Compressive strength of geopolymers while varying the raw materials

Geopolymers were synthesized using raw materials produced from two different areas: one was from Indonesia and the other was from Habcheon, Korea. The constituting phases of the Indonesian raw material were quartz and kaolinite, while those of the Habcheon sample were quartz, halloysite and albite. They were both calcined at 750°C for 6 hours, and solution of NaOH and water glass was added to activate the geopolymeric reaction. The compressive strength of geopolymer synthesized from the Indonesian raw material showed a low value of 151 kgf/cm² after curing for 28 days. However, it could be greatly increased by adding blast furnace slag powders of 1188 kgf/cm ² and 1969 kgf/cm² at 20 wt% and 40 wt% additions, respectively. The compressive strength of the geopolymer synthesized from the Habcheon raw material was high, at 557 kgf/cm² , after 28 days, and the very high early-stage (3 days) strength of 556 kgf/cm² for this sample was remarkable. Commercially available Habcheon metastate raw material, of which composition showed low CaO and Na₂O contents compared to the calcined Habcheon raw material, was also examined. It was found that the compressive strength of the commercial metastate type was nearly identical to that of the calcined Habcheon raw material except for the relatively low value at an early curing stage and at a high curing temperature of 60°C.