For the structural application of high-performance Steel Fiber Reinforced Expanded-shale Lightweight Concrete (SFRELC), a reliable bond of ribbed steel bar should be ensured. In this paper, an experimental study was carried out on the bond properties of ribbed steel bar embedded in SFRELC by the direct pull-out test. The SFRELC was produced with a strength grade of 35 MPa and a volume fraction of steel fiber as 0%, 0.8%, 1.2%, 1.6% and 2.0%, respectively. Fifteen groups of specimens were made with a central placed steel bar with diameter of 14 mm, 20 mm and 28 mm, respectively. Complete bond stress-slip curves were determined for each group of specimens, and the characteristic values of bond-stress and slip at key points of the curves were ascertained. Results show that the bond strength, peak-slip and residual bond strength increased with the increase of the volume fraction of steel fiber. With the increase of steel bar diameter, bond strength decreased while the peak-slip increased, and the descending curves became sharp with a decreased residual bond strength. Formulas for calculating the bond strength and peak-slip were proposed. The relationships were determined for the splitting bond strength, residual bond strength with the bond strength, the splitting bond slip and residual bond slip with the peak-slip. Combined with rational fitting analyses of bond strength and slip, a constitutive model was selected for predicting the bond stress-slip of ribbed steel bar in SFRELC.

To promote the efficient utilization of bulk solid wastes, including superfine river sand and fly ash, high-flowing steel-fiber-reinforced mixed-sand concrete (SFRMC) was developed in this study. Superfine river sand and coarse manufactured sand were mixed in a proportion of 4:6 to make the mixed sand. Fly ash, with a content of 30~75%, was blended with 0~12% silica fume on the premise of equivalent activity. The water dosage and sand ratio were adjusted with the volume fraction of steel fiber, which varied from 0.4 to 1.6%, to ensure the high flowability of fresh SFRMC. The mechanical properties, including cubic and axial compressive strengths, modulus of elasticity, splitting tensile strength, and flexural strength and toughness of the SFRMC, were analyzed, accounting for the influences of the contents of fly ash and steel fiber. The predictive formulas for the splitting tensile strength, modulus of elasticity, and flexural strength were proposed by introducing the influencing factors of steel fiber. The SFRMC showed an increased modulus of elasticity with increases in the steel fiber factor, and flexural toughness was enhanced with increased contents of both steel fiber and fly ash.