Pore Analysis and the Behaviour of the Unreacted Metakaolin Particles in the Networks of Geopolymer Cements Using Metakaolins From Kaolinitic and Halloysitic Clays

Abstract

This work aims to study the pore analysis and the behaviour of the unreacted metakaolin particles in the geopolymer cements from halloysitic and kaolinitic clays. The XRD patterns of the geopolymer cements show the unreacted metakaolin particles at about 21 °(2θ). The micrography images of the specimen from calcined kaolinitic clay confirm the presence of the unreacted metakaolin particles except the one using calcined kaolinitic clay from Bangoua. Whereas those from calcined halloysitic clay are compacts, homogeneous and denser microstructure. The compressive strength of the specimen from calcined halloysitic clay (88.50 ± 2.08 MPa) is higher compared to those from calcined kaolinitic clays (between 45.43 ± 1.84 and 57.20 ± 1.09 MPa). The pore analysis shows that the pore size diameters of the specimen from calcined halloysitic clay are in the range 7.4–16.2 nm while those from calcined kaolinitic clays are ranging from 5.5 to 12.3 nm. It was found that although the geopolymer cement from calcined halloysitic clay contains more unreacted metakaolin particles, it possesses the mesopores due to the inclusion of these fine unreacted metakaolin particles in its structure.