Influence of Pressure on the Annealing Process of β-Ca₂SiO₄（C₂S） in Portland Cement

【摘要】 Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-speciality grout. Dicalcium silicate（Ca₂SiO₄） is the primary constituent of a number of different types of cement. The β-Ca₂SiO₄ phase is metastable at room temperature and will transform into γ-Ca₂SiO₄ at 663 K. In this work, Portland cement is annealed at a temperature of 950 K under pressures in the range of 0–5.5 GPa. The high pressure experiments are carried out in an apparatus with six anvil tops. The effect of high pressure on the obtaining nano-size β-Ca₂SiO₄（C₂ S） process is investigated by x-ray diffraction and transmission electron microscopy. Experimental results show that the grain size of the C₂ S decreases with the increase of pressure. The volume fraction of the C₂ S phase increases with the pressure as the pressure is below3 GPa, and then decreases（P > 3 GPa）. The nano-effect is very important to the stabilization of β-Ca₂SiO₄. The mechanism for the effects of the high pressure on the annealing process of the Portland cement is also discussed.更多还原

【Abstract】 Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-speciality grout. Dicalcium silicate（Ca₂SiO₄） is the primary constituent of a number of different types of cement. The β-Ca₂SiO₄ phase is metastable at room temperature and will transform into γ-Ca₂SiO₄ at 663 K. In this work, Portland cement is annealed at a temperature of 950 K under pressures in the range of 0–5.5 GPa. The high pressure experiments are carried out in an apparatus with six anvil tops. The effect of high pressure on the obtaining nano-size β-Ca₂SiO₄（C₂ S） process is investigated by x-ray diffraction and transmission electron microscopy. Experimental results show that the grain size of the C₂ S decreases with the increase of pressure. The volume fraction of the C₂ S phase increases with the pressure as the pressure is below3 GPa, and then decreases（P > 3 GPa）. The nano-effect is very important to the stabilization of β-Ca₂SiO₄. The mechanism for the effects of the high pressure on the annealing process of the Portland cement is also discussed.更多还原