Incorporation of nanosilica in cement composites

ABSTRACT

The incorporation of the nanosilica has been studied as an alternative to improve the characteristics of cementitious materials because tends to increase the pozzolanic reactions and fill the interstitial spaces, decreasing the porosity and improving the compressive strength. In this context, the present study has the goal to evaluate the mechanical behavior and the microstructural characteristics of three cementitious composites: the reference e two with different levels of nanosilica dispersed in polycarboxylate (NDP), 0.2 and 0.4%, in relation to the cement mass. The mechanical behavior was evaluated through the compressive strength test and tensile test (Brazilian denomination). Furthermore, were done water absorption tests and microstructural analysis by Scanning Electron Microscope (SEM). From the analysis of the results, it was verified that the addition of NDP improved the mechanical properties and the microstructural characteristics of cementitious composites. The NDP content (0.4%) showed better results at 28 days, presenting a 55% increase in compressive strength, 79% tensile test and a 40% decrease in the absorption of water, in relation to the reference, possibly through the NDPs performance. However, when analyzing the incorporation of the two NDP contents, it was verified that when the content was doubled there was no significant improvement in the compressive strength, since the incorporation of 0.2% of NDP increased the compressive strength in 53% in relation to the reference. As for the microstructural analysis, a refinement of the structure was verified from the incorporation of NDP but no differences between the two incorporation was visualized.

Keywords
cementitious composite; nanosilica; mechanical strength