Co-authors​ :

 Carlo Amata (ITALY), Luca LAVAGNA (ITALY), Matteo PAVESE (ITALY) 

The importance of cement materials in modern society is undeniable, as it serves as a fundamental component for the construction of crucial infrastructure such as buildings, bridges, and roads. To enhance both the mechanical properties and electrical conductivity of cement, carbon allotropes can be employed. When optimally functionalized, the carbon reinforcement allows to improve not only strength and toughness of cement, but also electrical conductivity, making it suitable for self-monitoring applications. In this work the mechanical characteristics of cement were optimized through the use of carbon-based reinforcements (carbon fibers, carbon nanotubes, graphene nanoplatelets), obtaining a reinforced cement-based composite. For effective dispersion in water and good interaction with the matrix, carbon reinforcements were functionalized. To assess the improvement in mechanical properties, two different experimental designs were employed: a mixture design (MD) and a face-centered central composite design (FCCD). The construction of response surfaces for both experimental designs utilized flexural strength, fracture energy, and compression strength as key parameters. The mixture design is employed when there are various constituents or components that are blended to form a final product, and the goal is to understand the effect of different proportions of these elements on the system's response. This approach is particularly useful when there are restrictions on the total of the constituent proportions, as it takes into account the "mixed" nature of the design variable. The mixture design allowed the evaluation of the synergic effect among different carbon allotropes in cement. This synergistic effect can be observed through the values reported in the response surface, and through the values of the coefficients in the mathematical model. An improvement of approximately 20% in the compression strength has been observed, due to the combined effect of graphene nanoplatelets, carbon fibers, and carbon nanotubes, compared to samples containing carbon-based reinforcements of a single type. The FCCD, unlike the MD, involves the selection of specific combinations of factors at three levels. This arrangement facilitates the observation of responses to various factor combinations and allows for estimating responses in the points of the experimental domain. With this last approach to multivariate analysis, it is possible to derive a critical point, allowing the calculation of the quantities of carbon reinforcement in composite materials to maximize mechanical properties.