Study on the effect of porosity and aperture on the damage characterization of rock-filled concrete (RFC)

Rock-filled concrete (RFC) construction technology is to construct a force-transferring skeleton with large-size rocks, and to use self-compacting concrete (SCC) as the filling and bonding material. In which the defects with different distributions and sizes contained in SCC are often the key factors determining the mechanical properties and damage behaviors of RFC. In this research, by utilizing the excellent properties of super absorbent polymer (SAP), such as water absorption and expansion and dehydration shrinkage, non-introduction of impurities, and not easy suspension or settlement in concrete, RFC and SCC specimens with different numbers and sizes of defects were precisely prepared and subjected to unconfined uniaxial compression physical tests. The effects of porosity and pore aperture on the compressive strength and damage pattern of the specimens were studied. The mechanical behavior of the defective concrete specimens under compressive loading was analyzed from a mesoscopic perspective by using a combination of physical tests and numerical simulation using the Realistic Failure Process Analysis (RFPA) method to reveal the internal damage phenomenon and damage destabilization mechanism of RFC and SCC. The results show that: SAP material can accurately construct concrete specimens with stable and uniform defects; under the same porosity and aperture, the compressive strength of RFC is greater than that of SCC; the compressive strength of the specimen decreases linearly with the growth of porosity for the same aperture, the compressive strength of the specimen decreases with the increase of aperture for the same porosity and the trend tends to be flat, and the sensitivity of the compressive strength to porosity is higher than that of aperture. In addition, it was found that the internal penetrating shear damage during the fracturing process of SCC was the core cause of the overall damage. For RFC, the tensile fracture that penetrated through the force transmission skeleton of the stacked rock was the key factor causing the overall instability.