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Adding conductive materials to cement-based composites can lead to pressure-sensitive properties. In this study, different scales of conductive materials were incorporated, including macro-scale steel fibers, micro-scale carbon black powder, and nano-scale graphene. The coupling effect of three scales of materials ensured that the intelligent concrete had improved strength, lower cost, and comparable pressure-sensitive performance. The results show that the strength of intelligent concrete with multi-scale conductive materials is higher than that of the contrast group of ordinary concrete and intelligent concrete when adding nano-scale graphene alone. Especially, the addition of steel fibers significantly improved the crack resistance of the intelligent concrete. In the elastic stage, the resistivity of intelligent concrete of multi-scale conductive materials decreases with the increase in compression, and the decrease range of resistivity is approximately proportional to the external force. After reaching the peak load, the resistivity of the intelligent concrete gradually increases and can illustrate the damage evolution. This study lays a foundation for the application of intelligent concrete in deformation and damage monitoring.

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By using redispersible polymer powder (RPP) and carbon fiber (CF) to adjust the flexibility and electrical properties of the smart aggregate, a new kind of smart aggregate with Z type structure was proposed. The study shows that Z type aggregate is more sensitive to the feedback of external force than the prism aggregate in the same loading environment, and it indicates that Z type aggregate is more suitable for the research and application of concrete health monitoring. Although the incorporation of RPP would cause the compressive strength of the aggregates and the elastic modulus of hardened cement mortar to reduce slightly within the dosage of RPP by 2.25% because of the polymer film formed in the internal system, this would improve the deformability of the aggregates. In the early loading stage (in the first 60 seconds), the intelligent concrete specimens implanted with Z type smart aggregate do not show higher sensitivity as expected, although the resistance change rate changes a little bit more, the overall of it is still in balance. Adding RPP could improve the flexibility of smart aggregates exactly, and it plays an active role in prolonging the life of the smart aggregates. By implanting Z type aggregates the damage and failure of the concrete structure could be predicted accurately in this study. The results of this paper will help to promote further research and application of intelligent concrete. [ABSTRACT FROM AUTHOR]