The products transformation and leaching behavior in solidified cement matrices under the coupling actions of “water-heat-chemistry”

Zheng, Zhao; Bao, Zhitao; Yang, Jun; Cui, Maoxuan; Xue, Ming; Li, Yuxiang

doi:10.1016/j.conbuildmat.2022.126565

Cited by 9 publications

(3 citation statements)

References 33 publications

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“…It can be seen from Figure 10 that both the ADC of Ca 2+ and Sr 2+ in fly ash/cement waste forms increase with the rising leaching temperatures and concentrations of leaching solution. As seen in Figure 11, the relationship of the ADC between Ca 2+ and Sr 2+ in fly ash/cement waste forms is quadratic nonlinear (Y � 4.44 × 10 −5 − 0.21X + 1403.33X 2 ), which is different from the linear relationship in cement waste forms [31]. When the ADC of Ca 2+ is lower than 4 × 10 −4 cm 2 /d, the ADC of Sr 2+ and Ca 2+ can be approximately regarded as a linear relationship.…”

Section: Fitting Of Apparent Diffusion Coefficientmentioning

confidence: 93%

“…But the leaching of cations decrease at a specific leaching period, especially at high leaching temperature of 60 and 80 °C. is is mainly attributed to the crystallization of NH 4 Cl at the surface and inside of fly ash/cement waste forms, which led to a dense surface to restrain the leaching of cations [31]. Also, the high NH 4 Cl concentration has decreased the porosity of fly ash/cement waste forms (Figure 4 and Table 4), which contributed to the retention of radioactive nuclides.…”

Section: Transformation Of Products and Pore Structuresmentioning

confidence: 99%

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The Transformation and Leachability of Fly Ash/Cement Waste Forms Subjected to the Simultaneous Effect of Heat and Chemistry

Zheng

Hua

et al. 2022

Advances in Materials Science and Engineering

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The utilization of cement waste forms with high content of fly ash is a potential method in large-volume immobilization of low- and intermedium-level radioactive waste at near-surface. However, the migration behavior of radionuclides in fly ash/cement waste forms under geological environment is still unclear. This study researched the transformation of products, pore structure as well as the leachability of Ca2+, Na+, and simulated radioactive nuclides (Sr2+ and Cs+) in fly ash/cement waste forms under simultaneous effect through X-ray diffractometer (XRD), mercury intrusion porosimetry (MIP), and inductively coupled plasma optical emission spectroscopy (ICP-OES). Furthermore, the relationship between the decalcification and the leaching of Sr2+ and Cs+ was established by the fitting curves of apparent diffusion coefficient. The results indicated that the products of fly ash/cement waste forms were kept stable under simultaneous effect and the pore structure has excellent resistance to temperature. The increasing salt concentrations of leachant and temperature promoted the leaching of radionuclides while the protection layer formed at 60–80°C inhibited this phenomenon. The relationship of apparent diffusion coefficient between Sr2+ and Ca2+ was quadratic nonlinear, while the relationship between Cs+ and Ca2+ showed a linear relationship. Compared to cement waste forms, fly ash/cement waste forms were more stable. In addition, the long-term retention ability of fly ash/cement waste forms to Cs+ was more outstanding than Sr2+.

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Section: Fitting Of Apparent Diffusion Coefficientmentioning

confidence: 93%

Section: Transformation Of Products and Pore Structuresmentioning

confidence: 99%

The Transformation and Leachability of Fly Ash/Cement Waste Forms Subjected to the Simultaneous Effect of Heat and Chemistry

Zheng

Hua

et al. 2022

Advances in Materials Science and Engineering

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“…It has been reported that the leaching front of concrete submerged in still field water for 100 years is only about 5-10 mm [19]. Thus, for improving the test efficiency and satisfying different engineering environments, some aggressive solutions such as ammonium nitrate (NH4NO3) [20][21][22][23][24][25], ammonium chloride (NH4Cl) [26,27], sodium nitrate (NaNO3) [28], and sodium chloride (NaCl) solution [29,30], and some factors such as flow velocity [24], water-to-cement ratio (w/c) [29] and supplementary cementitious materials [31] are investigated to study the effect of calcium leaching on the microstructure and mechanical properties of cementitious materials.…”

Section: Introductionmentioning

confidence: 99%