The temperature-dependent action of sugar in the retardation and strength improvement of Ca(OH)₂-Na₂CO₃-activated fly ash systems through calcium complexation

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>This study reports the temperature-dependent strength improvement and retardation in Ca(OH)<SUB>2</SUB>-Na<SUB>2</SUB>CO<SUB>3</SUB>-activated fly ash binders with sugar. Without sugar, the system exhibited rapid stiffening due to the calcite formation. The addition of sugar clearly removed the false set; however, at room temperature, it retarded strength development because the calcium complexation of sugar inhibits the dissolved calcium ions from participating in calcite and C-S-H formation. However, at 90 °C, the use of sugar significantly improved the compressive strength by increasing the (1) degree of dissolution of fly ash and Ca(OH)<SUB>2</SUB>, (2) C-S-H formation, and (3) reduction of overall pore size and volume.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fly ash was activated with Ca(OH)<SUB>2</SUB>, Na<SUB>2</SUB>CO<SUB>3</SUB>, and sugar at different temperatures. </LI> <LI> The use of sugar delayed the rapid set of the cementless binder at room temperature. </LI> <LI> At the high curing temperature, the use of sugar improved the strength of the binder. </LI> <LI> The high temperature removed calcium complexation of sugar, increasing strength. </LI> </UL> </P>