Cylindrical Specimens Research Articles

Multiphysics Simulation and Experimental Investigation of the Densification of Metals by Spark Plasma Sintering

Multivariant experimental investigations and multiphysics microstructural modeling of the spark plasma sintering process of metallic powders have been performed up to a relative density of approximately 80%. In comparison, the effect of sintering temperature, pressure, and particle size on the interparticle contact area growth and axial shrinkage of cylindrical specimens of copper and nickel particles is measured in laboratory scaled tests. Herein, for the first time all relevant for sintering phenomena are considered simultaneously: the fully coupled thermo‐electro‐mechanical modeling of the spark plasma sintering processes, additionally taking into account for lattice, grain boundary, surface diffusion, electromigration, and thermomigration, has been carried out. The computational analysis of various physical phenomena allows to identify dominant and insignificant mechanisms. The two‐level numerical simulation includes the modeling of the sintering setup at the macroscopic level and the neck formation process in particle chain systems at the microscopic level. The results of the numerical simulations show a very good agreement with the experimental data. Therefore, the impact of electrical and mechanical loads as well as of particle size on microscopic distribution of temperature, inelastic strain, and on densification has been studied by the finite element simulations.

Use of Time–Temperature Superposition and Stepped Isothermal Method for Estimating Long-Term Properties of Recycled Aggregate Roller-Compacted Concrete

Abstract Although the use of recycled materials in civil engineering construction is a desirable option from a sustainability standpoint, the questionable long-term performance of these materials often hinders their widespread use in practice. The primary focus of this study was to perform accelerated aging and testing for estimating long-term properties of a roller-compacted concrete composed of crushed recycled aggregate, Type-I portland cement, and ASTM Class-F fly ash replacing up to 50 % of cement by weight. Accelerated aging was accomplished by curing cylindrical specimens at three different elevated temperature regimes for specific time durations. At the end of each time–temperature regime, the residual stiffness of the specimen was measured in a nondestructive fashion. Series of stiffness–time master curves were then constructed for each mix using the time–temperature superposition (TTS) technique and the stepped isothermal method (SIM). While the TTS method uses different sets of specimens for each elevated time–temperature regime, SIM uses a single set of specimens that are stepped up in temperature and held at each regime for a specified duration. Results indicated that for all mixes, the material stiffness degraded with time. Based on the Arrhenius equation, stiffness–equivalent age master curves were developed. Stiffness prediction was accomplished up to an equivalent age of almost 600 days, although the actual short-term test lasted only up to 6 days. It was also found that SIM and TTS provided comparable results, thus implying that the testing time and the number of specimens can be significantly reduced by using the SIM.

Very High Cycle Fatigue and Ultrasonic Testing in Multiaxial Loading

Abstract Fatigue damage has special relevance on the lifespan of mechanical components and structures, as it takes responsibility for the majority of registered structural failures. Most fatigue testing today still uses uniaxial loads, nonetheless it is generally recognized that multiaxial stresses occur in many full-scale structures. Nowadays, the growing need for greater lifespans forced the study of material behavior under what is nowadays very high cycle fatigue (VHCF) regime, fatigue research beyond 10E07 up to 10E10 cycles. However, most classic fatigue machines are often very costly, both in terms of time and energy, for such an elevated number of cycles. The high costs of equipment and time to conduct such experiments have seen a massive improvement with the introduction of high frequency ultrasonic machines. Presently, it is already possible to characterize materials VHCF response under axial and multiaxial loading conditions in a fraction of the time. Ultrasonic testing machines were first introduced for simpler uniaxial loading and more recently adapted for multiaxial loading conditions. The present work reviews the current background of ultrasonic fatigue testing machines working at 20-kHz frequency, with emphasis on multiaxial fatigue and VHCF. A review of a series of fatigue tests are presented, respectively, axial, shear, axial/shear, and in-plane bi-axial fatigue tests with different combining dimension specimens allowing different shear/axial stress ratios. Special attention will be put into the performance of multiaxial classical cylindrical specimens under tension/torsion and flat cruciform specimens under in-plane bi-axial testing using low-cost piezoelectric transducers. By comparing all so far developed and successfully reached multiaxial specimens and respective methodologies, two base approaches were possible to be established. When designing new specimens or ultrasonic machines, or both, one of the two methods must be followed. To have a well-comprehended methodology and successful design approach will undoubtedly guide future multiaxial ultrasonic method ideas.

Feasibility of additively manufacturing synthetic bone for sports personal protective equipment applications

Human limb surrogates, of varying biofidelity, are used in the performance assessment of sports personal protective equipment (PPE). Such biofidelic surrogates have incorporated soft tissue simulants (silicones) and synthetic bone (short fibre filled epoxy). Testing surrogates incorporating realistic synthetic bone could help to further our knowledge of fracture trauma mechanics, and applications such as the effectiveness of sports PPE. Limb surrogates with embedded synthetic bone are rarely tested to fracture, mainly due to the effort and cost of replacing them. This paper proposes additive manufacturing of synthetic bones, with appropriate bone like fracture characteristics, potentially making them more accessible and cost effective. A Markforged® X7™ printer was used as it prints a base filament (Onyx™) alongside a continuous strand of reinforcement (e.g., carbon fibre). The properties of specimens from this printer vary with the type, volume fraction and position of reinforcement. Bar specimens (10 × 4 × 120 mm) with varying amounts of carbon fibre reinforcement were printed for three-point bend testing to determine the feasibility of achieving mechanical properties close to compact bone (bending modulus of ∼15 GPa, bending strength of ∼180 MPa). Bending strength for the various bar specimens ranged from 32 to 378 MPa, and modulus values ranged from 1.5 to 25.8 GPa. Based on these results, four 140 mm long oval shaped cylindrical specimens of ø14 and ø16 mm were printed to represent a basic radius bone model. Three-point bend testing of these bone models showed similar bending modulus (3.8 to 5.3 GPa vs. 3.66 to 14.8 GPa) to radius bones reported in the literature, but higher bending strength (147 to 200 MPa vs. 80.31 ± 14.55 MPa).

Color stability of nanohybrid and microhybrid composites after immersion in common coloring beverages at different times: a laboratory study

Objective/AimThis in vitro study aimed to evaluate the color stability of microhybrid and nanohybrid restorative composites after exposure to immersion media common in Yemen for different periods.Materials and methodsTwo composite materials, nanohybrid Tetric N-Ceram and microhybrid Te-Econom Plus, were investigated. Six groups of 30 cylindrical specimens (n = 5/group; diameter, 10 mm; thickness, 2 mm; shade A2) of each restorative material were immersed for 1 week in distilled water, qat solution, Yemeni coffee, traditional Yemeni coffee (qishr), red tea, and Dilsi cola. Color changes were evaluated by colorimetry. The color data and pH were measured before and 1, 3, and 7 days after immersion. The data were statistically analyzed.ResultsTetric N-Ceram showed lesser discoloration than did Te-Econom Plus. Qat, coffee, and red tea caused highly significant discoloration than did Dilsi cola and distilled water (p < 0.05). The role of low pH in discoloration depended on the colorant.DiscussionNanohybrid Tetric N-Ceram composites are more resistant to discoloration than are microhybrid Te-Econom Plus composites. Qat and coffee have the highest effect on composite discoloration.ConclusionsThese findings will aid in selecting composite materials and patient instruction.

Assessing the Scale Effect on Bearing Capacity of Undrained Subsoil: Implications for Seismic Resilience of Shallow Foundations.

This research investigates the influence of the scale effect on the bearing capacity of fine-grained subsoil under undrained conditions. The analyses were conducted based on laboratory tests of silty clay. Uniformly compacted samples were subjected to an unconfined compression test. The research was performed on cylindrical specimens. Three different variants of the diameter D (38 mm, 70 mm, 100 mm) and the corresponding height H = 2D were analyzed. Based on the tests results, the unconfined compression strength qu was determined, and from this, the undrained shear strength cu was calculated. The obtained results showed a clear decrease in cu with increasing sample size. However, in the existing reference documents, there are no specific guidelines for calculations of bearing capacity with consideration of sample size effect on the soil shear strength. Therefore, this study utilized the laboratory soil test data to calculate the bearing capacity of undrained subsoil, taking into account the seismic impacts, with a particular focus on spread foundations.

Experimental study on impact toughness of multi-combination hybrid fiber-reinforced magnesium phosphate cement-based materials

In order to improve the brittleness of magnesium phosphate cement-based materials (MPC) and overcome the limitations of single fiber-reinforced cement-based materials, this study investigated the mechanical properties of hybrid fiber-reinforced magnesium phosphate cement-based composite materials (HFRMPC) by incorporating four types of fibers: hooked-end steel fiber (HSF), micro steel fiber (MSF), polyvinyl alcohol fiber (PVAF), and basalt fiber (BF). Cylindrical specimens were prepared by single and double hybridization of the fibers and subjected to drop hammer impact tests to analyze the effects of different fiber hybridization methods on the impact resistance of these materials. The two-parameter Weibull distribution was used to analyze the test results to predict failure probabilities and to investigate the fiber reinforcement and toughening mechanisms in MPC through microscopic structural analysis. The results showed that the impact resistance of the fiber hybridization group was much better than that of the single fiber group, and the impact resistance increased continuously with increasing fiber content. The fibers' impact resistance enhancement effects were in the following order: MSF > PVAF > BF. The fiber combination methods were ranked as follows from best to worst: HSF + PVAF > HSF + BF > HSF + MSF > PVAF + BF. The 1.5% HSF+0.6% PVAF hybridization had the best impact resistance performance, with an increase in initial cracking and impact energy dissipation at the failure of 7748.6% and 8921.2%, respectively, compared to the M0. The probability distribution of impact number of initial cracking (N1) and failure (N2) of the specimens followed the double-parameter Weibull distribution well. The multiscale strengthening and toughening zone composed of fibers with different geometric dimensions and elastic modulus was crucial to the material's performance, as the fibers acted in progressive briding under external impact loads, dissipating impact energy through the failure morphology of pull-out and breaking, significantly improving the HFRMPC's impact toughness. A comprehensive evaluation of the four indicators of impact resistance and manufacturing costs for various hybrid fiber compositions found that the combination of 1.5% HSF and 0.6% PVAF exhibits the most outstanding overall performance.

Film Boiling around a Finite Size Cylindrical Specimen—A Transient Conjugate Heat Transfer Approach

The DNS of film boiling requires strong computational resources that are difficult to obtain for daily CFD use by expert practitioners of industrial R&amp;D. On the other hand, film boiling experiments are associated with the usage of expensive and highly sophisticated apparatus, and research to this end is relatively difficult due to high heat flow rates that are present in the process itself. When combined with transient heat conduction in a solid, the problem becomes significantly difficult. Therefore, a novel method in computation of conjugate heat transfer during film boiling in a quiescent liquid is proposed in this paper. The method relies on the solution of mass, momentum and energy conservation equations in a two-fluid framework, supplemented with the appropriate closures. Furthermore, turbulent flow was determined as an important parameter in obtaining an accurate solution to temperature field evolution in a solid specimen, via the proper modeling of the turbulent kinetic energy (TKE) value, that was imposed as a constant value, i.e., the frozen turbulence approach. It was found, in addition, that the appropriate TKE value can be obtained by use of Kelvin–Helmholtz instability theory in conjunction with boundary layer theory. The obtained results show excellent agreement with the experimental data within the first 15 s of the experiment, i.e., the first ca. 10% of the total duration of the film boiling mode of heat transfer. Furthermore, the heat transfer coefficient matched the error bands prescribed by the authors of this paper, which presented the correlations, whilst the averaged values are far beyond this band, i.e., are slightly more than 30% higher. Further inspection revealed a measure of similarity between the computational result of the volume fraction field distribution and the experiment, thus confirming the capability of the method to obtain realistic interface evolution in time. The method shows full capability for further pursuing industrial-scale film boiling problems that involve turbulent flow and the conjugate heat transfer approach.

Theoretical Developments for the Interpretation of Cavity Flow Permeability Tests Conducted on Intact Lac du Bonnet Granite

The permeability of intact geologic media features prominently in many geo-environmental endeavours. The laboratory estimation of permeability is an important adjunct to the field estimation of bulk permeability values, which involves a great deal of supplementary in situ investigations to correctly interpret field data. Laboratory permeability estimation is also a viable method if core samples are recovered from in situ geological mapping of the region under study. The basic methodologies for permeability estimation rely on either steady-state or transient tests of the geologic material depending on the anticipated permeability value. This paper presents a steady flow test conducted on a partially drilled cavity located on the axis of a cylindrical specimen. Certain compact theoretical relationships are proposed for the estimation of steady flow from a cavity of finite dimensions located along the axis of a cylindrical specimen. The relationships are used to estimate the permeability of a cylinder of Lac du Bonnet granite obtained from the western flank of the Canadian Shield. The results from the cavity flow permeability experiments are compared with other estimates for the permeability of granitic rocks reported in the literature.

Grain Growth during Mechanical Processing of Austenitic Stainless Steel AISI 321

The kinetics of austenite grain growth during thermomechanical treatment of AISI 321 steel with a relatively high content of carbon (0.07 wt. %) and titanium (0.50 wt. %) were studied. Hot deformation was carried out by the uniaxial compression of cylindrical specimens on a Gleeble 3800 thermomechanical simulator. A dependence is obtained for calculating the kinetics of austenite grain growth for a temperature range of 1150–1250 °C. The proposed dependence makes it possible to evaluate grain growth under non-isothermal conditions. The verification of the adequacy of the proposed dependence and the method for calculating the grain size at cooling rates 0.2, 1 and 5 °C/s showed its high convergence. The difference between the calculated and experimental grain size did not exceed 8%. The suppression of grain growth is due to the precipitation of titanium carbides and carbonitrides. Using the developed grain growth model, an analysis was made of the reasons for the formation of large grains in the shell after the elongating in the production process.

Magnesium nanoparticle modified cement-based composites: Performance and compatibility in repair applications

Applying ordinary repair mortars onto the surface of degraded concrete elements has been a common approach in restoration operations. Since the properties of cement-based composites depend on nano-structural features, proper addition of nanoparticles can enhance performance. In the present study, the physico-mechanical performance of concrete and mortar mixtures incorporating magnesium nanoparticles was investigated. The workability and flowability of the mixtures, along with compressive, tensile, and flexural strengths of specimens were evaluated. A total of 284 cylindrical, cubic, and prismatic beam specimens having different dosages of magnesium nanoparticles as partial replacement for cement were assessed to quantify the effects of adding magnesium nanoparticles. Furthermore, analysis of the compatibility between the repair mortar and the existing concrete substrate was examined using four-point bending tests on repaired beam elements to characterize the different modes of failure. Two approaches of substrate surface preparation featuring smooth and rough interfaces were adopted, and the effect of interface texture on the mechanical properties of the repaired beam specimens was evaluated. The results show that specimens incorporating magnesium nanoparticles achieved 37%, 37%, and 63% higher compressive, tensile, and flexural strengths, respectively, compared with that of the reference specimens. Moreover, the set of concrete beams with rough interface showed compatible failure modes, while those with smooth contact interface had incompatible modes of failure.

Optimization of Johnson-Cook Constitutive Model Parameters Using the Nesterov Gradient-Descent Method.

Numerical simulation of impact and shock-wave interactions of deformable solids is an urgent problem. The key to the adequacy and accuracy of simulation is the material model that links the yield strength with accumulated plastic strain, strain rate, and temperature. A material model often used in engineering applications is the empirical Johnson-Cook (JC) model. However, an increase in the impact velocity complicates the choice of the model constants to reach agreement between numerical and experimental data. This paper presents a method for the selection of the JC model constants using an optimization algorithm based on the Nesterov gradient-descent method. A solution quality function is proposed to estimate the deviation of calculations from experimental data and to determine the optimum JC model parameters. Numerical calculations of the Taylor rod-on-anvil impact test were performed for cylindrical copper specimens. The numerical simulation performed with the optimized JC model parameters was in good agreement with the experimental data received by the authors of this paper and with the literature data. The accuracy of simulation depends on the experimental data used. For all considered experiments, the calculation accuracy (solution quality) increased by 10%. This method, developed for selecting optimized material model constants, may be useful for other models, regardless of the numerical code used for high-velocity impact simulations.

Influence of specimen geometry on torsion of bituminous mixtures

This investigation focuses on the measurement of linear viscoelastic properties of the bituminous mixture using different specimen geometries in Dynamic Shear Rheometer (DSR). Two different specimen geometries, cylindrical and prismoidal (rectangular cross-section) specimens are used for testing in torsion. The cylindrical specimen of 12 mm diameter and prismoidal specimen with width to thickness ratio of 1.3 are used in the study. The length of both specimen geometries is restricted to 50 mm. The linear viscoelastic limit for the bituminous mixtures was estimated by performing an amplitude sweep experiment. The linear viscoelastic parameters are measured using a strain amplitude of 0.001 % and at frequencies ranging from 45 to 0.1 Hz. The results show the difference in the linear viscoelastic parameters measured using cylindrical and rectangular specimens i.e., the absolute shear modulus of the prismoidal specimen is greater than the cylindrical specimen. Such an increase in absolute shear modulus is because of the end restraint in torsion for prismoidal specimen i.e., warping. This study has documented such results for a range of temperatures and frequencies. The difference in the linear viscoelastic properties is found to be insignificant at 15 °C for the frequencies above 0.5 Hz and predominant at 35 and 55 °C for all the frequencies. The absolute shear modulus of bituminous mixtures for prismoidal specimens is computed and it is seen that the difference in absolute shear modulus is contributed predominantly due to the restriction of the warping in the prismoidal specimen due to the end restraint. This study shows the necessity for the correction of the absolute shear modulus of the bituminous mixture measured using prismoidal specimen for a given aspect ratio.

NUMERICAL BUCKLING BEHAVIOR OF PERFECT AND IMPERFECT STEEL CYLINDERS UNDER EXTERNAL PRESSURE

The buckling capacity of steel cylindrical liquid tanks primarily depends on their geometric configuration, material properties, imperfections, the way they are stiffened, loading, and boundary conditions. The present study aimed to investigate the effect of R/t and H/R ratios and imperfections on the buckling strength of cylindrical tank specimens subjected to external pressure using the finite element technique. Twelve cylindrical tank specimens were considered with radius-to-thickness (R/t) ratios of 500 and 600, height-to-radius (H/R) ratios of 1.0 and 1.5, and imperfection depths of 4t and 8t. A linear and nonlinear buckling analysis using ANSYS workbench 2021 was conducted for all perfect and imperfect specimens to predict the critical buckling strength. The results are compared with the experimental results available in the literature and theoretical solutions. Numerical results show reasonably good agreement with experimental and theoretical results. It is found that the buckling pressure remarkably increases with the decrease of both R/t and H/R ratios; however, the effect of the R/t ratio is more dominant than the H/R ratio. Furthermore, it was observed that the geometric imperfections have little influence on the overall buckling capacity, especially for tanks with large H/R ratios and smaller R/t ratios.

Role of crack offset and loading condition on fracture behavior of wire specimen

Accurate stress intensity factor (SIF) solutions for cylindrical specimens with varied wire aspect ratios, crack aspect ratio, relative crack depth and crack offset are required to evaluate the fracture toughness of high strength yet brittle rods, cables, fibres and wire specimens. The mode I geometric factor (GF) solutions of various crack configurations in a cylindrical fracture specimen in tension have been determined using linear elastic fracture mechanics in earlier studies. In the present study, finite element analysis (FEA) was used to compute these as a function crack offset and wire aspect ratios for two different boundary conditions-constrained and unconstrained. In constrained loading condition, the GF was seen to decrease significantly with crack offset for wires at lower aspect ratio in all the 3 crack curvatures – concave, straight and convex. GF stabilized as the wire aspect ratio was increased beyond 40. In unconstrained loading the GF values were independent of the wire aspect ratio and crack offset for the 3 crack curvatures.

Evaluating the behavior and bond properties of FRP spike anchors under confined conditions and elevated temperature

The use of fiber-reinforced polymer (FRP) anchors in combination with the conventional externally bonded reinforcement (EBR) installation technique is an effective method to prevent or postpone the debonding of FRP sheets. However, their behavior under confined conditions and elevated temperatures is still unknown. In such a framework, in the first phase, the current research aims to assess pullout test results for single FRP anchors with dowels ranging from 50 to 75 mm in confined and unconfined conditions. To achieve this goal, three concrete slabs with the dimension of 1550 × 1250 × 250 mm3 were cast. Experimental results showed that the bond strength of FRP anchors in confined conditions increased by about 50% compared to the unconfined conditions. Additionally, a comparison was made between the experimental results and the literature models. In the second phase, eleven pullout tests were conducted on the cylindrical specimens with the dimension of 150 × 200 mm2 (diameter × height) under confined conditions and elevated temperatures by considering different sustained load levels.The results showed as the temperature increases and FRP anchor is constantly loaded, it fails in a shorter time before the adhesive reaches its glass transition. Finally, a bond strength vs. temperature model was developed for FRP anchors in confined conditions and high temperatures.

Quantification of inhomogeneity and anisotropy of bituminous mixtures using biaxial experimental data

Most of the existing mechanical characterization test methods and the analytical models for bituminous mixtures are developed based on the assumption of homogenous and isotropic material properties. However, the extent to which such assumptions hold good for bituminous mixtures is not very clear. A biaxial testing scheme in indirect tension mode can come in handy to collect the experimental data at different test temperature regimes. In this study, a bituminous mixture with a nominal maximum aggregate size (NMAS) of 13.2 mm is used to fabricate cylindrical test specimens with 150 mm diameter and 63.5 mm thickness for conducting the repeated load indirect tension (IDT) test. The input load level is selected as 5 to 13 % of the indirect tensile (ITS) failure load in the form of a haversine pulse of 0.1 s loading and 0.9 s rest period. Such loading is applied on zero-degree and ninety-degree orientations of the specimen. The resulting deformations in different directions are measured using linear variable differential transducers (LVDT) attached to both diametral faces of the specimen. The response of the bituminous mixture specimen is captured at three different temperatures of 20, 25, and 30 °C using two different gauge length (half and quarter gauge of the total diameter). A new framework is introduced in this study to evaluate the extent of inhomogeneity and anisotropy of bituminous mixtures. The deformation response of the test specimen captured in the same orientation at different diametral faces is compared to evaluate the extent of inhomogeneity. The extent of anisotropy is evaluated by comparing the deformation response of the test specimen captured at different orientations within the same diametral face. A 15 % variation in the average peak deformation is chosen as the demarcation for determining the extent of inhomogeneity and anisotropy. From this investigation, it is observed that half gauge length experimental data exhibits homogenous and isotropic behavior for all three test temperatures. The quarter gauge length data exhibit similar behavior at 30 °C, whereas it is observed as homogenous and anisotropic at the other two test temperatures.

Non-contact assessment of porosity in metal 3D printed parts by vibration spectra

Volumetric porosity as a common defect in metal 3D printing (3DP) that can significantly impede the mechanical properties of products. Traditional methods of porosity control (microscopy) and non-destructive testing (computed tomography) usually are not applicable at the production site. In this study, sensitivity of three examined testing modalities based on acoustic methods and vibration analysis to changes in the volumetric porosity of 3DP parts was examined. Test objects were cylindrical specimens made of AlMg powder by 3DP with a gradually dosed porosity from 0.5 to 4.0%. Ultrasonic testing by through transmission showed the best accuracy using ultrasound velocity and pulse intensity parameters. Shifts of resonant frequency and spectral density and appearance of side harmonics were the manifestations of increased porosity using vibration approaches. The method comprising a loudspeaker as a vibration exciter and an optoelectronic device for remote sensing of vibration is the most attractive from the point of view of application to objects of complex geometry.

Mechanical parameter assessment of fresh human cancellous bone of the femoral head in atraumatic femoral head necrosis and primary coxarthrosis

BackgroundAtraumatic femoral head necrosis is a rare pathological change of the femoral head. It is characterized by local necrosis of the cancellous bone as a result of reduced blood supply to the bone. Even today it remains unclear how to assess the hardness of the necrosis, whether it is soft tissue that is easily removed, or hard tissue that is difficult to resect. MethodsFemoral heads with primary coxarthrosis were selected as a comparison group. For this purpose, 49 femoral heads obtained during total hip arthroplasty surgery with either condition (23 femoral head necrosis, 26 coxarthrosis) were transferred to the testing laboratory in fresh condition. Cylindrical specimens were obtained using a tenon cutter along the main trabecular load direction in the subchondral region of the femoral head. Additionally, thin bone slices were extracted proximal and distal to the specimens for density measurements. Brass plates were glued to the circular surfaces of the specimens. After curing of the adhesive, the specimens were mounted in the testing machine and destructive uniaxial compression tests were conducted. FindingsThe recorded mean compressive strengths and elastic moduli were almost identical for both groups, but the necrosis group showed significantly higher data scattering and range regarding the elastic modulus. The mean density of the coxarthrosis specimens was significantly higher than that of the necrotic specimens. InterpretationThe mechanical properties of cancellous bone vary considerably in the presence of femoral head necrosis. The existence of hard necrosis implies a potential challenge regarding the clinical resection of these tissues.

PENGARUH SERBUK CANGKANG TELUR TERHADAP SIFAT MEKANIS BETON DAUR ULANG

In Indonesia, normal concrete construction is commonly used in the construction process. Excessive concrete waste is usually uncontrolled. Laboratory concrete testing waste can also accumulate and disturb the ecosystem and reduce the aesthetic value of a place. There have been many studies using recycled aggregate from concrete waste. Meanwhile, eggs are one of the foods frequently consumed by Indonesian. Eggshells are certainly becoming waste. According to data from the Indonesia Statistics (2019), chicken egg production in Indonesia reached 4,688,120 tons. Eggshell contains about 94% calcium carbonate with a weight of 5.5 grams. Meanwhile, calcium carbonate is the main constituent of Portland cement, accounting for 70% of other constituents. Based on the reasons above, this study was conducted to determine the effect of chicken eggshell powder as a partial replacement for cement on the mechanical properties of concrete with recycled coarse aggregate. The variations in the use of chicken eggshells in the concrete samples were 0%, 2.5%, 5%, 7.5%, and 10% of the weight of cement. To determine the mechanical properties of the concrete, compressive and splitting tensile tests were conducted using a cylindrical test specimen with a size of 10 x 20 cm. It is expected that the use of chicken eggshell powder can increase the compressive strength of recycled concrete. Based on the test results, the compressive strength of the concrete composition with 2.5% eggshell powder showed the greatest increase compared to the other compositions. This is supported by the UPV test, which showed the same result. The largest increase in splitting tensile strength was also found in the 2.5% composition. Meanwhile, good homogeneity levels were obtained in the concrete, based on the UPV test results on the test specimens at the age of 28 days.