Smart Graphite–Cement Composites with Low Percolation Threshold

The objective of this work was to obtain cement composites with low percolation thresholds, which would reduce the cost of graphite and maintain good mechanical properties. For this purpose, exfoliated graphite was used as a conductive additive, which was obtained by exfoliating the expanded graphite via ultrasonic irradiation in a water bath with surfactant. To obtain evenly distributed graphite particles, the exfoliated graphite was incorporated with the remaining surfactant into the matrix. This study is limited to investigating the influence of exfoliated graphite on the electrical and mechanical properties of cement mortars. The electrical conductivity of the composites was investigated to determine the percolation threshold. The flexural and compressive strength was tested to assess the mechanical properties. In terms of the practical applications of these composites, the piezoresistive, temperature-resistivity, and thermoelectric properties were studied. The results showed that the incorporation of exfoliated graphite with surfactant is an effective way to obtain a composite with a percolation threshold as low as 0.96% (total volume of the composite). In addition, the mechanical properties of the composites are satisfactory for practical application. These composites also have good properties in terms of practical applications. As a result, the exfoliated graphite used can significantly facilitate the practical use of smart composites.