom % > Ca atom % due to dissolution of calcite and C-S-H, as well as adsorption of carbon to cement matrix. The outer degraded zone of carbonated cement was porous and fractured because of dissolution-dominated reaction by carbonic acid exposure, which resulted in the increase in BJH (Barrett-Joyner-Halenda) pore volume and BET (Brunauer-Emmett-Teller) surface area. In contrast, cement-wet CO 2 (g) reaction at low P (0.1 MPa)-T (20°C) conditions for 1 to 3 months was dominated by precipitation of micron-sized calcite on the outside surface of cement, which resulted in the decrease in BJH pore volume and BET surface area. Cement carbonation and pore structure change are significantly dependent on pressure and temperature conditions, as well as the phase of CO 2 , which controls the balance between precipitation and dissolution in cement matrix. Geochemical modeling result suggests that ratio of solid (cement)-to-solution (carbonated water) has a significant effect on cement carbonation; thus, the cement-CO2 reaction experiment needs to be conducted under realistic conditions representing the in-situ wellbore environment of a carbon sequestration field site.Total porosity and air permeability for a duplicate cement column with water-to-cement ratio of 0.38 measured after oven drying by Core Laboratories using Boyle's Law technique and steady-state method were 31% and 0.576 mD. A novel method to measure the effective liquid permeability of a cement column using X-ray micr...

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“…degraded zone. The reprecipitation in degraded zones of ettringite and some other hydrated compounds during decalcification has been indicated by other authors (30,31) and is caused by diffusion phenomena from the non-degraded zone to the surface of the sample in contact with the aggressive solution. This presence of ettringite is confirmed by SEM, as shown in Figure 5a.…”

Section: Changes In the Cement Matrixmentioning

confidence: 98%

“…Este proceso ha sido descrito por otros autores, indicando que es causado por la difusión de iones desde la zona no degradada hacia la superficie de la muestra, en contacto con el medio agresivo (30,31). La presencia de ettringita fue corroborada por medio de MEB, como se muestra en la Figura 5a.…”

Section: Changes In the Cement Matrixunclassified

Estudio del proceso de descalcificación en morteros degradados en NH<sub>4</sub>NO<sub>3</sub> empleando técnicas ultrasónicas

Pérez¹,

Moragues²,

Macphee³

et al. 2009

Mater. construcc.

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Effects of porosity on leaching of Ca from hardened ordinary Portland cement paste

Cited by 223 publications

References 11 publications

Physical and Mechanical Properties of Cementitious Specimens Exposed to an Electrochemically Derived Accelerated Leaching of Calcium

Physical and Mechanical Properties of Cementitious Specimens Exposed to an Electrochemically Derived Accelerated Leaching of Calcium

Effective Permeability Change in Wellbore Cement with Carbon Dioxide Reaction

Estudio del proceso de descalcificación en morteros degradados en NH<sub>4</sub>NO<sub>3</sub> empleando técnicas ultrasónicas

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