Microstructure, composition and crystallography of Aalbrog Lion Brand Danish White cement

Abstract

The morphology and crystallography of fully hardened Aalbrog Lion Brand Danish White cement paste (water cement ratio 0.25) were examined using x- ray diffraction, optical and scanning electron microscopy with energy dispersive x-ray analysis (EDX) and transmission electron microscopy and EDX. These experiments showed the hardened cement to be mostly comprised of equiaxed particles of 3CaO.SiO2 with diameter of the order of 10 microns and larger often surrounded by inner and outer regions of an amorphous gel-like matrix with an average composition of about 1.75CaO.SiO2.3H2O (C-S-H) in which the CaO/SiO2 ratio varied from about 0.3 to 5.74. The hydrated regions were also found to contain significant amounts of Ca(OH)2. Small amounts of ettringite (Ca6Al2(SO4, SiO4,CO3)3 (OH)12.26H2O) were also detected. In addition, selected area electron diffraction of the C-S-H matrix revealed diffuse rings, indicating the presence of short range ordering. The morphology of C-S-H matrix was found to be comprised of small 'cells' of size approximately 5 nm which are no doubt responsible for the good mechanical properties of this particular hardened cement paste. These results were also found to be in excellent agreement with previous research on this topic