Regional metakaolin particle size reduction for higher strength geopolymer

Abstract The objective of this project was to further develop new composites and a testing program for the performance‐based specification for natural Amazonian geopolymer (GP) for use in ceramics and construction. While fly ash‐based alkali activated materials are now an established technology, metakaolin‐based GPs still need to be developed and optimized regarding the knowledge of the specific characteristics and properties of local resources. Amazonian kaolin was calcined into metakaolin (AMK). AMK particle size reduction for better reactive material was evaluated by means of dry and wet ball milling and sieving. Three types of metakaolin were analyzed for particle size distribution, and their size d 50 ranged from 7.9 to 2.8 µm. Further GP characterization followed physical and mechanical properties in flexural strength tests. In addition, scanning electron microscopy and energy dispersive spectroscopy were used to investigate the microstructure of the materials. Energy dispersive X‐ray fluorescence was used to measure the GP material composition. Analysis of the results revealed that the strength and stiffness of sodium–metakaolin‐based GP were inversely proportional to particle size. All distinct particle size GPs showed, in general, some increase in strength and stiffness within curing times ranging from 3 to 28 days.