Research on the mechanical properties of solid waste concrete based on acoustic emission and mesoscopic damage constitutive model

At present, there is a significant lack of research on the improvement effect of carbon nanotube dosage variability on the mechanical properties of solid waste recycled concrete, especially the correlation mechanism between macroscopic mechanical properties and microscopic structural characteristics has not been fully revealed. Therefore, based on the current research status of carbon nanotube reinforced concrete and acoustic emission, this paper conducted uniaxial compression tests on multi-element solid waste concrete with different dosages of carbon nanotubes (0%, 0.05%, 0.10%, 0.15%, 0.20%), 50% recycled coarse aggregate, and 50% iron tailings sand substitution rate. Acoustic emission information was collected synchronously during the loading process, and the stress-strain curve of solid waste concrete under uniaxial compression was fitted. A damage constitutive model was established to describe the stress-strain relationship of solid waste concrete. The results showed that when the CNTs content was 0.1%, the compressive strength of solid waste concrete reached its maximum value, and the final failure process of the specimen was mainly in the shear failure mode. The cumulative ringing, energy, and b-value of the specimen all occurred during the failure stage. Therefore, the instantaneous mutation of the acoustic emission signal can be regarded as a precursor to the failure of the specimen. In the damage constitutive model, the damage variable shows an S-shaped growth trend with the increase of strain, which can accurately describe the damage evolution process of solid waste concrete at a specific time.