Evaluation of the rheological behavior of cement pastes with addition of graphene oxide

ABSTRACT

The addition of graphene oxide (GO) in cementitious materials makes it possible to obtain more resistant and durable composites, with lower pollutant load associated with their production. Previous research has shown that the addition of nanomaterials to the cement paste can cause a reduction in the rheological parameters of viscosity and yield stress. This study aimed to investigate changes in the rheological behavior of cement pastes due to GO addition. In order to fulfill this objective, tests were carried out with GO produced and patented at CTNano / UFMG (Technology Center for Nanomaterials and Graphene at the Federal University of Minas Gerais) in the contents of 0.03% and 0.05%, on cement pastes classes CP-III and CP-V. Two methods of analysis were used, the mini-slump and the rotational flow rheometry. In the mini-slump test, reductions in the spreading radius of 42,94% (CP-III) and 23,34% (CP-V) were obtained in relation to the reference sample, considering an addition of 0.05%GO. For this same percentage of addition and using the rheometer, increases of 125,49% (CP-III) and 31,51% (CP-V) in viscosity were obtained, as well as increases of 82,24% (CP-III) and 38,87% (CP-V) in the yield stress. Both techniques used proved to be efficient in determining the influence of the addition of GO on the rheology of cement pastes, and pointed to an increase in the viscosity of the paste as a greater amount of GO is incorporated into the mixture. The main difference between the techniques presented is in the quality of the results obtained. While rotational flow rheometry is a more sophisticated method and produces a more complete and accurate results report, the mini-slump technique has the advantage of allowing the visualization of the effects of additions on the fluidity and consistency of cement pastes.

Keywords
Graphene oxide; Nanomaterials; Rheological behaviour; Cement composites