This research explores the innovative resilience and self-healing properties of engineered cementitious composites (ECC) reinforced with shape memory alloy (SMA) fibers, tailored for environments susceptible to saltinduced freeze-thaw damage from deicing salts, seawater, and saline soils. The study examines ECC composites enhanced with varying SMA fiber volumes 0 %, 0.5 %, 0.75 %, and 1 % and three fiber shapes linear, indented, and hook-shaped, with an additional sandblasting surface treatment. Systematic analyses of monotonic and cyclic flexural behavior, as well as self-healing efficacy, were performed across four distinct freeze-thaw cycles (0, 50, 100, and 150) within environments of fresh water and a 3.5 % NaCl solution. Digital Image Correlation (DIC) was employed to precisely monitor the self-healing performance. The results highlight substantial enhancements in SMA-ECC, particularly improved flexural strength by up to 35 %, 30 %, and 17 % for hook, indented, and linear fibers respectively in freshwater. These gains were slightly reduced under saltwater conditions to 32 %, 26 %, and 15 % respectively. Additionally, crack-closure efficiencies in significant self-healing with improvements of 45 %, 38 %, and 27 % for hook, indented, and linear fibers respectively. The Weibull probability distribution model was used to establish the damage evolution equation of the SMA-ECC in two freeze-thaw environments. The results of this study can serve as a reference for the development of freeze-thawresistant designs for SMA-ECC structures in future applications.

Salinity is an important environmental stressor in arid, semi-arid, and coastal regions, primarily due to poor drainage, excessive fertilization, and proximity to the sea. Treating plants with exogenous organic acids may enhance their ability to survive under stressful conditions. In the present experiment, the effects of oxalic acid (OA) on strawberry plant growth and fruit quality were studied under salinity conditions. Day-neutral 'Albion' strawberry cultivar strawberry plants were planted in pots and 1 month after planting, salinity (35 mM Sodium chloride) and OA treatments (2.5, 5, 10 and 20 mM) were carried out. The plants were evaluated 60 days after the treatment's initiation. OA treatments decreased the electrical conductivity (EC) value of the soil under salinity. Salinity stress decreased root:shoot dry weight and the relative growth rate of plant biomass. OA treatments improved leaf cortical cell expansion and xylem conduit diameter under salinity conditions. L-ascorbic acid and malic acid increased with OA treatments. The study revealed that a 10-mM dose of OA was more effective than the other doses, indicating reduced salt stress damage. The results demonstrate that OA can be effectively used in strawberry cultivation under saline conditions.

Background and aimsCalcium salts are prevalent in soils, and excessive amounts of these salts can subject crops to abiotic stress, leading to yield reduction or death. While the effects of Ca2+ in calcium salt stress have been widely reported, the role of the anions remains unclear.MethodsThe response of the calcium-secreting plant Ceratostigma willmottianum to five (0, 25, 50, 100, and 200 mM) equimolar concentrations (also iso-osmotic) of Ca(NO3)2 and CaCl2 in terms of growth, morpho-anatomy, photosynthesis, physiology and biochemistry, and ion content was evaluated.ResultsPlants were more sensitive to CaCl2 than to equal concentrations of Ca(NO3)2, which caused more severe water deficit, oxidative damage, and inhibition of photosynthesis and growth. The CaCl2 sensitivity may be related to the toxicity of Cl-, which accumulates in large amounts in leaves (661-2149 mM); however, under the Ca(NO3)2 treatments, the leaf NO3- concentrations were 42-210 mM. Cl- inhibited chlorophyll synthesis and accelerated chlorophyll degradation, leading to photosystem disruption, and its inhibition of photosynthesis may involve both stomatal and nonstomatal limitation. In contrast, NO3- was not ionotoxic but rather promoted nitrogen assimilation and chlorophyll synthesis. The inhibition of photosynthesis by 100-200 mM Ca(NO3)2 originated mainly from stomatal limitation triggered by osmotic water loss. In addition, the Ca2+ secretion rate increased under calcium salt stress, which may represent a strategy for adaptation to high-calcium environments.ConclusionThe present study provides valuable information for a comprehensive understanding of calcium salt injury mechanisms and plant adaptation to high-calcium environments.

Although significant theoretical and technological advancements have been made in the application of concrete in saline soil regions over the past two decades, newly constructed reinforced concrete structures in these areas still face severe issues of corrosion and degradation. This is due to the complex deterioration environment in saline soil regions, characterized by the combined effects of salt corrosion, dry-wet cycles, and freeze-thaw conditions. The reduced service life of concrete structures in this region is closely related to the diffusion and distribution patterns of high-concentration chloride salts and various corrosive ions within the concrete. These patterns affect the content, transformation, and microstructure of corrosion products, ultimately leading to a shorter service life compared to other environments. This paper simulates the saline-alkali soil environment using solutions of different concentrations of chloride sulfates and magnesium salts, studies the diffusion and distribution patterns of chloride ions and sulfate ions in concrete under this environment, and analyzes the mechanism of action in conjunction with changes in microstructure. The experimental system adopts a dry-wet cycle test that can represent the characteristics of the semi-arid continental climate in Western China. The results show that although the content of free chloride ions and total chloride ions entering the concrete in the saline-alkali soil simulation solution is the lowest, the binding capacity of chloride ions is significantly greater than that of sulfate ions and far exceeds that in other environments. Under the action of high-concentration chlorides alone, the content of chloride ions in concrete is the highest, and the binding capacity of chloride ions also increases with the concentration of chlorides. The content of free sulfate ions and total sulfate ions entering the concrete in the saline-alkali soil simulation solution and their binding capacity are higher than in the control solution. Due to the ability of sulfate ions to hinder the diffusion of chloride ions in concrete, magnesium ions play a hindering role in the early stage and an accelerating role in the later stage. This results in concrete corroded by the saline-alkali soil environment, which has a characteristic of low chloride ion content and high sulfate ion content. The ions in the saline-alkali soil solution that cause concrete damage are Cl-, SO42-, and Mg2+. These ions react with the concrete to form Friedel's salt, Aft and AFm phase calcium aluminate, gypsum, Mg-S-H, and Mg(OH)2, among other substances. These corrosion products significantly impact the microstructure of concrete, causing the microstructure of concrete to transition from dense to loose to cracked much earlier than in other environments.

Geotechnical seismic isolation (GSI) is a new concept that has been proposed recently. The injection of polyurethane into the soil layer (non-intrusive GSI) reduces seismic fragility without altering the original structure, which may provide an effective seismic isolation solution for existing bridge structures. The purpose of this study was to investigate the seismic isolation effect and isolation mechanism of non-invasive GSI applied to existing bridges. First, a noninvasive GSI site modeling method is described based on the results of existing soilpolyurethane resonance column tests and the OpenSees computational platform. Subsequently, a refined dynamic analysis model of site-existing bridge interactions was established by combining the rusting theory. The seismic isolation effect of the non-invasive GSI and its effect on the seismic response of the bridge were explored using a nonlinear dynamic time-course analysis. The results showed that non-invasive GSI soils can change the characteristic period of ground motion, thus reducing the site effect. The seismic isolation effect was positively correlated with the percentage of injected polyurethane. Altering the characteristic period of the site and avoiding as many of the preeminent periods of ground motion as possible is the result of noninvasive GSI. The non-invasive GSI soil layer reduces the structural response and provides seismic isolation throughout the life cycle of corroded piers, and its fragility is significantly reduced. Especially, the old piers have significant seismic isolation effect, effectively limiting serious damage or even collapse under earthquakes. The results of this study provide a reference for noninvasive GSI design of existing bridge structures.

The massive accumulation of waste PET plastic (WP) and coal gangue (CG) would induce a series of environmental problems such as causing soil and water pollution. For reducing the environmental pollution induced by these two wastes, this study attempts to utilize the combination of WP and CG into cement-based materials. Cement mortars incorporated with fine waste plastic (FWP) replacing part of sand and concrete blended with CG and coarse waste plastic (CWP) as part of coarse aggregate were prepared and their work-ability, mechanical strengths, dynamic elastic modulus (DEM), chloride ion permeability, hydration and microstructures were systematically investigated. In addition, metakaolin (MK) as a kind of active admixture was added into mortar or concrete and its effect of MK on the property of cement mortar or concrete was evaluated. The results show that the strengths of cement mortars containing various level of FWP decrease with increase of FWP and CG level. The mechanical strengths of concrete containing MK and 25-100 % CG and CWP are appropriate at different ages. Although the strengths of concrete blended with MK and wastes aggregate are lower than that of concrete without wastes, it is obviously higher than that of concrete only containing wastes but not MK. Its slump of fresh concrete significantly declines with CWP and CG contents growth. The coulomb electric flux and chloride migration coefficient of concrete at 28d generally increase with CG and CWP level, which indicates a declined tendency of resistance to chloride ion penetration. Its DEM for concrete measured with ultrasonic testing method slightly decrease with rise of CG and CWP content (25-100 %) and can give a basic prediction of strengths and chloride ion permeability. Hydration and microstructures tests including TG/DTA, MIP and SEM/EDS demonstrate that the pozzolanic reaction of MK can result in more gels generated and strengthen the ITZ between WP or CG and cement paste thus evidently improving its mechanical and durability of concrete when compared to the reference specimen without MK. Although the properties of concrete blended with CG and CWP as part of coarse aggregate are inferior to pure natural gravel contained concrete, its strengths and resistance to chloride ion permeability can achieve requirements of engineering structures.

Concrete pavements in saline soil environments of cold regions are not only subjected to vehicle loads but also severely impacted by freeze-thaw cycles (FTC) and composite salts, resulting in durability issues that shorten their designed service life. This paper induced fatigue damage in concrete based on the fatigue cycles derived from the residual strain method. It investigated the variations in the physical and mechanical properties of fatigue-damaged concrete during 100 cycles of FTC and chloride-sulfate attack, revealing the deterioration mechanisms through NMR, XRD, and SEM analysis. Utilizing the GBR algorithm, the prediction model for damage layer thickness were developed. The results showed that, due to physical crystallization, salt freeze-thaw damage, expansion of ionic attack products, and fatigue loading damage, Friedel's salt and ettringite were initially the primary products formed. Subsequently, gypsum emerged, and ultimately Friedel's salt underwent decomposition. After 10 attack cycles, the porosity and the proportion of macropores and capillary pores continued to increase, resulting in a rapid decrease in mass, dynamic elastic modulus, and flexural strength, accompanied by an increase in damage layer thickness. As fatigue damage degree increased, the pore structure degraded, thereby amplifying these changes in macroscopic properties. Incorporating basalt fibers into concrete could enhance its resistance to degradation, with the optimal dosages being 0.15 % and 0.10 %. The GBR-based model of damage layer thickness demonstrated a high degree consistency with experimental data, resulting in a correlation index of R2 = 0.989. This study lays the foundation for assessing the durability of pavement concrete in salt-freezing environments.

Subway station structures near coast are at risk of corrosion caused by chloride, resulting in material and structural component deterioration over time and impacting overall performance during earthquakes. This study proposes a numerical framework for the time-dependent seismic fragility analysis of subway station structures, considering chloride-induced corrosion, based on the IDA method. This study utilizes finite element simulations of typical subway station structures in Qingdao, Shandong, China, focusing on nonlinear dynamic interactions between soil and structure, as well as the impact of chloride-induced corrosion on aging effects. The time- dependent damage states within subway station structures are determined through a nonlinear static pushover analysis. Subsequently, the IDA method is employed to generate time-dependent seismic fragility curves and surfaces specific to subway station structures. The numerical results indicate that the impact of chloride-induced corrosion on the subway station structure cannot be ignored. In the corrosion environment, the seismic performance assessment of subway station structures must take into account time-dependent damage states resulting from the degradation of material properties and the reduction in seismic capacity. The probability of a subway station structure exceeding various damage states monotonically increases during its service life. The subway station structure primarily suffers minor to moderate damage under the ground motion with a return period of 2450 or 10000 years, as it reaches its design service life.

Salinity is one of the main stresses that negatively affect plant growth and development. The present research aims to reduce the harmful effects of salinity by Chitosan- Selenium nanoparticles. A factorial experiment was arranged based on a randomized completely design with three replicates, and one-year old grafted C. sinensis (cv. Valencia) seedlings imposed to control, and salinity stress by NaCl (100 mM). Two weeks after starting salinity stress the seedlings treated with distillated water (WT), Chitosan (CS; 0.1% W: V), 20 mg L-1 Selenium nanoparticles (Se NPs), and 10 and 20 mg L-1 Chitosan-Selenium (CS/Se NPs). Salinity stress continued about three month to appeared visual salinity stress symptoms. Then, evaluated the growth and biochemical parameters of seedlings, and concentration of elements in leaves. Our result showed, the salinity stress increased accumulation of Sodium (Na) by 112%, while decreased Potassium (K), Zinc (Zn) and Phosphorus (P) by 15, 12 and 28%, respectively in compared to non-saline conditions in leaves. Due to accumulation of Na intense, occurred an increase in reactive oxygen species (ROS) 39% and Malondialdehyde (MDA) by 118%, damaged cell membrane that appeared as a decrease in membrane stability index (MSI) by 29%. Also, activated the antioxidant system by increase in phenol, flavonoids and anthocyanin, increased osmolyts production such as, soluble carbohydrates (45%) and proline (347%). Furthermore, growth parameters such as leaf number, shoot fresh weight, root and shoot dry weight decreased by 58, 45, 19, and 43%, respectively. On the other hand, foliar spraying with CS/Se NPs (20 mg L-1) under the salinity stress conditions improved the negative effects of salinity stress by decrease in accumulation of Na (19%) and Na/K ratio (21%), due to decrease in the content of ROS (37%) and MDA (20%), and increase in MSI (47%). Finally, improved the growth parameters such as leaf number (268%), fresh weight of roots (32%) and shoots (26%), and dry weight of roots (19%). Our results supported the positive effect of CS/Se NPs application at 20 mgL-1 on managing the negative effects of the salinity stress on the quality of C. sinensis grafted seedlings by reducing Na accumulation and Na/K ratio, protecting against oxidative damage, regulating membrane stability and improving seedling growth.

Oceans and saline soil environments strongly demand for concrete with high compressive strength and high chlorine salt corrosion resistance. Herein, a new preparation process of geopolymer concrete with high compressive strength and chlorine salt corrosion resistance was established, and the process was optimized by adjusting the water/cement ratio, the proportion of Na2O and the amount of fly ash. Mechanical properties tests show that the compressive strength of geopolymer concrete increases with increase in Na2O proportion but decreases with increase in water/cement ratio and fly ash. The compressive strength of geopolymer concrete is as high as 96.20 MPa, when the water/cement ratio is 0.6, the proportion of Na2O is 0.12, and the amount of fly ash is 10%. This may be because the C-(A)-S-H gel makes the geopolymer concrete denser. At the same time, electrochemical impedance spectroscopy and Tafel results imply that the geopolymer concrete also has great chlorine salt corrosion resistance, the lowest weight loss rate of steel bar is only 0.06% after 240 h accelerated corrosion. The leaching tests indicate that at the same depth, the total and free chloride ions in geopolymer concrete are minimum and some chloride ions are combined. The high chlorine salt corrosion resistance could be attributed to the increase in C-(A)-S-H gel which refines the pore structure of concrete, improves concrete compactness and binds the chloride ions. This paper provides a new method for the high-quality utilization of solid waste and a potential clue for the preparation of high-performance concrete.