Hydrated lime/potassium carbonate as alkaline activating mixture to produce kaolinitic clay based inorganic polymer

Abstract

The stability as a function of storage time of an alkaline mixture developed by reacting hydrated lime (Ca(OH)2) with a solution of potassium carbonate (K2CO3) has been studied. The chemical and microstructure of alkali-activated kaolinite using the developed alkaline mixture were studied using XRD, ATR-FTIR, TGA and EDX-SEM. Over storage time of 24h, the developed alkaline mixture was always composed of solid and liquid fractions. The solid fraction was characterized as a mixture of hydrated lime, butschliite (Ca2K6(CO3)5·6H2O) and calcite (CaCO3), and the liquid fraction as a solution saturated with K+ ions in a highly alkaline environment (OH−). The inorganic polymer was dominated by hydrous phase of kaliophilite (K2Si2Al2O8·3H2O), hydrated lime, butschliite and calcite. Different mixing procedures of water, hydrated lime and potassium carbonate with kaolinitic clay were used to produce an inorganic polymer, whose strength and stability were evaluated in terms of unconfined compressive strength under dry and saturated conditions. A maximum dry strength of 39MPa and a maximum soaked and cycled strength of 11MPa were obtained. A low cost-environment friendly alkaline mixture was developed to produce kaolinitic clay based inorganic polymer for construction and industrial applications.