Temperature distribution in concrete is significant to the concrete structure’s macro properties and different factors affect the heat transfer in concrete, and therefore influence the temperature distribution. This work established a three-dimensional transient heat transfer model coupled with various environmental factors, using the finite element method for calculating the results and real-measured data for testing accuracy. In addition, a sensitivity evaluation of various factors was conducted. Due to various environmental factors, the results revealed that the prediction of temperature distribution in concrete by the three-dimensional model had great accuracy with an error of less than 4%. A particular hysteresis effect of temperature response in the concrete existed. Considering heat transfer in different spatial directions, the model can predict the temperature change of each spatial point instead of the spatial surface in different depths, proving the shortcomings of a one-dimensional heat transfer model. A greater solar radiation intensity caused a more significant temperature difference on the concrete surface: the surface temperature difference in July was twice as significant as that in December. Wind speed had a cooling effect on the concrete surface, and stronger wind speed accompanied with a stronger cooling effect made the surface temperature closer to the ambient temperature. Material properties had different effects on the temperature distribution of the surface part and internal part: the specific heat capacity determined the speed of the outer layer temperature change while the thermal conductivity determined the speed of the inner layer temperature change.

This paper is concerned with an analysis of the electrical conductivity of graphene/cement composites by means of DC (direct current) and AC (alternating current) techniques. Moreover, the micrograph and element composition of composites have been characterized through SEM (scanning electron microscopy) and EDS (energy-dispersive spectrometers) techniques, respectively. Results revealed that a percolation transition region Φ2–Φ1 (Φ2 and Φ1 values are determined as 0.8% and 1.8%, respectively) can be observed in the S-shaped curve. In addition, the logistic model has been recommended to characterize the relationship between the conductivity and the graphene concentration, which ranged from 0.001% to 2.5%. The micrographs obtained by SEM technique clearly indicate a complete conductive network as well as agglomeration of graphene slices when the graphene content reaches the threshold value. Furthermore, graphene slices can be distinguished from the cement hydration products by means of the analysis of element composition obtained through the EDS technique. It is promising to apply the graphene/cement composites as intelligent materials.

Alkali-activated materials (AAMs) offer an eco-friendly alternative to traditional Portland cement, yet their rheological properties, particularly in concrete mixtures, remain largely underexplored. This study conducted rheological tests to investigate the flow properties and thixotropic behavior of alkali-activated slag (AAS) concrete with varying water-to-binder (w/b) ratios and silicate modulus (Ms). The thixotropy of AAS concrete was assessed using the thixotropic index, breakdown area, and variations in apparent viscosity under different shear rates, revealing correlations between thixotropic behaviors and rheological parameters. Mixtures with lower Ms and w/b ratios showed limited slump values and rapid structural build-up due to increased interparticle connections. As Ms increased, enhanced thixotropic behaviors were observed, attributed to the rapid formation of early hydration products. This led to a significant increase in peak torque values and a slight decrease in equilibrium torque values at various rotational speeds. In turn, AAS concrete with higher Ms demonstrated improved fluidity and workability retention after thixotropic build-up was erased. The results of this study provide valuable insights into the flow and thixotropic behaviors of fresh AAS concretes for practical applications.