The Effect of Heat Treatment on Alkali Activated Materials

Abstract

The primary object of the present research was to investigate the porous low calcium alkali activated material (AAM). Traditionally Na+ ions for alkali activation solution ensure highly alkaline media which enhances the dissolution of amorphous phase in the raw materials forming solid cementitious material with sodium aluminosilicate hydrate (N-A-S-H) structure afterwards. Almost all alkali ions are partially hydrated filling the pores in the gel structure (N-A-S-H gel, type zeolite precursor) and neutralizing the charge on Al(OH)^-₄ groups. These alkali ions are available for leaching in water environment. Due to this property the application of porous AAM in this research is related to the water treatment systems similar to those of natural zeolites which are considered as effective sorbent because of their porous structure, high specific surface and ion exchange. Porous AAM was obtained from metakaolin, sodium silicate glass, modified sodium silicate solution with Ms = 1.68 and diethylene glycol (DEG) aluminium paste as pore forming agent. The density of AAM was 1150 ± 12 kg/m³ and compressive strength fc > 12 MPa. The effect of heat treatment to microstructure and structural properties of AAM was investigated. Heat treatment is an effective method for changing the alkali leaching kinetic form AAM structure.

DOI: http://dx.doi.org/10.5755/j01.ms.23.3.16280