Investigation of utilization of amorphous silica residues as supplementary cementing materials

This paper presents the results of a study on the use of amorphous silica (AS) residues as supplementary cementing materials. Standard ASTM tests on setting time and compressive strength development of cement paste and mortar with up to 30% AS residues were carried out. With increasing amounts of AS residue, the setting time of the pastes shortened and the compressive strength of the mortar increased at all ages. The hydrated phases in pastes were determined using X-ray diffractometry and scanning electron microscopy. Observations indicated that Ca(OH)₂ decreased or disappeared and C-S-H gel appeared in large quantity at early ages due to the addition of AS residue. The results obtained from the research confirmed that AS residue has a remarkable pozzolanic activity. It can be used as a supplementary cementing material and will significantly improve some basic properties of cement.