Electro-thermal actuation in recycled aggregate concrete with rapid self-reinforcement via smart cement-based composites

Abstract

With the growing call for low-carbon and environmentally friendly materials, recycled aggregate concrete (RAC) holds great promise for sustainable development. Nevertheless, significant challenges exist with respect to the material’s poor flexural carrying capacity. Development of an effective method for improving the flexural carrying capacity of RAC under a specific deflection deformation is important for enhancing the range of its structural applications. In this study, an intelligent structural optimisation strategy for compounding RAC with carbon-fibre (CF) reinforced cement-based composites (CFRCs) to realize rapid self-reinforcement via electro-thermal actuation is proposed. As a smart component, CFRC was first researched to investigate its electrical, mechanical, and microscopic properties. The optimal properties were obtained in specimens incorporating 0.5 vol%, CFRC0.5. CFRC0.5 exhibits an electrical resistivity of approximately 0.39 Ω∙m, accompanied by 65.3 % and 33 % increases in flexural and compressive strengths, respectively, when compared to the control mixture without CF. Furthermore, CFRC0.5 can maintain outstanding stability after multiple electro-thermal cycles. Analysis via microscopic characterisation revealed that a satisfactory conductive network can be formed at 0.5 vol% CF. Furthermore, CFs with excellent dispersity are particularly advantageous in improving the mechanical biting force within the cement matrix and restraining the further formation and expansion of microcracks. Thus CFRC0.5 was designed and fabricated as a pre-stress controller to realise rapid structural self-reinforcement, resulting in a 38.6 % improvement in the flexural carrying capacity of the RAC under specific midspan deflection conditions. Additionally, a response behaviour model for midspan deflection with temperature differential was established, showing an excellent correlation between the experimental results and theoretical simulation. This findings from this study highlight the significance of leveraging intelligent techniques to realise rapid self-reinforcement capabilities in concrete structures, facilitating their potential application in smart and adaptive structures.