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The Pristine Mayenite Ca12Al14O33 (C12A7) Cement was simply synthesized by using solid-state reaction. The C12A7 and Graphene Oxide (GO) composites (C12A7_GO-x) with various contents of the GO suspension loading (x = 0 wt%, 1 wt%, 2 wt%, 3 wt%, and 4 wt%) were directly prepared by mixing the C12A7 and GO. X-ray diffraction results of pristine C12A7 and all C12A7_GO composites indicated a pure phase corresponding to the standard of C12A7 cement. Raman spectroscopy confirmed the existence of GO in all C12A7_GO samples. Scanning Electron Microscopy (SEM) showed the micrometer grain sizes and the occurrence of grain boundary interfaces for GO incorporation in all C12A7_GO samples. UV–Vis spectroscopy revealed the absorption value of all C12A7_GO samples and red shift near longer wavelengths when increasing the GO concentrations. The dielectric constant of C12A7_GO composites can be explained by the high density of free electron charges for the interfacial polarization on the GO surface. The maximum specific capacitance of C12A7_GO-4 electrode of 21.514 at a current density of 0.2 A g−1 can be attributed to the increase in the electrochemically active surface area for the formation of the electrical double layer capacitors behavior and the effects of high surface area GO connections. Also, the mechanical properties exhibited an increase in Vickers indenter hardness (HV) values with increasing GO contents. The highest HV value was 117.8 HV/2 kg at the C12A7_GO-4 sample. These results showed that the composite materials of the pristine C12A7 cement with GO were highly efficient. All in all, the GO material contained a high potential for enhancing low-cost cement materials in multifunctional properties such as optical, dielectric, electrochemical, and mechanical properties.

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To investigate the effect of heat loss reduction due to thermal insulator and thermal interface resistance due to multi-layer structure in order to improve the efficiency of a thermoelectric device, a thermoelectric concrete brick was fabricated using a unileg n-type CaMnO3 thermoelectric module inside. CaMnO3 thermoelectric materials were synthesized by starting materials CaCO3 and MnO2 to produce a unileg n-type CaMnO3 module. Thermoelectric concrete brick consisted of two types: I-layer brick (one layer of concrete thermal insulator) and III-layer brick (three layers of different concrete insulators). The occurring temperature difference, electric current and voltage on the CaMnO3 module and thermoelectric concrete brick were measured in closed and open circuits. The temperature difference, thermal distribution, and output voltage when applying constant temperatures of 100, 200 and 400 °C were measured. Computer simulations of the Finite Element Method (FEM) were performed to compare with the experimental results. The trends of the temperature difference and the output voltage from the experimental and computer simulations were in good agreement. The results of the temperature difference during the hotter side temperature of 200 °C exhibited the temperature difference along the vertical direction of the thermoelectric concrete bricks for both types of the III-layer brick of 172 °C and the I-layer brick of 132 °C are larger than that of the CaMnO3 TEG module without using a thermal concrete insulator of 108 °C. The thermoelectric concrete bricks of the III-layer brick type of 27.70 mV displayed output voltage results being higher than those of the I-layer brick of 26.57 mV and the CaMnO3 TEG module without using a thermal concrete insulator of 24.35 mV. Thermoelectric concrete brick of the III-layer brick type displayed higher electric generation power than the I-layer brick and the CaMnO3 TEG module. Additionally, the results exhibited the capability of thermoelectric concrete brick in the III-layer brick model for electric generation power based on the temperature difference. The TEG concrete brick of I-layer concrete covering the series–parallel combination circuit of 120 modules of the unileg n-type CaMnO3 was constructed and then embedded on the outer surface of the furnace. During the maximum hotter side temperature of 580 °C of the concrete brick, the temperature difference between the hotter side and the cooler side of the brick occurred at 365 °C and the maximum output voltage was obtained at 581.7 mV.

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