Application of activated diatomite for dry lime mixes

•Thermal (700–900 °C) and chemical modification of diatomite increases its activity.•Modification of diatomite with silicic acid sol increases silica contents.•Lime mortars with chemically modified diatomite have higher amount of bound lime.•Lime mortars with chemically modified diatomite have higher strength.

Diatomite is a pozzolanic material containing mainly amorphous silica. In its natural form it possesses low reactivity and is a weak material. The aim of this study was to test and evaluate the diatomaceous deposits of Inza town region as a component of dry lime mixes. Methods of activation meant to change diatomite surface activity and its chemical composition were used to increase diatomite reactivity. Diatomite was activated thermally by burning in various temperatures and chemically by treatment with silicic acid. Modification of diatomite with silicic acid sol increases silica content, promotes hydrophilic properties of its surface, decreases pore dimensions, increases its activity as a mineral additive. Activated diatomite was mixed with lime in mass proportions lime:diatomite 1:4. The laboratory investigations indicated that pastes made with the modified diatomite have higher amount of bound lime and a structure with higher strength, they contain more calcium hydrosilicates and less portlandite than paste containing non-modified diatomite.