High Mechanical Durability Research Articles

Preparation of modified polylactic acid fiber containing anti‐hydrolysis agents

AbstractPolylactic acid (PLA) is a promising alternative to petroleum‐based polymers due to its biodegradability. However, its low mechanical properties in the presence of moisture are a challenge for textile applications. In this study, we investigated the effects of two anti‐hydrolysis agents, an epoxy‐based agent (ADR) and an aromatic carbodiimide‐based agent (ZIKA), on the mechanical properties and hydrolysis resistance of PLA fibers. A melt‐spinning process was used to prepare anti‐hydrolysis fibers by adding 0.3 and 0.5 wt% of ADR and ZIKA to PLA. The topology of ADR/PLA and ZIKA/PLA was determined by Fourier transform infrared spectroscopy (FT‐IR). Analysis of the compound chip revealed that ADR formed a branched chain in PLA, while ZIKA produced a linear molecular structure. The hydrolysis resistance of the fibers was evaluated by analyzing their crystallinity, hydrothermal shrinkage behavior, morphology, and tensile strength. ZIKA/PLA fibers showed higher orientation and crystallinity than ADR/PLA fibers. After hydrolysis, the tensile strength of ADR 0.5%/PLA fibers decreased by 31%, while that of ZIKA 0.5%/PLA fibers decreased by only 5% due to the linear molecular structure of ZIKA/PLA. Our findings indicate that ZIKA is more effective than ADR in producing hydrolysis‐resistant PLA fibers with high crystallinity, orientation, and mechanical durability.

The Mechanical and Self-Sensing Performance of Reactive Powder Cement Concrete with Nano-Stainless Steel Powder

In order to prepare cement concrete with high mechanical properties and durability, nano-stainless steel powder reactive powder cement concrete (RPC) was manufactured. The dosage of nano-stainless steel powder ranged from 0% to 1.2% by the total volume of the RPC. In this study, the compressive and flexural strengths of the RPC with nano-stainless steel powder were determined, the dry shrinkage rate of the RPC was tested and the electrical resistance and alternating current (AC) impedance spectrum of the RPC were measured; moreover, the corresponding strain-sensing properties were investigated, and the scanning electron microscope (SEM) was used for observing the microstructures of the RPC. The results showed that the RPC with 1.0% nano-stainless steel powder exhibited the threshold values of the mechanical strengths. The maximum flexural strength and compressive strength were 16.1% and 14.2% higher than the minimum values. The addition of the nano-stainless steel powders reduced the dry shrinkage rate by 12.1%–39.8%. The electrical resistance of the RPC decreased in the form of the cubic function with the volume fraction of the stainless steel powders. The 1.0% nano-stainless steel powder was the threshold value for the electrical resistance and piezoresistive performance. The relationship between the electrical reactance and electrical resistance fitted well with the quadratic function. As obtained from the SEM results, the addition of the nano-stainless steel powder could effectively improve the compactness of the hydration products.

Wearable and Flexible Nanoporous Surface-Enhanced Raman Scattering Substrates for Sweat Enrichment and Analysis

Surface-enhanced Raman spectroscopy (SERS), with high sensitivity to a broad range of molecules, can detect molecular “fingerprints” in a complex substance and thereby offers a promising solution for noninvasive medical diagnostics and personal healthcare monitoring. The eventual realization of such applications relies on SERS substrates with dense and uniform hot spots, good chemical stability, and high mechanical durability. With these criteria in mind, we developed a flexible nanoporous SERS substrate via the in situ synthesis of gold nanostars (AuNSs) on an ion-track-etched polycarbonate membrane. The nanoporous SERS substrate can realize analyte enrichment and exhibit excellent Raman performance by taking the advantage of hot spots on AuNSs. The SERS substrate yields highly repeatable and uniform signals for analytes (e.g., methylene blue) over a wide concentration range from 10–4 to 10–13 M. The flexible SERS substrate even can work well after 2000 times bending and exhibit excellent stability for long-term use. It can be prepared on a large scale with a low-cost and simple fabrication process and can be used repeatedly after cleaning to reduce the use-cost further. On-body experiments prove that the sweat SERS substrate allows effective identification of sweat contents, such as lactic acid and uric acid (UA), and the monitoring of diet-induced variation in sweat UA. The potential of the wearable nanoporous SERS substrates in sweat analysis thus has been demonstrated, opening possibilities for autonomous and noninvasive medical health monitoring.

3D‐Printed Inherently Porous Structures with Tetrahedral Lattice Architecture: Experimental and Computational Study of Their Mechanical Behavior

AbstractIncreasing demand in automotive, construction, and medical industries for materials with reduced weight and high mechanical durability has given rise to porous materials and composites. Materials combining nano‐ and microporosity and a well‐defined cellular macroporous architecture offer great potential weight reduction while maintaining mechanical durability. To achieve predictable mechanical performance, it is essential to apply experimental and computational efforts to precisely describe material structure–properties relationships. This study explores polymer structures with polymerization‐inherited porosity and well‐defined macroporous geometry, fabricated via digital light processing (DLP) 3Dprinting. Pore size and relative density are varied by ink composition and printing parameters to track their influence on the structure stiffness. Simulated stiffness values for the base polymer correspond to the experimentally determined elastic properties, showing Young's moduli of 554–722 MPa depending on the cosolvent ratio, which confirms the structure–properties relationship. Macroporosity is introduced in the form of a 3D tetrahedral bending‐dominated architecture with the resulting specific Young's moduli of 79.5 MPa cm3 g−1, comparable to foams. To merge the gap in stiffnesses, further investigation of structure–property relationships of various 3D–printed lattice architectures, as well as its application to other stereolithography methods to eliminate the negative effects from printing artifacts and resolution limit of the DLP 3D‐printing, are envisioned.

Start–Stop Cyclic Durability Analysis of Membrane–Electrode Assemblies Using Polyflourene-Based Electrolytes for an Anion-Exchange Membrane Water Electrolyzer

Highly durable anion-exchange membranes and ionomers are essential for developing cost-effective green hydrogen generation. The anion-exchange membrane and ionomer must withstand chemical attacks by OH– ions as well as nonlinear mechanical stress caused by irregular bubble formation when the electrolyzer is coupled with intermittent power sources. Herein, we examined the durability of a trimethylammonium-modified poly(fluorene-alt-tetrafluorophenylene) (PFT-C10-TMA)-based membrane and ionomer under dynamic operation to evaluate its competency to couple with intermittent power sources. The durability of membrane–electrode assembly (MEA) prepared using these polymer membrane and ionomer was evaluated by performing 1000 start–stop voltage cycles in 1 M KOH solution at 80 °C while varying the applied cell voltage. The electrochemical performances of the MEA and electrodes were simultaneously evaluated using an electrolyzer with reference electrodes, and the chemical structure of the polymer was examined before and after the durability test using NMR techniques. The MEA based on a commercial Sustainion XB-7 ionomer and X37-50 RT anion-exchange membranes showed the catalyst leaching during start–stop cycles, resulting in reduced cell performance. On the other hand, the MEAs with the PFT-C10-TMA membrane and ionomer demonstrated promising high chemical and mechanical durability under dynamic start–stop operation, encouraging the development of electrolyzers that can function with intermittent renewable power sources.

Predictive model of ice adhesion on non-elastomeric materials

Hypothesis:When ice accumulates on a surface, it can adversely impact functionality and safety of a platform in infrastructure, transportation, and energy sectors. Despite several attempts to model the ice adhesion strength on ice-shedding materials, none have been able to justify variation in the ice adhesion strength measured by various laboratories on a simple bare substrate. This is primarily due to the fact that the effect of underlying substrate of an ice-shedding material has been entirely neglected. Experiments:Here, we establish a comprehensive predictive model for ice adhesion using the shear force method on a multi-layered material. The model considers both shear resistance of the material and shear stress transfer to the underlying substrate. We conducted experiments to validate the model predictions on the effect of coating and substrate properties on the ice adhesion. Findings:The model reveals the importance of the underlying substrate of a coating on ice adhesion. Most importantly, the correlation between the ice adhesion and the coating thickness are entirely different for elastomeric and non-elastomeric materials. This model justifies different measured ice adhesion across various laboratories on the same material and elucidates how one could achieve both low ice adhesion and high mechanical durability. Such predictive model and understanding provides a rich platform to guide the future material innovation with minimal adhesion to the ice.

Detailed microstructure analysis through monomeric insertion modes of poly(propylene-co-norbornene) copolymers and poly(propylene-co-ethylene-co-norbornene) terpolymers with low norbornene contents

Polypropylene-based thermoplastic elastomers continue to be materials of enormous industrial interest because of their high mechanical performance and durability. These materials are especially important, for instance, in the automotive industry, where these polyolefins accounts for up to 32% of the total plastic used in a car. In the search for new grades, poly(propylene-co-ethylene-co-norbornene) terpolymers might be of interest for the production of a new class of thermoplastic elastomers, whose properties could be tailored by controlling the composition, as well as its distribution. Unfortunately, thorough characterization of these materials has not been possible so far, because of the complexity of their 13CNMR spectra. In this work, two series of poly(propylene-co-norbornene) copolymers and poly(propylene-co-ethylene-co-norbornene) terpolymers, containing low molar fractions of norbornene and ethylene-norbornene, respectively, have been synthesized and characterized in detail by NMR analysis. The comparison of 13CNMR spectra in both series and their respective changes with norbornene ratio in the feed enables a complete assignment of signals, which reveals that the terpolymers are featured by a well-defined microstructure, consisting of propylene sequences bound by both PEP triads and well-defined norbornene-ethylene sequences. Such a particular distribution results from an associated insertion of the ethylene and the norbornene that, in addition, accounts for the higher contents of both comonomers, when compared with their respective copolymers, obtained under the same reaction conditions.

Durable Nanofiber-Based Membrane with Efficient and Consistent Performance for Oil/Saltwater Separation

There is a large amount of oil-contaminated wastewater caused by oil/gas production and marine oil spills. It is still a major challenge for the development of oil/water separating membranes that have excellent separation efficiency, can withstand saline environments, and have long-term durability. We present a new membrane made of ultralong titanate nanofibers (TNF) (with diameter of 200 nm and length of 60 µm) and carbon nanofibers (CNF) (with a diameter of 150 nm and length of 50 µm) for efficient and consistent oil/saltwater separation. The intertwined structure of titanate and carbon nanofibers is critical to ensuring a high mechanical strength and durability for the new membrane. The carbon nanofiber works as a scaffold in this membrane to maintain mechanical integrity during multiple cycles of reuses, which is an important merit for its practical applications. The ultralong titanate nanofibers work as functional component to provide high hydrophilicity of the membrane. The new membrane has an oil/water separation efficiency of more than 99%, an oil content in treated effluent that is lower than US environmental discharge standards (42 ppm), and a high water flux of 1520 LMH/bar, due to its excellent superhydrophilicity and inter-connected pore structure. The new membrane also exhibits outstanding durability in a variety of salinity environments, as well as good resistance to oil fouling. This new type of membrane has a high potential for industrial application in treating oily wastewater due to its excellent environmental durability, oil-fouling resistance, high separation efficiency, and easy scalability.

In-Situ Computed Tomography — Analysis of a Single-Lap Shear Test with Composite-Metal Pin Joints

Lightweight design in the form of intelligent multi-material structures that combine the advantages of high strength steel and continuous fibre reinforced thermoplastics (CFRTs) gain increasing relevance. In this context, the joining operation is a major challenge as it has to be time and cost efficient and the resulting joint has to exhibit a high mechanical durability. One possible approach is the use of cold formed pin structures, which can be inserted into the CFRT to create a form fitting joint under avoidance of fibre damage as it is commonly the case for bolted or riveted joints. The deformation phenomena of pin joints are usually investigated by macrosectioning or (ex-situ) computed tomography. However, due to resetting elastic deformations and cracks that close after unloading an inaccurate state of the inner joint structure is measured. Furthermore, an investigation of different stages with increasing load and progressing failure is very time consuming, because multiple samples have to be tested and investigated. Alternatively, in-situ computed tomography (in-situ CT) can be used to investigate the testing of pin joints. In this paper, a method for in-situ CT analysis of a single-lap shear test with composite-metal pin joints is presented. The pins are plastically extruded to a height of approx. 1.8 mm from the metal sheet (1.5 mm thick) and are pressed into a locally heated glass fibre reinforced thermoplastic (FRT) sheet (approx. 2 mm thick) creating a form fit. Specimens with quasi-unidirectional fibre reinforcement in 0° and 90° direction are tested. With this procedure, the three-dimensional deformation of the joint can be observed and failure phenomena can be identified for each reinforcement direction respectively. Thus, this method can also be used for validating numerical simulations.

Combined Porous-Monolithic TiNi Materials Surface-Modified with Electron Beam for New-Generation Rib Endoprostheses.

TiNi alloys are very widely used materials in implant fabrication. When applied in rib replacement, they are required to be manufactured as combined porous-monolithic structures, ideally with a thin, porous part well-adhered to its monolithic substrate. Additionally, good biocompatibility, high corrosion resistance and mechanical durability are also highly demanded. So far, all these parameters have not been achieved in one material, which is why an active search in the field is still underway. In the present study, we prepared new porous-monolithic TiNi materials by sintering a TiNi powder (0-100 µm) on monolithic TiNi plates, followed by surface modification with a high-current pulsed electron beam. The obtained materials were evaluated by a set of surface and phase analysis methods, after which their corrosion resistance and biocompatibility (hemolysis, cytotoxicity, and cell viability) were evaluated. Finally, cell growth tests were conducted. In comparison with flat TiNi monoliths, the newly developed materials were found to have better corrosion resistance, also demonstrating good biocompatibility and potential for cell growth on their surface. Thus, the newly developed porous-on-monolith TiNi materials with different surface porosity and morphology showed promise as potential new-generation implants for use in rib endoprostheses.

Production of bio‐based concrete water reducers from renewable resources: a review

AbstractConcrete is a valuable construction material with high mechanical strength and durability, used extensively in the construction industry. It is produced by mixing sand, stones, cement, and water in different proportions depending on the desired quality of the final product. Water reducers are additional chemical ingredients used in concrete to reduce the quantity of water required in the concrete mixture. When added to concrete, water reducers increase the workability and flowability of concrete in the freshly mixed state and improve the mechanical strength and durability of the final hardened product. This review paper describes the different types and applications of concrete water reducers used in the construction industry including their working mechanisms and fluidity effects on concrete properties. It discusses the production of synthetic and bio‐based concrete water reducers and reviews the present challenges involved in the preparation of bio‐based concrete water reducers from renewable resources. © 2023 Society of Industrial Chemistry and John Wiley & Sons Ltd.

Pelletization Temperature and Pressure Effects on the Mechanical Properties of Khaya senegalensis Biomass Energy Pellets

Biomass pellets are one of the most crucial feedstocks for bioenergy production on a global scale due to their numerous advantages over raw biomass resources. Pellets provide improved energy density, bulk density, moisture content, and homogeneity thereby reducing storage, handling, and transportation costs. To produce high-quality solid fuel, it is necessary to comprehend the properties of wood fuel. This study explored the potential of Khaya senegalensis (khaya) as a dedicated energy crop (DEC) for the production of green energy. It thrives in less-than-ideal conditions and grows rapidly. The low durability of energy pellets raises the risk of dust and fire during handling and storage. In addition, the potential for fines and dust formation is strongly correlated with the mechanical strength of materials. Due to this necessity, the current study examines the effects of pelletization factors, including temperature and pressure, on pellet properties, particularly on its mechanical properties. The durability and compressive strength of pellets were determined using a sieve shaker and a universal testing machine, respectively. The highest mechanical durability was observed at 3 tons of pressure and 75 degrees Celsius, each with a value of 99.6%. The maximum axial compressive strength was measured at 57.53 MPa under 5 tons of pressure. When pelletized at 125 °C, the axial compressive strength increased by 13.8037% to 66.06 MPa compared to the strength obtained at 5 tons of pressure. Pelletizing Khaya feedstocks at 4 tons of pressure, on the other hand, produced a slightly lower diametral compressive strength of 7.08 MPa compared to 7.59 MPa at 125 °C. The experimental results revealed that the aforementioned factors significantly affect the mechanical properties of pellets. The elucidation of wood biomass, solid fuel qualities and pelletization parameters of this potential energy crop may facilitate the production of high-quality pellets from Khaya senegalensis wood to meet the increasing local and worldwide energy demands.

Flexible correlated 4d2 SrMoO3/mica thin films with enhanced optoelectronic performance and high bending stability

Recently, correlated metallic oxide (CMO) was proposed as a brand-new design strategy for transparent conductors (TCs). Among these CMOs, perovskite-type SrVO3 with an electronic configuration of 3 d1 has been most investigated. Herein, the SrMoO3 films, one 4 d2 perovskite CMO, were deposited on a flexible mica substrate using a pulsed laser deposition method. Our experimental results indicate that the SrMoO3 film possesses a superior optoelectronic performance compared with SrVO3, owing to the weaker electronic correlations and 4 d2 electronic configuration in SrMoO3. Bending cyclic tests indicate that the flexible SrMoO3/mica film has a high mechanical bending durability and stability. This 4 d2 SrMoO3/mica film demonstrates a great potential as a high-performance TC for flexible optoelectronics.

Lightweight ultra-high-performance concrete (UHPC) with expanded glass aggregate: Development, characterization, and life-cycle assessment

Ultra-high-performance concrete (UHPC) has high mechanical strengths and durability, but its density and carbon footprint are usually high. This paper developed a lightweight UHPC with low cost, low carbon footprint, low energy consumption, low thermal conductivity, and high ductility, by using three types of lightweight ingredients: hollow glass microsphere (460 kg/m3), expanded glass aggregate (800 kg/m3), and polyethylene fibers (970 kg/m3). Underlying mechanisms were investigated through thermogravimetry, X-ray diffraction, and mercury intrusion porosimetry analyses. Results showed that the hollow glass microsphere reduced the thermal conductivity of concrete; the expanded glass aggregate mitigated shrinkage while enhancing compressive strengths and flexural properties of concrete through internal curing; and the polyethylene fibers promoted multiple cracks, increasing ductility and toughness of concrete. With 20 % hollow glass microsphere, 1.5 % polyethylene fiber, and 25 % expanded glass, UHPC mixtures were developed to achieve high compressive strength (>127 MPa) and high flexural strength (>21 MPa), while reducing the density by 20 % and carbon footprint by 16 % as well as embodied energy by 27 %.

Customized structural and mechanical characteristics of Eu3+ imbued boro-telluro-dolomite glasses: effect of Dy3+ co-doping

Inorganic oxide glasses with high mechanical strength and durability became demanding. Thus, a new type of Eu3+/Dy3+ co-doped boro-telluro-dolomite glass system with customized structures and mechanical properties were prepared by the melt-quenching method and characterized. The densities, FTIR and Raman spectra of the glasses revealed a significant modification in the network structure with the increase of Dy3+ contents. The values of microhardness and elastic moduli of the glasses were increased with the increase of co-doping contents. In addition, a correlation between the glass hardness and applied load was established. The proposed glasses were shown to withstand about 300 g applied force without any distortion, confirming their usefulness to design mechanically stable screen shield and high strength surfaces.

Optimizing the Superhydrophobicity of the Composite PDMS/PUA Film Produced by a R2R System

Maintaining the surface of solar cell panels free from contaminants to ensure their efficiency is a time-consuming and tedious task. Therefore, several methods of fabricating artificial transparent superhydrophobic surfaces have been reported to overcome that problem. However, most of the proposed fabrication methods are unscalable due to their complexity. Herein, a facile and cost-effective roll-to-roll system to fabricate a highly flexible and optically transparent polydimethylsiloxane/polyurethane acrylate superhydrophobic (FTPPS) film was proposed. The superhydrophobicity of the film was achieved by the combination of the surface roughness─the ultraviolet curable polyurethane acrylate (PUA) microstructures and the low surface energy material coating─the thin polydimethylsiloxane layer coated on PUA structures using capillary force. The superhydrophobicity of the FTPPS film was carefully optimized using various designs of PUA micro-post and the material properties of the film were examined systematically by different characterization techniques. The highest measured static water contact angle (WCA) of the FTPPS film is 153.3° ± 1.8 and its lowest water sliding angle is ∼9.5° ± 0.2. Moreover, the film still exhibited high WCAs of more than 142° even after being impacted multiple times by an adhesive probe or sand grains. This result demonstrates the high mechanical durability and flexibility of the as-fabricated superhydrophobic film. Finally, the potential application of the film as a protective cover for solar cells was also illustrated through the consistent photovoltaic conversion efficiency of the solar cell module covered by the film compared to that of the uncovered solar panel.

Fabrication of superhydrophobic cotton fabric with multiple durability and wearing comfort via an environmentally friendly spraying method

Superhydrophobic durability of cotton fabric faces a great challenge due to the repeated washing and rubbing. The commercial pad-dry process method using polymer binders usually leads to wastewater discharge and the reduced wearing comfort. Herein, the superhydrophobic cotton fabric with strong durability was fabricated by a facile spraying method which did not produce any wastewater and can make efficient use of modifiers. The dopamine and 2-tetraethoxysilane can in-situ react to construct rough surface structure. The hexadecyltrimethoxysilane with long chain alkyl was firmly connected to cotton fiber surfaces to reduce the surface energy. The prepared sample not only obtained excellent superhydrophobicity with a water contact angle of 157 ± 1.2° and a shedding angle of 7.8 ± 0.3°, but also retained the inherent air permeability and hand feeling of cotton fabrics. Due to the strong covalent bonds between modifiers and cotton fibers, the modified cotton fabric exhibited high multiple mechanical durability and chemical stability in acid/base solution. The superhydrophobic cotton fabric showed a satisfactory self-cleaning performance toward the common stains in daily life. In addition, the modified fabric can serve as a separation filter for oil/water separation with high separation efficiency and reusability. This facile and clean preparation method showed great potential in large-scale production of durable superhydrophobic textile.

A novel miniaturized pH potentiometric electrode based on a nano bismuth oxide film deposited on a fluorine doped nano tin oxide glass substrate

A novel thin film of bismuth oxide (Bi2O3) deposited on a fluorine doped tin oxide glass substrate (FTO), using a spray pyrolysis technique, was prepared and used as a pH sensing membrane. The deposited Bi2O3 film was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM). Film prepared by pyrolysis at 550 °C displayed a tetragonal β-phase of Bi2O3 with a porous structure, high roughness surface and nano cracks. The fabricated Bi2O3/FTO film was used as a miniaturized potentiometric electrode for monitoring a wide range of pH (pH 2 – 12) in aqueous solutions. The electrode exhibited an ideal near-Nernstian response (slope of −60.2 ± 0.3 mV/decade), high potential stability, mechanical durability and good selectivity toward some common interfering cations and anions, supporting its applicability for quality control/quality assurance purposes. The performance characteristics of the electrode and validation measurements, according to the standard methods, were evaluated. The Bi2O3/FTO-based electrode was satisfactorily used for monitoring the pH of some real water, beverages and fruit juice samples and the results compared fairly well with data obtained by the conventional pH glass electrode.

Experimental studies on flexural action of RC beams made with hybrid rebars - A brief review

Reinforced Steel bars used in concrete constructions are particularly susceptible to corrosion since they don't have enough corrosion resistance, which decreases durability and long-term performance. The main cause of steel bar corrosion is moisture interaction, which results in rust, which causes cracks and spalling, which affects durability and long-term performance. FRP bars, which have several benefits over steel bars such as strong resistance to corrosion, higher tensile strength than steel bars, and a 1/4th of the weight of steel bars, which decreases shipping and labor costs, are now entering the market as a solution to the aforementioned issues. Polypropylene fibers in concrete have high mechanical strength, stiffness, and durability. This paper tells about the type of FRP bar and Fiber that has been chosen in order to enhance the studies on the performance of flexure of RC beams made with a combination of FRP and Steel bars. From previous studies, it has been concluded that 0.25% of fibers are used as optimum dosage in terms of volume fraction in order to improve the behavior of flexure and ductility of beams made with a combination of Steel and FRP bars.

Strength Design of Ultra-High-Performance Fiber-Reinforced Cementitious Composites Using Local Ecological Admixture

The ultra-high-performance fiber-reinforced cementitious composite (UHPFRC) is a new generation of building material with extremely high mechanical strength and durability, which can be used for ultra-high, thin-wall or long-span construction, that prolongs the service life of construction in severe environments. In this study, UHPFRC was prepared with a high range of local ecological admixture to decrease the material’s cost and the environmental impact. Raw materials’ proportions, water/binder ratio, fiber-volume contents, and hybrid-fiber ratio were studied on the property improvement of UHPFRC, and an F-test analysis was induced to reveal the important significance on compressive strength. The results demonstrated that the compressive strength of 237.8 MPa was achieved with mineral admixture substitution over 40%. The particle-packing density and the binder reactivity both succeeded on the compressive strength. Water/binder ratio determined the hydration degree and the flowability of UHPFRC, which affected compressive strength through hydration products and microstructure. Also, compressive strength was more sensitive with hybrid-fiber than fiber-volume content. The order of importance for compressive strength was powder proportion > hybrid-fiber ratio > fiber-volume content > water/binder ratio.