Significant Loss Of Strength Research Articles

Synthesis and characteristics of a novel dust suppressant with good weatherability for controlling dust in open coal yards.

This study aims to synthesize a dust suppressant for controlling coal dust pollution in open yards using natural polymers. Guided by graft copolymerization theory, potassium persulfate acts as an initiator to excite the free radicals of collagen and sodium alginate, allowing them to combine with acrylic acid and acrylamide to form a new polymer. The TG curve indicates that the thermal stability of the polymer is superior to that of the raw material. Scanning electron microscope (SEM) images show that the product can reduce the generation of dust by bonding the pulverized coal. With CCD method, when the monomer concentration increases in a certain range, the cohesive ability of the product to coal increases first and then decreases. Initiators and crosslinkers showed the same pattern. A series of performance experiments show that the product has a dust suppression rate of 98.7% at a wind speed of 14m/s, and maintain one of 94.5% at a wind speed of 8m/s after a rainstorm. In addition, there was no significant loss in dust suppression performance and compressive strength of the solidified layer after wind and rain. Sunlight, low temperature, and high temperature have little influence on the dust suppression effect of the product, which indicates that the product has better weather resistance and helps to suppress dust for a longer time in open air conditions.

Correlating in-situ process monitoring data with the reduction in load bearing capacity of selective laser melted Ti–6Al–4V porous biomaterials

Selective Laser Melting allows for the creation of intricate porous structures, that possess favourable biological properties. These structures are known as porous biomaterials. The focus of this paper is to evaluate the use of an in-line photodiode based process monitoring system, for the monitoring of the operational behaviour of the laser, and to correlate this with the resultant parts mechanical performance.In this study the production scale Renishaw 500M was used to produce porous structures, using Ti–6Al–4V feedstock powder. During the process, a co-axial process monitoring system was utilised to generate data relating to both the meltpool and the operational behaviour of the laser. An advanced scanning technique was used to produce the structures, whereby the laser parameters determine the strut dimensions. In this study, the laser input energy was reduced by 33%, 66% and 100%, at specific layers within the structures. Computer Tomography and Scanning Electron Microscopy was utilised to characterise the affected struts within the structures, while quasi-static compression testing was used to determine the structure's mechanical properties.It was demonstrated that as the level of input energy decreased and the number of affected layers increased, a corresponding decrease in the load bearing capacity of the structures occurred. With the structures experiencing a significant loss in strength also exhibiting a change in the failure mode during compression testing. Data generated during the processing of such structures was compared to the data generated during the processing of control structures, with the difference between the two been calculated on a layer-by-layer basis. A clear correlation was demonstrated between the total level of deviation between the two signal sets and a reduction in the load bearing capacity of the structures. This indicates that by comparing build data to a benchmark data set, valuable information relating to the structural integrity of the porous structures can be obtained.

Deterioration Process of Concrete Exposed to Internal Sulfate Attack.

Damage to concrete structures with gypsum-contaminated aggregate occurs frequently. Aggregates in much of the southern part of China are contaminated with gypsum. Therefore, in this study, the effects of using different quantities of gypsum-contaminated aggregate on the expansion and compressive strength of concrete were investigated over a period of one year. Two groups of concrete were designed with the gypsum-contaminated aggregate containing different parts of fine and coarse aggregate, respectively. The SO3 contents were 0%, 0.5%, 1%, 1.5%, 3%, 5%, and 7% by weight of aggregate. X-ray diffraction (XRD), thermogravimetry (TG), and differential scanning calorimetry (DSC) were used to analyze the change in mineral composition over time. The microstructure was also studied by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results showed that significant expansion and great loss in compressive strength did not occur in concrete if the content of SO3 lay below 1.5% and 3% in fine and coarse aggregates, respectively. The concentration of sulfate ions in concrete was not enough to form new a phase of gypsum. During the process of internal sulfate attack, the content of gypsum decreased and the content of ettringite increased. Ettringite was the main reason for the expansion damage of concrete. Additionally, the fracture mode of internal sulfate attack on concrete was the crack extension from gypsum to paste; finally, the aggregate separated from the paste.

Changes in muscle power after usual care or early structured exercise intervention in acutely hospitalized older adults

BackgroundA classic consequence of short‐term bed rest in older adults is the significant loss in skeletal muscle mass and muscle strength that underlies the accelerated physical performance deficits. Structured exercise programmes applied during acute hospitalization can prevent muscle function deterioration.MethodsA single‐blind randomized clinical trial conducted in an acute care for elders unit in a tertiary public hospital in Navarre (Spain). Three hundred seventy hospitalized patients [56.5% female patients; mean age (standard deviation) 87.3 (4.9) years] were randomly allocated to an exercise intervention (n = 185) or a control (n = 185) group (usual care). The intervention consisted of a multicomponent exercise training programme performed during 5–7 consecutive days (2 sessions/day). The usual‐care group received habitual hospital care, which included physical rehabilitation when needed. The main endpoints were change in maximal dynamic strength (i.e. leg‐press, chest‐press, and knee extension exercises) and maximal isometric knee extensors and hip flexors strength from baseline to discharge. Changes in muscle power output at submaximal and maximal loads were also measured after the intervention.ResultsThe physical exercise programme provided significant benefits over usual care. At discharge, the exercise group showed a mean increase of 19.6 kg [95% confidence interval (CI), 16.0, 23.2; P < 0.001] on the one‐repetition maximum (1RM) in the leg‐press exercise, 5.7 kg (95% CI, 4.7, 6.8; P < 0.001) on the 1RM in the chest‐press exercise, and 9.4 kg (95% CI, 7.3, 11.5; P < 0.001) on the 1RM in the knee extension exercise over usual‐care group. There were improvements in the intervention group also in the isometric maximal knee extension strength [14.8 Newtons (N); 95% CI, 11.2, 18.5 vs. −7.8 N; 95% CI, −11.0, −3.5 in the control group; P < 0.001] and the hip flexion strength (13.6 N; 95% CI, 10.7, 16.5 vs. −7.2 N; 95% CI, −10.1, −4.3; P < 0.001). Significant benefits were also observed in the exercise group for the muscle power output at submaximal loads (i.e. 30% 1RM, 45% 1RM, 60% 1RM, and 75% 1RM; all P < 0.001) over usual‐care group.ConclusionsAn individualized, multicomponent exercise training programme, with special emphasis on muscle power training, proved to be an effective therapy for improving muscle power output of lower limbs at submaximal loads and maximal muscle strength in older patients during acute hospitalization.

Freeze-thaw cycling impact on the shear behavior of frozen soil-concrete interface

The shear behavior of a frozen soil-structure interface plays a vital role in analyzing the performance of engineered structures in cold regions. This study investigates the freeze-thaw cycling impact on the shear behavior of a frozen soil-concrete interface by direct shear tests. Test specimens consisting of a Portland cement concrete disk and frozen loess with an initial moisture content ranging between 9.2% and 20.8% were prepared and conditioned at various sub-zero temperatures (i.e., −1 °C, −3 °C, and − 5 °C) and freeze-thaw (F-T) cycles (i.e., 0, 5, 10, and 20). Experimental results, including shear stress - horizontal displacement curves, the displacements and shear strengths at both peak and residual status, are presented and analyzed. In particular, the influence of F-T cycling on shear behavior is examined. The peak displacement is found to increase linearly with increasing initial moisture content, but their correlation weakens as the number of F-T cycling increases. However, the residual displacement is found to be insensitive to the initial moisture content, temperature, normal stress, and F-T cycling. While the residual friction angle is slightly larger than the peak one before F-T cycling, both gradually increase with an increasing number of F-T cycling. Large cohesion in the peak strength, especially at lower temperatures, completely diminishes in the residual strength due to damage of ice bondage, resulting in a significant shear strength loss between the peak and residual status. The impact of F-T cycling on the interface shear behavior can be attributed to moisture migration toward, formation and accumulation of ice films at the interface. The findings from this study including the shear strength parameters and the displacements at both peak and residual status, can be used to simulate the performance of engineered geotechnical assets such as pile foundations, retaining walls, and earth dams or irrigation channels with concrete linings in cold regions.

What Are the Effects of Remplissage on 6-Month Strength and Range of Motion After Arthroscopic Bankart Repair? A Multicenter CohortStudy.

Background:Patients who have undergone shoulder instability surgery are often allowed to return to sports, work, and high-level activity based largely on a time-based criterion of 6 months postoperatively. However, some believe that advancing activity after surgery should be dependent on the return of strength and range of motion (ROM).Hypothesis:There will be a significant loss of strength or ROM at 6 months after arthroscopic Bankart repair with remplissage compared with Bankart repair alone.Study Design:Cohort study; Level of evidence, 2.Methods:A total of 38 patients in a prospective multicenter study underwent arthroscopic Bankart repair with remplissage (33 males, 5 females; mean age, 27.0 ± 10.2 years; 82% with ≥2 dislocation events in the past year). Strength and ROM were assessed preoperatively and at 6 months after surgery. Results were compared with 104 matched patients who had undergone Bankart repair without remplissage, although all had radiographic evidence of a Hill-Sachs defect.Results:At 6 months, there were no patients in the remplissage group with anterior apprehension on physical examination. However, 26% had a ≥20° external rotation (ER) deficit with the elbow at the side, 42% had a ≥20° ER deficit with the elbow at 90° of abduction, and 5% had persistent weakness. Compared with matched patients who underwent only arthroscopic Bankart repair, the remplissage group had greater humeral bone loss and had a greater likelihood of a ≥20° ER deficit with the elbow at 90° of abduction (P = .004). Risk factors for a ≥20° ER deficit with the elbow at 90° of abduction were preoperative stiffness in the same plane (P = .02), while risk factors for a ≥20° ER deficit with the elbow at the side were increased number of inferior quadrant glenoid anchors (P = .003), increased patient age (P = .02), and preoperative side-to-side deficits in ER (P = .04). The only risk factor for postoperative ER weakness was preoperative ER weakness (P = .04), with no association with remplissage (P = .26).Conclusion:Arthroscopic Bankart repair with remplissage did not result in significant strength deficits but increased the risk of ER stiffness in abduction compared with Bankart repair without remplissage at short-term follow-up.

Brittleness increase in Eucalyptus wood after thermal treatment

ABSTRACTThermal treatments arise as an alternative to increase the physical and biological properties of wood, though they usually cause a reduction in mechanical strength. Therefore, the aim of the study was to determine the brittleness of Eucalyptus wood submitted to freezing and heat treatments. Freezing occurred with green condition specimens and the heat treatment with samples in equilibrium moisture content (20°C and 65% RH). The static bending test was carried out on an EMIC® universal testing machine. The freezing showed slight changes in the mechanical properties of Eucalyptus wood, not differing from natural wood. The treatments with high temperatures caused significant losses in mechanical strength, evidenced by decreases in maximum load and increases in brittleness. In the combined treatments, there was no sum of effects. Therefore, heat treatments modify the mechanical properties of wood, increasing its brittleness and following the tendency that, as the temperature increases, the mechanical resistance decreases.

The Effects of Resistance Exercise With Blood Flow Restriction on Flow-Mediated Dilation and Arterial Stiffness in Elderly People With Low Gait Speed: Protocol for a Randomized Controlled Trial.

BackgroundDuring aging, a significant loss of muscle mass, strength, and power is associated with a decline in daily functional capacities. Traditionally, resistance training is prescribed to prevent or reverse the skeletal muscle weakness, but the required training intensity may be too demanding for older people with poor physical performance. Resistance exercise with blood flow moderation (KAATSU training), originally developed in Japan, combines resistance exercise with blood flow restriction. It has been reported that KAATSU training enhances muscle hypertrophy in many populations. However, few studies have evaluated the effects of resistance exercises with blood flow restriction in elderly people and how this affects vascular structure and function.ObjectiveThe aim of this study was to evaluate (1) the acute and chronic effects of resistance exercise with blood flow restriction on vascular health in elderly people with low gait speed and (2) whether low-load resistance training with blood flow restriction elicits similar strength and gait speed gains to those elicited by conventional resistance training without blood flow restriction.MethodsThis is an ongoing randomized controlled trial in elderly people with low gait speed. Overall, two study arms of 13 participants each perform resistance exercise with and without blood flow restriction. The 2 groups are as follows: the control group will perform conventional resistance exercise (60% of 1 repetition maximum) and the KAATSU group will perform the low-load resistance exercise with blood flow restriction (20% of 1 repetition maximum) for 12 weeks. Pulse wave velocity, venous occlusion plethysmography, and flow-mediated dilation are used to assess arterial stiffness, muscle blood flow, and endothelial function, respectively. The secondary outcomes are gait speed, strength, and quality of life. All measures will be performed before and after the training program.ResultsThis research study is in progress. Recruitment has started, and data collection is expected to finish in August 2020.ConclusionsThe findings of this study will have important implications for the rehabilitation of elderly people.Trial RegistrationClinicalTrials.gov NCT03272737; https://clinicaltrials.gov/ct2/show/NCT03272737International Registered Report Identifier (IRRID)DERR1-10.2196/14691

Effect of Ambient and Elevated Temperature on the Residual Splitting and Flexural Tensile Strength of Normal and High Strength Concrete

Experimental test have carried out to investigate the behavior of residual tensile strength of concrete prepared using normal and high strength concrete. For the same purpose, cylindrical and prism-shaped specimens of concrete were caste and consecutively subjected to heating and cooling condition in the laboratory-controlled environment. A hold period of three hours was provided to impart the heating-cooling phenomenon inside the electrical furnace at four different sets of temperatures. The elevated temperatures chosen for the present tensile behavior study are 200oC, 400oC, 600oC, and 800oC. Strength was also determined at the ambient environment for the purpose of comparing the effects of thermal loads on the behavior of strength. A significant loss in tensile strength has been observed in concrete mixes at various temperatures. The outcomes of the current experimental work are termed useful for understanding key mechanical characteristics of concrete under the effect of thermal loads.

Excellent clinical outcome and low complication rate after proximal hamstring tendon repair at mid-term follow up.

Proximal hamstring tendon avulsions lead to a significant loss of strength and a functional deficit of the respective lower limb and surgery is the recommended treatment. Only little is known about the clinical outcomes and complications when comparing acute and chronic management as well as partial and complete tears. Therefore, the purpose of this study was to investigate the clinical results and the complication rate of patients after surgical treatment of proximal hamstring tendon injuries. It was hypothesized that surgical treatment of an acute proximal hamstring avulsion would lead to a superior clinical outcome with a low complication rate and high return to sports rate compared to chronic cases and partial avulsions. Patients who underwent proximal hamstring tendon repair between 2008 and 2015 were retrospectively evaluated with a minimum follow up of 2years. Outcome measurements were obtained by means of Lysholm score, Harris Hip Score, Visual Analog Scale, and Tegner Activity Scale. Return to sports (RTS) rate was determined. Postoperative adverse events were recorded and complications reported. Patients' outcomes were compared between acute/chronic repair and partial/complete injury patterns. Ninety-four of 120 (78.3%) were available for final assessment at a mean follow-up of 56.2 ± 27.2months. Clinical outcome measures were excellent and did not differ between the treatment groups or between the different injury patterns. RTS was achieved by 86.2% of the patients and was significantly superior after acute treatment (p < 0.05). The overall complication rate was 8.5% and significantly higher in complete tears compared to partial tears and in delay compared to acute surgery (p < 0.05). Surgical treatment of proximal hamstring tendon avulsions results in excellent clinical outcome scores and a high RTS rate. Open surgical treatment has shown to be a safe procedure with a low complication rate. Surgical timing is important, as early surgical intervention provides a higher RTS rate and a lower complication rate than delayed surgery and should therefore be preferred in clinical practice. Repair of partial and complete tears lead to similar clinical outcome, but a higher complication rate in complete avulsions. Level IV.

Long-term follow-up of conservatively treated midshaft clavicular fractures on functional outcome

BackgroundThe aim of this study was to examine the long-term effect of shortening after a midshaft clavicular fracture on strength deficiency in the shoulder. MethodThis study included 18 participants (14 males, 4 females) with a conservatively treated midshaft clavicular fracture. Mean age was 52.2 ± 13.8 years, range 32–76 years). The mean follow-up time was 13.5 ± 0.4 years. Participants filled in a QUICKDASH questionnaire and both clavicle lengths were measured using a caliper. The isometric strengths in internal rotation, external rotation and abduction of both arms were measured with a handheld dynamometer. ResultsAverage shortening of the clavicle in this group was 1.09 cm (SD 0.53). Nearly all strength measurements showed no significant difference between the shortened and the unaffected side. Multiple regression revealed a small (3N per mm length difference) but statistically significant relationship on external rotation between the relative extent of shortening of the clavicle, dominant side of the fracture and the isometric force difference between the unaffected and affected arm, F(2,15) = 5.746, p < .05, adj. R2 = .358. Over 14 years there was a reduction in mean DASH-score of 4.4 (8.8 ± 12.3; current DASH = 4.4 ± 7.7)In this group, long term effects of clavicular shortening were small. Based on these results we conclude that on the long term clavicular shortening will not result in significant strength loss.

The Influence of Natural Pozzolans Structure on Marl Soil Stabilization

Marl as a calcareous soil has heterogeneous nature in terms of structure and properties. Any change in the water content of marl can cause significant strength loss; therefore, prior stabilization while constructing civil infrastructures is necessary. A fundamental element in soil stabilization is the relationship between soil structure and stabilizers, but this important factor has been ignored in the available literature, especially in the case of marl soil. Lately, alternative environmentally friendly additives (natural pozzolans) as well as traditional chemical stabilizers (cement and lime) have been successfully used for stabilization of marl soil. This paper presents the results of an experimental study which investigates the influence of natural pozzolans structure on marl soil stabilization. Transmission electron microscopy (TEM), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR) tests were used for size and structure analysis of marl soil and two types of natural pozzolans called Qizkorpi and Mamaloo of Iran which have been successfully used for marl soil stabilization by the authors, recently. Based on the obtained results by TEM, FTIR, and XRF tests, due to the similarity of the structure and size of Gizkorpi volcanic ash and marl soil when compared to that of Mamaloo volcanic ash, it can be concluded that the electrostatic and magnetic interactions in marl and Gizkorpi volcanic ash lead to a better stabilization and strengthen of the marl, while these interactions are less in Mamaloo volcanic ash when mixed with the marl soil.

The intertwined roles of particle shape and surface roughness in controlling the shear strength of a granular material

Both the shape of individual particles and their surface properties contribute to the strength of a granular material under shear. Here we show the degree to which these two aspects can be intertwined. In experiments on assemblies of 3D printed, convex lens-shaped particles, we measure the stress–strain response under repeated compressive loading and find that the aggregate’s shear strength falls rapidly when compared to other particle shapes. We probe the granular material at mm-scales with X-ray computed tomography and $$\upmu $$ m-scales with high-resolution surface metrology to look for the cause of the degradation. We find that wear due to accumulated deformation smooths out the lens surfaces in a controlled and systematic manner that correlates with a significant loss of shear strength observed for the assembly as a whole. The sensitivity of lenses to changes in surface properties contrasts with results for assemblies of 3D printed tetrahedra and spheres, which under the same load cycling are found to exhibit only minor degradation in strength. This case study provides insight into the relationship between particle shape, surface wear, and the overall material response, and suggests new strategies when designing a granular material with desired evolution of properties under repeated deformation.

Chloride-induced corrosion of steel fiber near the surface of ultra-high performance concrete and its effect on flexural behavior with various thickness

The results of experimental investigation of ultra-high performance concrete (UHPC) by evaluating the flexural response are presented in order to qualitatively evaluate the effects of chloride-induced corrosion. The third-point bending test is carried out using the hydraulic servo-controlled testing machine. The experimental variables are thickness of specimen (10, 25 and 50 mm), immersion duration, and mixture design of UHPC. The specimens are immersed in 10 wt% NaCl solution up to a year to induce corrosion. The effect of chloride-induced corrosion of steel fiber of UHPC is evaluated in terms of compressive strength, flexural strength and flexural toughness. The experimental results indicate that there is no significant loss in flexural strength and toughness for the specimens which were thicker than 25 mm over a period up to 365 days of immersion in chloride solution; whereas, the specimen with thickness of 10 mm showed about 10% decrease in maximum stress and corresponding toughness after 180 days of the immersion. Furthermore, it is revealed by comparing the compressive strength with and without fibers that the presence of steel fibers in UHPC under corrosive environments do not lead to substantial strength decrease.

Ultra-violet and chemical treatment of crumb rubber aggregate in a sustainable concrete mix

ABSTRACTThis paper illustrates the usage of crumb rubber as a recycled aggregate in concrete. However, the presence of crumb rubber leads to a lower concrete compressive strength primarily due to its much lower stiffness. Under stress, the rubber deforms, re-distributing the load to the cement paste, which subsequently fails prematurely. Instead of reverting to conventional methods of increasing concrete compressive strength, such as lowering the water cement ratio facilitated through the addition of a superplasticiser or enhancing the binder effectiveness with the addition of silica fume, this paper will focus on some of the pre-treatment methods on crumb rubber that can help mitigate this loss of strength. These include accelerated aging and stiffening crumb rubber through exposing it to ultraviolet light to enhance its surface roughness characteristics or pre-treating crumb rubber by soaking it in sulphuric acid to develop a stiffer surface layer. By increasing the rubber’s stiffness, it is observed that its load share increases, thereby improving the crumb rubber concrete’s compressive strength and allowing a larger dosage replacement of normal aggregate without significant strength loss. In summary, identifying whether or not different pre-treatment of the crumb rubber aggregates are successful in avoiding a substantial loss in strength consequent upon its inclusion in concrete is the primary objective of this paper.

Dissimilar metal welding of P91 steel-AISI 316L SS with Incoloy 800 and Inconel 600 interlayers by using activated TIG welding process and its effect on the microstructure and mechanical properties

This study investigates dissimilar metal weldments between P91 steel and AISI 316 L austenitic stainless steel fabricated by activated TIG welding (A-TIG) with and without the use of interlayers of Incoloy 800 and Inconel 600. Through thickness penetration in 8 mm thick plates was achieved in a single pass A-TIG welding using a pre-coated mixture of metallic oxides. Hot cracking was eliminated in A-TIG weld joints in contrast to conventional TIG weld joints without flux. Fully martensitic structure was observed in the weld metal developed without the use of interlayer. Microstructural modifications were achieved with the use of interlayers. The weldment with Incoloy 800 interlayer exhibited martensitic-austenitic structure whereas fully austenitic structure was observed with Inconel 600 interlayer. Interlayers improved impact toughness and ductility of the weld joints without significant loss of tensile strength. The effect of interlayers on carbon migration after aging treatment (620 °C/500 h) was evaluated with the help of thermodynamic simulations and it was observed that the use of interlayers reduced the severity of carbon migration.

THIN-WALLED STEEL TUBULAR COLUMNS WITH UNIFORM AND GRADED THICKNESS UNDER CYCLIC LOADING

Thin-walled steel tubular circular columns are widely used as cantilever bridge piers due to their geometric efficiency, aesthetic appearance, and high earthquake resistance. However, local buckling, global buckling, or interaction between both is usually the main reason of significant strength and ductility loss in these columns, which eventually leads to their collapse. This paper investigates the behavior of uniform circular (C) and graded-thickness circular (GC) thin-walled steel tubular columns under constant axial and cyclic lateral loading. The GC column with size and volume of material equivalent to the C column is introduced and analyzed under constant axial and cyclic lateral loading. The analysis carried out using a finite-element model (FEM), which considers both material and geometric nonlinearities. The accuracy of the employed FEM is validated based on the experimental results available in the literature. The results revealed that, significant improvements in strength, ductility, and post-buckling behavior of thin-walled steel columns obtained using the GC column.

Experimental and Numerical Analysis of Liquid Metal Embrittlement Crack Location

Advanced high-strength steels used in automotive structural components are commonly protected using zinc coatings. However, the steel/zinc system creates the potential for liquid metal embrittlement during welding. Although liquid metal embrittlement cracks are known to form, the current literature does not include crack location when assessing crack severity. In this work, TRIP1100 joints showed that LME cracks decreased strength from 7.8 to 42.2%, depending on location, between the coated (cracked) and uncoated (non-cracked) condition. Liquid metal embrittlement cracks in critical locations were observed to propagate until fracture from lap shear testing. However, cracks in non-critically loaded areas were not part of the fracture path and did not result in a significant loss in strength. This shows LME crack location can be controlled to improve joint performance and vehicle safety. In addition, a model of lap shear testing in a cracked sample showed how the presence of a crack can affect the internal stress field depending on its location.

CHEMICALLY TREATED GLUED LAMINATED PARICÁ TIMBER (Schizolobium parahyba var. amazonicum)

ABSTRACT In the production of glue-laminated timber (GLT), boards derived from planted forest wood with easy workability are glued on top of one another. The main objective of the present work was to evaluate the performance of parica timber GLT beams (5 × 10 cm) on GLT. Three procedures were performed: (1) GLT beams (5 × 10 cm) were produced using natural lamellae without chemical preservatives; (2) the individual lamellae (2.5 × 5 cm) were chemically treated, and then glued together; and (3) the beams formed from the glued natural lamellae (5 × 10 cm) were treated chemically. The positions of lamellae on the beams were determined by their modulus of elasticity values (MOE), which were estimated by a non-destructive bending test with a three-point load. The analytical bends, determined by the homogenized section method, and the experimental bends, measured by the four-point bending test, were compared. The differences between the bends were statistically evaluated, and it was found that the experimental bend (21.65 mm) was less than the analytical bend (34.02 mm). There was no significant loss of shear strength or MOE. The axial strength of the chemically untreated beams (49.18 MPa) was significantly higher than that of the untreated beams fabricated from natural lamellae (40.48 MPa). The results indicate that the gluing of treated lamellae does not affect beam performance.

Experimental Study on Water Absorption and Weakening of Silurian Argillite

The objective was to analyse the water absorption and weakening of a Silurian argillite taken from the northwest of Hubei Province, China. Some experiments were conducted including measurement of the change in water absorption, the microstructure of the minerals, the porosity, and the strength of argillite samples, at different water absorptions, by scanning electron microscope, powder X-ray diffraction analysis, and needle penetration test. The results indicate that argillite was soaked in water for up to 0.5 days, water absorption rates were fast and the amount absorbed was large. At the same time, the rate of strength decrease was high and significant loss of strength was observed. Argillite soaked in water for 0.5 to 180 days had an increased water absorption at a slower rate, and the strength tended to be stable over time. The relationship between strength and water absorption was established: the strength decreases in the form of negative exponential function with increasing water absorption. Finally, the micro-mechanical model shows that, the decrease of attractive force of mineral grains and the increase in the force acting between mineral grains and the pore water are the main reason why this degree of water-weakening appeared in the argillite.