Fresh and Hardened Properties of Potassium Hydroxide Activated Metakaolin and Fly Ash-Based Geopolymer Mortars

This study investigates the fresh (i.e., workability) and hardened (i.e., compressive strength) properties of metakaolin and class F fly ash (MKFA) based geopolymer (GP) mortars cured at room temperature. The qualitative and quantitative workability results for the MKFA GP mortars revealed that incrementing water to GP(solids) (W/S) ratio and fly ash content leads to an increase in workability. However, in the case of compressive strength and density, increasing the W/S ratio and fly ash content increased the porosity, thus reducing the compressive strength. The increase in the porosity can be attributed to the delayed geopolymerization reaction due to the silica in fly ash being less reactive than in metakaolin. Moreover, MK(50)FA(50) K(2.79)21-45%RS is a very workable material with a flow spread diameter of 180.38 mm, exhibiting the highest compressive strength and density of 10.81 MPa and 1.86 g/cm(3). For future research, it is recommended to study different methods to enhance the compressive strength of MK(50)FA(50) K(2.79)21-45%RS.