Tailored Montmorillonite nanoparticles and their behaviour in the alkaline cement environment

This is the first time an analytical protocol is proposed to investigate and live-monitor the behaviour of montmorillonite nanoparticles, of different natures, in alkaline cement environment (pH of 12-13). In this study inorganic and organomodified montmorillonite nanoparticles were characterised via TEM, XRD, SEM-EDX and TGA. The inorganic montmorillonite used consisted of a purified montmorillonite commercially available as HPS-clay, and an organomodified montmorillonite, namely XDB-organoclay, consisted of purified montmorillonite modified with Noramonium MB2HT salt. Both montmorillonite nanoparticles were tailored to increase their compatibility with the hydrating cement environment. This gave rise to three different slurries: (i) reference-slurry, (ii) inorganic-slurry, and (iii) organic-slurry. The slurries were characterised and investigated through UV/vis, to measure suspension quality in terms of physical stability and rheological properties, and by AFM and FTIR to determine the chemical stability. The results indicated that the organic-slurry can offer a good stability, preventing aggregation of the clay particles at the targeted pH (13). The inorganic-slurry showed a reduction in surface charge and increased double layer repulsion. At pH 13 it was possible to obtain dispersion of the reference slurry although it underwent gelation and became viscous. The research findings informed that the inorganic slurry favours miscibility of the montmorillonite nanoparticles with cement particles and offers additional nucleation sites for CSH. Therefore it can be considered an alternative to organomodified montmorillonite as an addition in cement based materials.