Wet packing methods evaluate the packing density of fine materials through the determination of the apparent density and voids content of pastes with different water to solids (w/s) ratios. Its goal is to estimate the minimum water demand to achieve the maximum solids concentration in the mixture, a parameter applied to the mix design of cementitious composites based on particle packing theories. Since most methods based on apparent density are time-consuming and require a high volume of materials, this paper aims to evaluate the mixing energy method as an alternative for the wet packing method and to adapt it to be used for SCMs (supplementary cementitious materials). With a reduced time and material to perform the test, results demonstrate a better precision of the mixing energy due to its discrete measurement. The ideal water flow and initial volume of materials to perform the test on cement and SCMs are discussed.

The application of repair materials is essential for maintaining the service life of reinforced concrete structures. Dimensional compatibility with the substrate is crucial for the repair material. This study assesses the impact of graphene and carbon nanotubes on dimensional stability and bond strength. Bulk density and consistency index were analysed in the fresh state, while weight loss, dry shrinkage, coefficient of thermal expansion (CTE) and bond strength were evaluated in the hardened state. Scanning electron microscopy (SEM) was employed to assess the impact of carbon nanoparticles on the microstructure. Graphene particles can mitigate dimensional variation caused by dry shrinkage. However, incorporating carbon nanotubes led to higher shrinkage due to the refinement of the cementitious matrix and an increase in capillary pressure. Furthermore, using nanoparticles combined with superplasticisers enhanced bond strength by increasing adhesion points in the interfacial transition zone between the repair and the concrete substrate. SEM analyses demonstrated the formation of crystals on the graphene surface and the good dispersion of carbon nanotubes into the cementitious matrix.

This study evaluates the synergistic effects of carbon fibre and limestone powder on electrically conductive cementitious composites (ECCC) properties, considering fresh and hardened states, electrical conductivity, eco-efficiency, and microstructure. An experimental design comprising eight mixtures was adopted, varying the carbon fibre content (0.00, 0.50, and 1.00 wt.%) and replacing cement with limestone powder (0.00, 10.00, and 20.00 wt.%). The investigated properties included consistency, compressive and flexural tensile strengths, elastic modulus, water absorption, electrical resistivity, and microstructural analysis by scanning electron microscopy. A polynomial regression model was used to evaluate the significance of the main effects and their interactions. The combination of 0.5% carbon fibre and 10–20% limestone powder yielded the best results, with compressive strength gains of up to 46% and reductions in electrical resistivity exceeding 97%. The eco-efficiency indices (Bi and Bs) confirm that hybrid optimisation strategies significantly reduce cement demand while enhancing the overall performance of ECCC. This strategy represents a viable alternative to produce high-performance and eco-efficient ECCC suitable for applications in smart infrastructure.