Functionalized carbon material in cement-based composites, a multivariate approach

This work describes the process that led to the optimization of compressive strength and fracture energy of a cement-based composite material enhanced with carbon allotropes: carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), and carbon fibers (CFs). The goal was achieved through the use of a multivariate analysis system, modifying three variables corresponding to the quantities of CNTs, GNPs, and CFs. All the allotropes used in the study were subjected to functionalization to improve their wettability and interaction with the cement matrix. A face-centered central composite design (FCCD) was used as the experimental design, where these three variables were modified at three levels. The levels were predetermined to ensure that the total amount of functionalized carbon allotropes (CNTs, GNPs, and CFs) do not exceed 0.2% of the weight of the cement used in the mix design. For the graphical visualization of the data, the response surface methodology (RSM) was employed to identify the relative maxima for each response studied. The RSM, supported by the FCCD, represents a powerful method for improving the understanding of relationships between variables and optimizing results. The experimentation led to a significant improvement in compressive strength by 27% and fracture energy by 690% compared to the reference sample. Subsequently, the model was validated to assess the reproducibility of the obtained results, exploring how consistent the results could be over time.