To study the sulfate resistance of ultra-high performance concrete (UHPC) in saline soil area of western China, four kinds of sulfate solution concentrations (0 %, 5 %, 10 %, 15 %) and 18 drywet cycle tests for 540 days were carried out on UHPC specimens. The effects of sulfate dry-wet cycles on the evolution of UHPC strength and energy were studied, the characteristic stress points during uniaxial compression of UHPC under sulfate dry-wet cycle were determined, based on the evolution law of each energy (total energy U , dissipated energy U d , elastic stress U e ) at the characteristic stress points, the energy storage index was established to measure the damage degree of UHPC. The results show that the energy evolution process and damage mechanism of UHPC samples under sulfate-wet and dry cycle erosion are closely related to macro and micro changes. With the development of sulfate dry-wet cycle, the dissipative energy U d and elastic strain energy U e of UHPC at the characteristic stress points increased first and then decreased. The development trend of elastic strain energy U e and dissipative energy U d is more severe with the increase of sulfate solution concentration. The ratio of elastic strain energy at damage stress to elastic strain energy at peak stress ( U e ib /U i e ) is taken as the energy storage index K ib to measure the damage degree of UHPC, under 10%Na 2 SO 4 erosion, K ib can be increased by 21.41 % at the highest and decreased by 29.67 % at the lowest compared with the initial value. It shows that the damage process of UHPC is difficult and then easy, and this index can accurately reflect the external force required for the damage of UHPC under sulfate dry-wet cyclic erosion, and provide a reference for the safe and stable operation of UHPC in saline soil area.

In this study, hydroxypropyl cellulose (HPC) was utilized as the raw material, with the addition of beta-cyclodextrin (beta-CD), citric acid (CA) as the crosslinking agent, and sodium hypophosphite (SHP) as the catalyst to produce hydroxypropyl cellulose/beta-CD composite films. The inclusion of beta-CD resulted in an increase in the tensile strength of the film, with the maximum value of 13.5 MPa for the 1 % beta-CD composite membrane. Additionally, after degradation in soil for 28 days, the degradation ability was significantly enhanced, with the 1.0 % beta-CD composite film exhibiting the highest degradation rate of 27.21 %. Furthermore, the water permeability of the composite membrane was improved with the addition of beta-CD. Specifically, when the beta-CD content was 1.0 %, the water vapor transmission reached its lowest point at 2,445 g* ( m 2 * 24 d ) - 1 ${({m}{2}\ast 24d)}{-1}$ . The findings demonstrated that the 1 % beta-cyclodextrin/hydroxypropyl cellulose composite film effectively preserved the freshness of strawberries, reducing the weight loss rate by 1.65 % compared to the control group. In conclusion, this research highlights the potential for preparing composite membranes using HPC and beta-CD crosslinking, thereby expanding the application of hydroxypropyl cellulose and beta-CD in food preservation.

The harsh geological conditions in the northwest region of China, characterized by widespread saline-alkali soil rich in alkali ions, pose a high risk of Alkali-Silica reaction (ASR) in concrete, particularly due to the presence of ASR-active natural river sands. To address ASR hazards, locally applied concrete often employs High-Performance concrete (HPC) prepared with high proportions of mineral admixtures. In this paper, the alkali content is controlled by adding mixed water with NaOH to the initial configuration of concrete, and three different alkali content states are set up. A 1 mol/L NaOH solution was used to simulate alkaline conditions, and HPC specimens were immersed for an extended period to investigate the effects of equivalent alkali content, immersion time, concrete strength, and admixture on the flexural mechanical properties of HPC under the condition of long-term alkali immersion. Results indicate that, the strength grade was positively correlated with the flexural strength of HPC, but the alkali content was negatively. Initial immersion significantly enhances strength, followed by a gradual decline after long-term immersion. Among three types of admixture addition methods, the impact on flexural strength of HPC immersed in alkaline solution for 10 years follows the order: Double doped air entraining agent and rust inhibitor is greater than single doped air entraining agent is greater than single doped rust inhibitor. In the process of macroscopic test, it is difficult to observe the variation rule of stress and strain in detail, only the final aggregate failure mode can be analyzed. In order to analyze the strain change of the specimen and the failure process of the aggregates more accurately, a three-dimensional random aggregate concrete mesoscopic model was established, and equations relating microhardness to the mechanical properties of concrete components were derived from statistical analysis, providing a basis for parameter selection in the model. Results demonstrate that with increasing strength, the occurrence time of initial cracks is delayed, and the ratio of cracks bypassing aggregates (cracks develop along the ITZ between aggregate and mortar until complete failure) decreases, and the ratio of cracks penetrating aggregates (cracks develop directly through aggregates in an almost vertical direction) increases.

Conventional driven piles are made from steel, concrete, timber, or composite materials. These piling options have limitations with respect to corrosion, durability, driveablity, and performance. Ultra-High-Performance Concrete (UHPC) pile is a new alternative that has already been adopted by various state Departments of Transportation in the United States for addressing the limitations that exist with conventional piles. UHPC piles are made of a cementitious composite material mixture that possesses exceptional properties such as higher strength, low capillary porosity, and high resistance to corrosion, making them a suitable option for use as a deep foundation. For several reasons, it is necessary to cast piles with a shorter length and splice them at the site to reach the desired lengths. These reasons include shipping limitations, unpredictable soil condition, reducing transportation costs, construction time, and damage during installation. This study aims to explore and summarize the currently available options for connecting UHPC pile segments. Accordingly, after a brief introduction on driven piles, this paper investigates various splicing systems that can be used for UHPC piles through reviewing previous research studies and field applications. The applicable splices are then compared based on several criteria such as capacity, durability, cost, and ease of application.