Assessing the effect of adding TiO₂ and calcined montmorillonite clay nanoparticles on the mechanical properties of cement mortar

The study analyses the influence on the mechanical strength of titanium dioxide TiO2 and calcined montmorillonite (CMMT) particles added individually and combined to cement mortar mixes. Having both similar and complementary properties, the combined solution of TiO2 and CMMT nanoparticles can induce positive effects on the overall properties of cementitious composites. However, this combination has been tackled only in a couple of studies, with different approaches regarding the design mix, but without comparing the results with the individual-nanomaterial mixes. In this study, the bulk density, flexural strength, compressive strength, and material microstructure were analyzed at 28 days of curing, for an addition of 0.5 wt% and 0.75 wt% TiO2, of 1 wt%, 1.5 wt% and 2 wt% calcined montmorillonite (CMMT), and of nanomaterial combinations. From the flexural strength point of view, the CMMT-modified cement mortar mix registered the highest value of all modified mixes for a cement replacement of 1.5 wt%, reaching a 10.27% improvement compared to the reference mix. The highest compressive strength was recorded for the mix comprised of 1 wt% CMMT and 0.75 wt% TiO2, with an increment of 3.19% compared to the reference mix. The obtained results were confirmed by means of Scanning Electron Microscopy (SEM) investigations showing that the highest amount of CSH was observed for 1% wt% CMMT and 0.75% wt% TiO2, corresponding to the highest compressive strength value.