To cope with the problem that the setting time and hardening time of high-belite sulphoaluminate cement (HBCSA) is too fast and not easily controlled, three common retarders, citric acid (CA), β-cyclodextrin (β-CD), and borax (B), were selected and compounded with polycarboxylate superplasticizer (PCE). Based on the cement slurry fluidity, fluidity loss, setting time, and mechanical properties of cement mortar, combined with X-ray diffraction (XRD), scanning electron microscopy (SEM), and Zeta potential tests, the interaction and mechanism of different retarders and high-belite sulphoaluminate cement were studied. The results show that β-CD and CA can significantly delay the hydration process of HBCSA cement, effectively improve the fluidity loss, and make the dispersion more stable, but the strength of cement mortar decreases, which is not conducive to the development of strength. However, the addition of B has no obvious retarding effect on the HBCSA cement, and the dispersibility of the cement paste decreases. In microscopic tests, XRD and SEM tests verified that the combination of retarder and PCE had a certain inhibitory effect on the early hydration of HBCSA, and the zeta potential indicated that the addition of retarder would interact with PCE to improve the fluidity loss of HBCSA. In addition, when the retarders CA and B were, respectively, compounded with β-CD, the two would have a synergistic effect. The retardation effect is more obvious, and the time interval between the initial and final setting is shorter, which is more controllable. The initial fluidity is also improved under the auxiliary plasticization of cement paste by β-CD.

A new method of controlling the residual stress in laser directed energy deposition additive manufacturing (DED AM) products proposed based on constraints used in manufacturing and the substrate design. The simulation results of the residual stress, which were validated with the experimental measured data, showed that weaker constraints on the substrate could greatly decrease the residual stress in the laser DED AM products. In addition, by designing local reduced thickness regions into the substrate, such as long strip holes or support legs, the residual stress in DED AM products could be further decreased. In this study, when long strip holes were designed in the substrate, the tensile residual stress was decreased by 28%. An even smaller amount of residual stress was achieved when the design structure was changed to support legs. The tensile residual stress decreased by more than 30%. The fewer support legs, the smaller the residual stress. The residual stress in DED AM products could be well-controlled by design, while the stiffness can be weakened with fewer constraints.

This paper studies the influence of the characteristics of the near‐fault ground motion on the seismic responses of the structure with energy dissipation devices including soil‐structure interaction (SSI). A ten‐story reinforced concrete frame rested on soft site is introduced, and the viscous dampers added in the frame are designed. The numerical analysis method of the soil‐structure system with viscous dampers is established through ANSYS program. In addition, the response spectra of the main characteristics of the near‐fault ground motion, like hanging wall effect, velocity pulse‐like effect, and forward‐directivity effect, are investigated carefully to learn the features of spectra energy distribution. And then, the dynamic time‐history analysis is performed on the SSI system with and without viscous dampers subjected to the selected near‐fault ground motion. The study reveals that the seismic responses of the structure subjected to near‐fault ground motion with hanging wall effect are obviously larger than those of the footwall effect, indicating the distinct hanging wall effects on the structural dynamic responses. In addition, the performance of the structure with viscous dampers is more influenced by the ground motion containing fling‐step effect than that with forward‐directivity effect. Moreover, the influence of the horizontal component of forward‐directivity ground motion on the seismic responses of the structure is more obvious than that of parallel component ground motion. Consequently, the hanging wall effect, velocity pulse, and horizontal component in forward‐directivity effect of the near‐fault ground motion have distinct influence on the seismic responses of the structure with energy dissipation devices considering SSI effect, providing insight towards the performance‐based seismic design of buildings rested at the near‐fault sites considering the seismic SSI effect.