Effect of Method and Duration of Curing on the Compressive Strength of the Lime-Fly Ash Geopolymer Concrete

The use of lime to produce ambient cured Geopolymer concrete is one of a practical solution to avoid heat curing in the production of geopolymer concrete. The addition of lime in the geopolymer system will add another hardened mechanism, i.e. hydration in addition to condensation-polymerisation. This research aims to determine the influence of air and water curing on the strength of geopolymer concrete which uses class F fly ash and lime as raw materials. The geopolymer concrete was produced by varying the activator (sodium silicate and sodium hydroxide) with the variation of the activator to binder ratio of 0.45, 0.50, 0.55, and 0.60. Five per cent of the fly ash was replaced by slaked lime and the water added to the mix to maintain the ratio of water to solid (activator + binder) to 0.32. The test specimens were 100 mm dia x 200 mm height cylinder. Water-immersion curing was performed for 7, 14, and 21 days and the compressive strength test was done at 28 days. The results show that there is a difference in the curing process between the geopolymer concrete and the normal concrete. In the geopolymer concrete, there is a decrease in compressive strength if soaked for seven days and recovered with the increase in the age of immersion. Whereas for normal concrete, the compressive strength continues to increase with increasing age of immersion.