*3.1. Consistency, Density and Setting Time*

Consistency of the fresh MWCNT-mortar samples was determined by flow table. The loading of MWCNTs in mortars resulted in consistency values lower than that of the control mortar. As the MWCNT addition ratio increased, the consistency values decreased (Table 4). However, density values increased as the MWCNT loading increased (Table 4).

Both density and consistency are related to MWCNTs dispersion, since these fresh mortar properties are indicative of homogeneity and porosity. Well dispersed MWCNTs are expected to contribute to better homogeneity and promote filling effects on the porous structure of cement composites. Our results show an increase in density with MWCNTs content, which can be attributed to the reduction of air content in the cement matrix as CNTs are added and occupy empty sites within the pore structure. This itself is an indicative of good MWCNTs dispersion. Coherently, increase in consistency with MWCNTs content should be expected, leading to more fluid mixes as porous structure is refined and mix fine particles get better dispersed. However, taking in account that no superplastifier nor surfactant agent was added along with MWCNTs, the decrease in consistency displayed in our results should be understood as an effect of large water retention in the mortar, mainly due to the higher water-demand of the pastes because of the MWCNTs' high specific surface.


**Table 4.** Physical properties of the fresh mortars.

Regarding the setting time, it was observed that for MWCNT-mortar both the initial and final setting times are shorter than that of the control mortar. Some researchers [41] state the same results. However, initial setting time differences are more significant than final time, although changes in the MWCNT loading did not significantly modify the overall trend. According to [42], this behavior can be explained by a rapid nucleation during the initial steps which later leads to a barrier effect, slowing the formation of additional hydration products in the MWCNT-mortar [14].
