After thermal braising and magnetic separation, steel slag is often ground into steel slag powder (SSP), which contains active silica (SiO₂) and can be used as a cementitious material to replace part of the cement and applied in concrete. However, there have been relatively few studies on the influence of SSP on the performance of pavement cement concrete (PCC). In this paper, SSP was used as an admixture to replace part of the cement in the cement paste, cement mortar, and PCC, to investigate the effect of SSP on the fluidity of SSP-cement slurry, the mechanical properties, and the durability of PCC. Results showed that SSP can lead to the secondary hydration reaction with Ca(OH)₂ in the cement paste and affect the hydration products, morphology, pore characteristics, and strength of the cement paste. When the SSP mixing amount was less than 20 and up to 1.3 superplasticizer was added, the fluidity of the cement slurry could be optimized. For the samples with the SSP mixing amount of less than 20, the concrete compressive strengths were greater than 50MPa, and the flexural strengths were greater than 5.0MPa. As the SSP mixing amount increased, concrete displayed a better anticarbonization performance. Finally, using 15 SSP, the best performance in terms of the concrete antipermeability (chloride ion diffusion coefficient and electric flux) and frost resistance was achieved.

In this paper, a kind of steel slag, concrete-filled double-skin steel tube (CFDST) T-joint is proposed to promote sustainable structural development. In order to examine the seismic performance of the steel slag CFDST T-joint, a series of hysteresis experiments were carried out on 4 CFDST T-joints with the main pipe under axial compression load and the brace pipe subjected to cyclic axial loading. The seismic performance of the CFDST T-joint was experimentally investigated in terms of the failure mode, load–displacement hysteresis relationship, stiffness degradation, energy dissipation and ductility. The effects of the hollow ratio and the steel slag concrete of the CFDST main pipe on the seismic performance of CFDST T-joint specimens were compared and analyzed. The experimental results show that the failure modes of the CFDST T-joint mainly included two kinds of failure, with those being main pipe fracture and joint area compression-bending failure. The seismic performance of the joints could be improved with a 12% ultimate bearing capacity and 54% ultimate deformation capacity with the hollow ratio of the CFDST main pipe increasing from 0 to 0.5. The seismic performance of the joints could be improved with a 54% ultimate deformation capacity by filling the steel slag concrete with a 0.5 hollow ratio.

Reliable damage detection in operational offshore wind turbines (OWTs) remains challenging due to the inherent non-stationarity of environmental excitations and signal degradation from noise-contaminated partial measurements. To address these limitations, this study proposes a robust damage detection method for OWTs under non-stationary ambient excitations using partial measurements with strong noise resistance. The method is first developed for a scenario with known non-stationary ambient excitations. By reformulating the time-domain equation of motion in terms of non-stationary cross-correlation functions, structural stiffness parameters are estimated using partially measured acceleration responses through the extended Kalman filter (EKF). To account for the more common case of unknown excitations, the method is enhanced via the extended Kalman filter under unknown input (EKF-UI). This improved approach enables the simultaneous identification of the physical parameters of OWTs and unknown non-stationary ambient excitations through the data fusion of partial acceleration and displacement responses. The proposed method is validated through two numerical cases: a frame structure subjected to known non-stationary ground excitation, followed by an OWT tower under unknown non-stationary wind and wave excitations using limited measurements. The numerical results confirm the method’s capability to accurately identify structural damage even under significant noise contamination, demonstrating its practical potential for OWTs’ damage detection applications.

After undergoing thermal braising and magnetic separation, steel slag is typically ground into steel slag powder (SSP). Owing to its hydraulic and pozzolanic activity, SSP has emerged as a promising supplementary cementitious material for partial replacement of cement in mortar. However, its effects on the performance of polyvinyl alcohol fiber-reinforced cement mortar (PVA-CM) remain insufficiently explored. This study systematically examines the influence of SSP substitution on the workability, mechanical properties (compressive and flexural strength), flexural toughness, microstructure, and pore structure of PVA-CM. The findings indicate that SSP incorporation marginally improves the fluidity of fresh mixtures. While both compressive and flexural strengths are largely maintained at SSP contents up to 20 wt%, flexural toughness shows a marked reduction beyond 10 wt%. This reduction is primarily attributed to the decreased formation of calcium silicate hydrate (C–S–H) gel, which weakens the fiber–matrix interfacial bond. scanning electron microscopeobservations reveal a dense and well-bonded fiber–matrix interface at 10 wt% SSP, whereas higher replacement levels induce micro-cracking and interfacial debonding. Based on these results, an optimal SSP dosage of 10 wt% is recommended to achieve a balance between mechanical performance and the sustainable utilization of industrial by-products.