Search Results (215)

Organic polymer introduction effectively enhances the toughness, bond strength, and durability of ordinary cement-based materials, and is often used for concrete repair and reinforcement. However, the entrained air effect simultaneously induced by polymer and the inhibitory action on cement hydration kinetics often lead to degradation in mechanical performances of polymer-modified cement-based composite (PMC). Nanomaterials provide unique advantages in enhancing the properties of PMC due to their characteristic ultrahigh specific surface area, quantum effects, and interface modulation capabilities. This review systematically examines recent advances in nano-reinforced PMC (NPMC), elucidating their synergistic optimization mechanisms. The synergistic effects of nanomaterials—nano-nucleation, pore-filling, and templating mechanisms—refine the microstructure, significantly enhancing the mechanical strength, impermeability, and erosion resistance of NPMC. Furthermore, nanomaterials establish interpenetrating network structures (A composite structure composed of polymer networks and other materials interwoven with each other) with polymer cured film (The film formed after the polymer loses water), enhancing load-transfer efficiency through physical and chemical action while optimizing dispersion and compatibility of nanomaterials and polymers. By systematically analyzing the synergy among nanomaterials, polymer, and cement matrix, this work provides valuable insights for advancing high-performance repair materials. Full article

To investigate the impermeability of foam concrete in various challenging environments, this study evaluates its water resistance by measuring the water contact angle and water absorption. Polyurethane (PU) was used to fabricate polyurethane foam concrete (PFC), enabling a monolithic hydrophobic modification to improve the permeation performance of foam concrete. The study also examines the effects of carbonation and freeze–thaw environments on the permeation resistance of PFC. Graphene oxide (GO), KH-550, and a composite hydrophobic coating (G/S) consisting of GO and KH-550 were employed to enhance the permeation resistance of PFC through surface hydrophobic modification. The functionality of the G/S composite hydrophobic coating was confirmed using energy dispersive X-ray spectrometry (EDS) and Fourier transform infrared spectroscopy (FTIR). The results showed the following: (1) The water contact angle of PFC increased by 20.2° compared to that of ordinary foam concrete, indicating that PU-based hydrophobic modification can significantly improve its impermeability. (2) After carbonation, a micro–nano composite structure resembling the surface of a lotus leaf developed on the surface of PFC, further enhancing its impermeability. However, freeze–thaw cycles led to the formation and widening of microcracks in the PFC, which compromised its hydrophobic properties. (3) Surface hydrophobic modifications using GO, KH-550, and the G/S composite coating improved the anti-permeability properties of PFC, with the G/S composite showing the most significant enhancement. (4) GO filled the tiny voids and pores on the surface of the PFC, thereby improving its anti-permeability properties. KH-550 replaced water on the surface of PFC and encapsulated surface particles, orienting its R-groups outward to enhance hydrophobicity. The G/S composite emulsion coating formed a hydrophobic silane layer inside the concrete, which enhanced water resistance by blocking water penetration, reducing microscopic pores in the hydrophobic layer, and improving impermeability characteristics. Full article

This study investigates the hydrogen permeability of injection-molded polyamide 6 (PA6) nanocomposites reinforced with organo-modified montmorillonite (OMMT) at varying concentrations (1, 2.5, 5, and 10 wt. %) for potential use as Type IV composite-overwrapped pressure vessel (COPV) liners. While previous work examined their mechanical properties, this study focuses on their crystallinity, morphology, and gas barrier performance. The precise inorganic content was determined using thermal gravimetry analysis (TGA), while differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and scanning electron microscopy (SEM) were used to characterize the structural and morphological changes induced by varying filler content. The results showed that generally higher OMMT concentrations promoted γ-phase formation but also led to increased agglomeration and reduced crystallinity. The PA6/OMMT-1 wt. % sample stood out with higher crystallinity, well-dispersed clay, and low hydrogen permeability. In contrast, the PA6/OMMT-2.5 and -5 wt. % samples showed increased permeability, which corresponded to WAXD and SEM evidence of agglomeration and DSC results indicating a lower degree of crystallinity. PA6/OMMT-10 wt. % showed the most-reduced hydrogen permeability compared to all other samples. This improvement, however, is attributed to a tortuous path effect created by the high filler loading rather than optimal crystallinity or dispersion. SEM images revealed significant OMMT agglomeration, and DSC analysis confirmed reduced crystallinity, indicating that despite the excellent barrier performance, the compromised microstructure may negatively impact mechanical reliability, showing PA6/OMMT-1 wt. % to be the most balanced candidate combining both mechanical integrity and hydrogen impermeability for Type IV COPV liners. Full article

With the continuous improvement in technology, the construction industry is constantly advancing. Traditional concrete can no longer meet modern market demands, making research on new types of concrete imperative. This study reviews the application of common nanomaterials in concrete and their impact on concrete performance. It provides a detailed explanation of the characteristics of three common nanomaterials: nano-silica, nano-calcium carbonate, and carbon nanotubes. This study analyzes how these materials improve the microstructure, accelerate hydration reactions, and enhance interfacial transition zones, thereby enhancing the mechanical properties, durability, and workability of concrete. For conventional engineering projects, nano-calcium carbonate is the preferred choice owing to its low cost and its capacity to improve workability and early-age strength. For high-strength and durable structures, nano-silica is selected due to its high specific surface area (ranging from 100 to 800 m²/g) and its superior compactness and impermeability. In the context of intelligent buildings, carbon nanotubes are the most suitable option because of their exceptional thermal conductivity and electrical conductivity (with axial thermal conductivity reaching 2000–6000 W/m*K and electrical conductivity ranging from 10³ to 10⁶ S/cm). However, it should be noted that carbon nanotubes are the most expensive among the three materials. Additionally, this study discusses the issues and challenges currently faced by the application of nanomaterials in concrete and looks ahead to future research directions, aiming to provide a reference for further research and engineering applications of nanomaterials in the field of concrete. Full article

Grouting is an effective method for enhancing the stability of poor strata such as sand layers. The performance of the grouting materials directly influences the effect of stratum reinforcement. To meet the urgent demand for efficient grouting materials, this study selected a high-permeability, flexible polymer (PFP) as the grouting material. The influences of the PFP content, curing time, and dry density on the mechanical and impermeable properties of PFP-improved sand were systematically analyzed via unconfined compressive tests, split tensile tests, and variable head permeability tests. Moreover, the section morphology and pore characteristics of the PFP-improved sand were qualitatively described and quantitatively analyzed by scanning electron microscopy (SEM) and image processing software. The results indicated that the mechanical properties and impermeability of the test sand were significantly improved by adding the PFP, and the improvement effect continued to increase with increasing PFP content, curing time, and dry density. The compressive strength and splitting tensile strength of PFP30 (PFP content of 30%, curing time of 28 d, dry density of 1.5 g/cm³) reached 8.3 MPa and 1.4 MPa, respectively. The permeability coefficient reduced to 5.41 × 10⁻⁶ cm/s. The microscopic results revealed that the PFP effectively cemented the isolated sand particles through bridging, filling, and encapsulation as well as substantially filled the internal pores of the test sand. The percentage of the pore area, the total number of pores, and the maximum pore diameter of the test sand were significantly reduced. The pore area percentage, the total number of pores, and the maximum pore diameter of PFP30 were reduced to 0.124, 30, and 213.84 μm, respectively. This study reveals that PFP has potential for application in the grouting construction of poor strata, such as sand layers. Full article

Meloxicam is a promising non-steroidal anti-inflammatory drug (NSAID) for acute and chronic pain prevention and treatment. Due to its poor water solubility, the clinical use of meloxicam is limited. In addition, for transdermal applications, the impermeability of the skin makes it difficult to conceive an appropriate NSAID-based delivery system that can penetrate through the skin barrier. Hydrophilic/hydrophobic gels, designed as transdermal drug delivery systems, can considerably improve other drug administration types (such as oral or intravenous), avoiding or limiting the side effects. The main purpose of this paper is to present some physicochemical and pharmaceutical considerations about meloxicam and to review the most important research concerning the gels used for the transdermal delivery of meloxicam. Thus, smart polymeric networks, semi-solid systems (lipogels, emulgels), β-cyclodextrin-based gels, liposomes (ethosomes, niosomes, flexosomes, transferosomes, menthosomes, invasomes), and nanostructured lipid carriers, with analgesic and anti-inflammatory activity, are discussed. The key objective of this study was to highlight various gel formulations with enhanced properties, which could be used in a minimally invasive manner for the sustained administration of meloxicam. Full article

Coal mine underground reservoirs play a significant role in energy utilization while also contributing to energy security. Prolonged immersion in mine water reduces the long-term strength of coal, subsequently leading to continuous creep damage in coal pillars. This manifests as the propagation of damage, ultimately resulting in instability, which affects their load-bearing capacity and impermeability. A multi-faceted approach involving laboratory experiments, similar model tests, and numerical simulations was employed to investigate the mechanical properties of water-immersed coal and the continuous creep damage process in coal pillars. Key findings reveal that water immersion significantly diminishes the long-term strength of coal; for example, initial instantaneous strain rose from 0.16% (non-immersed) to 0.25% (8-week immersion), with final creep strain reaching 1.15% versus 0.78%, respectively. The combined modeling methods effectively replicated the creep damage process, demonstrating that when concentrated stress exceeds the reduced long-term strength of coal, damage propagates toward the center of the pillar, forming continuous creep damage extending approximately 3.8 m within 7 years. This study contributes to our understanding of the creep damage mechanism in coal pillars and supports the long-term stability evaluation of CMURs. Full article

In order to broaden the means of resource utilization of waste soil and steel slag produced in the process of urban construction, in this study, steel slag was used to replace part of the cement with waste soil, to prepare flowable waste soil. Through unconfined compressive strength (UCS), permeability, and dry–wet cycle tests, the mechanical properties of flowable waste soil under different steel slag replacement ratios and moisture contents were studied. The results show that the UCS of the flowable waste soil increases with the increase in curing age. When the steel slag replacement ratio is less than 66.7%, the UCS of the sample after 7 days of curing is more than 100 kPa. When the moisture content of the sample is 58% and the steel slag replacement ratio is 58.3%, the UCS can reach 101 kPa after 1 day of curing, which can meet the requirements of rapid construction. The UCS, resistance to the dry–wet cycle, elastic modulus, failure stress, and failure strain of flowable waste soil all decrease with the increase in the moisture content and steel slag substitution ratio. The permeability coefficient of the steel slag mixed sample decreased from 2.1 × 10⁻⁶ cm/s to 7.4 × 10⁻⁷ cm/s, and the permeability coefficient of the flowable waste soil after 28 d curing extended below 6 × 10⁻⁶ cm/s, indicating that the flowable waste soil has good impermeability and can be applied well in engineering. Full article

Membrane processes are extensively employed in a range of industrial and food applications. Due to growing environmental concerns and the introduction of regulatory measures, it is imperative to develop innovative membrane materials that can effectively replace petrochemical-based polymers, in line with the principles of a circular economy. The focus of this review is the use of polysaccharides for obtaining films/membranes for food and industrial applications using selected case studies. Besides the polysaccharides extracted from biomass, the valorization of agrifood residues and the use of plants adapted to arid lands (i.e., cactus) to produce polysaccharide films for food packaging is addressed. Moreover, microbial polysaccharides produced using renewable resources present a significant alternative to commercial hydrophilic membranes for gases and ethanol dehydration. To meet industry requirements, the mechanical and barrier properties of the films can be improved by the inclusion of inert impermeable fillers and/or the chemical modification of the polysaccharides. The adsorption of proteins, dyes, and pharmaceutical compounds using a cellulose-based polymer is discussed. Despite their unique characteristics, polysaccharide production costs are still higher than most synthetic polymers. This is a challenge that can be overcome by scaling up the production and by valorizing agro-industrial wastes and by-products to make the application of polysaccharide membranes/films in the food and industry sectors more widespread. Full article

The high water head of some pumped storage power stations will induce the cracking of the concrete lining of their diversion tunnel and the leakage of high-pressure water, which will affect the safety of the tunnel and the surrounding rock. At present, there is no solution to the problem of impermeability of concrete materials after cracking. This paper proposes a composite lining to solve this problem. The composite lining with modified polydimethylsiloxane coating can effectively prevent high-pressure water, but its crack resistance needs to be further studied. Therefore, the tensile mechanical properties, constitutive relationship of modified polydimethylsiloxane impermeable coating, and the crack resistance mechanical properties of modified polydimethylsiloxane impermeable composite lining were studied by laboratory tests and numerical simulations. The results show that the true fracture elongation of the modified polydimethylsiloxane impermeable coating is as high as 118.98%, and its mechanical behavior can be described by a simplified polynomial hyperelastic constitutive model. The in situ stress will affect the crack width of the concrete lining. When the lateral pressure coefficient is less than 1, the crack width decreases with the increase in the lateral pressure coefficient. When the lateral pressure coefficient is greater than 1, the crack width increases with the increase in the lateral pressure coefficient. To prevent the cracking of modified polydimethylsiloxane coating, its spraying thickness needs to increase with the increase in crack width. The ratio of the coating’s thickness to crack width is recommended from 0.162 to 1.930 for internal water pressure from 1 MPa to 10 MPa, respectively. The suggestion provides a reference for designing the impermeable composite lining structure subjected to high internal water pressure. Full article

In this paper, a novel approximate triangular fuzzy finite element method (FEM) is proposed to solve the one-dimensional second-order unsteady nonlinear fuzzy partial differential Boussinesq equation. The physical problem concerns the case of the drought flow of a horizontal unconfined aquifer with a limited breath B and special boundary conditions: (a) at x = 0, the water level is equal to zero, and (b) at x = B, the flow rate is equal to zero due to the presence of an impermeable wall. The initial water table is assumed to be curvilinear, following the form of an inverse incomplete beta function. To account for uncertainties in the system, the hydraulic parameters—hydraulic conductivity (K) and porosity (S)—are treated as fuzzy variables, considering sources of imprecision such as measurement errors and human-induced uncertainties. The performance of the proposed fuzzy FEM scheme is compared with the previously developed orthogonal fuzzy FEM solution as well as with an analytical solution. The results are in close agreement with those of the other methods, with the mean error of the analytical solution found to be equal to $1.19·{10}^{-6}$. Furthermore, the possibility theory is applied and fuzzy estimators constructed, leading to strong probabilistic interpretations. These findings provide valuable insights into the hydraulic properties of unconfined aquifers, aiding engineers and water resource managers in making informed and efficient decisions for sustainable hydrological and environmental planning. Full article

It is challenging for mortar to simultaneously enhance the transmission property of water vapor while maintaining excellent waterproofness and impermeability. However, in some applications, both are necessary. Therefore, three different kinds of modifiers, i.e., cementitious capillary crystalline waterproof materials (XYPEX), γ-methacryloxy-propyl-trimethoxy-silane (KH570), and styrene-butadiene rubber latex (SB), are employed to explore how modified mortar can possess excellent waterproofness, impermeability, and the water vapor transmission property simultaneously. Combining characterization techniques, the influencing factors of these three properties are studied. The results indicate that XYPEX promotes the formation of hydration products within pores, improves waterproofness and impermeability, but decreases the water vapor transmission property. KH570 introduces numerous pores ranging from 0.1 to 5 micrometers and enhances the hydrophobicity of mortar; at 1.25% and 2.5% contents, the modified mortar exhibits excellent waterproofness and water vapor transmission property but poor impermeability. SB introduces numerous air pores and forms polymer films; at 20% content, the modified mortar exhibits excellent waterproofness and water vapor transmission property, with impermeability remaining unchanged, making SB a favorable modifier that combines these three properties. Finally, the mechanisms of these three properties are discussed, which provides a theoretical reference for the control of mortar’s waterproofing, impermeability, and water vapor transmission. The selection of modifiers is based on the actual performance requirements. Full article

This study investigates the influence of various cementitious materials on the performance of alkali-activated green ultra-high performance concrete (GUHPC). Alkali-activated GUHPC was prepared by substituting cement, quartz powder, and limestone powder with slag powder and fly ash. The mechanical properties, durability, hydration products, and microstructure were systematically analyzed. The results demonstrate that, with a cement dosage of 264 kg/m³, the alkali-activated GUHPC incorporating 40% slag powder and 28% fly ash as cement replacements exhibited superior mechanical performance, achieving compressive and tensile strengths of 165.3 MPa and 7.7 MPa, respectively, after curing. The GUHPC displayed a dense internal structure with an extremely low porosity of 6.76%, along with superior impermeability and frost resistance compared to conventional UHPC. Slag powder exhibited high pozzolanic reactivity under alkali activation, enabling effective cement replacement. These findings provide valuable insights for the formulation of alkali-activated GUHPC. Full article

Basalt fiber has advantages in enhancing the mechanical properties of concrete, but the comprehensive effects of fiber content and length, as well as the relationship between mechanical and impermeability performance, remain unclear and require systematic verification. This study aims to quantify the effects of basalt fiber content and length on mechanical properties (compressive strength, tensile strength, and flexural strength) and concrete permeability performance and reveal the underlying mechanisms. The macroscopic performance results indicate the following: (1) the optimum fiber content of compressive strength and flexural strength of basalt fiber-reinforced concrete is 1.5 kg/m³; (2) the optimum content of tensile strength is 1.0 kg/m³; and (3) the impermeability performance of the fiber-reinforced concrete is most significantly improved when the fiber content reaches 1.0 kg/m³ and the fiber length is 18 mm. During the permeability tests, a nonlinear functional relationship exists between two indicators, electric flux and chloride ion migration coefficient. Microscopic analysis showed that mineral admixtures (fly ash and silica fume) promoted the secondary hydration reaction in the cementitious material, generating a significant amount of C-(A)-S-H gels to increase the density of the concrete matrix. After incorporating basalt fibers, they tightly envelop the concrete matrix, reducing the number of internal voids and achieving a synergistic stress-bearing effect with the concrete, confirming that the addition of fibers optimizes the mechanical and impermeability properties of the concrete. This study provides a quantitative reference for the basalt fiber reinforcement design of engineering concrete structures and helps extend the service life of concrete buildings. Full article

This review explores the development and application of the impregnation of graphene-based materials into polymeric coatings to enhance corrosion resistance. Derivatives of graphene, such as graphene oxide (GO) and reduced graphene oxide (rGO), have been increasingly integrated into polymer matrices to enhance polymers’ mechanical, thermal, and barrier properties. Various synthesis approaches, viz., electrochemical deposition, chemical reduction, and the incorporation of functionalised graphene derivatives, have been explored for improving the dispersion and stability of graphene within polymers. These graphene-impregnated coatings have shown promising results in improving corrosion resistance by enhancing impermeability to corrosive agents and reinforcing mechanical strength under corrosive conditions. While the addition of graphene notably enhances coating performance, challenges remain in achieving uniform graphene dispersion and addressing the trade-offs between thickness and flexibility. This review highlights current advancements, limitations, and future directions, with a particular emphasis on optimising the synthesis techniques to maximise corrosion resistance while maintaining coating durability and economic feasibility. Full article