Prediction model and measurement of fracture parameters in eco-friendly coarse copper slag-SFRSCC based on semi-circular bending test

Abstract

This research has used 16 concrete mix designs containing 0.1, 0.3, and 0.5% steel fiber (SF), and 20, 30, 40, 50, and 60% copper slag (CS) to examine their fresh and hardened characteristics, and study their microstructural features with the help of scanning electron microscope (SEM) images. In addition, it has tried to evaluate the fracture characteristics of semi-circular bending (SCB) samples under loading modes I, I/II, II/I, and II. According to the results, increasing CS will improve the fresh concrete properties and reduce the negative SF effects on its performance. At 60% (fixed) CS, using 0.1% SF reduces the compressive strength by 10.08%, and applying 0.5% SF increases it by 17.24%, compared to the control sample. Increasing SF and CS improves the tensile strength of all concretes in the 14.02–86.02% range, compared to the control design. SEM images show that up to 30% replacement, the WCS-steel fiber reinforced self-compacting concrete (SFRSCC) microstructure is homogeneous, integrated and dense, and the fracture toughness and energy are higher under, respectively, pure loading modes II and I than other modes. Fracture toughness of concretes with the highest SF and CS volumes, compared to plain concrete, has increased 1.45, 1.61, 1.67, and 1.36 times under loading modes I, I/II, II/I, and II, respectively. Compared to ANN, using ALK to estimate the fracture features reduces the need for training data by 36.53%, and R2 (correlation coefficient) reduces by 0.91 and 1.52% for estimating the fracture energy and fracture toughness, respectively. Using ANN and ALK can provide a robust prediction model to estimate the fracture energy parameters of the CS-FRSCCs (R2 ≥ 0.970).