Mechanical, electrical, and piezoresistive properties of modified conductive recycled fine aggregate smart mortar

The application of recycled fine aggregates (RFA) in smart conductive mortar is of great significance for conserving natural resources and protecting the environment. However, the high water absorption and microstructural defects of RFA limit its widespread use in smart conductive mortar. This study employs an agar gel impregnation treatment containing graphite particles to improve the properties of RFA. The resulting modified conductive recycled fine aggregate (MRFA) exhibited a 2.8 % reduction in water absorption. The workability, mechanical properties, electrical properties, and self-sensing capabilities of the modified recycled fine aggregate mortar (M-RFAM) were studied. It was found that the workability and mechanical properties of the smart conductive mortar prepared with M-RFA were slightly reduced but remained within acceptable ranges (28-day compressive strength greater than 33 MPa). At the same time, it achieved low resistivity and high strain-sensing sensitivity, with the highest strain-sensing sensitivity being 61.9 (30 times higher than ordinary strain gauges). The influence of loading rate and moisture content on the self-sensing ability of conductive mortar was also investigated, revealing a positive correlation between moisture content and stress-sensing ability. Furthermore, the study found that factors such as AC frequency, curing age, moisture content, and temperature significantly affect resistivity. These factors should be considered in practical applications and further research.