Effect on fresh C-S-H gels of the simultaneous addition of alkali and aluminium

• Published in: Cement and concrete research Vol. 40; no. 1; pp. 27 - 32
• Main Authors: García Lodeiro, I., Fernández-Jimenez, A., Palomo, A., Macphee, D.E
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 2010; Elsevier
• Subjects: Applied sciences; Buildings. Public works; Calcium-Silicate-Hydrate (C-S-H) [B]; Cement concrete constituents; Cements; Exact sciences and technology; Materials; Properties and test methods; Properties of anhydrous and hydrated cement, test methods; Spectroscopy [B]; Strätlingite [D]; TEM [B]; Strätlingite [D]; Spectroscopy [B]; Calcium-Silicate-Hydrate (C-S-H) [B]; TEM [B]; Addition; Ettringite; Aluminium; Experimental study; Portland cement; Alkali; CSH phase; Spectrometry; Environment impact
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2009.08.004

Reducing Portland cement content in cementitious binders offers a means to address the adverse environmental impacts of Portland cement manufacture. This paper investigates the impacts on hydration product chemistry of partially replacing Portland cement with alkali-activated aluminosilicates. Here, short-term effects of soluble alkali and aluminium, likely to be available in an alkali-activated system, on the structure of synthetic C-S-H gels are assessed. .C-S-H gels (synthesized at pH values of over 13) were mixed with different concentrations of aluminium nitrate and sodium hydroxide. The gels were characterized by FTIR, TEM/EDX and XRD 72
h later. The results showed that both alkali and aluminium increased the degree of silicate polymerisation in the C-S-H gels and precipitated a crystalline calcium aluminosilicate phase.