Cement nanocomposites containing montmorillonite nanosheets modified with surfactants of various chain lengths

To investigate the dispersion of montmorillonite (MMT) nanosheets in cement, MMT was modified with three organic surfactants of various alkyl chain lengths (C1-OMMT, C10-OMMT and C16-OMMT) and then compounded with cement. Of all nanocomposites, the one containing 0.5 wt% of C10-OMMT exhibited the most significant enhancement in compressive strength by 11.2% and in the hydration degree by 11% with low porosity, corresponding to the improved microstructure and durability. The high performance is determined by two factors: (i) the filling effect - the surfactants promote the dispersion of MMT nanosheets in cement and (ii) the reinforcement by the modified nanosheets, which may be compromised by the unnecessarily high fraction of long-chain surfactants. These two conflicting factors can be balanced by selecting an appropriate surfactant chain length, which is key to the resulting composite morphology and thus high mechanical performance and durability in terms of resistance to water penetration.