Medium-Term Mechanical Properties of Cement Mortar Modified with Bentonite Nanoparticles

In the current study, the influence of adding bentonite nanoparticles to cement mortar on mechanical strengths is analyzed at 56 days of curing. Various percentages of bentonite were used as replacement for the Portland cement type II. The results show a decrease in the flexural strength when adding these nanoparticles, whereas the compressive strength registers a slight increase, especially for the 1.5 wt% bentonite. The mechanical strength results are in correlation with the density analysis. For the modified sample with the highest density value, i.e. 1.5 wt% bentonite, the highest compressive strength is registered. The SEM images provided an insight into the microstructure of the material and they confirmed the mechanical strength results. The most uniform aspect was recorded for the 1.5 wt% bentonite sample, where the presence of CSH crystals is prevalent. For the modified sample with 2 wt% bentonite, important cracks and voids were present in the specimen – sample for which the compressive strength registered a decrease in value. To conclude, the addition of bentonite slightly improves the compressive strength at 56 days of curing but has a detrimental effect on flexural strength at the considered age. Further studies should be conducted at even later ages, taking into account the characteristics of bentonite and Portland cement type II.