Studies of model macroscopic-defect-free materials. Part 2.—Microstructure and open porosity in the system 4CaO·Al2O3· Fe2O3–4CaO·3Al2O3· SO3–hpmc–H2O

Abstract

Model macroscopic-defect-free materials (MDFs) representing selected compositions in the system 4CaO · Al₂O₃· Fe₂O₃–4CaO · 3Al₂O₃· SO₃–hmpc–H₂O have been investigated by means of electron microscopy and mercury intrusion porosimetry. ‘Smooth spatial flow’ of unreacted grains into an intergranular hydrated-aluminium-monosulfate-related (AFm-like) phase and rigid linkage of clinker phase–intergranular mass–solidified polymer are demonstrated. Solidification of an intergranular Afm–like phase in the presence of hpmc and pressure during syntheses causes partial elimination of pores; electron microscopy shows the remaining pores to be isolated at the micrometre level. Pore size distributions reveal the role of pressure in packing the pores with diameter r > 100 nm. Careful control of the mixing and pressing of reaction mixtures results in porosities in the range typical of MDFs. A scheme interrelating the atomic- and particle-level phenomena is outlined, and includes formation of Al(Fe)–O–C crosslinks between cement clinker and polymer.