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Nondestructive methods are a fast and accurate way to obtain information about the mechanical properties of plywood panels. The objective was to determine the modulus of rupture and compare the modulus of elasticity (MOE) in plywood boards made with Pinus spp. and Eucalyptus urograndis using the destructive method of three-point static bending and the nondestructive method of ultrasound in parallel and perpendicular directions, as well as in complete board and test specimens, both with the ultrasound method and the correlation between the variables studied. The plywood boards evaluated were 18, 25 and 30 mm nominal thickness. Five structures were evaluated using pine and pine–eucalyptus veneers. Three boards were collected per structure, and 28 specimens were made from each board (14 in a parallel direction and 14 in a perpendicular direction). The elastic modulus was determined by the ultrasound method in complete plywood boards and in specimens obtained from them using the IML Micro Hammer® equipment and through the conventional bending test, carried out in an Instron® universal mechanical testing machine. The Tukey test of means (p < 0.05) shows that in the nominal thickness of 18 mm, the modulus of elasticity by ultrasound was lower compared to the result obtained by static bending in four of the five structures in the perpendicular direction and lower in all the structures evaluated in the parallel direction; while in the nominal thickness of 25 and 30 mm, it was greater in all structures and in both directions. The results of static bending by ultrasound, in complete boards and specimens, show that the only significant difference (p < 0.05) occurs in the nominal thickness of 30 mm in the treatment made with pine–eucalyptus with urea formaldehyde resin being lower in the parallel direction and in complete boards The correlation between the modulus of elasticity determined on specimens using the nondestructive method and the destructive method was r = 0.75 and Pr < 0.05; while comparing the nondestructive method on test specimens and complete plywood panels, r = 0.73 and Pr < 0.05 were obtained. It is concluded that the mechanical bending property of plywood boards can be characterized by the ultrasound method. [ABSTRACT FROM AUTHOR]

Concrete can be cast and cured at freezing temperatures when additive-based freeze protection (ABFP) is included in the concrete mixture. However, the effects of extremely cold temperatures on the mechanical properties of concrete with ABFP have not been studied. In addition, the impact of cold temperatures on shear strength and modulus of rupture of concrete with or without ABFP have not been measured. The present study measures the effects of decreasing temperatures on the compressive strength, modulus of elasticity, shear strength, and modulus of rupture of concrete with and without ABFP. Different types of aggregates and ABFP systems were used to manufacture conventional concrete (without ABFP) and concrete with ABFP. Concrete with ABFP is mixed, cast, and cured at −5°C and conventional concrete, at 20°C. Specimens are conditioned at 20°C, −5°C, −20°C, −40°C, or −60°C for 24 h and then tested. Generally, it was found that the mechanical properties of both types of concretes increased as the test temperature decreased. However, ABFP lowers the pore solution's freezing point and lowers the relative compressive strength increase rate compared with conventional concrete. Concrete with ABFP can have a higher rate of increase in relative elastic modulus than conventional concrete. This is due to the two-phase system of an ABFP pore solution at low temperatures, where ice fills voids, and the unfrozen concentrated pore solution continues to fill capillary voids and wet calcium silicate hydrate. The increase in shear strength from the aggregates and hydration products is greater than the contributions of the pore solution's frozen properties. Finally, the rise in rupture strength is attributed to the increase in the strength of concrete materials because there is no significant change in the tensile strength of ice with decreasing temperature. [ABSTRACT FROM AUTHOR]

The feasibility of using the Semicircular Bending (SCB) test to control the quality of concrete for application in pavements was investigated. Two concrete mixtures incorporating high-strength cement with specified compressive strengths of 30 MPa and 40 MPa were manufactured. The results of the SCB test were correlated with those of the flexural strength of standardized beams and the compressive strength of cylinders. A statistical analysis of the goodness of fit of all the empirical models obtained was conducted to study the degree of association between the variables. Power models were the most appropriate to relate the mechanical properties studied, with Pearson's correlation coefficients higher than 0.93. These equations can feed the database of levels 1 and 2 of the Mechanistic-Empirical (ME) design method for concrete pavements. Models with unique values that allow quick calculations with good precision were also found. The results show that the SCB test is a promising option when estimating the flexural strength of concrete for use in pavement, as well as carrying out its control and quality assurance. [ABSTRACT FROM AUTHOR]

Tropical hardwoods, often used as outdoor wood products, are frequently exposed to the hot and humid conditions in Malaysia. This has led to many studies attempting to develop suitable coatings and establishing maintenance cycles so that product service life can be extended. The objective of this study was to evaluate the surface quality and mechanical properties of both uncoated and coated three Malaysian hardwood species, namely dark red meranti (Shorea spp.), keruing (Dipterocarpus spp.) and keranji (Dialium spp.) after exposure to outdoor condition at different time spans. Surface quality of uncoated and coated with exterior transparent alkyd finished of the samples was evaluated visually as well as employing a profilometer-type equipment. Bending characteristics of outdoor exposed samples were also tested. The results showed that the surface of all coated samples degraded after 48 months of exposure. In addition, after 48 months of outdoor exposure, the modulus of rupture (MOR) values for dark red meranti, keruing and keranji decreased by more than 15% while the modulus of elasticity (MOE) values decreased by approximately 20% for both uncoated and coated samples. Generally, refinishing and maintenance should be performed within 2 years, and the cost of the maintenance should be calculated to ensure that the condition of the wood remains suitable for use as a building material in Malaysia's climate conditions. [ABSTRACT FROM AUTHOR]

Recycling crushed clay bricks (CCB) in concrete is a sustainable and cost-effective process. Huge quantities of crushed clay bricks waste cause many serious environmental problems around the world. To deal with this problem, crushed bricks were recycled in the concrete industry as an alternative to natural resources, and the brick powder was reused as a partial replacement for cement. The objective of this paper is to study the effect of crushed clay bricks on the characteristics of concrete. 7 concrete mixtures containing coarse crushed brick aggregate (CCBA) and fine crushed brick aggregate (FCBA) were prepared as a complete substitute for sand and dolomite, respectively. Clay brick powder (CBP) and silica fume were used as a partial substitute for cement by 5%, 10%, and 15% of its weight. The water-to-cement ratio was 0.35. For comparison, a control mixture was prepared. Various tests were conducted to evaluate the performance of concrete. The results showed that the workability of the different mixtures containing CCB decreased compared to that of the reference mixture. The compressive strength values of mixtures containing CCBA had a clear decrease compared to the reference mix at 7, 28, and 56 days of curing. The modulus of rupture results had the same path as compressive strength results. The thermal conductivity coefficient for mixtures including CCBA decreased compared to the control mix. Scanning Electron Microscope images indicated crystals of calcium silicate hydrate because of the pozzolanic interaction between the brick powder and the fine crushed clay bricks with calcium hydroxide. [ABSTRACT FROM AUTHOR]

In the last two decades, the utilization of timber in construction has gained increasing attention among researchers and sustainable building designers. Therefore, studies of climate impact on timber structures have been conducted, many of them focusing on the moisture content caused changes in timber. In the present study, four-point bending tests have been performed on three testing groups, containing 30 samples each. The first group has been tested under its natural conditions, while the second and the third groups were fully saturated with water. The third group was glazed with a protection material. The results show the changes in the modulus of elasticity and the modulus of rupture caused by the moisture content increase. In the same time the material behavior changed from brittle to semi-ductile or ductile for some samples. [ABSTRACT FROM AUTHOR]

Predicting the initial crack load in concrete is important to detect early warning of a problem. In this study, a model for predicting the first crack load on a hollow-cored rectangular beam point loaded at mid-span was developed by combining a numerical method and an experimental approach. The modulus of rupture was introduced into the governing moment-curvature relationship. Experimentally, flexural testing with point loads at mid-span was performed on fifteen (15) beams made up of three (3) beam types at 1 kN intervals for a span of 750mm using the Universal Testing machine. The beams were simply supported by roller points. The dimensions of the beams were kept constant and later varied while investigating the following hollow diameters: 0, 30, 60, 75, and 105mm. Numerically, the beams were designed as a beam element point loaded at mid-span with a span of 700mm centers, and the support conditions were defined as pinned support. Governing equations relating failure load with the modulus of rupture, stiffness matrix, shape functions, and moment of inertia were developed. The equation for predicting the first crack load, incorporating the modulus of rupture, was derived. The moment of inertia was calculated by discretizing the hollow-cored beam section using an isoparametric geometric transformation. The experimental results were used to validate the numerical model. 90.55% agreement between experimental and numerical results was observed. The overall average percentage difference between the two methods recorded is 9.45%. This shows that at about 91% confidence level, both approaches are the same and can be applied with confidence in the prediction of the first crack load on hollow-cored reinforced concrete beams. [ABSTRACT FROM AUTHOR]

The physico-mechanical quality of the seed bed is extremely important not only for the soil air-water dynamics, but also for the germination, seedling emergence, and development of the plants. The crust layer formed after precipitation and irrigation in soils with poor structural properties is among the most important indicators of the lower seedbed quality. While there are different applications to increase the physico-mechanical quality of the seedbed, there are also cement applications that provide rapid aggregate formation and stability. The effects of cement application on the soil mechanical quality and seedling emergence of clay textured soil with poor structural characteristics were investigated in the present study. For this purpose, a total of 36 small plots with a size of 2.4 m2 were created. Cement was applied at 0.25–0.5–1 and 2% doses to 18 plots in the fall period, and to the other 18 plots in the spring period. After the treatment, soil samples were taken for analysis before the planting period and the number of seedling emergence was determined by planting the bean plant during the planting period. According to the results of the study, it was found that cement applied in two periods caused an increase in soil aggregate stability, decreased penetration resistance, modulus of rupture, and dispersion rate, and increased water holding capacity to a limited extent. On the other hand, cement application also had positive impacts on the emergence of the bean plant. The 1% dose of the spring application of cement was more effective on the determined soil structural characteristics and seedling emergence. [ABSTRACT FROM AUTHOR]

This study analyzed the diversity of physical properties and mechanical properties of white jabon (Neolamarckia cadamba (Roxb.) Bosser) from various locations and ecological conditions in West Java and Banten Indonesia. White jabon wood samples were taken from 8 locations in West Java and the Banten region. Tree ages ranged from 5 to 6 years. This wood was then tested to compare physical characteristics (density or specific gravity) and mechanical characteristics (modulus of rupture (MOR) and modulus of elasticity (MOE)). The results showed that wood density ranged from 0.29 to 0.43 g.cm-3, MOR ranged from 361 to 641 kg.cm-2, and MOE ranged from 31,117 to 58,910 kg.cm-2. The highest density average (0.43 ± 0.004 g.cm-3) was produced from Cianjur, and the lowest density average (0.29 ± 0.010 g.cm-3) was from Tanjungsari Sumedang. Environmental factors (precipitation and altitude) affect the density of wood. Separately, rainfall has a low effect and a negative relationship to jabon wood density, while altitude has a high influence and a negative relationship to jabon wood density. Andosol soil types tend to produce low density wood. [ABSTRACT FROM AUTHOR]

Concrete pavements develop cracks with the accumulation of fatigue damage caused by the combined effect of vehicular and environmental loadings. In Mechanistic-Empirical (ME) design, the ratio of stresses to some measure of strength is used to evaluate incremental damage, which is then related to cracking. Typically, this measure is the Modulus of Rupture (MOR) of a beam made of the same material. The flexural strength is also known to vary with the thickness of the beam. However, the variation of flexural strength due the presence of eigenstresses from temperature or moisture distributions has not received sufficient attention. A non-linear fracture mechanics model demonstrated that the thickness-adjusted flexural strength can also be used for characterising the maximum elastic stress under a linear temperature distribution. However, under a non-linear temperature distribution, the material may sustain a higher or lower maximum elastic stress than the flexural strength. To model this, a practical analytical expression for the apparent flexural strength was derived and showed excellent agreement with numerical simulations as well as with a model based on equivalent elastic deformation energy. The model was used to show that the fatigue capacity under a typical axle load varies with various non-linear temperature distributions. [ABSTRACT FROM AUTHOR]

In a context where there is an increasing need for thermal treatments of wooden products, the current research contributes a description of the torrefaction treatment of two of the composite wood materials available on the international market. The present paper presents the importance of the torrefaction process for poplar plywood and medium-density fiberboard. In this paper, the positive aspects of the torrefaction process (decrease in water absorption, thickness swelling and shrinkage, and color) but also the negative aspects of mechanical resistance to static bending are presented. Poplar plywood (PW) and medium-density fiberboard (MDF) panels, with the initial dimensions of 2000 × 1250 mm, were used. From these, 300 × 300 mm samples were cut and torrefied using two different temperatures (170 and 190 °C) and two different periods (for 1 and 2 h). After the treatment, the samples were cut in different sizes (as necessary for each type of evaluation method) from different zones of the panels and used to evaluate the water absorption and thickness swelling, to determine their modulus of rupture, roughness, and color changes. The obtained results emphasize that the mass loses increase at high temperature as the main disadvantageous characteristics of torrefaction. Also, while the calorific power increases with the increase in the parameters of the torrefaction regime, the hygroscopicity and some mechanical properties of the material simultaneously decrease. [ABSTRACT FROM AUTHOR]

Pervious concrete (PC) has gained popularity as an environmentally friendly solution for mitigating the urban heat island effect and promoting sustainable construction. However, its lower compressive strength, attributed to its higher porosity required for permeability, poses challenges for withstanding heavy vehicle loads on pavements. Our study aims to improve the flexural strength of regular PC by adding advanced reinforcing materials like steel wire mesh or glass fiber mesh. This results in reinforced pervious concrete, referred to as RPC, which offers enhanced strength and durability. The primary objective of our research is to investigate the mechanical behavior of RPC, with a specific emphasis on essential design parameters such as PC elastic modulus, modulus of rupture, and stress–strain characteristics under both single and repeated loading conditions. Our findings reveal that the influence of repeated loading on the compressive strength and elastic modulus of PC pavement is negligible, as there are no significant differences observed between the two loading protocols. Notably, our statistical analysis indicates that the PC strength (fc′) averages around 15 MPa. Moreover, empirical formulas for the elastic modulus (Ec = 3072 f c ′ ) and modulus of rupture (fr = 0.86 f c ′ ) are derived from our research. Furthermore, our study establishes that the stress–strain behavior of PC closely aligns with the general concrete model proposed by a previous scholar, providing valuable insights into the material's structural performance. These findings contribute to a better understanding of RPC's mechanical properties and offer potential solutions for improving its suitability for heavier vehicular loads. [ABSTRACT FROM AUTHOR]

The effect of nanocellulose on mechanical, physical, and morphological properties of composites made of walnut shell and cement was investigated. The mixing ratio of walnut shell as a lignocellulosic material with cement at three levels (10:90, 20:80, and 30:70) and nanocellulose at three levels (0%, 1%, and 3%, based on dry weight of cement) were considered as the variables. Boards were prepared according to the ISO 11925-2 (2020) specifications for the fire resistance properties and according to the DIN EN 634-1 (1995) specifications for the mechanical and physical properties. Morphological properties of composites and nano distribute were evaluated by scanning electron microscopic (SEM) imaging. The results showed that boards containing nanocellulose increased the mechanical properties compared with cement board without nanoreinforcement. The modulus of rupture, modulus of elasticity, and internal bonding of the boards decreased with increased walnut shell amount, and its maximum value was obtained when using 10% walnut shell. Nanocellulose remarkably reduced the fire resistance of the boards. The results from SEM showed that nanocellulose can fill the pores of the composite and create a uniform structure, and thus improved the strength of the boards. [ABSTRACT FROM AUTHOR]

The air voids in the bituminous mix are filled with a cementitious grout to create cement grouted bituminous (CGB) mix, which is a semi-flexible material. The material has a high resistance to permanent deformation at high temperatures and under heavy loads because of the cementitious grout used in the mixture. Despite their increased brittleness, CGB layers are more prone to cracking when used as thin (40–60 mm) surface or base layers. Increase in binder content in mix decreases air void content and grout content, which leads to reduction in rutting resistance and expected to improve the fatigue cracking resistance. The results of an investigation into the impact of aggregate gradation and binder content on the fatigue performance of CGB mixes are presented in this paper. In a four-point bending test mode at 25 °C, beam specimens of CGB Mixes made with four different aggregate gradations and four different binder contents were tested at four strain levels. The fatigue life measured at higher strain levels of 225 and 250 µε and various mechanical properties like indirect tensile strength and modulus of rupture showed good correlation. By analysing pavements with CGB layers used as the base or surface layer, the fatigue cracking susceptibility of the CGB layer in a typical highway pavement has been determined. It has been found that using the CGB mix as the surface layer is a good choice because the mix also provides a very strong rut as well as an oil and chemical-resistant layer. [ABSTRACT FROM AUTHOR]

The most widespread wood species in the Portuguese forest and the most widely utilized are maritime pine (Pinus pinaster) and eucalyptus (Eucalyptus globulus Labill). In the case of eucalyptus, except for the pulping sector, it might have limited usage due to drying issues and low permeability. Microwave (MW) treatment is a technology that has been used to improve wood species' permeability. Therefore, the present paper aimed to evaluate the MW treatment of both Portuguese wood species and to investigate the effects of different MW treatments on wood's density, water uptake capability, modulus of rupture (MOR), and modulus of elasticity (MOE). Using small clear wood specimens, two MW powers were used, 700 and 1200 W, and the samples were submitted to successive MW cycles of 2 min till they reached the required dryness. The results showed that each wood species had a different behavior during the MW drying in terms of drying rate, supply, and consumption of energy. In general, with the increase in MW power, the densities of both species decreased and the water uptake increased, as a possible indicator that a certain level of microstructural damage might have occurred. Regarding the mechanical properties of MW-treated maritime pine and eucalyptus wood specimens, under the harshest conditions (MW power of 1200 W), MOR and MOE were reduced compared with the wood sample without MW treatment. [ABSTRACT FROM AUTHOR]

A full factorial experiment was conducted to analyze the main and interaction effects on the physical and mechanical properties of Cupressus funebris Endl. wood subjected to vacuum heat modification. The response variables evaluated were mass loss rate (ML, %), moisture resistance (MR, %), and modulus of rupture in bending (MOR, MPa). The results reveal significant variations in the effects of modification time, holding temperature, and vacuum pressure as independent factors, along with varying degrees of interaction effects among them. Simplifying the analysis model, a regression equation was derived to describe the relationship between the response variable (mass loss rate) and the factors: The model achieved an R-squared value of 96.0% and an R-squared (predicted) value of 73.7%, indicating good overall predictive performance. Optimal process parameters for mid-temperature vacuum heat modification of cypress were determined based on the mass loss rate and modulus of rupture (MOR), resulting in a modification temperature of 120 °C, holding time of 5 h, and a pressure intensity of 0.1. The reliability of the full factorial experiment was further confirmed through orthogonal testing. [ABSTRACT FROM AUTHOR]

The effects of cattail/poplar straw weight ratio, sandwich panel thickness, and the number of kraft paper layers at the core of sandwich panels on the modulus of rupture (MOR) of the panels were predicted using an artificial neural network (ANN) and an adaptive neuro-fuzzy inference system (ANFIS). The prediction accuracy of the MOR based on experimental data, in terms of the mean absolute percentage error, was smaller than 1.4 and 1.1%, with coefficients of determination 0.94 and 0.995 for the ANN and ANFIS models, respectively. These models can easily predict the bending strength of lignocellulosic-based sandwich panels with a high precision in the manufacturing process. [ABSTRACT FROM AUTHOR]

Copyright of Refractories / Naihuo Cailiao is the property of Naihuo Cailia (Refractories) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Restricted formaldehyde gas emissions and a scarcity of lignocellulosic raw materials have particleboard companies in Iran concerned about raw materials and adhesive use. The particle slenderness ratio is one of the main parameters that leads to the required mechanical characteristics of particleboard, together with the simultaneous decrease of density (raw materials) and the quantity of adhesive. The objective of this study was to evaluate the mechanical properties of particleboard composed of poplar particles with variables of density, adhesive quantity, and slenderness ratio using response surface technique. The variables were then optimized for the examined responses according to the EN 312-3 (1993) standard for the manufacturing of particleboard for domestic use as well as home and office furniture. Particleboard with minimum allowable properties according to EN 312-3 (MOR = 11 MPa, MOE = 1.6 GPa, and IB = 0.35 MPa) with a density of 0.65 g/cm3, adhesive percentage of 10.54, and a slenderness ratio of 37.5 can be produced, according to optimization findings. Through raising the density to 0.69 g/cm3 and the slenderness ratio to 46.99, the quantity of adhesive utilized in particleboard manufacturing could be decreased from 10.54 to 8.9% while keeping the minimum allowable resistances of EN 312-3 (1993) standard. [ABSTRACT FROM AUTHOR]

Due to the high cost of laboratory testing, many researchers are considering developing methods to predict the behavior of unreinforced and reinforced wood beams. This work aims to create either numerical or analytical models useful for extrapolating already conducted tests to other schemes/materials used as reinforcement. In the case of timber structures, due to the complexity of timber, this task is difficult. The first part of the article presents an analysis of the suitability of using a simplified mathematical model based on the equivalent cross-section method to describe the behavior of unreinforced and reinforced with carbon-fibre-reinforced polymer (CFRP) composite full-size laminated veneer lumber (LVL) beams. The theoretical results were compared with the results of conducted experimental tests. The scope of the analysis includes the estimation of modulus of rupture, bending stiffness, and determination of the neutral axis position. The equivalent cross-section method showed good agreement in determining the bending stiffness and neutral axis position of the strengthened sections. However, the suitability of using the equivalent cross-section method to estimate the load-carrying capacity of a cross-section reinforced with fiber composites still needs to be confirmed, which, according to the authors, is due to the differences between the assumed (linear) and actual (nonlinear) strain distribution in the compression zone. The second part uses the equivalent cross-section method to estimate the predicted bending stiffness of LVL beams strengthened with aramid-fibre-reinforced polymer (AFRP), glass-fibre-reinforced polymer (GFRP), and ultra-high modulus carbon-fibre-reinforced polymer (CFRP UHM) sheets. The proposed method can be used for preliminary evaluation of strengthening effectiveness of LVL beams. [ABSTRACT FROM AUTHOR]

Copyright of Ingeniería Solidaria is the property of Universidad Cooperativa de Colombia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Concrete is the most widely used construction material throughout the world. Extensive experiments are conducted every year to study the physical, mechanical, and chemical properties of concrete involving a hefty amount of money and time. This work focuses on the utilization of Machine Learning (ML) algorithms to predict various concrete properties for avoiding unnecessary experimentation. In this work, six mechanical properties of concrete namely modulus of rupture, compressive strength, modulus of elasticity, Poisson's ratio, splitting tensile strength, and coefficient of thermal expansion are estimated by applying five different ML algorithms viz. Linear Regression, Support Vector Machine, Decision Tree, Random Forest, and Gradient Boosting models on the Wisconsin concrete mixes database. Further, these ML models were evaluated to identify the most suitable model that can reliably predict the mechanical properties of concrete. The approach followed in this research was verified using the 10-fold Cross-Validation technique to eliminate training and testing split bias. The Grid Search Cross Validation method was used to find the best hyperparameters for each algorithm. Root mean squared error (RMSE) and coefficient of determination (R2) results showed that the Support Vector Machine outperformed the other models applied on the datasets. Support Vector Machine predicted the modulus of rupture of concrete after a curing time of 28 days with an R2 score of 0.43, which is better than the R2 scores of Random Forest and Gradient Boosting advanced algorithms by 34% and 26%, respectively. [ABSTRACT FROM AUTHOR]

Glued laminated (glulam) beams are used in the roofs, ceilings and walls of buildings as well as in bridges and towers. At present, with the limitation of tree harvesting, the production of glulam beams from recycled wood sources is implemented with the proviso that their mechanical properties and resistance to pests, fire and weathering will not be aggravated. This work deals with the primary effect of aging Norway spruce wood (Picea abies Karst. L.) lamellas on the moduli of rupture (MOR) and elasticity (MOE) in bending of three-layer glulam beams composed of sound and aged lamellas and polyurethane (PUR) glue. Three methods of lamella aging were used: (A) natural, lasting 60 years in the form of roof trusses with a greater or lesser degree of bio-attack by woodworm (Anobium punctatum De Geer); (B) artificial, caused by increased temperatures from 160 to 220 °C for 4 h; (C) artificial, caused by 2% water solutions of inorganic preservatives, namely, CuSO4 × 5H2O, ZnCl2, H3BO3 or (NH4)2SO4, for 28 days. The lowest MOR values were determined for glulam beams in which all three lamellas or two surface lamellas had a greater degree of bio-attack (60.5 MPa, a decrease of 25.9%) or were exposed to primary aging at 220 °C (62.6 MPa, a decrease of 23.3%). On the contrary, the exposure of lamellas to 160 or 180 °C did not significantly influence the MOR of beams (76.0–82.7 MPa, an average decrease of 1.6%). The MOE of glulam beams ranged from 7540 to 10,432 MPa without an obvious influence of the method of lamella aging or their location in the beams. Linear correlations between the MOR or MOE of glulam beams and the shear strength (σ) of glued joints, if both composite types consisted of similarly aged lamellas, were only slightly significant or insignificant. [ABSTRACT FROM AUTHOR]

In this study, the effect of bacteriacellulose nano fiber gel as reinforcement on physical, mechanical and morphological properties of composites made of bagasse and cement was studied. Nano fiber in three levels (0, 1 and 3% by weight of cement), the mixing ratio of bagasse as lignocellulosic material - Portland cement, in three levels (90:10, 80:20, 70:30%) were the variable factors. The target density of 1.1 g/cm³ and 5% calcium chloride were kept constant for all treatments. The mechanical and physical properties of composites including modulus of rupture, modulus of elasticity, internal bonding, thickness swelling after 2 h and 24 h immersion in water and density of boards were measured according to the standard DIN-EN-634. In this study, the morphological charecteristics of composites and the distribution of nano fibers was investigated using SEM microscopic images) taken from the fractured cross-section of the samples. The results showed that boards made using bactericellulose nano fiber are exhibit higher modulus of rupture, modulus of elasticity and internal bonding. The results also showed that with increasing nano fiber, the density, dimensional stability of the boards and heat hydration of cement mortar increased. The results from SEM microscopic imaging showed that bacteriacellulose nanofiber can fill the pores of the composite and create a uniform structure, thus improved strength of the boards. [ABSTRACT FROM AUTHOR]

This paper investigates bending and compressive strengths as mechanical characteristics of cement-based repair mortar containing nano-silica (NS) and micro-silica (SF) as cement replacements particles and polyvinyl alcohol (PVA) fibers. The mentioned materials were added to the mortar in three different conditions, including single (just one material), binary (mixture of two admixtures), and ternary (mixture of all three admixtures) modes. The use of PVA fibers, nano-silica and micro-silica in the triple combination of a cement-based mortar is the primary objective of the current research. In total, 28 mix designs with various percentages of particles and fiber were employed in the current study, and 112 different specimens were prepared to conduct the experimental research. The compressive and flexural strength results have been selected as the criteria for obtaining the optimum mix design for each condition. In order to specify the mechanical characteristics of specimens, a compressive test was carried out according to ACI 318, and the three-point bending test was utilized according to BS EN 1015-11. The results obtained from this study show that the mixture containing 10% silica fume (SF10) can be considered the optimum mix design for the single-mode condition. For such a mix design, a flexural strength increase of 27% and a compressive strength improvement of 48% were determined in comparison to the reference mixture design. The mixture containing nano-silica at 2% and silica fume at 8% (NS2SF8) was the optimum mix design in the binary mode condition. With the current mix design, a flexural strength improvement of 24% and a compressive strength increase of 49% in a 28-day specimen were recorded. Finally, under the ternary mode condition, a flexural strength enhancement of 3.5% and a compressive strength improvement of 4.6% were obtained. Additionally, the mixture design containing a PVA content of 0.75% and an SF content of 10% (PVA0.75SF10) was considered optimum. [ABSTRACT FROM AUTHOR]

The main goal of the present research is to investigate the possibility of recycling agricultural residues for producing different types of pressed wood. All experimental work was conducted using a mixture of wood saw dust + linen sass + corn stalks with equal percentages, to produce samples of different types of pressed wood. The main experiments were carried out to control and study the effect of some different operating parameters (pressing pressure (1, 3, 5, 7 MPa), pressing time (5, 10, 15, 20 min.) and resin type (Urea formaldehydes and Speria formaldehyde) affecting the pressed wood production processes. The produced pressed wood was evaluated taking into consideration physical properties (Density, thickness swelling and water absorption), mechanical properties (Modulus of elasticity, modulus of rupture, and internal bond strength) and final product quality. The obtained data reveal that the produced pressed wood quality were meeting the required physical and mechanical properties as stated in the standard quality guidelines under conditions of 5 MPa pressing pressure and 15 min.. pressing time with the use of urea formaldehyde resin. The findings also illustrated that by controlling both pressing pressure and pressing time, a mixture of wood saw dust + linen sass + corn stalks with equal percentages could be used to produce different types of pressed wood (Particleboards, PB; Medium density fiberboards, MDF and High density fiberboards, HDF). [ABSTRACT FROM AUTHOR]

Efforts have been dedicated to developing sustainable alternatives for conventional construction materials, resulting in the development of densified wood as an innovative, environmentally friendly, and high-performance material. This study focuses on investigating the effects of treatment parameters (e.g., partial delignification boiling time, chemical concentrations, and hot-pressing pressures) on the chemical, morphological, and mechanical properties of the densified wood. Results revealed that the partial delignification process of low-density Balsa wood reduced lignin content by 50–80%, which enhanced the crystallinity of the wood by 21–54%. However, prolonged periods of partial delignification caused a degradation in the crystalline regions in wood. The modulus of rupture (MOR) and modulus of elasticity (MOE) of the densified wood samples increased by 90–680% and 10–810% compared with those of the raw wood samples, respectively. The MOR of the densified wood also showed a dependency on lignin content and porosity. An optimal lignin content of approximately 10% was associated with the highest MOR in densified wood. Moreover, the relationship between the MOR and porosity suggested that the MOR improvement occurred in two stages. The first stage of MOR improvement is controlled by the reduction in the porosity and the second stage is controlled by the improved hydrogen bonding among cellulose nanofibrils. • Partial delignification reduced lignin content and enhanced crystallinity of wood. • Strength was largely improved through chemical treatment and hot pressing. • Prolonged boiling treatment degrades wood crystalline structure. • Porosity reduction and enhanced nanofibril bonding control strength of treated wood. [ABSTRACT FROM AUTHOR]

This paper studies the effect of thermal cyclic loading on the mechanical properties of concrete such as cylinder and cube compressive strength, splitting and flexural tensile strengths, and weight loss. The specimens were exposed to 7–28 thermal cycles with peak temperatures of 100, 200 and 300 °C. A total of 120 specimens consisting of cubes, cylinders and prisms were tested in this study. The compressive strength of concrete enhances up to 7 or 14 thermal cycles and subsequently decreases but remains greater than the strength at ambient temperature at all temperature levels. The test results highlight the difference in compression behaviour of concrete cylinders and cubes. The effect of thermal cycles on splitting tensile strength of concrete is more pronounced than its effect on the modulus of rupture. Although the splitting tensile of concrete decreases with rise in the peak temperature and number of thermal cycles, the modulus of rupture increases up to seven cycles for exposure to the temperature cycles of 100 and 200 °C, which is even higher than the control. Models are developed to predict residual mechanical properties of concrete after exposure to the thermal cycles, which show close conformance with experiments. [ABSTRACT FROM AUTHOR]

This paper focuses on developing ultra-high-strength concrete (UHSC) with mechanical properties comparable to those of ultra-high-performance concrete (UHPC) and with production procedures similar to those used for high-strength concrete. A concrete mixture was developed to achieve a compressive strength of 17 ksi (117 MPa) at 28 days without using silica fume and with a slump flow as high as 35 in. (889 mm). Another concrete mixture with compressive strength of 20 ksi (138 MPa) was designed using only 130 lb/yd3 (77.1 kg/m3) of silica fume. In addition to these two mixtures, a UHPC mixture was also designed with a compressive strength of 24 ksi (165 MPa). Laboratory tests were conducted to investigate predictions of modulus of elasticity, flexural strength, creep, and shrinkage for the developed mixtures. This paper demonstrates that using UHSC and 0.7 in. (18 mm) diameter strands will produce adequate flexural strength to design 300 ft (91.4 m) long prestressed concrete I-girders that have service stresses within safe limits. [ABSTRACT FROM AUTHOR]

The increase in world population has led to a significant increase in the numbers of cars and used tyres. These tyres must be disposed of on an ongoing basis as a result of their consumption or deterioration. This can result in negative effects on the environment that must be preserved, especially from those materials, i.e., these waste materials are difficult to dispose of without special treatments. Hence, extensive experimental investigations and numerical simulations need to be conducted to use and recycle these wastes by exploring the possibility of using them as alternative ingredients in construction materials. For example, waste rubber pieces can be used as one of the main components of concrete. In this study, the main aim was to numerically simulate the flexural behaviours of rubberised concrete under the influence of an applied vertical loading with different contents of added rubbers by using the commercial finite element software ANSYS. The obtained numerical results were compared with the experimental results of a previous study and showed a good agreement with the deflections and moduli of rupture, with the variances from 2–7% in the deflections. However, the differences in the moduli of rupture varied between 5% and 9%. Finally, the statistical analyses indicated that these numerical mean values and standard deviations were acceptable and were very close to the experimental values. [ABSTRACT FROM AUTHOR]

Many thermal and chemical treatments are known to inhibit wood decay despite the wood grade processed, but their impact, e.g., chemicals’ leaching and decay resistance, may not be similar. The aim of this study was to test whether some model treatments retain their performance in different wood species. Additionally, the effects of thermal modification and linseed oil-based varnish treatments as means to mitigate water-soluble chemicals leaching were assessed. The mass loss caused by Trametes versicolor was measured after a 12-week exposure to analyze whether the different treatment approaches prevented the fungal decay after a standard leaching test. The mechanical properties before and after exposure were tested independently to determine whether the mechanical properties of different wood species were affected by the tested treatments and wood decay. The responses of the tested wood species were found to vary by treatments, but thermal and chemical fixation methods for water-soluble tannins were beneficial in all cases considering the mass loss and the degradation of modulus of rupture and modulus of elasticity of treated wood. Varnish was overall the most effective treatment against decay, but the results emphasize the need for testing potential preservation methods and chemicals on several species. [ABSTRACT FROM AUTHOR]

Recycled waste materials are increasingly being used as low carbon construction materials in civil infrastructure works, as recycled materials have significant carbon savings compared with virgin quarried materials. In this research, the stiffness and modulus of rupture properties of crushed rock (CR) blended with recycled glass (RG) were evaluated. The engineering properties of the four cement-treated CR/RG blends evaluated were: 100% CR100 (100CR), 90% CR with 10% RG (CR90/RG10), 80% CR with 20% RG (CR80/RG20), 70% CR with 30% RG (CR70/RG30). 3% dosage of general blend (GB) cement was used in all the RG/ CR blends. The results indicated that cement-treated RG/CR blends, with up to 20% RG, are suitable as pavement subbase materials. Unconfined compression strength (UCS) values met the minimum requirement for 7 days of curing for all the CR/RG blends. The results of repeated load triaxial (RLT) tests and flexural beam tests were found to be within the ranges reported for the previous testing on other accepted recycled and quarry products. Based on this laboratory assessment, RG can be recommended for incorporation as a supplementary material in cement-treated CR pavement applications, which will increase the uptake of recycled products as a civil engineering construction material. [ABSTRACT FROM AUTHOR]

Although the uniaxial tensile strength (ft) of concrete is one of the most essential properties in designing and analyzing the tensile performance of a concrete member, a rational consensus to assess it is still lacking because of experimental difficulties. The objective of the present study is to generalize ft through mathematical analysis based on the plasticity of concrete. The principle of equivalent resultant tensile forces at failure planes is introduced to straightforwardly determine the splitting tensile strength (fsp) and modulus of rupture (fr) from ft. The accuracy and reliability of the proposed equations are confirmed at different ranges of the compressive strength and unit weight of concrete by comparing with test data, including 219, 674, and 242 data sets for uniaxial tension tests, splitting tension tests, and flexural tests, respectively. Thus, the present mathematical approaches proved the significance of considering the concrete unit weight and maximum aggregate size in predicting the tensile resistance capacities of the concrete. However, with the variations of the compressive strength and unit weight of concrete, the empirical equations recommended in previous studies and code provisions are insufficient. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate some mechanical properties of OSB/3 after one to ten cycles of soaking and oven/drying (accelerated aging). The modulus of rupture (MOR), modulus of elasticity (MOE), found by 3-point bending and screw withdrawal load (SWL), were determined in dry and wet conditions in the face and back surface, and in the cutting edge. The specimens were soaked for 24 hours and dried for 48 hours in a ventilated drying box. The MOR, MOE and SWL values dropped significantly after the first cycle, continued to decrease after three cycles and stabilized in the last cycles of soaking and drying. The surface and cross-sections of the samples were also studied using the X-ray technique. This analysis explained a significant decrease in the values of the studied properties after the first soaking cycle as a result of non-restored plastic deformation of the resin matrix. The low retention values of the studied properties could raise the durability issue of the investigated commercial OSB/3 boards as they should be moisture resistant according to EN 300:2006. [ABSTRACT FROM AUTHOR]

Small-diameter logs are intended to function as high-value structural timber. Bending strength properties is an essential phenomenon for structural lumber. Herein, the modulus of elasticity, the modulus of rupture and the allowable bending stress (ABS) of domestic (Korea) small and large-diameter larch and large diameter Douglas fir timber were measured and compared according to the standard of ASTM D 2915. Samples were visually graded as Grade 1 to Grade 4 following the provisions included in KS F 3021.2013. The large-diameter Douglas fir timber (Grade 1 to Grade 4) exhibited the highest MOE value, but in Grade 4, it showed the lowest MOR value compared with the small and large diameter of larch timber. The ABS of small-diameter larch was 12.0 MPa, higher relative to KBC 2009 Grade 1 structural lumber (8.0 MPa). The ABS of large-diameter of larch and Douglas fir timber exhibited 15.5 and 18.1 MPa, respectively. [ABSTRACT FROM AUTHOR]

Liana abundance and biomass are increasing in neotropical and Asian tropical seasonal forests over the past decades. Stem mechanical properties and hydraulic traits influence the growth and survival of plants, yet the differences in stem mechanical and hydraulic performance between congeneric lianas and trees remain poorly understood. Here, we measured 11 stem mechanical and hydraulic traits for 10 liana species and 10 tree species from Bauhinia grown in a tropical common garden. Our results showed that Bauhinia lianas possessed lower stem mechanical strength as indicated by both modulus of elasticity and modulus of rupture, and higher stem potential hydraulic conductivity than congeneric trees. Such divergence was mainly attributed to the differentiation in liana and tree life forms. Whether the phylogenetic effect was considered or not, mechanical strength was positively correlated with wood density, vessel conduit wall reinforcement and sapwood content across species. Results of principle component analysis showed that traits related to mechanical safety and hydraulic efficiency were loaded in the opposite direction, suggesting a trade-off between biomechanics and hydraulics. Our results provide evidence for obvious differentiation in mechanical demand and hydraulic efficiency between congeneric lianas and trees. [ABSTRACT FROM AUTHOR]

The interrelationships among specific gravity (SG), modulus of elasticity (MOE), and strength (modulus of rupture, MOR) are largely the foundational basis for non-destructive evaluation and testing. Resource monitoring and commercial structural lumber production often rely upon such non-destructive evaluation to predict the bending and/or tension strength of individual members. These technologies require routine calibration. In addition, it is important to know the extent to which a given resource may change over time. To that end, this study investigated the relationship among SG, MOE, and MOR of small clear specimens from three samples taken across an approximate 50-year period; 1965 to 2018. Coefficients of determination among these variables are presented along with the prediction equations. These findings can be used to gain insight into the reliability and stability of these relationships over time. [ABSTRACT FROM AUTHOR]

The effects of a three-layer structure and age on the mechanical properties of moso bamboo were investigated. The ages of 1-, 3-, and 5-year-old bamboo were chosen to make test samples, and specimens from each age of moso bamboo were divided into three groups (raw bamboo, bamboo removed from outer layer, and bamboo removed from inner layer) for evaluation of modulus of rupture and parallel-to-grain compressive strength. The regression analysis was completed to evaluate the relationship between mechanical properties and bamboo age. The results showed that the age of moso bamboo was positively correlated with the flexural and parallel-to-grain compressive strengths. The mechanical strength of moso bamboo increased with the increased age of moso bamboo. For the moso bamboo with same age, the flexural and parallel-to-grain compressive strengths decreased for the samples without bamboo outer layer. However, for the samples without bamboo inner layer, the parallel-to-grain compressive strength remained unchanged, but the flexural strength increased. The outer layer of bamboo with high toughness and flexibility played an important role during bending. However, the inner layer of bamboo is relatively brittle, which has negative effects on its flexural strength. These results provide an important basis for the bamboo used in engineering. [ABSTRACT FROM AUTHOR]

The use of innovative technologies in building construction using locally available materials can lead to affordable housing and boost the socio-economic development of a nation. Laterite soils were stabilized with varying percentages (0, 2, 4 and 6%) of 1M phosphoric acid (H3PO4) and 5% lime to ascertain its suitability as sustainable material for hollow lateritic bricks production. The bricks were cured for 7, 14 and 28 days under ambient air condition. The compressive strength (fc), bulk density (pb), dry density (pd), modulus of rupture (fr). The results were a maximum fc of 0.93 and 0.87 N/mm2 at 5% lime and 4% H3PO4. Maximum pb and pd of 15.2 and 14.9 kN/m3, respectively were obtained at 4% H3PO4 stabilization. Maximum fr of 0.2 N/mm2 was obtained at combined 4% H3PO4 and 5% lime. In conclusion, the fc suggests that both lime and H3PO4 have great potential in stabilizing laterite soils. [ABSTRACT FROM AUTHOR]

This study aims to investigate whether it is possible to predict the modulus of elasticity (MOE) and modulus of rupture (MOR) of lumber produced from different heights using the stress-wave velocity of standing trees or the dynamic Young's modulus of logs in Siberian larch (Larix sibirica). A total of 190 pieces of lumber (38 by 89 mm in cross section) were cut from 111 logs obtained from 25 standing trees. Significant positive correlation coefficients were found between the stress-wave velocity of standing trees and MOE (r = 0.776) and MOR (r = 0.702) of this lumber. The dynamic Young's modulus of the logs also correlated significantly with MOE (r = 0.745) and MOR (r = 0.584) values. The results obtained in the present study suggest that stress-wave velocity and dynamic Young's modulus are useful for selecting superior trees in tree breeding and sorting logs for producing structural lumber. [ABSTRACT FROM AUTHOR]

Standard ceramic tiles doped with powdered, micro-sized lead oxide (PbO) were manufactured with weight fractions (2.5%, 5%, 7.5% and 10%) and investigated for γ-ray shielding ability. Several methods were used to characterize the newly fabricated ceramic samples. These included Fourier transform infrared spectrophotometer (FT-IR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), energy dispersive X-ray (EDX), scanning electron microscope (SEM) and high-resolution transmission electron microscope (HR-TEM). The mechanical properties of assembled ceramic composites were examined and their modulus of rupture (MOR) was calculated. Results revealed that the values of MOR varied between 1.884 and 2.158 MPa, as the content of PbO increased from 0.0 to 10.0 wt% in the ceramic body. Physical properties, such as density and percentage of water adsorption, were determined. To evaluate γ-ray attenuation coefficients (μ m) of the investigated samples, different energies in the range of 59.53–1332.50 keV were applied and a NaI detector was used to measure photon intensities, as a function of the weight percentage of PbO. Confirmation of the accuracy of these results was performed, when a comparison was made with the theoretical values obtained from the XCOM simulation code. Two more parameters were tested to ensure the shielding capabilities of the new composites, namely the half value layer (HVL) and the mean free path (MFP). These values were calculated to reveal that the ceramic composite containing 10 wt% PbO exhibited the highest μ m and lowest MFP and HVL values of all other tested composites. The outlined results confirm the significant improvement in γ-ray shielding properties of ceramic tiles as the wt% of PbO increased from 0.0 to 10.0 wt%. [ABSTRACT FROM AUTHOR]

Due to the availability, high tensile strength, cheapness, recyclability, and ecofriendly characteristics of the plant fibers, there is an interest nowadays for using them in the construction materials in order to improve the weak properties of several construction products and works. In this study, two types of plant fibers (sisal and hemp) have been added to pure gypsum in order to study their effects on some gypsum properties. Different volumetric percentages (0.3, 0.6, 0.9, 1.2 %) of each fiber type have been added to gypsum in order to produce several mixes. Moreover, silica fume has been added alone to gypsum with percentages of 1, 1.5, 3, 5 % by weight of gypsum, and it has been added to the mixes with the sisal fibers in order to study their common effect. A 5 cm cube specimen and prisms with dimensions of 5×5×30 cm have been used for testing the compressive strength and modulus of rupture respectively and for various curing periods of (2, 7, 30, 90) days. The results show that the addition of hemp and sisal fibers with percentages of no more than 0.3% for hemp and 0.6% for sisal can improve the compressive strength and the modulus of rupture of gypsum products. [ABSTRACT FROM AUTHOR]

Red oak and white oak are common names of species that grow in the eastern United States with great economic importance. This study aimed to evaluate the visual, physical, and mechanical properties of small clear wood specimens of red oak (Quercus spp.) and white oak (Quercus spp.). The experiments were carried out on defect-free specimens extracted from boards supplied by the Stairbuilders Manufacturers Association (SMA) members. The material was obtained from sawmills located in the eastern half of the United States. A total of 181 boards (90 boards of red oak and 91 boards of white oak) were submitted for tests. Compression strength was found to be higher than the values published in past studies. Red oak exhibited higher MOE and MOR values compared to white oak. The mechanical properties for red oak and white oak have not changed substantially because the average values remain in a range that is very close to the values published in the past 100 years. Thus, the values from the Wood Handbook can still be used for engineering purposes. [ABSTRACT FROM AUTHOR]

Rapid growth rates and the accompanying reduced rotation ages of forest plantations have resulted in increased proportions of juvenile wood. Growing space markedly influences growth rate and may be manipulated by stand density management. The objective of this study was to evaluate the effect of stand density on the modulus of elasticity (MOE), modulus of rupture (MOR) and other selected properties of young (16–20 years) South African-grown Pinus patula lumber. Thirty-seven trees from two commercial stands were processed into 71 logs, cant sawn into lumber and tested for MOE, MOR, wood density and distortion. The first stand was planted at 1334 stems ha−1 and thinned to 827 stems ha−1 at age 11. The second stand was planted at 1667 stems ha−1 and was unthinned. Lumber from a previous study on 17 different commercial stands from more conventional (lower) stand density management regimes was also analysed using linear mixed-effect models. Only lumber from the 1667 stems ha−1 stand conformed to the requirements for structural use and had a considerably higher mean MOE of 8967 MPa compared to 7134 MPa for the 1334/827 stems ha−1 stand and 5556 MPa for the more conventional stands. MOR values were adequate for all stands. Unlike previous studies on other species, slenderness did not seem to have a profound effect on the MOE of the lumber from these P. patula trees. Stand density management therefore has the potential to increase lumber stiffness of P. patula and should be considered as a forest management intervention for wood quality improvement by saw-log growers in South Africa. [ABSTRACT FROM AUTHOR]

There is a current and pressing need to develop engineering standards for timber- and other wood-based mats. In 2018 a group of mat producers and users began discussing a potential grading specification standard specific to mats. There are large gaps in the literature regarding the performance of the available raw materials as well as bolt-laminated mat systems. This work represents a novel attempt to begin to assess the mechanical properties of timber mats. Eight-inch deep mixed hardwood timbers were graded according to an experimental specification standard. Then, they were drilled and bolt laminated into 28 three-timber composite mats that were 24 inches (60.96 cm) in width. The bending stiffness (modulus of elasticity [MOE]) and strength (modulus of rupture [MOR]) performance were evaluated with a static bending test. The 5th percentile nonparametric tolerance limit (5% NTL) and design value for fiber stress in bending (Fb) were calculated. The nonparametric design value compared favorably with that of graded timbers, as described in the 2018 National Design Specification (NDS) for wood. [ABSTRACT FROM AUTHOR]