Relationship between clinker porosity and interstitial phase morphology

The results of interstitial phase morphology variations of two clinkers with respect to their porosity differences are presented in this paper. Single clinker nodules with an average diameter of 10–15 mm were used in the analyses. Porosity ratios and phase compositions were determined on scanning electron microscope images of polished clinker surfaces by using image processing techniques and, in addition, morphological characterisation of interstitial phases was realised. The results showed that the porosity distribution of a single clinker nodule is heterogeneous and a relationship exists between the average interstitial phase thickness and porosity. A dendritic interstitial phase morphology is associated with porous clinker structure. The porosity ratio depends on the degree of dendritic structure formation. Dendritic structures form because local heat transfer conditions produce an undercooled liquid, which produces an unstable liquid-solid interface and crystallites which propagate in front of such an interface become surrounded by a liquid showing an increasing degree of undercooling. As crystalline solids typically occupy space more efficiently than their liquids, the solidification of the interdendritic regions then produces porosity at that stage of cooling. The morphological variations in interstitial phases and porosity may cause differences in the performance of cements produced from these clinkers.