Influence of pozzolans and slag on the microstructure of partially carbonated cement paste by means of water vapour and nitrogen sorption experiments and BET calculations

摘要

The influence of water-to-binder ratio (0.33 to 0.50) and additions (fly ash, slag, silica fume) on themicrostructure of partially carbonated cement pastes was studied by nitrogen sorption and static and dynamicwater vapour sorption. The selected technique affects macropore condensation and accessibility of pores,while predrying influences removal of CSH interlayer water. BJH calculations showed the increased amount ofcapillary pores with higher water-to-cement ratio, and the decrease of micropores (b2 nm), in pastes with 50%or more fly ash or slag. Paste with 10% SF showed a high amount of gel pores, related to the higher amount ofCSH gel, calculated from adsorption at 23% RH. A linear relation was observed between BET specific surface andwater-cement ratio. Thermogravimetric analysis illustrated the influence of water-cement ratio andpozzolanic materials on the portlandite content. Introduction of silica fume, increased the specific surfaceaccessible to water, but not to nitrogen molecules.