Flexural Strength Research Articles

Milling of TiBbm2 Particle Reinforced High-Modulus Steel

TiB2 particle reinforced high-stiffness steel is one of the composite materials that aim to improve Young’s modulus by compositing TiB2 particles into a stainless steel base phase. This material is designed to exhibit higher rigidity and strength than conventional iron-based materials by using TiB2 particles as the reinforcing phase, and is expected to reduce the weight of high-load components in engines. For this reason, tool life is very short when machining this material. Therefore, high Young’s modulus steel containing TiB2 particles is known to be one of the most difficult-to-cut materials. The purpose of this study was to investigate how to extend tool life in the milling of high-Young’s-modulus steel. Cutting speed dependence of tool life was investigated by end milling using a binderless CBN tool with excellent hardness and bending strength. In addition, the tool damage mechanism was also investigated. The results showed that tools composed of binderless CBN tool have a longer life than conventional CBN tool. In this type of binderless CBN tool, the tool wear rate tended to increase with increasing cutting speed. In addition, the longest tool life was obtained at a cutting speed of 1.25 m/s, though wear rate increased at a boundary cutting length of 1300 m. The wear rate was found to increase with increasing cutting speed. Temperature measurement results indicate that the primary cause of tool damage was mechanical wear, as the temperatures were much too low for a reaction between cBN and Fe. Friction tests revealed scratch marks on the tool originating from crushed cBN particles produced by the crushing of the cutting edge. This indicates that wear is accelerated by the high frictional energy of the cBN powder rubbing against the flank face.

Amazon açaí fiber-Portland cement compatibility: a challenge to produce cement-bonded fiberboards?

The açaí waste from Amazon contains short fibers that show potential for reinforcing cement-bonded fiberboards (CBFBs), although their compatibility with cement matrix is still unknown. This work aimed to characterize raw and pretreated açaí fibers and analyze their compatibility with Portland cement by different techniques, besides developing a CBFB. The fibers were subjected to thermal (180, 200, and 220 °C), cold and hot water, alkaline (NaOH), and bleaching (NaOH-H2O2) pretreatments. The chemical and water pretreatments raised the fiber crystalline indexes (28%-57%). The chemical pretreatments individualized the fiber bundles and removed hemicelluloses. Alkali-pretreated and raw fibers had the highest (96%) and lowest (65%) cement compatibility indexes. Portlandite and ettringite appeared after 24 h for most pastes but were delayed for raw and 220 °C-pretreated fibers. In contrast, only the raw fiber specimens reached the required compression strength of 34 MPa after 28 days; hence, they were chosen to produce a CBFB. The boards showed proper thickness swelling (1.4%), but low bending strength (MOE = 647.8 MPa; MOR = 1.9 MPa). Overall, the fiber modifications improved the compatibility with cement, but not the composite's mechanical strength. Açai-fiber CBFB is a promising building material, but future studies must overcome its poor mechanical performance.

Development of resin‐based dental composites containing hydroxyapatite and zirconia nanoparticles

AbstractIn clinical applications, resin‐based dental composites primarily face challenges with fractures and secondary caries. To overcome these issues, the physical characteristics of dental composites, especially mechanical properties, need to be improved. Hydroxyapatite (HA), present in the structure of the teeth, is preferred due to its biological properties, and zirconia (ZrO2) nanoparticles are known to enhance the mechanical properties of this type of composites. The aim of this study is to develop resin‐based dental composites containing HA and ZrO2 nanoparticles. The study also aims to explore the synergistic effect of these two nanoparticles on the physical properties of the developed composites. Composites with nine different compositions were prepared by mixing the components with the help of a mortar mill. The flexural and compressive strength, polymerization shrinkage, depth of cure and water sorption, and solubility properties of the prepared composites have been investigated. All composites have been found to meet the requirements of ISO 4049 standard. Among them, composite containing 5 wt. % HA and 1 wt. % ZrO2 (H5Z1) has exhibited the highest flexural strength with an increase of 58% compared to the control sample, and composite containing 3 wt. % HA and 2 wt. % ZrO2 (H3Z2) has exhibited the highest compressive strength with an increase of 22% compared to the control sample. Other physical properties of the composites have been found to be in an acceptable level.Highlights Dental composites with HA and ZrO2 fillers were developed by a mortar mill. Synergistic effect of HA and ZrO2 nanoparticles was investigated. Mechanical properties of dental composites were significantly improved. Physical properties of dental composites were found to be at acceptable levels. Depth of cure decreases with increasing HA and ZrO2 loading.

Bending Strength Evaluation of Japanese Wooden Cultural Heritage Building Columns Based on a Non-Destructive Testing Method

ABSTRACT Column failure assessment is essential for seismic diagnosis of Japanese wooden cultural heritage buildings. Achieving accurate column failure assessment depends on accurately estimating the bending Young’s modulus (E b ) and characteristic bending strength (F b ) of columns. This study extends the application of a non-destructive testing (NDT) method to estimate E b and F b of Japanese cedar columns generally used in wooden cultural heritage buildings. For this purpose, a correlation between the dynamic bending Young’s modulus (E p ) and E b of Japanese cedar columns is established and the variations in the E p –E b relationship across different wood provenances and species are clarified. Using the proposed method, a statistical analysis of the estimated E b of Japanese wooden cultural heritage buildings is provided. Furthermore, estimated E b is used to determine F b of the columns using the mechanical grade classification system. The results show that most Japanese cypress and Japanese cedar columns feature higher F b than those used in conventional seismic diagnosis. Conversely, two-thirds of the Japanese red pine columns feature a lower F b than that used in conventional seismic diagnosis. The proposed F b evaluation method offers an NDT method that can be widely applied to Japanese wooden cultural heritage buildings to assess column failure more accurately.

Exploring Flexural Strength Variation in Polymeric Materials for Provisional Fixed Prosthetic Structures: Comparative Analysis with and without Reinforcement through Laboratory Experimentation and Statistical Evaluation

Exploring Flexural Strength Variation in Polymeric Materials for Provisional Fixed Prosthetic Structures: Comparative Analysis with and without Reinforcement through Laboratory Experimentation and Statistical Evaluation

Laboratory Evaluation of Concrete Bridge Girders Flexural Strengthened with Near-surface Mounted Titanium Alloy Hooked Bars

The use of near-surface mounted (NSM) titanium alloy bars (TiABs) has emerged as a potential solution to provide flexural strengthening to in-service, reinforced-concrete bridge girders with flexural strength deficiencies. An experimental program was performed to evaluate the behavior of large-scale, reinforced-concrete bridge girders using NSM TiABs with hooked ends for both positive- and negative-moment flexural-strengthening purposes. The experimental program involved testing four positive-moment strengthened specimens including one control specimen while also testing two TiAB types. Additionally, three negative-moment strengthened specimens were tested including one control specimen using one TiAB type. Specimens were strengthened in accordance with the AASHTO Guide for the Design of Near-surface Mounted Titanium Alloy Bars, and the requirements of ACI 318-19 were used to handle the effect of stress concentrations at TiAB termination locations. The test results indicate that flexural strengthening using NSM TiABs with hooked ends is effective when the effect of stress concentrations at the TiAB termination locations and the potential formation of inclined shear cracks in the flexural tension region are considered in the design. ACI 318-19, which has provisions to account for the impact of stress concentrations at internal reinforcement termination locations, should be used in addition to the AASHTO Guide for the Design of Near-surface Mounted Titanium Alloy Bars. Additionally, the two TiAB types that were evaluated provided similar flexural behavior and either type can be used to strengthen bridge girders.

Mechanical Properties of Direct Composite Resins and CAD/CAM Composite Blocks

The widespread application of CAD/CAM technology in contemporary dentistry led to the development of promising restorative materials, such as resin composite blocks (RCBs). Thus, the present study aims to evaluate the mechanical properties of RCBs, comparing this material to the direct composite resin from the same manufacturer. Samples retrieved from three CAD/CAM resin composite blocks (Tetric CAD (TC), Ivoclar Vivadent, Grandio blocs (GB), VOCO GmbH and Brilliant Crios (BC), Coltene/Whaledent) and four direct composite resins (Tetric EvoCeram (TEC), Ivoclar Vivadent, GrandioSO (GS), VOCO GmbH, Brilliant EverGlow Translucent (BET) and Universal Shade (BEU), Coltene/Whaledent) were submitted to three-point bending flexural test and Vickers microhardness test. The resulting data of the flexural strength were analyzed using one-way ANOVA considering Bonferroni correction for post hoc tests (α = 0.05). The flexural modulus and Vickers microhardness results were analyzed using Welch’s ANOVA considering Games–Howell correction for post hoc tests (α = 0.05). Regarding results, flexural strength and flexural modulus values ranged from 81.1 MPa (BEU) to 246.5 MPa (GB) and 10.6 GPa (BEU) to 20.3 GPa (GB), respectively. GS (121.2) and GB (136.2) groups were associated with the highest microhardness values. According to the post hoc tests, statistically significant differences in flexure strength were found in RCBs (BC, GB, and TC) compared to all direct composite resins. Flexural modulus and Vickers microhardness of RCBs (BC, GB, TC) were also significantly different from the direct composite resin (BET, BED, and TEC), except when comparing GS and GB for microhardness. In conclusion, differences between RCBs and direct composite resins were observed regarding flexural strength, flexural modulus, and microhardness, revealing that RCBs have enhanced mechanical properties compared to direct composite resins.

Investigating of epoxy nanocomposites structure and properties that contain both pristine and aminosilane-treated silicon carbide (SiC) particles

This article presents a methodology for functionalization of silicon carbide (SiC) through chemical modification using γ-aminopropyltriethoxysilane (APTES) and its subsequent dispersion in an epoxy composition. The research revealed that functionalizing SiC particles with γ-aminopropyltriethoxysilane (SiC(APTES)) enhanced their chemical compatibility with the epoxy composition, facilitating the dispersion of SiC particles. Furthermore, it was observed that the functionalization of the filler had a profound impact on the structure, curing kinetics, and physical and mechanical properties of epoxy nanocomposites. The addition of SiC(APTES) into the epoxy composition resulted in a significant reinforcement of the material. Specifically, the flexural stress and flexural modulus of elasticity increased by 179% and 74%, respectively, while the impact strength experienced a remarkable improvement of 462%. Additionally, the tensile strength and tensile modulus of elasticity increased by 83% and 70%, respectively, compared to the epoxy composite without SiC. The application of SiC(APTES) also played a crucial role in initiating the polymerization process through the involvement of reactive amino groups, leading to a reduction in the initial curing temperature and an amplification of the thermal effects of the polymerization reaction. Moreover, the presence of functionalized SiC significantly influenced the structure of the epoxy composite, thereby contributing to its enhanced strength. In summary, the inclusion of SiC in the epoxy composition not only bolstered the material but also improved its thermal stability.

Resistance to torsion of cement vs screw-retained abutments under a tangential load: A pilot study.

To compare the resistance to torsion between two implant systems with internal hexagon connection, one using screw-retained abutments (Titanium Fix) and the other using cementable abutments (ITEC) under a tangential load. An in vitro experimental study was carried out. Fourteen implants, seven implants from each system, were included in this study. The implants were placed at a 45-degree angle into metal blocks to simulate their position in the maxilla. Then, implants were subjected to a resistance test on a CMT5L universal testing machine, and the maximum load was applied to each sample. The maximum force with which the torsion was achieved in each sample was analyzed. The data were tested using the Shapiro-Wilk test and showed normal distribution. Student t-test was used to examine statistical significance between the two groups, and the p-value was set at P < 0.05. There was a statistically significant difference between the two groups (P = 0.001). ITEC implants with a cementable abutment showed greater flexural strength compared to the Titanium fix with a screwed abutment implant system. The cemented abutment showed more resistance to torsion against a tangential load in comparison with the screwed abutment.

Mechanical Testing of Sliding on Pivot-Locking Clamp (SOP-LC) Fracture Repair System in Four-Point Bending and Torsion.

The first objective of this study was to compare the mechanical performance of a straight and contoured rod for the sliding on pivot-locking clamp (SOP-LC) system. The second objective was to compare single-cycle bending and torsion of the SOP-LC rod-bone constructs to a bone gap model between two clamp configurations. First experiment, 5 mm diameter rods from the 3.5 mm SOP-LC system, 4 straight and 4 bent rods were mechanically compared in four-point bending. The second experiment, 8 constructs with clamps on a single side of the rod and 8 constructs with clamps on alternating sides were compared in four-point bending and torsion. A torque limiting screwdriver at 2.5N was used for all constructs. There were not significant differences between the noncontoured versus contoured rods. Constructs with clamps on a single side had a significantly higher yield load, yield displacement and bending strength, but the constructs with alternating clamps had a significantly higher initial torsional stiffness. There were no other significant differences. Mild clamp slippage and mild screw bending were noted in all the torsion tested constructs graphically with multiple stiffness slopes and visually on the post-tested constructs. Torque applied to initial screw placement may play a role in reducing clamp slippage. Although bending yield load, bending yield displacement, bending strength and torsional stiffness were improved by different clamp placement, clinically this will depend on fracture type. Further studies are needed for clinical significance.

A study on the effect of the geometric properties and surface defects on silicon chip flexibility for wearable electronics

Purpose The purpose of this paper was to investigate how variations in the geometry of silicon chips and the presence of surface defects affect their static bending properties. By comparing the bending radius and strength across differently sized and treated chips, the study sought to understand the underlying mechanics that contribute to the flexibility of silicon-based electronic devices. This understanding is crucial for the development of advanced, robust and adaptable electronic systems that can withstand the rigors of manufacturing and everyday use. Design/methodology/approach This study explores the impact of silicon chip geometry and surface defects on flexibility through a multifaceted experimental approach. The methodology included preparing silicon chips of three distinct dimensions and subjecting them to thinning processes to achieve a uniform thickness verified via scanning electron microscopy (SEM). Finite element method (FEM) simulations and a series of four-point bending tests were used to analyze the bending flexibility theoretically and experimentally. The approach was comprehensive, examining both the intrinsic geometric factors and the extrinsic influence of surface defects induced by manufacturing processes. Findings The findings revealed a significant deviation between the theoretical predictions from FEM simulations and the experimental outcomes from the four-point bending tests. Rectangular-shaped chips demonstrated superior flexibility, with smaller dimensions leading to an increased bending strength. Surface defects, identified as critical factors affecting flexibility, were analyzed through SEM and atomic force microscopy, showing that etching processes could reduce defect density and enhance flexibility. Notably, the study concluded that surface defects have a more pronounced impact on silicon chip flexibility than geometric factors, challenging initial assumptions and highlighting the need for defect minimization in chip manufacturing. Originality/value This research contributes valuable insights into the design and fabrication of flexible electronic devices, emphasizing the significant role of surface defects over geometric considerations in determining silicon chip flexibility. The originality of the work lies in its holistic approach to dissecting the factors influencing silicon chip flexibility, combining theoretical simulations with practical bending tests and surface defect analysis. The findings underscore the importance of optimizing manufacturing processes to reduce surface defects, thereby paving the way for the creation of more durable and flexible electronic devices for future technologies.

Fluorinated graphite reinforced polytetrafluoroethylene/poly(butylene terephthalate) composites as friction materials for deep‐sea applications

AbstractThe application of polymer composites is one of the most effective methods for preventing lubrication failure in deep‐sea engineering. In this study, fluorinated graphite (FGr) microsheets were incorporated into polytetrafluoroethylene (PTFE) microparticle‐filled poly(butylene terephthalate) (PBT) composites. The tribological performance in the simulated deep‐sea environment at elevated seawater pressure equivalent to 3000 m ocean depth was investigated. The results showed that FGr enhances the flexural and compressive strengths, thermal stability, and seawater resistance of the PTFE/PBT composite. The wear rate was decreased to 96% at the critical FGr content of 4% by improving the transfer onto the metallic counterfaces, preventing direct contact and shear between friction couples. Moreover, the seawater pressure impedes composite transfer, leading to a 29% increase in the wear rate.

EXPERIMENTAL AND NUMERICAL STUDY OF INCREASED CORE SURFACE AREA ON THE PERFORMANCE OF ADDITIVELY MANUFACTURED HONEYCOMB SANDWICH STRUCTURES

Abstract Sandwich composite structures have an efficient structural design that provides high bending stiffness and strength at low weight. However, these structures are plagued with weak core-to-facesheet bond strength. In this work, the effect of increasing the contact area between the composite facesheet and honeycomb core was studied. Sandwich panels were manufactured using two different honeycomb structures, a regular and a modified honeycomb, and their respective bond strengths were evaluated using the flatwise tension test (ASTM C297). The honeycombs were additively manufactured using selective laser melting (SLM) process. The modified honeycomb was designed to have a larger surface area while retaining the same relative density as the regular honeycomb. The facesheets were made out of carbon-fiber, while the core was additively manufactured using 304L stainless steel powder. Impact specimens were manufactured and tested for impact resistance. A finite element model was created to study the integrity of the sandwich structures subjected to localized impact damage. The finite element model of the damage resistance due to impact showed a good agreement with the experimental results. Samples with increased contact area showed higher impact resistance. The average impact strength of the modified samples was 41.3% higher than the average impact strength of the regular samples. Flatwise tension results showed that by increasing the contact area between the core and the facesheet the core-to-facesheet bond strength increased.

Feasibility study of an integrated pre‐curing and forming process for 6061 Al alloy and carbon fiber hybrid composites

AbstractThis article proposes a 6061‐T6 Al alloy and carbon fiber hybrid composite material pre‐curing and forming integrated new process, which can significantly reduce the hybrid composite material processing time, improve the production efficiency, and provide the possibility of hybrid composite materials in automotive parts applications. The process started by placing hand‐stacked carbon fiber reinforced plastic (CFRP) composites on the surface of 6061 Al alloy sheets, followed by bonding and pre‐curing of the CFRP to the Al alloy sheets through two different sets of dies in a hydraulic press, and ultimately full curing in an aging furnace. Mechanical properties of the CFRP/Al hybrid composite material were measured by flexural tests. The results show that the flexural strength of CFRP/Al hybrid composites with different layups ([90]12, [0/45/90/−45]3, and [0]12) was increased by 159%, 93.4%, and 67.9%, respectively, compared with the single 6061 Al alloy. According to the macro‐morphological observation, [90]12 lay‐up parts have the least thinning. According to the microstructure observation, no obvious cracks or voids were found in the [90]12 lay‐up parts. Elongated cracks and void defects could be found in the [0]12 lay‐up parts. For the [0/45/90/−45]3 lay‐up parts, voids are mainly exist in ±45°layups. The results of the spring‐back analysis show that the standard deviation of the formed parts obtained from the three lay‐up methods is within 1 mm, indicating that the forming effect is good.Highlights New process improves productivity and reduces production costs The flexural strength of CFRP/Al hybrid parts is greatly improved [90]°12 lay‐up parts have the least thinning and no cracks were found The forming precision of the three lay‐up parts is good

Mechanical properties enhancement of 3D-printed HA-PLA composites using ultrasonic vibration assistance

ABSTRACT 3D-printed HA-PLA composites have attracted much attention because of their excellent biodegradability and osteointegration properties. However, HA particles negatively affect the mechanical properties of the composite parts. In this study, ultrasonic vibration-assisted 3D printing was used to improve the mechanical properties of HA-PLA composite specimens, and the effects of different infill angles and ultrasonic vibration power on the mechanical properties were investigated. The results demonstrated that the degradation and anisotropy of the mechanical properties of HA-PLA composites were alleviated by the use of ultrasonic vibration. By applying the ultrasonic vibration, the tensile and flexural strengths of the 20 wt% HA-PLA specimens fabricated with a 90° infill angle demonstrated the largest improvement of 104.3% and 112.7%, respectively. The high-frequency ultrasonic vibration waves promoted the spreading and fusion of the extruded materials, thereby reducing overlapping voids within the specimens and improving the interface bonding strength, also facilitated the refinement and dispersibility of the HA particles, which inhibited the formation of stress concentrations within the specimens and ultimately improved the mechanical properties. The printing process developed in this study can also be adapted to other particle (or other reinforcement types) reinforced composite to improve their mechanical performance.

Effect of magnetic induction intensity and steel fiber rate on strength improvement of cementitious filling composites

The underhand cut-fill backfill mining manner (UCFBMM) is widely employed in nonferrous metallic mines, and stability of the artificial backfill top plate directly determines the safety of operators and equipment, which puts forward higher requirements on fill’s bending properties. The purpose of the current research is to advance steel-fiber reinforced cemented tailings backfills’ (SFCTBs’) mechanical features by employing steel fibers. 17 groups of specimens were prepared by considering the effects of diverse steel fiber doping and magnetic induction strength on SFCTB’s bending properties. Steel fiber reinforced SFCTB’s bending evolution was studied by utilizing three-point bending tests, SEM interpretations, and X-ray computed tomography. Lab findings exhibited that directional distribution of steel fibers was effective in increasing SFCTB’s flexural strength, and the flexural strength was positively correlated with fiber doping and magnetic induction strength. The presence of steel fibers and their directional distribution well inhibited crack development, and thus the crack resistance and toughness of SFCTBs, enabling them to bear greater tensile force. The unadulterated steel fiber reinforced SFCTBs showed sudden fracture when reaching the peak load, while the steel fiber adducted SFCTB specimens showed the characteristics of good ductility. Due to gravity and magnetism, steel fibers were distributed at the bottom of SFCTBs and showed a directional distribution along the length of the specimens. Besides, SFCTBs produced further CSH-gels and Aft in process of hydration. The overall outcomes of the current study could run an academic guide to construction of artificial backfilling roofs in UCFBMM in terms of cost and operational stages.

Experimental study on Corn Straw Fiber (CSF) toughening EPS concrete

The natural Corn Straw Fiber (CSF), it has the advantages of light weight, high strength, good toughness and renewable, can delay the cracking and improve the toughness of cement-based materials. The effects of different mass fractions of CSF and Expanded-Polystyrene (EPS) particles on the compressive strength, flexural strength, splitting tensile strength and their failure modes, load-displacement curves and toughness of EPS concrete were analyzed by full factorial experimental design method. The compressive toughness index (I0, I1) and fracture energy (Gf) were defined to evaluate the effect of CSF on toughening EPS concrete. The results show that the addition of CSF can improve the compressive strength, flexural strength and cracking toughness of EPS concrete to a certain extent. The maximum compressive strength occurred in the E1F3 specimen with a CSF content of 3 % in Group I, which was 1.12 MPa, and the improvement rate was also the highest among the four groups, reaching 69.7 %. The compressive toughness index I1 also reached its maximum in the E1F3 specimen; The maximum flexural strength occurred in the E3F4 specimen with a 4 % CSF content in Group III, which was 0.885Mpa, with the highest improvement rate of 127.38 %. The maximum fracture energy Gf reached 0.827 in the E3F4 specimen. However, another additive, EPS particles, did not significantly improve the physical and mechanical properties of concrete. According to the SEM images and toughening mechanism analysis, it was discovered that tight adhesion between EPS particles and CSF with cement matrix, and the failure mode of CSF was tensile fracture, which could maximize the effect of CSF high tensile toughness. On the basis of mechanical properties and toughening effect, the relationship formulas between variable factors and strength, toughness index were fitted, and the optimal content of EPS and CSF were determined to be 1.3 % and 3 %, respectively.

INFLUENCE OF STEEL FIBRES OF CRIMPED AND HOOKED-END SHAPE ON THE MECHANICAL PROPERTIES OF PORTLAND CEMENT

Cement mortar without fibers might crack due to shrinkage or volume changes. Cracking in cement mortar leads to elastic deformation. The development of these cracks causes elastic deformation of cement mortar. This study examined the influence of two steel fibers' geometrical forms (crimped and hooked with just one end) in different amounts by volume (Volume fraction = 0.25%, 0.5%, and 0.75%) on the cement mortar's mechanical features. Among the characteristics were splitting, compressive as well as flexural strength. The samples were prepared, poured into cubic molds for compressive strength testing cylindrical molds used for splitting strength testing, and prismatic molds for flexural strength testing, and processed at various times 3, 14, and 28 days before the tests. According to the findings, the highest increase was obtained after adding 0.75% of crimped fibers, the compressive strength increased by 13.3 %21.29%, and 44.8%, for 3,14.28 days respectively, and split tensile strength increased by 66.17%,68.9%, and 79.48% for 3.14 and 28 days respectively and flexural strength increased by 72 %,91% and 92% for 3.14 and 28 days, respectively.

Evaluating the fresh and mechanical properties of steel slag aggregate concrete reinforced with steel fiber

In this study, steel slag (SS) and steel fiber (SF) were used to make environment-friendly high-strength concrete. Natural coarse aggregate (NCA) was initially substituted partially with SS at various substitution levels, i.e., 25 %, 50 %, 75 %, and 100 %, respectively, for getting the optimum substitution levels of SS in concrete. Afterward, SF, having an aspect ratio of 60, was considered with volume fractions of 0.15 %, 0.3 %,0.45 %, 0.6 %, 0.75 %, 0.90 %, 1.05 %, and 1.2 % in concrete. The water-to-binder ratio was taken as 0.35 for all the concrete mixes. For the fresh property, slump and compaction factor of concrete were determined. Similarly, for the mechanical property compressive strength (CS), split-tensile strength (STS), and flexural strength (FS) have been tested after the curing age of 28 and 56 days. Additionally ultrasonic pulse velocity (UPV) test was conducted to measure the quality of concrete. X-ray diffraction (XRD) was also performed to analyze crystalline phases and identify mineralogical composition within the concrete matrix. All the tests were compared with the standard concrete made with NCA. It has been found that the addition of steel slag aggregate (SSA) and SF enhances the mechanical properties of concrete, whereas it reduces workability. Substituting 50 % of SSA for NCA alongside 1.05 % of SF results in the highest CS, while employing 1.2 % SF achieves maximum STS, FS, and UPV.

Performance modulation and optimization of PE fiber reinforced 3D-printed geopolymer

This paper aims to develop an environmentally friendly and low-carbon geopolymer for 3D printing, which has excellent mechanical and rheological performance. The effect of ground granulated blast furnace slag (GGBS), NaOH and sand on mechanical strengths, 3D printing performance and rheological behavior was investigated to determine the optimum mix proportion for 3D-printed geopolymer. Moreover, polyethylene (PE) fibers were introduced to reinforce the performance of 3D-printed geopolymer. Results show that when the ratio of GGBS, NaOH and sand is 1:0.13:2.67, geopolymer exhibits superior mechanical, 3D printing and rheological properties. Increasing the dosage of GGBS and sand leads to an overall increase in the yield stress but a decrease in the consistency coefficient, indicating that it benefits the stacking and fluidity performance of 3D-printed geopolymer. However, with an increase of NaOH content, the stacking performance increases while the fluidity decreases. Although increasing NaOH and sand content benefits the viscosity recovery performance, an increase in GGBS content has an opposite effect. Incorporating PE fibers significantly increases the flexural strength with an increase of up to 27.8% and 21.3% in 7-d and 28-d flexural strength, respectively, given a PE fiber volume of 0.6%. Increasing the volume of PE fibers leads to a significant rise in the stacking performance but a reduction in the fluidity. Furthermore, adding PE fibers negatively affects the geopolymerization but benefits the hydration process given an increase of Si/Al and Si/Ca ratio identified in PE fiber reinforced 3D-printed geopolymer.