The role of particle technology in developing sustainable construction materials

This paper presents a brief review of the role of particle technology in the development of low-CO₂ aluminosilicate ‘geopolymer’ binders and concretes as an alternative to traditional Portland cement-based materials. The role of particle shape in particular is highlighted, both in the context of its effect on paste rheology and on water demand. The spherical particles of fly ash and the platy particles of metakaolin show opposite effects in each of these areas, and this must be understood and controlled if an effective geopolymer concrete is to be designed. The angular particles of blast furnace slag are also important in determining paste rheology and porosity. The selection of the correct combination of aggregate gradings is critical in maximising concrete durability, as the ability of aggregates to pack sufficiently densely in a hardened concrete product then hinders the ability of aggressive external agents to migrate into the concrete and cause structural damage to either the binder or the embedded steel reinforcing.