Influence of Fixation of Consistency or Superplasticizer Content on Strength of Cement Pastes with Silica Fume or Nanosilica

Currently, the production of pastes, mortars and concretes with replacement of Portland cement by highly reactive cementitious materials to reduce the environmental impact caused by cement production is studied. Among these materials, silica fume and nanosilica stand out due to their properties that improve the mechanical performance and durability of pastes, mortars and concretes. Most of the research involving these materials uses superplasticizer to fix the consistency of the researched material. Despite this, there are researches that fix the superplasticizer content in their research. Thus, the objective of this research is to verify the influence of the fixation of the consistency or the superplasticizer content on the mechanical performance of cement pastes with silica fume or nanosilica. For this, five specimens were studied replacing Portland cement by 2% of colloidal nanosilica or 10% of silica fume. The specimens were molded by fixing the superplasticizer content or fixing the consistency of the pastes by the mini slump test. The compressive strength of three specimens at 1, 3 and 7 days was verified. The results showed that when incorporating silica fume or nanosilica in Portland cement, it became difficult to mold the pastes when the superplasticizer content was fixed, which influenced its mechanical performance. In order to carry out research with replacement of Portland cement by highly reactive cementitious materials for the production of pastes, mortars and concretes, it is recommended to fix the consistency of these materials.