Contents Of Volume Research Articles

Viscosity‐coupled curing simulation model for L‐shaped composites considering flow and compaction

AbstractComputational methods provide effective tools for the prediction of the curing behavior of composites, especially for large‐scale complex composite structures. The flow‐compaction analysis during curing receives insufficient attention in current studies. In this work, an integrated framework considering the heat transfer, the cross‐linking reaction, the flow and compaction, and the stress–strain module is established. A comprehensive resin flow termination criterion is proposed. L‐shaped composites with a stacking layer of [45/90/−45/0]s were fabricated, and the good agreement between the experimentally measured and the numerically predicted contour data validated the current model. Compared with Hubert's model, the prediction accuracy of the thickness and fiber volume content increases by 4.24% and 3.92%, respectively. Correlation analysis between the fiber volume ratio predicted by numerical methods and experimental results (94% for this method, −41% for Hubert's model) demonstrates the well‐capture of nonuniform fiber distribution in curved composites for the current strategy. The overall framework provides an accurate and promising tool for the prediction of the curing behavior of complex composite components.Highlights An integrated numerical methodology is proposed considering the resin flow and compaction. The viscosity‐temperature coupled feature of resin is considered in the permeability coefficients. A comprehensive resin flow termination criterion is proposed for an accurate prediction. The resin content, thickness, and spring‐in angle of L‐shaped laminates are characterized. The good correlation between the experimental and numerical results validates this method. Compared with the model proposed by Hubert, the prediction accuracy improves.

Ultrasonic and micrograph-based quantification of material characteristics for in-situ AFP composite structures

Achieving the maximum potential of parts manufactured with in-situ consolidation thermoplastic Automated Fiber Placement without a final bulk consolidation is a challenging task. This is due partially to the continual development of the technology itself and partially due to material defects which are not fully removed during part manufacturing. In this paper, a methodology is presented for the evaluation of prepreg tape and laminate quality relevant to the manufacturing process. A novel approach is presented to quantify tape quality and the fiber volume content distribution, porosity, all of which are identified as significant influences on laminate quality. A new approach to ultrasonic testing is applied for quantitative porosity analysis promising advantages over conventional methods. Laminate porosity was successfully measured using the proposed pulse-echo ultrasonic attenuation method. The fiber content distribution from the tape used in testing shows characteristics interpreted as unfavorable for high quality in-situ AFP.

Study on mechanical properties of E-glass mat reinforced basic magnesium sulfate cement thin-slab

To achieve sustainable development and reduce the carbon footprint in building material production, the E-glass fiber mat was impregnated with basic magnesium sulfate cement (BMSC) by lamination impregnation. This process reduces environmental pollution from cement preparation, increases fiber volume content, and enhances the mechanical properties of cementitious composite materials. The study examined axial tensile, four-point bending resistance, drop weight impact resistance and pendulum impact resistance of BMSC thin-slab reinforced with dispersed short glass fiber (SGF), short glass fiber mat (SGFM) and continuous glass fiber mat (CGFM) of varying gram weights. The results show that the mechanical properties of BMSC thin-slab reinforced with fiber mat are much higher than those of SGF reinforced thin-slab. The tensile strength of BMSC thin-slab reinforced with CGFM is higher than that of BMSC thin-slab reinforced with SGFM at the same gram weight, and the tensile strength increases as the weight of CGFM increases. Specifically, the axial tensile strength of BMSC thin-slab reinforced with 450 g of CGFM is nearly 8 times higher than that of SGF reinforced BMSC thin-slab. BMSC thin-slab reinforced with 450 g of CGFM has the maximum proportional limit load and bending strength. The impact strength and toughness indexes of BMSC thin-slab reinforced with CGFM are the highest, followed by SGFM reinforced BMSC thin-slab. The addition of 300 g CGFM significantly enhanced flexural toughness during the early stage of thin-slab cracking, while 450 g CGFM showed significant improvement in flexural toughness during the middle and late stages of cracking. When comparing thin-slabs with the same glass fiber volume ratio, those reinforced with 450 g CGFM exhibited the best impact resistance. SEM results indicated superior adhesion between 450 g CGFM and the cement matrix, as well as between adjacent CGFM layers, with fiber breakage being the main cause of specimen failure.

Thermo-mechanically joined hybrids from carbon fiber-reinforced PA12 with die-cast alloy AlSi10Mg: how surface and interlayer design affect shear strength and fracture behavior

ABSTRACT Infrared radiation was used as a tool to heat laser-structured AlSi10Mg for subsequent fusion bonding with thermoplastic carbon fiber-reinforced PA12. When the two adherends are brought into contact, the bond is formed by melting of the surface-near polymer matrix and pressing it into the laser structure of the aluminum alloy. When investigating different fiber volume contents, the amount of fusible material was identified as a key parameter for the achievable bonding strength. Therefore, the best results were achieved with low fiber volume content (25 vol.-%) or under the use of an additional PA12 interlayer. Moreover, the influence of different surface texture parameters was investigated and the aspect ratio between structure depth and width was found to correlate best with the measured shear strengths. Aspect ratios from 0.18 to 1.15 increased the bond strength up to the interlaminar shear strength of the thermoplastic composite. Especially, aspect ratios of 0.61 or greater proved to be very effective, with resulting mean strength values of almost 30 MPa. While even lower ratios allowed higher loads on the joints compared with untreated surfaces, greater aspect ratios show lower bond strengths, as the laser structures were no longer completely filled with fused PA12.

Analysis of damage and fracture characteristics for concrete subjected to cryogenic freeze-thaw cycles: An acoustic emission and digital image correlation study

This study examines concrete's performance under cryogenic (−170 °C) freeze-thaw cycles (CFTCs), inspired by the development of all-concrete liquefied natural gas (ACLNG) tanks. Focusing on plain concrete (PC) and concrete with 3 % volume content steel fiber (SFRC3), the impact of fibers and moisture content on concrete's damage and failure characteristics pre and post cryogenic exposure is investigated. The compressive strength variation laws of concrete before and after 10 CFTCs were summarized in air-dried and water-saturated condition. Acoustic emission (AE) and digital image correlation (DIC) techniques were employed in the study to delineate the variances in failure process and fracture characteristics attributed to cryogenic exposure. Findings indicate a decline in the compressive strength of both PC and SFRC3 post exposure, more pronounced in water-saturated condition. Post-cryogenic exposure, AE signals exhibit decreased activities. The failure process of concrete is categorized into four stages based on the trends of severity index Sr and historical index Hs, both of which diminished, reflecting reduced signal strength and rate of change. AE frequency-amplitude characteristics differs between PC and SFRC3 during failure, with significant reduction in high frequency signals in SFRC3, suggesting weakened fiber-matrix bonding and increased fracture scale. The rise in the number of shear cracks nearing failure is discerned from variations in rise angle (RA) and average frequency (AF), proposing the ratio of RA to AF equal to 15 as a precursor of concrete failure. The DIC analysis shows increased crack width and numbers in both PC and SFRC3 post exposure, along with localized spalling. SFRC3 can still effectively maintain the integrity without complete breakage despite severe cracks are generated.

Behavior of steel fiber-reinforced coal gangue concrete beams under impact load

In order to promote the use of new sustainable steel fibers (SF) reinforced coal gangue aggregates (CGA) concrete, impact tests were performed in this paper. The impact resistance of steel fiber-reinforced coal gangue concrete was investigated using a self-developed drop-weight facility. The test variables were the CGA replacement rate (0 %, 50 %, and 100 %), the SF volume content (0 %, 0.75 %, and 1.5 %), and the drop height of the drop-weight (0.5 m and 1.0 m). Using 15 kg of hard steel as a drop-weight, the drop-weight impact test was performed on steel fiber-reinforced coal gangue concrete beams with a span of 300 mm; the damage pattern, impact reaction force-time, displacement-time relationships, and energy absorbed by steel fiber-reinforced coal gangue concrete beams were studied. The test shows that, compared with natural aggregate, CGA reduces concrete's static mechanical properties and impact resistance, and adding SF improves the static mechanical properties and impact resistance of coal gangue concrete. As the CGA replacement rate increased from 0 % to 50 % and 100 %, the reaction force of impact of the specimens decreased by 2.54 %− 6.06 % and 3.69 %− 12.33 %. The SF volume content was increased from 0 % to 0.75 % and 1.5 %, and the reaction force of impact of the specimens was increased by 23.05 %− 32.34 % and 72.27 %− 81.84 %, respectively. The impact resistance of steel fiber-reinforced concrete beams under impact loading was investigated numerically using a nonlinear explicit finite element model in LS-DYNA. The Finite Element results were validated with experimental results. Based on the validated finite element model, a parametric study was carried out to investigate the effects of coal gangue replacement rate, steel fiber volume content, and drop height of the drop weight on the behavior of the beams. This study might provide a basis for the future engineering project applications of steel fiber-reinforced coal gangue concrete under impact conditions.

Comparative study on calculation methods for compressive strength of low strength aggregate concrete

The compressive strength of concrete with low strength aggregate volume fractions of 10%, 20%, and 30% was calculated using both the graphical analysis method and mesomechanics method. In the calculation method based on graphical analysis, three-dimensional random spherical aggregate models of concrete with different volume contents of low strength aggregate were established and sliced. The results show that the graphical analysis method can effectively calculate the compressive strength of concrete with different volume contents of low strength aggregate. In the graphical analysis method, the relative errors of the calculated compressive strength of concrete with low strength aggregate volume fractions of 10%, 20%, and 30% were 4.84%, 4.84%, and 6.43%, respectively. Three-phase concrete models composed of mortar, aggregate, and interfacial transition zone were analyzed through the method of mesomechanics. The calculation results of the mesomechanics method show that the compressive strength of concrete was controlled by low strength aggregate, and the calculated compressive strength of concrete decreased with the increase in low strength aggregate volume content. In the mesomechanics method, the relative errors of the calculated compressive strength of concrete with low strength aggregate volume fractions of 10%, 20%, and 30% were 1.36%, 1.74%, and 3.7%, respectively. It can be found that the calculation results of the mesomechanics method are closer to the test values and have smaller relative errors, which indicate that the calculation method of mesomechanics theory is superior to the method of graphical analysis.

Mild modification of sponge-like carbon: Ammonia post-treatment for enhanced CO2 adsorption and suitability for supercapacitors

During the synthesis of carbon-based CO2 adsorbents and supercapacitors, the introduction of nitrogen atoms into the carbon matrix has been identified as a means to enhance their performance. Nevertheless, the intricate effects of nitrogen doping on material properties pose a significant challenge in developing efficient methodologies. In this investigation, porous carbons resembling sponges were fabricated utilizing macadamia nut shells as a precursor and a dual salt comprising K2C2O4-KCl as an activating agent. Subsequent modification of the materials through ammonia post-treatment facilitated the production of nitrogen-doped porous carbon. The alterations in surface characteristics and pore morphology after ammonia treatment were meticulously examined to unravel the underlying mechanism of this modification process. The samples under scrutiny showcased remarkable CO2 adsorption capacities, peaking at 6.97 mmol/g at 0 °C and 4.65 mmol/g at 25 °C. Employing mathematical models to probe the influence of pore structure and surface properties on CO2 adsorption efficacy proved to be fruitful. A linear correlation was established to depict CO2 adsorption behavior, underscoring the joint impact of ultramicropore volume and nitrogen content on the adsorption process. Notably, the material exhibited a specific capacitance of 290.4F/g at a current density of 0.5 A/g within a three-electrode configuration, demonstrating commendable rate capability and cyclic stability. The pivotal findings from this inquiry emphasize that ammonia post-treatment represents a gentle modification strategy exerting minimal influence on the pore architecture, thereby efficaciously enhancing both CO2 adsorption and electrochemical performance.

Non-invasive optoacoustic imaging of dermal microcirculatory revascularization in diet-induced obese mice undergoing exercise intervention

Microcirculatory dysfunction has been observed in the dermal white adipose tissue (dWAT) and subcutaneous white adipose tissue (scWAT) of obese humans and has been proposed as an early prediction marker for cardio-metabolic disease progression. In-vivo visualization and longitudinal monitoring of microvascular remodeling in these tissues remains challenging. We compare the performance of two optoacoustic imaging methods, i.e. multi-spectral optoacoustic tomography (MSOT) and raster-scanning optoacoustic mesoscopy (RSOM) in visualizing lipid and hemoglobin contrast in scWAT and dWAT in a mouse model of diet-induced obesity (DIO) undergoing voluntary wheel running intervention for 32 weeks. MSOT visualized lipid and hemoglobin contrast in murine fat depots in a quantitative manner even at early stages of DIO. We show for the first time to our knowledge that RSOM allows precise visualization of the dWAT microvasculature and provides quantitative readouts of skin layer thickness and vascular density in dWAT and dermis. Combination of MSOT and RSOM resolved exercise-induced morphological changes in microvasculature density, tissue oxygen saturation, lipid and blood volume content in dWAT and scWAT. The combination of MSOT and RSOM may allow precise monitoring of microcirculatory dysfunction and intervention response in dWAT and scWAT in a mouse model for DIO. Our findings have laid out the foundation for future clinical studies using optoacoustic-derived vascular readouts from adipose tissues as a biomarker for monitoring microcirculatory function in metabolic disease.

Study of the Performance of Emulsified Asphalt Shotcrete in High-Altitude Permafrost Regions

To improve the performance of shotcrete in high-altitude and low-temperature environments, emulsified asphalt shotcrete (EASC), which can be used in negative-temperature environments, was prepared by using low-freezing-point emulsified asphalt, calcium aluminate cement, and sodium pyrophosphate as modified materials. The effect of emulsified asphalt on the performance of shotcrete was investigated through concrete spraying and indoor tests. Then, the modification mechanism of emulsified asphalt with respect to EASC was analyzed by combining scanning electron microscopy images and the pore structure characteristics of EASC. The results showed that in a negative-temperature environment, the incorporation of emulsified asphalt delayed the formation of the peak of the cement hydration exotherm, slowed the rate of the cement hydration exotherm, reduced the thermal perturbation of permafrost by EASC, increased the cohesion of the concrete, improved the bond strength between EASC and permafrost, and reduced the rate of rebound. The mechanical strength of the studied EASC decreased upon increasing the amount of emulsified asphalt in the admixture, and its resistance to cracking gradually improved. A content of less than 5% emulsified asphalt could improve the internal pore structure of EASC, thus improving its durability. Increasing the content of emulsified asphalt affected the hydration process of the cement, and the volume content of the capillary pores and macropores increased, which reduced the durability of the EASC.

Study on the fatigue life and toughness of recycled aggregate concrete based on basalt fiber

This paper studies the influence of basalt fibers on the mechanical properties, fatigue life, and toughness of Mechanically Recycled Aggregate Concrete (MRAC). Basalt fibers of varying volume fractions and lengths, along with quantified amounts of mineral powder and fly ash, are incorporated into MRAC to prepare Basalt Fiber Mechanically Recycled Aggregate Concrete (BFMRAC). The results of basic mechanical tests and fatigue tests showed that mineral powder and fly ash reduce cement consumption, achieve the effect of green construction, and basalt fibers improve the mechanical properties and toughness of concrete. The results of the response surface method (RSM) model indicate that the volume fraction of basalt fibers has a greater influence on the mechanical properties of BFMRAC compared to fiber length. The fatigue test results indicate that under different fiber volume fractions and lengths, the uniaxial compressive fatigue life (N) of specimens for each mix proportion is consistently improved. When the length of basalt fibers is 12 mm and the volume fraction is 0.3 %, the uniaxial compressive fatigue life of BFMRAC reaches its maximum (231638), which is twice that of MRAC. When the survival rate (P) is set to 0.5, with a basalt fibers volume content of 0.3 % and a length of 12 mm, the fatigue limit strength (Se) attains its maximum (0.8648 fc). When stress levels (S) reach 0.75 and the basalt fibers length is 12 mm, the relative CI Intensifying Coefficient achieves its maximum (1.133), resulting in optimal fatigue toughness. When the basalt fibers length is 6–12 mm, Se generally increases with the increase of fiber length, and the enhancement effect is best at 12 mm.

Evaluating Sex-specific Differences in Abdominal Fat Volume and Proton Density Fat Fraction at MRI Using Automated nnU-Net-based Segmentation.

Sex-specific abdominal organ volume and proton density fat fraction (PDFF) in people with obesity during a weight loss intervention was assessed with automated multiorgan segmentation of quantitative water-fat MRI. An nnU-Net architecture was employed for automatic segmentation of abdominal organs, including visceral and subcutaneous adipose tissue, liver, and psoas and erector spinae muscle, based on quantitative chemical shift-encoded MRI and using ground truth labels generated from participants of the Lifestyle Intervention (LION) study. Each organ's volume and fat content were examined in 127 participants (73 female and 54 male participants; body mass index, 30-39.9 kg/m2) and in 81 (54 female and 32 male participants) of these participants after an 8-week formula-based low-calorie diet. Dice scores ranging from 0.91 to 0.97 were achieved for the automatic segmentation. PDFF was found to be lower in visceral adipose tissue compared with subcutaneous adipose tissue in both male and female participants. Before intervention, female participants exhibited higher PDFF in subcutaneous adipose tissue (90.6% vs 89.7%; P < .001) and lower PDFF in liver (8.6% vs 13.3%; P < .001) and visceral adipose tissue (76.4% vs 81.3%; P < .001) compared with male participants. This relation persisted after intervention. As a response to caloric restriction, male participants lost significantly more visceral adipose tissue volume (1.76 L vs 0.91 L; P < .001) and showed a higher decrease in subcutaneous adipose tissue PDFF (2.7% vs 1.5%; P < .001) than female participants. Automated body composition analysis on quantitative water-fat MRI data provides new insights for understanding sex-specific metabolic response to caloric restriction and weight loss in people with obesity. Keywords: Obesity, Chemical Shift-encoded MRI, Abdominal Fat Volume, Proton Density Fat Fraction, nnU-Net ClinicalTrials.gov registration no. NCT04023942 Supplemental material is available for this article. Published under a CC BY 4.0 license.

Effects of amount and geometrical properties of steel fiber on shear behavior of high-strength concrete beams without shear reinforcement

This study aims to investigate the effects of the geometrical properties and volume content of steel fibers on the shear resistance of reinforced high-strength concrete (HSC) beams without stirrups. Hooked-end and twisted steel fibers with different aspect ratios ranging from 60 to 100 were used at volume fractions of 0.5%–1.0%. The shear strength of HSC beams without stirrups significantly increased due to the addition of steel fibers and by increasing their volume fraction by up to 1.0%, resulting in approximately 1.7 times higher shear resistance. A higher fiber aspect ratio was effective in improving the resistance to shear failure of HSC beams without stirrups and in enhancing beam deformability relative to the increase in shear strength. Using twisted steel fibers led to better shear resistance than hooked-end steel fibers, resulting in 1.11- and 3.34-times higher shear strength and ductility at the same fiber volume fraction on average. The shear strength of steel fiber-reinforced concrete (SFRC) beams was also predicted using eight different models. Narayanan's model most precisely predicted the shear strengths of reinforced SFRC beams without shear reinforcement, with an average vu,exp/vu,pred ratio of 1.16. The shear strength increased with the decrease in shear span-to-depth (a/d) ratio and the increase in the fiber factor. The contribution of steel fibers to shear strength was greater for deep beams than slender beams. The predicted shear strengths of deep beams and high-strength SFRC showed a significant deviation from the actual value and required careful consideration.

The GWAS SNP rs80207740 modulates erythrocyte traits via allele-specific binding of IKZF1 and targeting XPO7 gene.

Genome-wide association studies have identified many single nucleotide polymorphisms (SNPs) associated with erythrocyte traits. However, the functional variants and their working mechanisms remain largely unknown. Here, we reported that the SNP of rs80207740, which was associated with red blood cell (RBC) volume and hemoglobin content across populations, conferred enhancer activity to XPO7 gene via allele-differentially binding to Ikaros family zinc finger 1 (IKZF1). We showed that the region around rs80207740 was an erythroid-specific enhancer using reporter assays, and that the G-allele further enhanced activity. 3D genome evidence showed that the enhancer interacted with the XPO7 promoter, and eQTL analysis suggested that the G-allele upregulated expression of XPO7. We further showed that the rs80207740-G allele facilitated the binding of transcription factor IKZF1 in EMSA and ChIP analyses. Knockdown of IKZF1 and GATA1 resulted in decreased expression of Xpo7 in both human and mouse erythroid cells. Finally, we constructed Xpo7 knockout mouse by CRISPR/Cas9 and observed anemic phenotype with reduced volume and hemoglobin content of RBC, consistent to the effect of rs80207740 on erythrocyte traits. Overall, our study demonstrated that rs80207740 modulated erythroid indices by regulating IKZF1 binding and Xpo7 expression.

Natural bio-waste-derived 3D N/O self-doped heteroatom honeycomb-like porous carbon with tuned huge surface area for high-performance supercapacitor

Supercapacitor electrodes (SCs) of carbon-based materials with flexible structures and morphologies have demonstrated excellent electrical conductivity and chemical stability. Herein, a clean and cost-effective method for producing a 3D self-doped honeycomb-like carbonaceous material with KOH activation from bio-waste oyster shells (BWOSs) is described. A remarkable performance was achieved by the excellent hierarchical structured carbon (HSC-750), which has a large surface area and a reasonably high packing density. The enhanced BWOSs-derived HSC-750 shows an ultrahigh specific capacitance of 525 F/g at 0.5 A g−1 in 3 M KOH electrolyte, as well as high specific surface area (2377 m2 g−1), pore volume (1.35 cm3 g−1), nitrogen (4.70%), and oxygen (10.58%) doping contents. The SCs also exhibit exceptional cyclic stability, maintaining 98.5% of their capacitance after 10,000 charge/discharge cycles. The two-electrode approach provides a super high energy density of 28 Wh kg−1 at a power density of 250 W kg−1 in an alkaline solution, with remarkable cyclability after 10,000 cycles. The study demonstrates the innovative HSC synthesis from BWOSs precursor and cost-effective fabrication of 3D N/O self-doped heteroatom HSC for flexible energy storage.

Stress-Strain State of Steel Fiber-Reinforced Concrete under Compression Taking into Account Unloading from Inelastic Region

The purpose of the study is to examine the physical and mechanical characteristics of steel fiber-reinforced concrete under compression, including: modulus of elasticity, Poisson ratio, values of ultimate strains under compression, values of compressive strength with different percentages of dispersed reinforcement. An experimental investigation program, which included the production of cube samples measuring 100×100×100 mm, as well as a compression test under static loading, taking into account unloading from the region of inelastic deformations, was developed and carried out. Two types of steel fiber were chosen as dispersed reinforcement: hooked end and wave shape. The volume content of steel fiber in the cube samples was 0.5, 1.0, 1.5 and 2.0 %. As a result of the investigation, the strength and deformation characteristics of steel fiber reinforced concrete under compression were obtained. Based on the experimental data, actual strain diagrams of steel fiber reinforced concrete were constructed, taking into account the type of reinforcing fibers and the percentage of reinforcing fiber. Based on the obtained diagrams, a law of deformation of steel fiber reinforced concrete is proposed, which can be described by a polynomial function of the fourth order with constant coefficients that determine the shape of the stress-strain curve. The presented research results can be used in developing a methodology for physically nonlinear analysis of steel fiber reinforced concrete elements with a percentage of dispersed reinforcement from 0.5 to 2.0 %.

Effect of Nano-TiO2 and Polypropylene Fiber on Mechanical Properties and Durability of Recycled Aggregate Concrete

In order to promote the engineering application of recycled concrete, the effects of PPF and nano-TiO2 dioxide on the mechanical properties and durability of recycled concrete were studied.Polypropylene fiber recycled concrete(PRAC) and nano-TiO2 recycled concrete(TRAC) were prepared by adding different volume contents of PPF and nano-TiO2. The experimental findings demonstrated that the PPF and nano-TiO2 improved the splitting tensile strength of RAC better than the compressive strength. When the volume content of nano-TiO2. and PPF is 0.8% and 1.0%, respectively, the corresponding splitting tensile strength of concrete reaches the maximum value(3.4 and 3.7 MPa). The contribution rates of nano-TiO2 and PPF with different volume contents to the mechanical properties of RAC have optimal values, which are 0.4 and 1.0%, respectively. The incorporation of nano-TiO2 and PPF can effectively inhibit the loss of RAC mass and the generation of pores under freeze–thaw conditions, and slow down the decrease of dynamic elastic modulus. When the volume content of PPF is 1.0% and the volume content of nano-TiO2 is 0.4%, the protection effect on the internal structure of RAC is better, and its carbon resistance is better. The results of RSM model analysis and prediction show that both PPF and nano-TiO2 can be used as admixture materials to improve the mechanical properties and durability of RAC, and the comprehensive improvement effect of PPF on RAC performance is better than that of nano-TiO2.

Mechanical and durability performance of self-compacting mortars made with different industrial by-products as fillers

This study evaluated the performance over time of Self-Compacting Mortars (SC mortars) with different industrial by-products simultaneously; Electric Arc Furnace Dust (EAFD) and fly ash, conforming (FA) or not conforming (NcFA), from coal-fired power plant or recovery filler from hot-mix asphalt plant (RF). Different SC mortars mixes were produced; three mixes with different EAFD ratio incorporation (0 %, 10 %and 20 %) for each the other industrial by-products (FA, NcFA and RF) substituted of cement at 30 %; and additional three mixes with 60 % of cement replacement by FA and the same EAFD incorporation ratios. To study the performance over time of these SC mortars, tests such as electrical resistivity, ultrasonic pulse velocity, drying shrinkage, capillarity, compressive and flexural strength were carried out up to 91 days of curing. The SC mortar compositions was evaluated by TGA/DTA and DRX analysis. Previously, the by-products used were characterized. The EAFD incorporation showed a strong influence in SC mortars, independently of the industrial by-product used. The initial inhibition of development of hardening in SC mortars due to the presence of ZnO in EAFD was lifted over time up to some extent. The simultaneous use of different industrial-by products in SC mortars in high volume content walks towards the sustainability in the construction sector.

Experimental Investigation on Shear Behavior of Non-Stirrup UHPC Beams under Larger Shear Span–Depth Ratios

Due to the extraordinary mechanical properties of ultra-high-performance concrete (UHPC), the shear stirrups in UHPC beams could potentially be eliminated. This study aimed to determine the effect of beam height and steel fiber volume content on the shear behavior of non-stirrup UHPC beams under a larger shear span–depth ratio (up to 2.8). Eight beams were designed and fabricated including six non-stirrup UHPC beams and two comparing stirrup-reinforced normal concrete (NC) beams. The experimental results demonstrated that the steel fiber volume content could be a crucial factor affecting the ductility, cracking strength, and shear capacity of non-stirrup UHPC beams and altering their failure modes. Additionally, the height of the beam had a considerable effect on its shear resistance. French standard formulae were more accurate for the UHPC beams with larger shear span–depth ratios, PCI-2021 formulae greatly overestimated the shear capacity of UHPC beams with larger shear span–depth ratios, and Xu’s formulae were more accurate for the steel fiber-reinforced UHPC beams with larger shear span–depth ratios. In summary, French standard formulae were the most suitable formulae for predicting the shear capacity of UHPC beams in this paper.

Minimum Shear Reinforcement for Reactive Powder Concrete Beams

The aim of this research was to determine the minimal requirements for shear reinforcement for reactive powder concrete (RPC) rectangular cross-sectional beams with a compressive strength of 157 MPa and a steel fiber volume content of 2.0% that remained constant for all the tested beams. Additionally, the recommendations of KCI-2012 and AFGC-2013 for the design of RPC beams as well as the shear design requirements of ACI 314-2014 when applied to RPC beams were studied. Utilizing a three-dimensional finite element program, a computational model was designed for forecasting the deformations and shear strength of the examined RPC beams. Both the shear-span-to-depth relationship (a/d) and the minimal reinforcement web ratio, represented by the distance between stirrups and the diameter of the stirrup bars, are the key study parameters in this regard. According to this study’s experimental findings, increasing the given reinforcement of the web ratio has little influence on both the ultimate shear strength as well as the diagonal cracking strength of the beams. Additionally, the findings demonstrated that the ACI 318-2014 maximum stirrup spacing requirement of 0.5 d can safely be extended to 0.75 d for beams that are relatively short. Compared to what ACI 318-2014 mandates, the suggestions of AFGC-2013 and KCI-2012 are more cautious and safe. According to the AFGC-2013 criteria, the mean proportion of Vfb to projected Vu,AFGC is roughly 58.3%, whereas the mean proportion of vs. and Vc is just 41.7%. The deformation response and ultimate shear strength of the examined RPC beams were well predicted by the designed model using finite elements when metal fibers were taken into account.