Tantawy M A, Shatat M R, El-Roudi A M, Taher M A, Abd-El-Hamed M
Chemistry Department, Faculty of Science, Minia University, Minia 61111, Egypt.
Chemistry Department, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt.
Int Sch Res Notices. 2014 Oct 29;2014:873215. doi: 10.1155/2014/873215. eCollection 2014.
This paper describes the low temperature synthesis of belite (β-C2S) from silica fume. Mixtures of lime, BaCl2, and silica fume with the ratio of (Ca + Ba)/Si = 2 were hydrothermally treated in stainless steel capsule at 110-150°C for 2-5 hours, calcined at 600-700°C for 3 hours, and analyzed by FTIR, XRD, TGA/DTA, and SEM techniques. Dicalcium silicate hydrate (hillebrandite) was prepared by hydrothermal treatment of lime/silica fume mixtures with (Ca + Ba)/Si = 2 at 110°C for 5 hours. Hillebrandite partially dehydrates in two steps at 422 and 508°C and transforms to γ-C2S at 734°C which in turn transforms to α'-C2S at 955°C which in turn transforms to β-C2S when cooled. In presence of Ba(2+) ions, β-C2S could be stabilized with minor transformation to γ-C2S. Mixture of silica fume, lime, and BaCl2 with the ratio of (Ca + Ba)/Si = 2 was successfully utilized for synthesis of β-C2S by hydrothermal treatment at 110°C for 5 hours followed by calcination of the product at 700°C for 3 hours.
本文描述了由硅灰低温合成贝利特（β-C2S）的过程。将氧化钙、氯化钡和硅灰按（Ca + Ba）/Si = 2的比例混合，在不锈钢反应釜中于110 - 150°C水热处理2 - 5小时，然后在600 - 700°C煅烧3小时，并通过傅里叶变换红外光谱（FTIR）、X射线衍射（XRD）、热重/差示热分析（TGA/DTA）和扫描电子显微镜（SEM）技术进行分析。通过将（Ca + Ba）/Si = 2的氧化钙/硅灰混合物在110°C水热处理5小时制备了硅酸二钙水合物（硅钙石）。硅钙石在422°C和508°C分两步部分脱水，并在734°C转变为γ-C2S，γ-C2S又在955°C转变为α'-C2S，冷却时α'-C2S再转变为β-C2S。在Ba(2+)离子存在的情况下，β-C2S可以稳定存在，仅有少量转变为γ-C2S。将硅灰、氧化钙和氯化钡按（Ca + Ba）/Si = 2的比例混合，通过在110°C水热处理5小时，然后将产物在700°C煅烧3小时，成功用于合成β-C2S。
