Incorporation of Al in C-A-S-H gels with various Ca/Si and Al/Si ratio: Microstructural and structural characteristics with DTA/TG, XRD, FTIR and TEM analysis

Systems of different Ca/Si and Al/Si molar ratios were investigated. Incorporation of Al increases main basal spacing, amount of bounded water and decreases crystallinity of C-(A)-S-H (calcium (aluminium) silicate hydrate). Transmission electron microscope observations showed that aluminium results in formation of more compacted, foil-like microstructure. FTIR revealed the presence of rings within the structure of C-(A)-S-H. Low Ca/Si ratio promotes Al incorporation into C-(A)-S-H, while in case of high Ca/Si ratio aluminium is also incorporated into AFm. The results show, that Ca/Si ratio is of key significance deciding on Al incorporation into C-(A)-S-H in hydrating SCMs bearing blended systems.