Impact of precursor granulometry on mechanical properties of geopolymers activated by potassium silicate.

Current tendencies in the field of waste management are influenced by environmental issues, putting among others an emphasis on waste reuse rather than landfilling. By-products of brick industry represent a typical example of a material with a great potential to be further processed to contribute to the environmental protection efforts. Due to its proper phase composition, ceramic powder can be effectively used as a precursor in alkali-activated materials. Focusing on the particle size distribution, this paper therefore deals with a quantification of precursor's parameters on the properties of the alkali-activation final products. Four different particle sizes of the precursors were assumed, being activated by the potassium water glass mixed with the potassium hydroxide to control the silicate modulus (1.0). All the materials studied exhibited consistent basic physical and mechanical properties except the mixture containing the precursor with particles smaller than 0.5 mm which could be caused by a suitable reaction kinetics. Having the smallest pore volume, this material exhibited the highest bulk density as well as the 7-day flexural and compressive strength. After 28 days, the materials exhibited an inverse proportion between the precursor's particle size and 28-day mechanical properties. [ABSTRACT FROM AUTHOR]