Correlation Analysis of Heat Curing and Compressive Strength of Carbon Nanotube–Cement Mortar Composites at Sub-Zero Temperatures

Heating Performance of Cementitious Composites with Carbon-Based Nanomaterials

Active research has been conducted in recent years on heating construction materials using nanotechnology to solve the problem of black ice, which is often the cause of frequent traffic accidents during winter. To determine the optimal heating construction material, this study analyzed the heating performance of carbon-based nanomaterials, such as multiwalled carbon nanotubes (MWCNTs), conductive carbon black (CB), and graphene nanoplatelets (GNPs). Heating and electrical resistance experiments were performed based on the parameters of the selected nanomaterial, concentrations, and curing days to analyze the heating efficiency. Results showed that compared with OPC, the heating performances of GNP, CB, and MWCNT cementitious composites improved by 132, 171, and 224 times, respectively. Furthermore, the MWCNT cementitious composite exhibited excellent heating efficiency.

Sensitivity Analysis for Transient Thermal Problems Using the Complex-Variable Finite Element Method

Solving transient heat transfer equations is required to understand the evolution of temperature and heat flux. This physics is highly dependent on the materials and environmental conditions. If these factors change with time and temperature, the process becomes nonlinear and numerical methods are required to predict the thermal response. Numerical tools are even more relevant when the number of parameters influencing the model is large, and it is necessary to isolate the most influential variables. In this regard, sensitivity analysis can be conducted to increase the process understanding and identify those variables. Here, we combine the complex-variable differentiation theory with the finite element formulation for transient heat transfer, allowing one to compute efficient and accurate first-order sensitivities. Although this approach takes advantage of complex algebra to calculate sensitivities, the method is implemented with real-variable solvers, facilitating the application within commercial software. We present this new methodology in a numerical example using the commercial software Abaqus. The calculation of sensitivities for the temperature and heat flux with respect to temperature-dependent material properties, boundary conditions, geometric parameters, and time are demonstrated. To highlight, the new sensitivity method showed step-size independence, mesh perturbation independence, and reduced computational time contrasting traditional sensitivity analysis methods such as finite differentiation.