Flexural Strength Research Articles

Experimental study on chemical and thermomechanical properties of concrete incorporating Washingtonia robusta fibres

The aim of this work is to provide a new composite material for applications in the thermal insulation of buildings. The composite was made with mortar reinforced with natural fibres extracted from the petiole of the Washington robusta (WR) palm tree. The fibres used were first chemically characterised by energy-dispersive X-ray spectroscopy, scanning electron microscopy, X-ray and infrared diffractometry spectroscopies alongside tensile testing to discover their morphological structure. Afterwards, the fibres were incorporated into mortar with mass percentages varying from 0 to 4% to determine experimentally the thermomechanical properties of the manufactured samples. The chemical findings indicated that WR fibres are rich in cellulose, hemicellulose and lignin, and possess a high crystallinity index, which enhances the mechanical properties and durability of the composite. The density obtained for the composite W2RC4% is 1305 kg/m3 and less than 2000 kg/m3; this composite can thus be classified as a lightweight concrete according to the standard NF EN 206 + A2/CN (2022). The thermal conductivity and thermal effusivity dropped by about 60% and 42%, respectively. Moreover, the WR reduces the compressive strength (76%) and the flexural strength (36%) to minimum values, respectively, of 5.9 MPa and 3.8 MPa. These values meet the mechanical requirements of lightweight concretes (> 3.5 MPa).

Acoustic Emission Monitoring for Damage Assessment of a Magnetite Ultra-High-Performance Concrete (MUHPC) Block in a Bending Test

Ultra-high-performance concrete (UHPC) is widely used because of its exceptional properties, such as high compressive and flexural strength, low permeability, and resistance to abrasion and chemical attack. It is commonly employed for intricate constructions like skyscrapers, precast concrete components, and infrastructure. Nevertheless, the incorporation of appropriate fibers into UHPC is carried out in order to accomplish objectives such as augmenting strength, enhancing toughness, and regulating cracking. This study employed magnetite as an additive to a UHPC block in order to examine the mechanical characteristics of a newly cast UHPC block. Acoustic emission was employed to evaluate the damage to the UHPC block for tracking purposes. Acoustic emission is a non-invasive testing technique that does not cause harm to the specimen when it is exposed to a load. On the basis of this, many critical locations that indicated the propagation of cracks were analyzed, as well as various loading stages across the specimen. The b-value is a method that can evaluate the extent of damage by analyzing the amplitude distribution. Distinct paths of b-values were noted for each loading stage, indicating major damage scenarios based on their slopes.

Effect of the Inorganic Modification Mode on the Mechanical Properties of Rubber Recycled Concrete

The reasonable and effective application of waste tires and discarded concrete in concrete is an important branch of green concrete development. This paper investigates the effects of the inorganic modification mode on the basic mechanical properties of rubber recycled concrete based on indoor tests. Inorganic modification, such as water washing, acid washing, and alkaline washing modification, was mainly used to treat and modify rubber particles. The factors affecting the compressive strength, the splitting tensile strength, the flexural strength, the axial compressive strength, and the modulus of elasticity of modified rubber recycled concrete were analyzed. The study results show that the incorporation of recycled aggregates and rubber reduced the mechanical properties of concrete, with the compressive and splitting tensile strengths showing the greatest reductions of 27.36% and 27.24%, respectively. Three modification methods significantly improved the mechanical properties of rubber recycled concrete. The alkali washing modification method was the most effective, maximally improving the mechanical properties of rubber recycled concrete by 7.53–15.51%. The effects of the three modifications on the mechanical properties of concrete were ranked as follows: alkali washing > acid washing > water washing. This study provides a data basis for the practical application of rubber recycled concrete in engineering and a test basis for the development of green concrete.

Comparative Assessments of Dental Resin Composites: A Focus on Dense Microhybrid Materials.

The performance of dental resin composites is crucially influenced by the sizes and distributions of inorganic fillers. Despite the investigation of a variety of functional particles, glass fillers and nanoscale silica are still the predominant types in dental materials. However, achieving an overall improvement in the performance of resin composites through the optimization of their formulations remains a challenge. This work introduced a "dense" microhybrid filler system with 85 wt % filler loading, leading to the preparation of self-developed resin composites (SRCs). Comparative evaluations of these five SRCs against four commercial products were performed, including mechanical property, polymerization conversion, and shrinkage, along with water sorption and solubility and wear resistance. The results showed that among all SRC groups, SRC3 demonstrated superior mechanical performance, high polymerization conversion, reduced shrinkage, low water absorption and solubility, and acceptable wear resistance. In contrast to commercial products, this optimal SRC3 material was comparable to Z350 XT in flexural and diametral tensile strength and better in flexural modulus and surface hardness. The use of a "dense" microhybrid filler system in the development of resin composites provides a balance between physicochemical property and wear resistance, which may be a promising strategy for the development of composite products.

Utilization of Silica Filler as Reinforcement Material of Polylactic Acid (PLA) in 3D Printing Applications: Thermal, Rheological, and Mechanical Performance

Glass was introduced as an additive to filaments used for the manufacturing of composite materials, employed by Additive Manufacturing applications. Glass accounts for a large waste electric and electronic equipment (WEEE) percentage, and its recovery and recycling can lead to the production of sustainable composite materials. In this work, poly(lactic acid) (PLA)/commercially available silicon oxide composite filaments were manufactured and their structural, thermal, rheological, and mechanical properties were assessed. Scanning Electron Microscopy confirmed the 1:2 ratio of silicon: oxygen, along with the relatively low adhesion between the filler and the matrix. Differential Scanning Calorimetry presented steady glass transition and melting temperatures of composites, whereas a crystallization temperature of 10% wt. and a crystallinity of 15% wt. composite slightly increased. Rheological analysis showcased that the viscosity of the composite filaments decreased compared to PLA (10–100 compared to 300–400 Pa·s), with a more shear-thinning behavior. Dynamic mechanical analysis exhibited increased elastic, flexural moduli, and flexural strength of composites (up to 16, 23, and 11%, respectively), whereas tensile strength and elongation decreased. The affordability of raw materials (with the future introduction of recycled ones) and the minimal processing steps can lead to the potential scaling up of the study.

Experimental analysis of 3D printed continuous carbon/glass hybrid fiber reinforced PLA composites: Revealing synergistic mechanical properties and failure mechanisms

AbstractThis study investigates the mechanical properties of continuous carbon/glass hybrid fiber‐reinforced polylactic acid (PLA) composites (HFRC) produced through the three dimensions (3D) printing process, comparing them with single carbon fiber‐reinforced PLA composites (CFRC). Initially, composite prepreg filaments are prepared using an impregnation device, followed by fabrication using a 3D printer. The mechanical performance results reveal a 13% increase in tensile strength for HFRC compared with CFRC. Due to differing elongation rates of carbon and glass fibers, HFRC exhibits two strength peaks, while CFRC demonstrates a 37% higher bending strength than HFRC. Scanning electron microscope images indicate that the tensile failure mechanism involves fiber brittle fracture and fiber‐matrix interface debonding, while the bending failure mechanism includes fiber pullout, fiber debonding, fiber cluster buckling, and interlayer interface failure.Highlights To realize the moldless rapid manufacturing of continuous hybrid fiber‐reinforced PLA composites. The stress–strain curves of single fiber‐reinforced composites and hybrid fiber‐reinforced composites are obviously different. Elucidating the effect of single fiber/hybrid fiber in composites on mechanical properties and failure mechanism according to micro‐morphology.

Improving the fracture toughness, electrical conductivity and electro‐thermal performance of hybrid glass/carbon fiber reinforced epoxy composites with surface‐sulfonated polypropylene fabrics

AbstractHybrid glass/carbon fiber (GCF) reinforced polymer composites are one of advanced composites with reduced cost, desired mechanical properties and special electrification performance. In the work, surface‐modified polypropylene (PP) non‐woven fabric was used as the interleaf for toughening these composites. The effects of the surface‐sulfonated PP fabric (PP/S) interleaves on various mechanical properties of the GCF reinforced epoxy (GCF/EP) composites were investigated firstly, including the mode II interlaminar fracture toughness and flexural strength. Comparing to the blank control sample, the GIIC of the hybrid composites interleaved with the sulfonated PP fabric was increased evidently, as well as its flexural strength. These demonstrate the great interleaving effect of PP/S fabric on the GCF/EP laminated composites. Moreover, the heterogeneous electrically conductive behavior and electro‐thermal effect of GCF/EP interleaved with and without PP/S were studied. Interestingly, comparing to the control sample, the conductivity of the interleaved GCF/EP composites increased in both two in‐plane direction. Due to the hybrid character of the plain woven GCF fabric, both the temperature increase rate and the equilibrium temperature of the GCF/EP composites were much larger than that of pure carbon fabric reinforced composites under the same electrification condition.Highlights Polypropylene fabric grafted with sulfonate group (PP/S) was fabricated. The tensile property of fabric almost unchanged after the sulfonation reaction. PP/S was more effective in toughening glass/carbon fiber/epoxy composite (GCF). PP/S increased the conductivity in in‐plane directions of the hybrid composites. GCF/EP displayed superior electro heating effect to CF/EP.

Synergistic surface modification of anhydrous calcium sulfate by polydopamine/oleylamine and its application in reinforced HDPE composites

AbstractIn the study, polydopamine and oleylamine cooperated to modify the surface of anhydrous calcium sulfate prepared from phosphogypsum, and HDPE matrix composites with different filler content were prepared by filling HDPE before and after modification. The results show that when the filler content is 5 wt%, the elongation at break of mCSA/HDPE composite is 31.7% and 89% higher than that of HDPE and CSA/HDPE. Respectively, when the filler content is as high as 25 wt%, the flexural strength is still 16.8% higher than that of HDPE. After modification, the compatibility and dispersibility of anhydrous calcium sulfate in HDPE were improved, and the crystal structure of anhydrous calcium sulfate was not significantly changed, thus the mechanical properties and thermal stability of mCSA/HDPE composites were improved. Overall, after modification, not only the mechanical properties of the composites are improved, but also the content of inorganic powder as filler added to HDPE is increased, which can be regarded as a method for effective utilization of phosphogypsum.Highlights Calcium sulfate was modified by polydopamine and oleylamine The mechanical and thermal properties of the modified calcium sulfate/HDPE composites are good. The resource utilization of phosphogypsum was carried out

Studies on partial replacement of waste high density polyethylene (HDPE) and polypropylene (PP) plastic with fine aggregate (FA) on mechanical, durability and thermal properties of M30 and M40 grade concrete

The aim of the present paper is to incorporate two different waste plastic materials that is High-Density Polyethylene (HDPE) and Poly-Propylene (PP), were replaced with Fine Aggregate (FA) at a 10% by 2.5% increment. The widespread formation of HDPE and PP waste plastics has become a major environmental issue, endangering ecosystems and human health. Traditional disposal techniques, such as landfills and incineration, lead to pollution and resource depletion. Incorporating these polymers into concrete provides a long-term solution that reduces environmental effect while improving material qualities. The Different tests conducted are compressive strength (3, 7, 28 and 60 days) (150 × 150x150 mm), flexural strength (3, 7, 28 and 60 days) (100 × 100x500 mm), acid attack (28, 56 and 90 days) (100 × 100x100 mm), sulphate attack (28, 56 and 90 days) (100 × 100x100 mm), and thermal conductivity (180 mm dia x 20 mm thick). The compressive strengths of 40.52 MPa and 38.41 MPa for PP and HDPE material were observed in M30-grade concrete, respectively. Similarly, for M40-grade concrete, 43.6 MPa and 41.8 MPa are for PP and HDPE material, respectively. The optimum percentages of 5% and 7.5 for PP and HDPE material, respectively, can be replaced in concrete for flexural strength in both M30 and M40 grades. The least percentage loss in acid attack was observed at 28 days for both HDPE and PP material, but for 56 days and 90 days, the percentage loss of weight was significantly less (< 5%). The sulphate attack for both M30 and M40 grade concrete showed less than 10% percentage loss in weight after 90 days. Thermal conductivity (k) was also reduced by 30–35% for both HDPE and PP material, with 10% replacement in concrete for M30 and M40 grades. The use of Waste HDPE and PP material can be used to improve the mechanical, durability & thermal property of M30 and M40 grade concrete under controlled conditions.

From cement to geopolymers: Performances and sustainability advantages of ambient curing

The production of Portland cement results in substantial carbon emissions. Geopolymers are regarded as highly promising alternative binder materials to cement due to their low energy consumption and excellent mechanical properties. However, it should be noted that the thermal curing process of geopolymers diminishes their low-carbon advantage. In this study, ground granulated blast furnace slag (GGBS) was used to replace metakaolin (MK) by the ratio of 10 %, 20 %, 30 %, 40 %, and 50 % to produce geopolymers. The aim was to examine the impact of GGBS content on the thermal curing performance of MK-based geopolymers. The microstructure of the specimens was analyzed using SEM and XRD analysis techniques. Lastly, a comprehensive assessment of their sustainability potential was carried out. As a result, slag may increase flow spread, decrease the setting time, and effectively improve the mechanical properties which curing on ambient temperature. The group with 50 % slag content had the highest compressive and flexural strengths, reaching 55.9 MPa and 8.45 MPa at 28 d, respectively. The drying shrinkage of geopolymers increases as the GGBS content goes up. Notably, owing to the evolution of chemical transformation and gel structure, MK exhibits a significant mitigation on shrinkage. Ultimately, with a 50 % slag content, the carbon dioxide emissions of geopolymer can be reduced to 265.36 kg CO2-eq, which is a 43.6 % decrease compared to that of OPC. With a comprehensive consideration of the performance and sustainability potential of geopolymers, it is recommended to introduce GGBS content in the range of 30 %–40 %.

Mechanical investigation for enhancing jute fibre vinyl ester composite performance through garnet waste utilization

This study explores the potential utilization of garnet waste, a byproduct of the Abrasive Water Jet Machining process, as a promising filler material in composite manufacturing. The disposal of garnet waste presents significant environmental and economic challenges, underscoring the need for sustainable waste management strategies. To tackle these challenges, this research investigates the incorporation of garnet waste into composites to create value-added materials. Consequently, the study focused on developing garnet-filled jute fibre-reinforced vinyl ester composites using the hand layup method. Various mechanical properties including flexural strength, tensile strength, hardness, and impact strength were assessed. The findings demonstrate that the inclusion of garnet filler enhances the mechanical strength of the composites. Particularly, composites containing 10 wt% garnet exhibit notable improvements in tensile, flexural, impact, and hardness strengths, with increases of 40%, 124%, 26%, and 15%, respectively. This research has the potential to advance the development of advanced materials across diverse industries, marking a significant stride towards sustainable and value-driven composite manufacturing practices.

The effect of span length on the flexural properties of glass and basalt fiber reinforced sandwich structures with balsa wood core for sustainable shipbuilding

The current research aims to analyze the mechanical characterization of sandwich materials through a three-point flexural test. The sandwich structures in question composed of balsa wood as a core and four different types of fiber reinforced vinyl ester composite facesheets, namely Glass, Basalt, Glass/Carbon, and Basalt/Carbon. The sandwich panels were prepared using the vacuum infused processing method. The primary objective of this investigation is to explore the feasibility of utilizing basalt fibers for the production of structural parts in shipbuilding and replacing the already existed glass fibers. The flexural test was carried out with using three-point flexural test with varying the span length from 120 mm, 180 mm, 220 mm. Additionally, an analysis of variance (ANOVA) was then carried out to compare the mean values of properties deduced from these tests. The results showed that using basalt fibers instead of glass fiber reinforced enhanced the flexural stiffness of the sandwich structure. The flexural strength and modulus are shown to depend on span length and fiber type. The flexural modulus increases with an increase in span length. Similarly, flexural strength increases in glass fiber-based structures, while a slight reduction is observed in basalt fiber-reinforced structures the larger span length. The findings of this research suggest that basalt fibers hold potential as a replacement for glass fibers in producing structural components in shipbuilding. These results offer valuable information that can aid in the design and optimization of sandwich materials in shipbuilding.

Mechanical and fracture properties of mortars reinforced with glass fibre and prepared with different cement types

PurposeThe main aim of the current study is to investigate the effect of Anti-Crack HP 67/36 glass fibre on the mechanical performance of mortars made of cement, with a focus on post-cracking evaluations using the digital image correlation (DIC) technique.Design/methodology/approachExperimental tests were carried out on 36-mm long fibres at 0.8% by volume and added to the normal strength (NSM), high strength (HSM) and high strength mortar with fly ash (HSMFA) mortars. CEM I 52.5 CP2 NF, CEM II/A-L 42.5 NF and CEM III/C 32.5 N-SR PM were used for each series of mortar to assess the performance of the glass fibres with the types of cement. F-class fly (FA) ash was used to reduce global CO2 emissions.FindingsThe mortar’s strength decreased as the cement types changed from CEM I to CEM II and III. However, due to changes in the portlandite content of the cement, water porosity increased for both types of mortar, without and with fibre. It was also found that using glass fibre increased flexural strength more than compressive strength, regardless of the type of cement used. For all the strength classes, it was found that the mortar mixes with CEM I had the highest critical crack opening (wc) and fracture energy (GF), followed by CEM II and III. No significant effects were observed in the mortar’s property by replacing fly ash (12%).Research limitations/implicationsOnly mortars were formulated in this study, but the results must be verified at the concrete scale.Practical implicationsValidation of the DIC technique to characterize the post-cracking behaviour of cement-based material. Use of glass fibres to improve the material’s resistance to cracking.Social implicationsUse of CEM II and CEM III cements with low CO2 footprint instead of CEMI without altering the mechanical performance of the material.Originality/valueThe work is a further contribution to studying the cracking behaviour of several series of variable mortars depending on the resistance class and the type of cement used.

Improved interfacial adhesion of carbon fiber‐reinforced polydicyclopentadiene layered composite material by modification of norbornene derivatives

AbstractSurface chemical grafting modifications of carbon fibers (CFs) using 5‐(triethoxysilyl)norbornene (TOS), norbornene carboxylic acid tert‐butyl ester (NB‐TBE), and 5‐norbornene‐2,3‐dicarboxylic anhydride (NA) improved interfacial interactions between CFs and poly(dicyclopentadiene) (PDCPD) resin. The ring‐opening metathesis polymerization (ROMP) of DCPD, catalyzed by Grubbs catalyst II, enabled the fabrication of PDCPD/CF layered composite materials with resin and fibers tightly adhered. The optimal composite exhibited remarkable mechanical properties, with a tensile strength of 654.6 MPa and flexural strength of 510.7 MPa. Excellent thermal stability with a maximum weight loss rate in temperatures above 450°C and good chemical resistance with a weight change of about 1% in both acidic and alkaline media highlight the promising potential of these materials for use in harsh environments. The simple yet efficient approach of TOS, NB‐TBE, and NA‐enhanced layered CF shows great promise as advanced composite materials for industrial applications.Highlights Norbornene derivatives such as TOS, NB‐TBE, and NA are suitable modifiers for CF. ROMP of DCPD and norbornene group onto CFs, fabrication of PDCPD/CF composite materials. The composite exhibited remarkable interfacial adhesion and mechanical properties.

Preparation and Application of CO2-Resistant Latex in Shale Reservoir Cementing

With the application of CO2 fracturing, CO2 huff and puff, CO2 flooding, and other stimulation technologies in shale reservoirs, a large amount of CO2 remained in the formation, which also lead to the serious corrosion problem of CO2 in shale reservoirs. In order to solve the harm caused by CO2 corrosion, it is necessary to curb CO2 corrosion from the cementing cement ring to ensure the long-term stable exploitation of shale oil. Therefore, a new latex was created using liquid polybutadiene, styrene, 2-acrylamide-2-methylpropanesulfonic acid, and maleic anhydride to increase the cement ring’s resistance to CO2 corrosion. The latex’s structure and characteristics were then confirmed using infrared, particle size analyzer, thermogravimetric analysis, and transmission electron microscopy. The major size distribution of latex is between 160 and 220 nm, with a solid content of 32.2% and an apparent viscosity of 36.8 mPa·s. And it had good physical properties and stability. Latex can effectively improve the properties of cement slurry and cement composite. When the amount of latex was 8%, the fluidity index of cement slurry was 0.76, the consistency index was 0.5363, the free liquid content was only 0.1%, and the water loss was reduced to 108 mL. At the same time, latex has a certain retarding ability. With 8% latex, the cement slurry has a specific retarding ability, is 0.76 and 0.5363, has a free liquid content of just 0.1%, and reduces water loss to 108 mL. Moreover, latex had certain retarding properties. The compressive strength and flexural strength of the latex cement composite were increased by 13.47% and 33.64% compared with the blank cement composite. A long-term CO2 corrosion experiment also showed that latex significantly increased the cement composite’s resilience to corrosion, lowering the blank cement composite’s growth rate of permeability from 46.88% to 19.41% and its compressive strength drop rate from 27.39% to 11.74%. Through the use of XRD and SEM, the latex’s anti-corrosion mechanism, hydration products, and microstructure were examined. In addition to forming a continuous network structure with the hydrated calcium silicate and other gels, the latex can form a latex film to attach and fill the hydration products. This slows down the rate of CO2 corrosion of the hydration products, enhancing the cement composite’s resistance to corrosion. CO2-resistant toughened latex can effectively solve the CO2 corrosion problem of the cementing cement ring in shale reservoirs.

Hydration, strength, and microstructure evolution of Portland cement-calcium sulphoaluminate cement-CSH seeds ultra-early strength cementitious system

Improving the very early age strength of precast concrete components at ambient temperature and ensuring the development of later strength is of significant engineering importance. This objective was successfully achieved by incorporating a specific percentage of 0–3% CSH seeds (CSHs) and 5%-20% calcium sulphoaluminate cement (CSA) into Portland cement (PC). The hydration, strength and microstructure evolution of Portland cement-calcium sulphoaluminate cement-CSH seeds cementitious system were investigated. Hydration heat tests reveal that CSHs effectively accelerated the early hydration of the slurry within the first 12 h without affecting its later hydration. CSHs and CSA acted synergistically to enhance hydration kinetics. However, it is crucial to control the proportion of CSA within the range of 5%-10%; exceeding this ratio can severely inhibit the hydration of silicates. Strength tests indicate that the addition of CSHs and CSA can increase the compressive and flexural strengths of mortar within the first 12 h by 282% and 208%, respectively, without impacting the development of its later-age strength. Together, they synergistically provide favorable support for the strength and toughness of matrix. Based on linear regression analysis and nitrogen adsorption and desorption tests, it was concluded that CSHs enhance the hydration dependence of matrix strength, while CSA diminishes this characteristic. This is because CSHs refine the pore size distribution of the paste, increasing the proportion of micropores, whereas CSA promotes the formation of more mesopores and macropores, leading to coarser pores; however, 5% CSA is beneficial for further refining the pore structure. The microcosmic phase evolution of the early-strength cementitious system was analyzed through X-ray diffraction and scanning electron microscope-energy dispersive spectrometer experiments. Results demonstrate that low proportions of CSA and CSHs promote the co-growth of ettringite and C-S-H gel, ensuring a more rapid formation of a dense hydration network in the early stages, thereby accelerating strength development. These findings provide a reference for the design and preparation of precast concrete.

Exploring Olive Pit Powder as a Filler for Enhanced Thermal Insulation in Epoxy Mortars to Increase Sustainability in Building Construction

This article explores the use of olive pit powder (OPP) as a promising resource for enhancing the thermal insulation properties of epoxy mortars. A comprehensive analysis of the chemical and physical characteristics of OPP was conducted, employing analytical techniques including scanning electron microscopy (SEM), thermogravimetric analysis and emitted gas analysis (TG-MS-EGA), and proximal analysis. Experimental samples of epoxy grout were prepared by using different proportions of a conventional inorganic filler, quartz powder, and OPP within an epoxy mortar matrix. As the percentage of OPP in the formulation increased, the microstructure of the samples gradually became more porous and less compact. Consequently, there was a decrease in density with the increase in OPP content. The 28-day compressive strength decreased from 46 MPa to 12.8 MPa, respectively, in the samples containing only quartz (Sample E) and only OPP (Sample A) as a filler. Similarly, flexural strength decreased from 35.2 to 5.3 MPa. The thermal conductivity decreased from 0.3 W/mK in Sample E to 0.11 in Sample A. Therefore, increasing the %wt of OPP improved insulating properties while reducing the mechanical resistance values. This study highlights the potential of OPP as an environmentally friendly and thermally efficient filler for epoxy mortars, thereby promoting sustainable construction practices.

Laboratory Evaluation of Strength Performance of Full-Depth Reclamation with Portland Cement Material

Full-depth reclamation with Portland cement (FDR-PC) represents an innovative cold recycling technology for pavements, holding significant promise due to its capacity to reuse deteriorated pavement base layers. This paper investigates the key factors influencing the strength properties of FDR-PC. The results indicate that, compared to the static compaction method, the vibratory compaction method yields cold-recycled mixtures with higher maximum dry density and unconfined compressive strength (UCS). Increasing the cement content and base-to-surface ratio, extending the curing time, and raising the curing temperature all contribute to enhancing UCS. Furthermore, increasing the base-to-surface ratio and cement content enhances both indirect tensile strength and flexural strength. An approximate linear correlation exists between indirect tensile strength and UCS, as well as between flexural strength and UCS. The strength characteristics of FDR-PC were comprehensively characterized in this study, providing effective verification of its applicability.

Effects of oil heat treatment on poplar wood properties: A pilot scale study

Pilot-scale oil heat treatment was conducted to enhance the quality of poplar wood obtained from a fast-growing plantation. Three target temperatures, namely 180, 190, and 200 ˚C, were chosen for the oil heat treatment process. Clear, small specimens were cut from the lumber, following the prescribed standards for assessing wood quality. Light microscopy revealed the ruptures and deformation of the wood cell wall as the treatment temperature increased. The volumetric swelling of the treated specimen decreased proportionally with the increase in treatment temperature. The impact of oil heat treatment on the mechanical properties of wood varied depending on the specific type of mechanical strength and processing temperature. The modulus of rupture, toughness, and hardness of the treated specimens drastically decreased at 200°C. However, the specimens treated at 200°C exhibited much lower mass loss during the fungal decay test. The results of the analytical test showed an increase in the crystalline cellulose content and thermal stability of the treated wood, due to the thermal degradation of hemicelluloses and amorphous regions of cellulose. Overall, it is concluded that oil heat treatment of poplar wood in the optimal temperature is an efficient approach to upgrade its quality with minimal reduction in mechanical strength.

Hybridization of woven kenaf and unidirectional glass fibre roving for unsaturated polyester composite

Hybridization of woven kenaf and unidirectional glass fibre roving for unsaturated polyester composite