Static Modulus Of Elasticity Research Articles

Effect of hybrid polypropylene fibers on mechanical and shrinkage behavior of alkali-activated slag concrete

The growing global demand for cement in construction led to an increase in environmental concerns from the carbon dioxide gas release associated with its production. To foster the acceptance of other alternatives, such as alkali-activated slag (AAS) systems, mitigation of their main drawbacks, notably high shrinkage, is imperative. This study explores the influence of macro and micro polypropylene (PP) fiber hybridization in AAS concrete. Seven mixes with different fiber volume fractions (VF) of macro and hybrid fibers, in addition to a control mix, were investigated. Three macro-PP fiber mixes had fiber VFs of 0.3 %, 0.6 %, and 0.9 %. The other three hybrid PP fiber mixes were like macro fiber mixes with the addition of 0.1 % microfibers. The influence of PP fiber hybridization was explored concerning flowability, static elastic modulus, compressive, splitting tensile, and 3-point flexural strength and compared to control and macro-PP fiber mixes. Additionally, Shrinkage was measured for control and optimum fiber mixes. The results showed that the hybridization of PP fibers led to reductions in shrinkage up to 15 % compared to the control mix, while macro-PP fibers reached a maximum reduction of 6 %. Furthermore, the study evaluates the applicability of various literature and current code guidelines for predicting elastic modulus and tensile strength with the experimental results. ACI 318 could provide relatively accurate predictions in terms of splitting tensile and flexural strengths. Apart from that, with some exceptions, other codes and proposed equations in the literature were inadequate in providing satisfactory predictions.

Smart sustainable concrete: enhancing the strength and durability with nano silica

A detailed investigation was conducted to analyse the mechanical and durability features of a mixture of binary cement concrete modified with nanomaterials. In the context of the concrete matrix, the substitution of fractional cement content was carried out using Nano silica (NS) at concentrations of 1%, 2%, and 3%. Four distinct cementitious blends were subjected to a comprehensive match of tests, which encompassed compressive strength, flexural strength, split tensile strength, static modulus of elasticity, bulk density, water absorption, permeability, carbonation resistance, acid attack resistance, and rapid chloride penetration. The compositions of the mixes were investigated through the use of various microstructural analysis techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (SEM-EDS), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The research revealed significant improvements in the mechanical and durability characteristics of the material. An increment in the mechanical and durability properties of mixtures were seen due to inclusion of marble power and Nano silica due to enhanced pozzolanic activities of composite and its filling effect. It is worth mentioning that Nano silica has shown the potential to mitigate the degradation caused by exposure to sulfuric acid. The SEM-EDX analysis demonstrated a decrease in the Ca/Si ratio when compared to the reference combination, suggesting an increase in the consumption of calcium hydroxide (CH) and the creation of a more compact calcium-silicate-hydrate (C-S-H) gel. The X-ray diffraction (XRD) findings indicate that NS has the ability to act as an accelerator for pozzolanic processes. This is achieved by consuming calcium hydroxide (CH) and promoting the creation of extra calcium silicate hydrate (C-S-H), which ultimately enhances the overall performance of the concrete mixture.

Crack Resistance of Concrete Using Granulated BlastFurnace Slag Sand under Flexural Stress

AbstractGranulated blast‐furnace slag sand (BFS) has the potential to be used as an alternative to fine aggregates in concrete production. The interface between the cement paste and the aggregate in concrete is densified when BFS is used, due to the hydrates that are generated by its latent hydraulicity. This fact suggests that the crack resistance of concrete, which is closely related to the conditions at the aggregate interface, would be enhanced by the use of BFS. The fracture energy (GF) of concrete under flexural stress is here measured to evaluate the crack resistance of concrete made using BFS. BFS samples from three different steel mills in Japan are used as the fine aggregates for concrete production, and mountain sand is used as a natural sand for comparison. Compressive strength, static modulus of elasticity, and fracture energy tests are conducted at the material ages of 28 and 91 days. The GF of the BFS concretes increase with increasing compressive strength; on the other hand, the GF of the concrete made using mountain sand decrease. Thus, it is concluded that BFS concrete has superior properties to concrete made using natural sand in terms of the crack resistance under flexural stress, especially in high‐strength regions for large material ages.

Rock Plate Impact Experiment Based on ANSYS Workbench

The study of the physical properties of laminate mainly focuses on the static strength and elastic modulus. Its impact resistance has not attracted enough attention. However, the impact resistance of the multi-layer board used in climbing walls is particularly important to protect the safety of climbers. Using the display dynamics solver ANSYS Workbench and referring to the test method in EN 12572-1-2007, a finite element model of the rock slab impact test was established. The maximum stress and strain of each part during impact were solved, and the vulnerability point of the structure was analyzed. By changing the impact height and solving the influence on the rock slab under each test condition, the results show that the maximum stress of the slab changes nonlinearly. The numerical simulation results provide reference data and new development modes for the development of test methods and testing equipment in the next step of improving national standards.

The influence of the temperature on the hydration behavior and hardening process of PCC

AbstractPCC exhibit improved durability, chemical resistance and adhesion strength compared to unmodified variants. Commonly, the modifiers consist of thermoplastics. Despite the distinct temperature‐dependent behavior of these polymers, the properties of PCC were barely investigated within different temperatures. To make statements about the effect of different temperatures on the hardening process and therewith on the load bearing and deformation behavior of PCC, the properties of the materials have to be experimentally assessed at a defined temperature range. Accordingly, the degree of hydration, the structure development, the compressive and flexural strength as well as dynamic and static modulus of elasticity of different PCC were characterized while the samples were exposed to service temperatures of ‐20 °C, 20 °C, and 60 °C. After the specimens were thermally conditioned, the samples were tested in the proposed temperature scope. The results reveal influential changes in all tested attributes for the PCC within the applied service temperature range compared to a reference. This knowledge is essential to further investigate the temperature impact on the material and develop appropriate prediction models for the application of PCC and the integration in guidelines.

Cross-laminated secondary timber: Validation of non-destructive assessment of structural properties by full-scale bending tests

The demolition of buildings creates a vast quantity of secondary timber, which is currently chipped, downcycled or incinerated. This study examines a higher value use of secondary timber as lamellae for cross-laminated timber (CLT), which will address the increasing demand for wood products that is expected in the coming decades. The longitudinal vibration test method was used to determine the dynamic modulus of elasticity (dMoE) for secondary timber. Then, four-point bending tests were conducted for the secondary timber to obtain the static modulus of elasticity (sMoE) and modulus of rupture (MoR). The test results showed a good linear relationship between dMoE and sMoE, so the dMoE results could be used to predict sMoE of secondary timber. Furthermore, the static bending stiffness of cross-laminated secondary timber (CLST), sMoECL, was predicted by the dMoE from transverse vibration tests of CLST and longitudinal vibration tests of secondary timber. Four-point bending tests of CLST showed that the latter predicted sMoECL more accurately. CLST panels were also found to meet the structural requirements in relevant standards. Finally, analytical models were used to predict the bending stiffness and strength of CLST. The closest prediction came from combining the shear analogy method and bearing model for CLT. This paper demonstrates the feasibility of using secondary timber as a feedstock for CLT/CLST production.

Evaluation of some physical and mechanical properties of Acacia hybrid BV10 planted in Quy Chau, Nghe An

This study aimed to evaluate some major physical and mechanical properties of 7 year old Acacia hybrid BV10 planted in Quy Chau district, Nghe An province. Small specimens with dimensions of 20 (Radial) × 20 (Tangential) × 320 (Longitudinal) mm3 were cut near the pith and near the bark at breast height from each sample tree, then placed in a standard laboratory setting until their weights reached a constant value. The resulting mean air-dry density (AD), stress wave velocity (SWV), static modulus of elasticity (MOE) and modulus of rupture (MOR) were 0.53 g/cm3, 4,241 m/s, 10.00 GPa, and 82.17 MPa, respectively. Statistical analysis showed that SWV and these wood properties examined near the bark were always higher than those values measured near the pith. Stress wave technology can be used to predict MOE and MOR; however, AD is still a more reliable indicator for predicting mechanical properties since it showed a strong correlation with MOE (r = 0.86; P < 0.001) and MOR (r = 0.80; P < 0.001).

Mechanical Properties of PVC Fiber-Reinforced Concrete—Effects of Fiber Content and Length

This paper presents the key mechanical properties of PVC fiber-reinforced concrete. Six concrete mixtures were produced using plastic fibers obtained from clear PVC sheets. Three concrete mixtures were made using 20 mm long PVC fibers, whereas the other three were prepared with 40 mm long PVC fibers. The fiber content was varied in the range of 0–1.5 wt.% of cement for each length of fiber. The fresh concrete mixtures were tested for workability in terms of the slump. The hardened concretes were tested for their compressive and splitting tensile strengths, flexural strength and toughness, static elastic modulus, and impact resistance and toughness. The effects of the fiber content and fiber length on the workability and above-mentioned mechanical properties were observed. In addition, the correlations between various mechanical properties were sought. The test results revealed that the workability of concrete was reduced for both fiber lengths as the fiber content increased. The compressive strength, flexural strength and toughness, elastic modulus, and impact resistance and toughness increased at up to 1 wt.% fiber content, then decreased for 1.5 wt.% fibers. A similar trend was also noticed for the splitting tensile strength, particularly in the case of 20 mm long PVC fibers. Compared to the fiber length, the fiber content exhibited a more pronounced effect on the mechanical properties of concrete. The optimum fiber content was 1 wt.%, which produced the best performance in this study. Furthermore, excellent correlations were observed for the tested mechanical properties of concrete, except for splitting tensile strength, which was not well-correlated with compressive strength.

Effect of Mud Powder on the Performance of Bridge Deck Leveling Concrete in a Seasonally Frozen Region.

Mud powders in aggregates are often found to cause deterioration of concrete properties. Based on a study of the mechanical properties of bridge deck leveling concrete (BDLC) containing different mud powders at various ages, the effects of mud powders on concrete durability were evaluated through rapid chloride permeability testing, freeze-thaw testing, and the coupling of salt solution and a freeze-thaw test. The properties of the interfacial transition zone (ITZ) were also investigated via microhardness testing. The test results showed that mud powder reduced the compressive strength, static compressive elastic modulus, and bond strength at early stages of curing. Moreover, mud powder was found to reduce the tensile properties and durability of concrete, with clay powder causing a greater reduction than mud powder in river sands and coarse aggregate. In addition, the width of the ITZ of concrete containing mud powder was found to increase by 23.1-48.3%. A significant correlation between the ITZ and the tensile properties, as well as the durability of concrete, was also observed. Therefore, in order to improve the tensile properties and durability of BDLC in seasonally frozen regions, the content of mud powder in the aggregates should be minimized according to the different compositions of mud powders. The coupling effect of salt solution and a freeze-thaw cycle should also be taken into consideration.

Corn pomace as a substitute for wood raw material in lignocellulosiccomposite technology

Corn pomace as a substitute for wood raw material in lignocellulosic composite technology. Composites made from polymers PE, PP, PLA and modified starch with addition of corn pomace were produced and subjected quality parameters test. There were examined such parameters as: density, static bending strenght and modulus of elasticity and also water absorption and thickness swelling after 2 h and 24 h soaking in water, wettability and surface roughness. In general, the addition of corn pomace to polymers caused changes of parameters and through comparing parameters of different composites and control samples it was possible to indicate corn composite variants that occurs to have similar properties to pure polymer samples. Waste products should be seriously considered as a valuable substitute of wood raw material, but characteristics of composites should be improved through further research.

Estimation of compressive strength of cement mortars using impulse excitation technique and a genetic algorithm

Compressive strength, a crucial mechanical property of cement mortars, is typically measured destructively. However, there is a need to evaluate the strength of unique cement-based samples at various ages without causing damage. In this paper, a predictive framework using a genetic algorithm (GA) is proposed for estimating the compressive strength of ordinary cement-based mortars based on their dynamic elastic modulus, measured non-destructively using the impulse excitation technique. By combining the Popovics model (PM) and the Lydon–Balendran model (LBM), the static elastic modulus of samples was calculated using constant coefficients, representing an equivalent compressive strength. A GA was then employed to determine optimal values for these coefficients. The results showed that the LBM-based strength was dominant in the middle range of the dynamic Young's modulus while the PM-based strength was dominant for higher and lower values of the dynamic Young's modulus. The model was found to have a small root mean square error (3.1%). The findings suggest that this non-destructive model has potential for predicting the mechanical properties of cement mortars. It allows efficient evaluation of compressive strength without destructive testing, offering advantages for reliable assessments of cement-based materials.

Nonlinear dynamic responses of ballasted railway tracks using concrete sleepers incorporated with reinforced fibres and pre-treated crumb rubber

Abstract Damages on railway sleepers due to heavy impact loads induced by the movement of trains can be reduced by improving their impact resistance. Fibre-reinforced/pre-treated crumb rubber concrete sleepers (RCSs) have the potential to display significant impact resistance to withstand a high-magnitude impact load. The ideal proportions of pre-treated crumb rubber, steel fibres, and polypropylene fibres (PFs) can be identified based on the minimum cost-to-impact energy ratio after conducting a drop weight impact test on prisms. The numerical model developed to assess the behaviour of ballasted tracks has been validated using both simulation results and field measurements. Numerical studies have been conducted on ballasted rail tracks with steel and PF-reinforced/pre-treated RCSs using LS-DYNA software. Dynamic strain rate-dependent material parameters are introduced in the numerical simulations. The nonlinear effect of higher train speeds on dynamic track responses has been highlighted in this article. Although the static load-carrying capacity and modulus of elasticity of rubber concrete are low, their dynamic performance controls the track displacements from exceeding permissible limits. The outcome of this study will provide new insights into the effects of railway concrete sleepers incorporated with reinforced fibres and pre-treated crumb rubber on railway track performance in order to ensure safety and reliability before it is put into services.

Correlation between sonic pulse velocity and flat-jack tests for the estimation of the elastic properties of unreinforced brick masonry: Case studies from Croatia

Historic urban cores in southern Europe are characterized by a significant number of existing unreinforced masonry structures that are known for their seismic vulnerability. The first step in the preservation of such damaged buildings is condition assessment and characterization of the mechanical properties of the masonry, which can be achieved using non-destructive, semi-destructive and destructive methods. In this paper, the emphasis is on determining the modulus of elasticity of unreinforced masonry through flat-jack and sonic pulse velocity tests. Both methods are explained in detail and results from eight different case studies are presented. The results are compared and correlations among the techniques are observed, showing that both methods can be suitable for estimating the elastic properties of existing masonry. The paper provides a wide set of experimental data that has been made available. Finally, a sensitivity analysis was performed. Differences between static and dynamic modulus of elasticity and operational and practicability issues regarding on-site testing are discussed.

STUDY ON PREPARATION AND PROPERTIES OF ANTI-ULTRAVIOLET AGING WOOD-PLASTIC COMPOSITES

The degradable wood-plastic composites (WPC) were prepared by compression molding in this study. Polylactic acid (PLA), poly (butylene adipate-co-terephthalate) (PBAT) and salix powder were used as the main raw materials and nano-titanium dioxide (nano-TiO2) was used as anti-ultraviolet filler. The results show that when the addition amount of nano-TIO2was 2%, the static bending strength and elastic modulus of WPC reach 41.88 MPa and 3730MPa, respectively, which can meet the commercial application of WPC in building formwork. At this time, the composite material has a better effect of absorbing and reflecting ultraviolet light. The static bending strength, elastic modulus, tensilestrength and impact strength of WPC were reduced by 68.3%, 61.5%, 51.9% and 57.4%, respectively. The mass loss rate and water absorption were 6.1% and 22.6%, respectively, that shows its good degradation performance. This study provides a low-cost and simple method for the design of anti-UV aging, high-performance and degradable WPC, which has broad application prospects inpackaging, construction and other fields.

Utilizing halloysite nanotube to enhance the properties of cement mortar subjected to freeze-thaw cycles

This study investigates the impact of the long-term pozzolanic properties of halloysite nanotube (HNT) on the physical and mechanical properties, permeability, durability, and microstructural characteristics of cement mortar subjected to repeated freeze-thaw cycles. For this purpose, the two-year cured samples were exposed to 300 freeze-thaw cycles. Deterioration of the cement mortar surface was visually assessed and regularly quantified by mass loss and length change. Furthermore, helium porosity, electrical resistivity, and ultrasonic pulse velocity (UPV) were performed on cement mortar mixtures to elucidate the effect of repeated freeze-thaw cycles on permeability. In terms of mechanical properties, compressive and flexural strength tests were conducted; static elastic modulus and flexural toughness were also calculated. The frost durability of samples was analyzed using the relative dynamic modulus of elasticity and durability factor as the indexes to assess mortar's freeze-thaw resistance. Moreover, the microstructures of specimens before and after 300 freeze-thaw cycles were analyzed by scanning electron microscopy. Visual comparisons and experimental results demonstrated that the HNT introduction in cement mortars markedly enhances the frost resistance of plain mortar. It leads to the refinement of the cement paste pore structure and a reduction in its porosity due to the nucleating, filling, and long-term pozzolanic effects of HNT. It was found that the contribution of HNT's pozzolanic activity is the most important of these mechanisms. Therefore, less water penetration into the hardened cement composites occurs, which results in higher frost durability. The samples containing 2 wt.% HNT (by weight of cement) exhibited the lowest mass loss, expansion, porosity, and UPV loss due to repeated freeze-thaw cycles. The highest electrical resistivity and residual mechanical strengths also pertained to samples with 2 wt.% HNT. Hence, the HNT replacement dosage of 2 wt.% can be regarded as an optimal content for the cement mortars studied in this work. Finally, the two-way ANOVA revealed that HNT percentage is the factor with the greatest impact on mass loss, electrical resistivity, and compressive strength. In terms of length change, porosity, and flexural strength, the freeze-thaw cycle was the most statistically important factor.

Influence of laser texturing along with PTFE topcoat on slurry and cavitation erosion resistance of HVOF sprayed VC coating

This research investigates the slurry and cavitation erosion resistance of a polytetrafluoroethylene (PTFE) top-coat applied to standalone high velocity oxy-fuel (HVOF) sprayed and laser textured Vanadium Carbide (VC) coating over SS316 steel. The static contact angle, microstructural characterization, EDS mapping, microhardness, fracture toughness, elastic modulus, slurry erosion, and cavitation erosion of all the samples namely SS316, HVOF sprayed VC, Laser textured VC, and PTFE modified VC were evaluated. Results demonstrate that the inclusion of a PTFE top-coat significantly enhances the erosion resistance over HVOF sprayed and laser textured VC coatings. Further, the laser textured VC surface was also found to be successful in reducing the slurry and cavitation erosion of SS316 steel, which could be attributed to its higher microhardness, presence of circular textures, and higher H/E ratio. When the failure mechanism was examined using SEM images, it was found that brittle failure occurred on hard surfaces while ductile failure occurred on soft surfaces.

Influence of confining pressure on rubberised cement bound aggregate behaviour during static triaxial test

The aim of this research was to better understand the influence of adding waste rubber in cement bound aggregate (CBA) by testing both the unconfined and triaxial stress state. CBA with waste rubber was tested in this manner aiming to analyse influence of the confining pressure on the material behaviour. The results indicate that adding 20% rubber to a high cement content mix can assimilate the high stiffness caused by the high cement paste content, resulting in a mixture with increased cement paste content to facilitate in situ compaction. Additionally, a low confining pressure of 40 kPa has the most impact on the elastic properties/stiffness and it would be more appropriate to measure the CBA elasticity modulus with moderate lateral (confining) pressure. Finally, the practical implication of this research is that, in pavement mechanistic-empirical design, a correction of the measured uniaxial static modulus of elasticity by 10–15% should be adopted.

Experimental research on compressive properties of recycling polypropylene (PP) fiber recycled coarse aggregate concrete

Recycling polypropylene (PP) fiber recycled coarse aggregate concrete refers to the incorporation of PP as a synthetic fiber into concrete, thereby improving the physical properties of concrete. As a synthetic fiber, PP fiber has been widely used in field concrete in recent years because of its high cost performance, no water absorption, light weight and excellent corrosion resistance.The effects of waste PP fiber volume fraction, length-diameter ratio and substitution ratio of recycled aggregate(RA) on the axial compressive properties of waste PP fiber recycled aggregate concrete(RAC) were studied. The compressive stress-strain curve, axial compressive strength, static elastic modulus, peak compressive strain and equivalent compressive toughness index were obtained by axial compressive test. The research reveals that compressive strength rises initially and then diminishes with the augmentation of fiber volume and aspect ratio, and diminishes with the augmentation of RA substitution rate. The measured stress-strain curve proposes a modified stress-strain constitution model for waste PP fiber recycled aggregate concrete, wherein static elastic modulus decreases with the growth of fiber volume fraction, length-diameter ratio, and RA substitution ratio, while equivalent compressive toughness index initially increases, then declines with the rise of fiber volume fraction and aspect rate.

Estimation of the static bending modulus of elasticity in glulam elements by ultrasound and modal-updating NDT techniques

Glulam timber is gaining popularity as a structural element due to its cost-effectiveness, strength, and environmental benefits. However, being an organic material, it is susceptible to degradation. Therefore, nondestructive testing (NDT) methods are essential for assessing its structural health. In this study, two NDT approaches, ultrasound-based and modal updating, were used to predict the static bending modulus of elasticity (MOE) in Pinus Sylvestris and Spruce species. The results demonstrated that the modal updating and linear regression models outperformed the ultrasound technique in accurately determining the static MOE. Additionally, considering the influence of knots improved the accuracy of ultrasound predictions.

Determination of the relationship between static and dynamic modulus of elasticity in beech wood

In this study, the relationship between the dynamic modulus of elasticity determined using the stress wave method, which is one of the non-destructive test methods, and the static modulus of elasticity determined according to the TS ISO 13061-2 (2021) standard was investigated. In this context, randomly selected beech (Fagus orientalis Lipsky) timbers of 12x13x110 cm3 in dimensions were used. The time of flight of the timber in the radial and longitudinal directions was determined by using a FAKOPP microsecond timer with an accuracy of 1 μs. Oven-dry densities of the beech timbers were determined according to the TS ISO 13061-2 (2021) standard. Firstly, stress wave velocity and then dynamic modulus of elasticity values were calculated with the obtained data. The beech timbers were then cut into 20x20x320 mm dimensions for the static modulus of elasticity tests. Static modulus of elasticity resistance tests of the specimens were carried out in a Shimadzu AGIC/20/50KN universal test machine according to the TS ISO 13061-4 (2021) standard. Linear regression analyses of static and dynamic modulus of elasticity results were performed. According to the results of the analyses, it was determined that there is a strong relationship between the static and dynamic modulus of elasticity.