The deterioration of early-age concrete performance caused by SO₄²⁻ internal diffusion in concrete is a critical factor of concrete durability. In this study, the mechanical properties, heat of hydration, and pore structure of early-age cast-in-situ concrete with different sodium sulfate (Na₂SO₄) concentrations were studied. The mechanism of SO₄²⁻ internal corrosion was evaluated by measuring the dynamic elastic modulus, compressive strength, and heat of hydration rate. Scanning electron microscopy, energy dispersive spectroscopy, X-ray computed tomography, X-ray diffraction, thermogravimetry-derivative thermogravimetry, and differential scanning calorimetry were applied to analyze microstructural variations and complex mineral assemblages of concrete samples. The results indicated that during the hardening process of cast-in-situ concrete, Na₂SO₄ first promoted and then hindered the hydration rate of cement, and also hindered the early strength development of the cement. As the concentration of Na₂SO₄ solution increases, the corrosion products of ettringite (AFt) and gypsum (Gyp) gradually increase, causing cross cracks in the concrete. The proportion of small and medium pores first increases and then decreases, and the large pores first decrease and then increase. The mechanical properties of concrete gradually decrease and diminish the mechanical properties of the concrete (thereby accelerating the damage to the concrete).

There have been many railway construction projects in the loess region of China. Embankment is typically required for rail projects in these regions, since the railway basement is restricted by longitudinal slope requirements. However, there has been little study of the dynamic response of compacted loess embankment under moving train loading. The 2.5D finite element method was adopted to investigate this process and characterize the effects of train speed, height of embankment, and axle weight on the dynamic behavior of subgrade. A rectangular core zone of subgrade was determined, and a prediction model was established to evaluate the long-term settlement of embankment generated by moving train loading. The results showed that embankment height had negligible influence on the variation of dynamic stress. Decays of stress amplitude in both the vertical and horizontal directions slowed with increased train speed. Additionally, the dynamic stress increased linearly with the increase in axle weight due to the linear stress-strain relationship of soil. In the practical speed range (≤ 100 m/s), the dynamic influence depth increased with increasing speed in a range of 3–6 m. A core zone depth of 6 m reflects the effects of moving train loading, with a width of 4 m. For practical conditions (v ≤ 100 m/s), only slight settlement of embankment was observed (≤ 6 mm). However, it is difficult to achieve the same physical parameters used in the experiments (moisture content and compaction degree) in engineering practice. Further work should explore long-term dynamic settlement with relation to the degree of compaction of the embankment.

The long-term permanent deformation behavior of subgrade soil repeatedly subjected to traffic loading has a significant effect on the settlement of pavement during operation. Many studies conducted on this topic have focused on granular materials, marine soft soils, frozen soils, or fouled ballast. However, the deformation behavior and cyclic strength of compacted loess subjected to traffic loading have undergone limited investigation. In this study, the development of permanent strain in compacted loess was addressed using a number of cyclic triaxial tests. The effects of cycle number, cyclic amplitude, and confining pressure were examined in detail. Permanent strain was separated into two broad categories: the initial strain generated by the first cycle and the accumulated strain generated by subsequent cycles. Furthermore, a predictive formula was proposed in order to describe the mechanism by which permanent strain varied according to cycle number, cyclic amplitude, and confining pressure. Linear fitting was employed in order to establish the relationship between the initial strain and the amplitude of cyclic stress, and a log function was used to establish a correlation between accumulated strain and cycle number. In addition, the cyclic strength of compacted loess was also addressed. The results indicate that initial strain exhibits an ostensibly significant effect on the distribution of cyclic strength versus cycle number and contributes to a large proportion of overall permanent strain, especially at a low cyclic-stress level.

Polyurethanes are widely used in interventional devices due to the excellent physicochemical property. However, non-specific adhesion and severe inflammatory response of ordinary polyurethanes may lead to severe complications of intravenous devices. Herein, a novel phospholipid-based polycarbonate urethanes (PCUs) were developed via two-step solution polymerization by direct synthesis based on functional raw materials. Furthermore, PCUs were coated on biomedical metal sheets to construct biomimetic anti-fouling surface. The results of stress–strain curves exhibited excellent tensile properties of PCUs films. Differential scanning calorimetry results indicated that the microphase separation of such PCUs polymers could be well regulated by adjusting the formulation of chain extender, leading to different biological response. In vitro blood compatibility tests including bovine serum albumin adsorption, fibrinogen adsorption and denaturation, platelet adhesion and whole-blood experiment showed superior performance in inhibition non-specific adhesion of PCUs samples. Endothelial cells and smooth muscle cells culture tests further revealed a good anti-cell adhesion ability. Finally, animal experiments including ex vivo blood circulation and subcutaneous inflammation animal experiments indicated a strong ability in anti-thrombosis and histocompatibility. These results high light the strong anti-adhesion property of phospholipid-based PCUs films, which may be applied to the blood-contacting implants such as intravenous catheter or antithrombotic surface in the future.

Previous studies have centred on the long-term permanent deformation behaviour of soil under traffic loading while neglecting the dynamic parameters as it is affected by cycle number. In this study, forty tri-axial dynamic tests were conducted to assess the effects of cycle number, confining pressure, and dynamic stress on the dynamic modulus and damping ratio of compacted loess. Empirical models of both parameters were established and examined, from which emerged a nearly linear relationship between the dynamic stress-strain points when dynamic stress fell below a given threshold value. The representative dynamic modulus in the linear range initially increased and then decreased. The maximum representative dynamic modulus linearly increased as confining pressure increased, while confining pressure had no clear effect on the damping ratio. As the dynamic stress increased, the damping ratio was initially stable and then gradually increased until becoming stable again at a higher level.