title: Low Temperature Synthesis of Belite Cement Based on Silica Fume and Lime.
abstract: 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.
authors.affiliation: Chemistry Department, Faculty of Science, Minia University, Minia 61111, Egypt.
authors.forename: M A
authors.initials: MA
authors.lastname: Tantawy
authors.affiliation: Chemistry Department, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt.
authors.forename: M R
authors.initials: MR
authors.lastname: Shatat
authors.affiliation: Chemistry Department, Faculty of Science, Minia University, Minia 61111, Egypt.
authors.forename: A M
authors.initials: AM
authors.lastname: El-Roudi
authors.affiliation: Chemistry Department, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt.
authors.forename: M A
authors.initials: MA
authors.lastname: Taher
authors.affiliation: Chemistry Department, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt.
authors.forename: M
authors.initials: M
authors.lastname: Abd-El-Hamed