Nanomontmorillonite Reinforced Fibre Cements and Nanomontmorillonite-Nanosilica Reinforced Mortars

In this study the effects of an organomodified nanomontmorillonite (nMt) dispersion (nC2) and of a powder type nMt (nC4), were compared in quaternary low carbon footprint fibre-reinforced cementitious nanocomposites and mortars. 60% Portland cement, 20% limestone (LS) and 20% fly ash plus fibres/superplasticizer comprised the reference paste. nMt was added at 1% by mass. Pastes were investigated in terms of flexural strength, thermal properties, density and water impermeability. Neither of the two types offered strength enhancement. nC2 showed some potentials at late ages (90 days). Thermal gravimetric analyses showed limited additional pozzolanic activity towards the production of additional C–S– H at day 90, in agreement with flexural strength results and X-ray diffraction analysis, which showed the consumption of Ca(OH)₂ even at day 28. No change in density was observed, whereas water impermeability tests showed that nC2 was more effectively organomodified not allowing water to be absorbed neither in the short nor in the long term, while nC4 at later ages seemed to be absorbing water back. Lastly, cubes of mortars were prepared and tested in compression in an attempt to fully investigate the potentials of the formulations. The effect of using simultaneously nMt and nanosilica (nS) was also recorded, however no increase in compressive strength was observed. The long-term density of the mortars was also investigated, results suggesting poor compaction which was not adjusted with the use of admixtures. These results are in support of previous studies undertaken in the field, showing that the purpose of use of organomodified nMt’s must be clearly defined before any formulations are designed.