Current state of K-based geopolymer cements cured at ambient temperature

Abstract

The increasing focus on global climate change, the public and consumer preferences for “green” products and the associated markets in carbon credits have promoted the use of alternate cements in place of pure Portland cement binders. Using alkali activation method, waste materials such as fly ash and slag can be modified to replace ordinary Portland cement. In the present study, a combination of sodium hydroxide pellets and sodium silicate solution is used for the alkali activation of fly ash to prepare geopolymer cement. In the same way, a mixture of KOH (pellets) and K-silicate solution has been used with fly ash and slag (used in British Columbia, Canada) for comparison. Ambient temperature curing has been considered in addition to oven curing. Compressive strength tests indicate that both duration and intensity of the temperature affect the properties of the geopolymer. Higher intensity of the temperature accelerates the polymerization process much faster and gives higher compressive strength for the same duration of curing. On the other hand, longer duration of curing leads to improved hardened properties compared to shorter span at the same intensity. This paper presents data for curing done at ambient temperatures and the effectiveness of using potassium- and sodium-based solutions for geopolymer cement. Further recommendations for future work are also included.