The sintering behavior of hydroxide/metakaolin hydroxyapatite alkali-activated material, the resulting volume shrinkage and microstructure analysis are influenced by metakaolin contribution and alkali activator ratio. The alkali-activated material is initially produced by alkaline activation of hydroxyapatite and metakaolin with alkaline activator solution and sintered at from 875°C to 950°C with a dwell time of 2 hours. It has been found that, the optimum volume shrinkage of 41.92% at 900°C sintering temperature for sample activated by 1.0 alkaline activator ratio. As increasing the ratio of alkaline activator ratios up to 1.25, the rough surface with larger pores are obtained on the microstructure surface. The evolution of microstructure on hydroxyapatite/metakaolin alkali-activated material at higher sintering temperatures up to 1250°C, are analyses. Porosity were found as a key role in determining the properties of sintered hydroxyapatite/metakaolin alkali-activated material.
