High Mechanical Durability Research Articles

Development and Characterization of Lime-Based Mortars Modified with Graphene Nanoplatelets

Materials for the conservation of cultural heritage must meet specific demands, such as high durability, service life, and compatibility with other materials used in the original building structures. Due to their low permeability to water and water vapor and their high rigidity, the use of Portland cement (PC) mortars, despite their high mechanical resistance and durability, does not represent an appropriate solution for the repair of historic masonry and structures. Their incompatibility with the original materials used in the past, often on a lime basis, is therefore a serious deficiency for their application. On the other hand, lime-based mortars, compared to PC-based materials, are more susceptible to mechanical stress, but they possess high porosity, a high water vapor transmission rate, and moderate liquid water transport. This study aims at the development of two types of lime-based mortars, calcium lime (CL) and hydraulic lime (HL). The modification of mortars was conducted with a carbon-based nanoadditive and graphene nanoplatelets (GNs) in three dosages: 0.1%, 0.3%, and 0.5% of the binder weight. The enhancement of CL mortars by GNs greatly increased mechanical strength and affected heat transport characteristics, while other characteristics such as porosity, water absorption, and drying rate remained almost similar. The application of GNs to HL not only enhanced the strength of mortars but also decreased their porosity, influenced pore size distribution, and other dependent characteristics. It can be concluded that the use of graphene nanoplatelets as an additive of lime-based composites can be considered a promising method to reinforce and functionalize these composite materials. The improved mechanical resistance while maintaining other properties may be favorable in view of the increasing requirements of building materials and may prolong the life span of building constructions.

Anti/de-icing superhydrophobic coating with durability and self-healing by infiltrating photothermal self-stratifying organic layers into plasma-sprayed porous Al2O3–13%TiO2 underlayer

Superhydrophobic coatings simultaneously exhibiting high substrate binding, mechanical durability and self-healing properties are of great significance for anti/de-icing applications. In this study, we fabricated a high substrate binding and mechanical durability anti/de-icing superhydrophobic coatings (SL-AP/SPS-SiO2) with self-healing performance by spray-coating a photothermal self-healing organic layers (AP/SPS-SiO2) plasma-sprayed porous Al2O3–13%TiO2 underlayer (SL), the resulting soft-hard interlocking structure significantly increased the adhesion strength of the coating to 16.7 ± 0.36 MPa while reducing the ice adhesion strength to 46.5 ± 3.0 kPa. In the as-obtained organic layers, self-stratifying acrylic resin (AR)/20%polymethylsiloxane (PDMS) (AP), not only enhanced the bonding strength with the underlayer but also imparted photothermal self-healing capability to the coating through the action of the photothermal agent (SPS-SiO2). And sodium alginate (SA) guided the self-oxidative polymerization of dopamine (DA) and its deposition on hydrophilic SiO2 to form a π-π stacked fiber structure photothermal agent (SPS), after hydrophobic SiO2 modification increased the coating's roughness and photothermal performance. Remarkably, the coating achieved a contact angle of up to 158.4 ± 0.89° and a rolling angle of 3.5 ± 0.89°, maintaining its superhydrophobic properties even after exposure to acid-base immersion and mechanical abrasion. Furthermore, the coating exhibited self-healing capabilities in superhydrophobicity against O2 plasma etching, with a contact angle recovery rate of up to 98.9% after undergoing 10 cycles of O2 plasma etching and light exposure. Enhancing mechanical and chemical stability with self-healing capabilities is beneficial for extending the lifespan of superhydrophobic coatings used in anti-/de-icing applications.

Tailoring Mechanical and Optical Properties of Sputtered SiNx/BN Coatings.

The swift evolution of contemporary electronics products, such as flexible screens and wearable electronic devices, highlights the significance of flexible protective coatings, which combine superior mechanical and optical properties. Even though the recently developed polymer protective coatings can satisfy requirements for flexibility and transparency, their intrinsic nature often results in a hardness below 1 GPa, rendering them susceptible to scratches. On the other hand, traditional inorganic coatings, known for their high hardness and transparency, fall short of meeting flexibility requirements. In the present study, a SiNx/BN periodical nanolayered coatings (PNCs) structure has been tailored to achieve high mechanical durability, transparency, and flexibility. In SiNx/BN PNCs, the optical and mechanical properties of the single-layer SiNx film are crucial to the overall performance of the PNCs. Therefore, pulse direct current (DC) magnetron sputtering was optimized first to enhance the ionization efficiency of Si and N, thereby promoting their reaction and diminishing the presence of elemental silicon in SiNx. The effects of the pulse frequency and duty cycle on SiNx were evaluated. Additionally, the influence of the thickness ratio and modulation periods on the overall performance of the SiNx/BN PNCs was investigated. As a result, a SiNx/BN coating with sapphire-grade hardness, almost no optical absorption in the visible-near-infrared (vis-NIR) range, high wear resistance, and exceptional flexibility was demonstrated.

Test Procedures and Mechanical Properties of Three-Dimensional Printable Concrete Enclosing Different Mix Proportions: A Review and Bibliometric Analysis

Three-dimensional printable concrete (3DPC) has become increasingly popular in the building and architecture industries due to its low cost and fast design. Currently, there is great interest in the mix design methods and mechanical properties of 3DPC, particularly in relation to yield stress analysis. The ability to extrude and build 3D-printed objects can be significantly affected by factors such as the rate of extrusion, nozzle size, and type of pumps used. It has been observed that a yield stress lower than 1.5 to 2.5 kPa is not sufficient to maintain the shape stability of concrete, while a yield stress above this range can limit the material’s extrudability. Furthermore, the strength properties of 3DPC are influenced by factors such as changes in yield stress and superplasticiser dosages. To meet the high mechanical strength and durability requirements of 3DPC in the construction industry, it is essential to analyse the material’s early-age mechanical properties. However, the development of standardised test methods for 3DPC is still deficient. To address this issue, a bibliometric analysis was conducted to comprehensively review the diverse test methods and mechanical characteristics of 3DPC with different mix proportions. To produce high-performance concrete from various additives and waste materials, it is critical to have a basic understanding of the hydration processes of 3DPC. Moreover, a detailed analysis of the environmental impact and energy efficiency of 3DPC is necessary for its widespread implementation. This review article will highlight the recent trends, upcoming challenges, and benefits of using 3DPC. It serves as a taxonomy to navigate the field of 3DPC towards sustainable development.

Durable TPU/PDA/MXene Fiber‐Based Strain Sensors with High Strain Range and Sensitivity

AbstractWith the development of the ageing society, wearable strain sensors have great application prospects in the fields of health detection, artificial intelligence, and motion recognition. However, traditional forms of film‐like strain sensors suffer from low sensitivity, adhesion, and impermeability during use, which severely limit their practical applications. To overcome these problems, we propose a strategy to fabricate polyurethane/polydopamine/MXene (TPU/PDA/MXene) composite fibers by wet spinning. Furthermore, the outside is wrapped with (PDMS), giving mechanical strength and chemical resistance. Through a simple and low‐cost wet spinning process, TPU/PDA/MXene fibers are achieved in the preparation of flexible strain sensors, and they can be woven into various forms with good flexibility and comfort according to practical needs. The results indicated that the prepared flexible strain sensor exhibits a high gauge factor (GF) of 57.15 over a large strain range (300 %), which are superior to those of many fiber‐based sensors. Their application properties were also measured by attaching them to fingers, wrists and knees, showing high sensitivity, mechanical durability and chemical stability, and has great potential for wearable strain sensors and flexible strain sensors in complex environments.

Recycling of human teeth for piezoelectric energy harvesting

In the human body, non-centrosymmetric biological structures exhibit piezoelectric effect across from microscopic biomolecular building blocks to macroscopic tissues and organs. However, the fabrication of piezoelectric devices from discarded natural tissues and organs has rarely been exploited for energy harvesting applications. Herein, the extracted human teeth were recycled as an active layer in a piezoelectric nanogenerator for power generation. Due to the piezoelectric effect of enamel and dentin, a human teeth-based sandwiched piezoelectric nanogenerator was fabricated, producing high and stable power outputs with an open-circuit voltage of approximately 0.9 V under an external force at 60 N. Furthermore, the high mechanical durability of the piezoelectric nanogenerator was also verified after 1600 pressing-and-releasing cycles without noticeable output degradation. Notably, for the first time, a light-emitting diode (LED) was illuminated by the human teeth-based piezoelectric device. This work exemplifies a sustainable strategy to recycle the extracted human teeth by fabricating a piezoelectric nanogenerator for energy harvesting, providing inspiration for converting waste into wealth toward green energy in bionanotechnology.

Construction of robust superhydrophobic surfaces with electrothermal, photothermal properties using simple spraying method

In this study, robust superhydrophobic surfaces with electrothermal, photothermal properties were fabricated by simple spraying method. In more detail, multiwall carbon nanotube (MWCNT) and silica were deliberately sprayed onto the wet poly(amide imide) (PAI) surface to construct intensive conductive network with hierarchical porous structure. The composite coating showed superhydrophobic with a water contact angle (CA) of greater than 155o and sliding angle (SA) of lower than 5o, conductivity of approaching to 1 kΩ sq-1. As expected, the composite coating possessed passive anti-icing property owing to its high CA, and the freezing time at -20 °C was obviously delayed from 150 to 600 s. On the other hand, the surface temperature respectively increased by 40 °C and 35 °C under the assistance of electric (voltage of 36 V) or light (0.23 W cm-2 irradiation) power, and the active anti-icing function can still work even under a such low temperature of -15 °C. It is worth noting that the heat generated by Joule effect was fixed on the conductive surfaces, and thus the composite coating showed good thermal insulation due to the low thermal conductivity of PAI substrate (0.298 W/mK) and hierarchical porous structure of composite coating. In addition, the surfaces showed high mechanical robust and durability, and the superhydrophobic and conductive properties were nearly unaffected even they suffered from lots of tests such as sandpaper abrasion, ultrasonic treatment, strong acid or strong alkali immerse, UV irradiation, and hot water jet impacting. Therefore, this study offered a simple way to fabricate electrothermal and photothermal surfaces for practical anti-icing/de-icing applications.

Molecular Insights into Adhesion at Interface of Geopolymer Binder and Cement Mortar.

The degradation of concrete and reinforced concrete structures is a significant technical and economic challenge, requiring continuous repair and rehabilitation throughout their service life. Geopolymers (GPs), known for their high mechanical strength, low shrinkage, and durability, are being increasingly considered as alternatives to traditional repair materials. However, there is currently a lack of understanding regarding the interface bond properties between new geopolymer layers and old concrete substrates. In this paper, using advanced computational techniques, including quantum mechanical calculations and stochastic modeling, we explored the adsorption behavior and interaction mechanism of aluminosilicate oligomers with different Si/Al ratios forming the geopolymer gel structure and calcium silicate hydrate as the substrate at the interface bond region. We analyzed the electron density distributions of the highest occupied and lowest unoccupied molecular orbitals, examined the reactivity indices based on electron density functional theory, performed Mulliken charge population analysis, and evaluated global reactivity descriptors for the considered oligomers. The results elucidate the mechanisms of local and global reactivity of the oligomers, the equilibrium low-energy configurations of the oligomer structures adsorbed on the surface of C-(A)-S-H(I) (100), and their adsorption energies. These findings contribute to a better understanding of the adhesion properties of geopolymers and their potential as effective repair materials.

Effects of Materials and Riblets on Erosion Mitigation Induced by Multiple Collapses of Cavitation Bubbles

The current research investigates the effects of materials and riblets on cavitation-induced erosion morphology, depth, and cross-sectional area through experimental approaches. To achieve these aims, the erosion of pure aluminum (1xxxAl or Al) and alpha brass (CuZn37 or CZ108), in the presence and absence of bio-inspired sawtooth riblets, was examined after exposure to multiple collapses of single cavitation bubbles with a wall distance of 1.8 (dimensionless). The results indicate that the erosion morphology resembles a rounded cone with a circular cross-section. Brass provides 21.6% more erosion resistance compared to that of Al in terms of material properties. Furthermore, the erosion for both Al (depth by 3.8% and width by 18.3%) and brass (depth by 7.9% and width by 27.4%) decreases in the presence of riblets compared to the results for flat surfaces. The greater erosion resistance of brass compared to Al is attributed to the superior mechanical stability of brass, making it a potentially suitable alloy for use in propellers and hulls in the shipping industry. In summary, the results reveal that riblet-equipped materials with high mechanical durability are promising erosion-resistant materials for the shipping industry. However, the potential for chemical reactions in a cathodic environment should be addressed to provide a comprehensive perspective in regards to reducing corrosion intensity.

Vitrification as a Key Solution for Immobilisation Within Nuclear Waste Management

AbstractVitreous materials in the form of both relatively homogeneous glasses and composite glass crystalline materials (GCM) incorporating disperse crystalline phases are currently the most reliable wasteforms effectively used on industrial scale for nuclear waste immobilisation. Glasses are stable solid-state materials with a topologically disordered atomic structure in the form of solid solutions, i.e. solutions frozen via vitrification to a solid state without forming regular crystalline phases. Nuclear waste vitrification is attractive because of technological and compositional flexibility enabling hazardous elements to be safely immobilised and providing a glassy material characterised by high corrosion resistance, mechanical and radiation durability, as well as effectively reducing the volume of the resulting wasteform.

Numerical Analysis on Frictional Heat Effect in Polyether-Ether-Ketone (PEEK)/Steel Pair by using OpenFOAM Model

The PEEK material has been applied to a sliding bearing system in a power plant system because of its high mechanical durability. In the solid friction of the PEEK materials, the frictional heat becomes the important factor because the temperature increase due to the frictional heat causes the rapid increase of the frictional coefficient of the specimen. To maintain the low frictional coefficient of the PEEK materials, an effective cooling method for the PEEK materials needs to be developed. In this study, the passive cooling method, which attaches the heat sink to the PEEK materials, was suggested. For evaluating the suggested cooling method of the PEEK materials, the calculation model adopting OpenFOAM, which is open-source software, has been developed. Adopting some functions and libraries of OpenFOAM, the frictional heat, heat resistance, and heat transfer coefficient on the heat sink were modelled. The sliding bearing experiment was conducted and time variation of the temperature and friction coefficient in the ring specimen were measured. The temperature variation in the ring specimen was compared with the calculation result. From the numerical calculation results, the developed calculation model could simulate the temperature-time variation of the ring obtained in the experiment, when the variation of the frictional coefficient, heat resistance, and heat transfer coefficient was modelled appropriately. Based on the friction and wear test results, by applying a heat dissipation mechanism to the ring test piece, the calorific value of the PEEK material can be reduced, and it is stable. It was suggested that the friction was maintained.

Scalable multifunctional MOFs-textiles via diazonium chemistry

Cellulose fiber-based textiles are ubiquitous in daily life for their processability, biodegradability, and outstanding flexibility. Integrating cellulose textiles with functional coating materials can unlock their potential functionalities to engage diverse applications. Metal-organic frameworks (MOFs) are ideal candidate materials for such integration, thanks to their unique merits, such as large specific surface area, tunable pore size, and species diversity. However, achieving scalable fabrication of MOFs-textiles with high mechanical durability remains challenging. Here, we report a facile and scalable strategy for direct MOF growth on cotton fibers grafted via the diazonium chemistry. The as-prepared ZIF-67-Cotton textile (ZIF-67-CT) exhibits excellent ultraviolet (UV) resistance and organic contamination degradation via the peroxymonosulfate activation. The ZIF-67-CT is also used to encapsulate essential oils such as carvacrol to enable antibacterial activity against E. coli and S. aureus. Additionally, by directly tethering a hydrophobic molecular layer onto the MOF-coated surface, superhydrophobic ZIF-67-CT is achieved with excellent self-cleaning, antifouling, and oil-water separation performances. More importantly, the reported strategy is generic and applicable to other MOFs and cellulose fiber-based materials, and various large-scale multi-functional MOFs-textiles can be successfully manufactured, resulting in vast applications in wastewater purification, fragrance industry, and outdoor gears.

Fabrication of a durable corrosion-resistant superamphiphobic CeO2–TiO2 ceramic nanocomposite coating on AZ31B Mg alloy by plasma electrolyte oxidation

A liquid-repellent and corrosion resistant surface was fabricated on AZ31B Mg alloy by the usage of CeO2 and TiO2 nanoparticles (NPs), plasma electrolyte oxidation (PEO) method, and subsequent surface modification. The whole process included two main steps: a) applying PEO with CeO2–TiO2 NPs on AZ31B and b) decreasing surface energy by using a fluorinating agent. Elements that were present on the surface were investigated by XRD and EDS analyses. Surface morphology and its roughness were scrutinized by FESEM images and AFM tests, respectively. Contact angles (CA) of water and some oils (Ethylene glycerol and Glycerol) on the prepared surface were measured. CAs of water and ethylene glycerol were reported at 175.6° and 151.4°, respectively. Also, the corrosion behavior of the prepared surface was assessed by EIS and potentiodynamic polarization analyses. Results showed that the corrosion rate of the neat AZ31B decreased noticeably from 127.78 to 0.027 mpy for superamphiphobic PEO-NPs AZ31B. The prepared sample showed high mechanical durability, which was scrutinized by water floatation, abrasive with grit SiC paper, adhesive tape peeling, and bending tests. After immersion of the sample in 5 wt% NaCl solution for various hours, results showed that the prepared sample had a noticeable corrosion resistance stability.

Intrinsically Stretchable Floating Gate Memory Transistors for Data Storage of Electronic Skin Devices.

To propel electronic skin (e-skin) to the next level by integrating artificial intelligence features with advanced sensory capabilities, it is imperative to develop stretchable memory device technology. A stretchable memory device for e-skin must offer, in particular, long-term data storage while ensuring the security of personal information under any type of deformation. However, despite the significance of these needs, technology related to stretchable memory devices remains in its infancy. Here, we report an intrinsically stretchable floating gate (FG) polymer memory transistor. The device features a dual-stimuli (optical and electrical) writing system to prevent easy erasure of recorded data. An FG comprising an intermixture of Ag nanoparticles and elastomer and with proper energy-band alignment between the semiconductor and dielectric facilitated sustainable memory performance, while achieving a high memory on/off ratio (>105) and a long retention time (106 s) with the ability to withstand 50% uniaxial or 30% biaxial strain. In addition, our memory transistor exhibited high mechanical durability over multiple stretching cycles (1000 times), along with excellent environmental stability with respect to factors such as temperature, moisture, air, and delamination. Finally, we fabricated a 7 × 7 active-matrix memory transistor array for personalized storage of e-skin data and successfully demonstrated its functionality.

Construction of highly robust amino orange peel cellulose for Cu2+ adsorption study

ABSTRACT In this paper, a kind of cellulose aerogel (HRCNFs) with high mechanical robustness and durability was prepared by using orange peel cellulose and polyethylenimine, and it was used for high-efficiency adsorption of Cu (II). Fourier analysed the structure and morphology of HRCNFs transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and the pore structure characteristics of the materials were evaluated by BET. The adsorption capacity of HRCNFs as adsorbent to remove Cu (II) ions from aqueous solution was further studied. The maximum adsorption capacity was 167.21 mg/g. Adsorption is mainly a single-layer chemisorption process. Based on FTIR and BET analysis, the adsorption mechanism is the strong surface complexation of amino, carboxyl, and hydroxyl groups with Cu (II). Through many cycles, HRCNFs retain their integrity and high mechanical robustness. Therefore, the synthesised HRCNFs material can be considered a promising adsorbent for the removal of Cu (II) ions from polluted water bodies.

Design of hybrid Ag–Au nanostructure based fully elastomeric nanocomposite electrodes for soft integrated electronics

Recent advancements in stretchable devices have opened new avenues for constructing soft electronics for use in applications such as health-monitoring wearables, advanced integrated circuits, and soft robotics. Meeting the increasing demand for enhanced functionality in soft electronics requires the development of soft conductors with high electrical conductivity, mechanical durability, and cost-effectiveness. Researchers have addressed this challenge by creating percolated networks within the elastomer as a nanocomposite using low-dimensional conducting nanomaterials to endow non-stretchable metallic materials with mechanical stretchability. For example, silver nanowires (AgNWs) have found wide application as essential fillers in soft conductor nanocomposites owing to their remarkable aspect ratio and cost-efficiency. However, their application is limited by their susceptibility to environmental degradation and poor compatibility with semiconducting materials. In this work, the hybrid Ag–Au based nanomaterials as a filler nanomaterial within an elastomer in a nanocomposite format was generated, as it exploits the strengths of each material while mitigating their respective weaknesses. Specifically, the work introduces the merit of the hybrid elastomeric electrodes that consist of AgNWs decorated with Au nanoparticles (AANWs), and Au nanosheets (AuNSs) embedded in a polydimethylsiloxane (PDMS) elastomer. These electrodes exhibit remarkable mechanical resilience and electrical conductivity, making them suitable for application in transistors, logic gates, integrated electronics, and soft displays. The work explores the synthesis and properties of hybrid materials comprising AgNWs and AuNSs, highlighting the promising potential of these materials for future research and development.

Dynamic multicolor emissions of multimodal phosphors by Mn2+ trace doping in self-activated CaGa4O7

The manipulation of excitation modes and resultant emission colors in luminescent materials holds pivotal importance for encrypting information in anti-counterfeiting applications. Despite considerable achievements in multimodal and multicolor luminescent materials, existing options generally suffer from static monocolor emission under fixed external stimulation, rendering them vulnerability to replication. Achieving dynamic multimodal luminescence within a single material presents a promising yet challenging solution. Here, we report the development of a phosphor exhibiting dynamic multicolor photoluminescence (PL) and photo-thermo-mechanically responsive multimodal emissions through the incorporation of trace Mn2+ ions into a self-activated CaGa4O7 host. The resulting phosphor offers adjustable emission-color changing rates, controllable via re-excitation intervals and photoexcitation powers. Additionally, it demonstrates temperature-induced color reversal and anti-thermal-quenched emission, alongside reproducible elastic mechanoluminescence (ML) characterized by high mechanical durability. Theoretical calculations elucidate electron transfer pathways dominated by intrinsic interstitial defects and vacancies for dynamic multicolor emission. Mn2+ dopants serve a dual role in stabilizing nearby defects and introducing additional defect levels, enabling flexible multi-responsive luminescence. This developed phosphor facilitates evolutionary color/pattern displays in both temporal and spatial dimensions using readily available tools, offering significant promise for dynamic anticounterfeiting displays and multimode sensing applications.

УТИЛИЗАЦИЯ ШЛАМОВЫХ ПРОДУКТОВ ПРОМЫВКИ ОТСЕВОВ ШАРХИНСКОГО КАРЬЕРА В ПРОИЗВОДСТВЕ СТЕНОВЫХ СТРОИТЕЛЬНЫХ МАТЕРИАЛОВ

Abstract. The effect of semi-dry pressing on the strength of samples has been studied. It is shown that the optimal specific pressure for pressing samples from molding mixtures containing 10, 20, 30% slag-portland cement is 30Mpa. With the help of RCCP, static processing of experimental results was carried out and a regression equation was obtained for the dependence of the strength of the samples on the pressing pressure and the content of slag-portland cement in the molding mixture.
 When examining the microstructure of the samples, it was found that the resulting material is a homogeneous and durable conglomerate, the crystals of neoplasms are evenly distributed over the mass and bind the sludge particles. A pilot test of the semi-dry pressing process of products has established the possibility of obtaining high-quality hollow bricks of the M100-M300 grades with a content of slag-portland cement in the mixture in the range of 10-30% (wt.).
 The subject of the study: sludge products of flushing the screenings of the Sharkhinsky quarry in the production of wall building materials.
 Materials and methods: sludge from the Sharkhinsky quarry and slag-portland cement from the Bakhchisarai cement Plant were used in the work. The structure of the samples was studied using electron scanning microscopy on a REM-106 SELMI microscope. Experimental and industrial tests were carried out on the equipment of the Aggregate company. The physical and mechanical properties of bricks and paving slabs were studied in accordance with the norms and standards established in GOST 6133-2019.
 Results: The microstructure of the samples was investigated and it was found that the resulting material is a homogeneous and durable conglomerate, the crystals of neoplasms are evenly distributed over the mass and bind the sludge particles. Experimental and industrial testing of the semi-dry pressing process of products from molding mixtures based on the sludge of the Sharkhinsky quarry was carried out. It was confirmed that it is possible to produce high-quality hollow bricks marked M100-M300 using slag-portland cement in a mixture in the range of 10-30% (by weight), which fully meets the requirements set out in GOST 6133-2019
 Conclusions: Sludge products from the flushing of the Sharkhinsky quarry screenings can be successfully used in the production of wall building materials, which contributes to waste disposal and improvement of the ecological state of the environment. Effective methods of disposal of sludge products make it possible to obtain high-quality building materials with high physical and mechanical properties and durability.

Properties of Basalt Fiber-reinforced Lightweight Geopolymer Mortars Produced with Expanded Glass Aggregate

Geopolymers are new-generation construction materials that have attracted attention recently and can be an alternative to cement. In the production of these materials, aluminosilicate powder materials are used together with alkali or acid solutions. Geopolymers have different types of superiorities, such as rapid strength gain, high mechanical properties and good durability. This experimental study investigated the properties of expanded glass aggregate-bearing Class F fly ash-based lightweight geopolymer mortars. The fresh unit weight, water absorption capacity, compressive strength and high-temperature resistance (upon exposure to 900°C) of the mortars were determined. In addition, basalt fiber addition's effects on these properties were investigated. The inclusion ratios of basalt fiber were 0.1%, 0.2% and 0.4% by volume. The compressive strengths of fiber-free lightweight mixture and mixtures, including 0.1%, 0.2% and 0.4% basalt fiber, were found to be 8.2, 8.9, 9.0 and 8.0 MPa, respectively. The compressive strength of all lightweight mortars increased between 61.3% and 76.4% after the high-temperature effect. The results proved that it is possible to produce expanded glass aggregate-bearing lightweight geopolymer mortars with acceptable mechanical properties.

Experimental Research on Fatigue Behavior of Reinforced UHPC-NC Composite Beams under Cyclic Loading.

Ultra-high-performance concrete (UHPC), a new cement-based material that offers high mechanical strength and good durability, has been widely applied in construction and rehabilitation projects in recent years. An optimum bending system is achieved by positioning the UHPC layer at the bottom tensile zone of the composite beam and placing the normal-strength concrete (NC) layer at the upper compression zone, which is described as the UHPC-NC composite beam. The fatigue behavior of reinforced UHPC-NC composite beams was described in this study, with an emphasis on the effects of UHPC layer thickness and fatigue load level on the fatigue life of the beam, deformation of the interface between UHPC and NC layers, as well as the bending stiffness of the beam. A total of 9 reinforced UHPC-NC composite beams were tested under cyclic loading. The test variables include UHPC layer thicknesses (zero, 200, and 360 mm), reinforcement ratios (1.184% and 1.786%), and the upper load levels (0.39~0.65). The results showed that good bonding had been achieved without delamination between UHPC and NC layers prior to the final fatigue failure of the beam, and the bending stiffness of the composite beam experienced a three-stage reduction under cyclic loading. Furthermore, an equation was proposed to predict the stiffness reduction coefficient of UHPC-NC composite beams under cyclic loading.