Flexural Tests Research Articles

Moisture-induced mechanical property changes in natural hybrid composites with mwcnt fillers

ABSTRACT This study investigates the moisture absorption behaviour and its effects on the mechanical properties of polyester composites reinforced with jute and hemp fibres. The differences in moisture absorption between distilled water and saltwater are examined. Tensile and flexural tests are conducted on pure jute fibre-reinforced polyester composite, pure hemp fibre-reinforced polyester composite, and jute (J-P) and hemp (H-P) fibre-reinforced polyester composite. Changes in mechanical properties due to varying moisture conditions are analysed. Furthermore, the impact of a synthetic nano filler, multiwall carbon nanotubes (MWCNTs), on these composites is assessed. The study reveals that MWCNTs enhance mechanical properties, particularly in moist conditions. Fracture behaviour analysis aids in understanding the interaction between natural fibres, the matrix, and nano-reinforcement. At maximum natural fibre weight fractions (40%), moisture absorption reaches 8.17% for the J-P composite in distilled water and 9.61% in saltwater, while the H-P composite shows maximum absorptions of 6.61% and 8.27%, respectively. The hybrid composite records 4.18% and 7.17% under similar conditions. Compared to the plain jute fibre-reinforced composite, the addition of multiwall carbon tubes into the polymer matrix significantly reduces the moisture absorption capacity of the jute composite to 34.89% and 31.30% for distilled water and saltwater, respectively.

Effect of recycled molybdenum tailings on mechanical properties of ultra-high-performance concrete

This paper presents experimental studies on mechanical properties and micro-structures of ultra-high performance concrete (UHPC) made of recycled molybdenum tailings. The particle size distribution and chemical compositions of recycled molybdenum tailings were analysed at first. Then, compressive and flexural tests were conducted on UHPC in which different volume fractions of recycled molybdenum tailings were used to replace silica sand. The effects of recycled molybdenum tailings replacement ratio on the compressive and flexural strengths were determined through comparisons. Besides, X-ray diffraction tests and backscattered electron tests were carried out to analyse the effect of molybdenum tailings on the micro-structure of UHPC. Based on test data, an optimal replacement ratio of molybdenum tailings was determined which could significantly reduce the cost of UHPC but maintain the mechanical properties in compression. A molybdenum tailings replacement ratio of 30% was recommended to maximise the economic effect and to reduce the carbon emission.

The Flexural Strength and the Effect of the Autoclave Sterilization of Polypropylene/Natural Rubber Blended Materials

Background: Rubber dam clamps are used extensively in dentistry, especially during root canal treatment. However, existing rubber dam clamps have several drawbacks, including discomfort and potential damage to vital tissue in the oral cavity. To address these existing issues, a new rubber dam clamp should be developed. The aim of this study was to identify the optimum ratios of polypropylene and natural rubber (PP/NR) for a customized rubber dam clamp in dentistry. This study was focused on the flexural strength of PP/NR in various ratios. Moreover, the impact of autoclave sterilization was also considered. Methods: Six proportions of PP/NR blends (100/0, 90/10, 80/20, 70/30, 60/40 and 50/50) were prepared and assessed for flexural strength using a three-point bending test. After this test, the PP/NR blends with 100/0, 90/10 and 80/20 ratios were selected and underwent autoclave sterilization for 1, 5 and 10 cycles. Eventually, the flexural strength testing was repeated and investigated. An analysis of variance and Tukey’s test were used to evaluate the flexural strength of various PP/NR blends before autoclave sterilization at p < 0.05. An analysis of variance and Dunnett’s T3 test were used to evaluate the flexural strength of selected PP/NR blends before and after autoclave sterilization at p < 0.05. Results: The results revealed that the flexural strength of PP/NR blended materials showed a statistically significant difference in every group of this study. The autoclave sterilization test revealed that the flexural strength of the PP/NR 90/10 and 80/20 ratios was significantly increased after sterilization for 1, 5 and 10 cycles. In addition, the PP/NR 90/10 ratio was also comparable to the 100/0 ratio. The lower NR content in PP/NR blends resulted in significantly higher flexural strength, and autoclave sterilization had an effect on this property. Conclusions: This study suggested that the PP/NR blend with a 90/10 ratio might be considered as an alternative material for developing rubber dam clamps.

Performance Analysis of FFF-Printed Carbon Fiber Composites Subjected to Different Annealing Methods

Annealing is a popular post-process used to enhance the performance of parts made by fused filament fabrication. In this work, four different carbon-fiber-based composites were subjected to two different annealing methods to compare their effectiveness in terms of dimensional stability, surface roughness, tensile strength, hardness, and flexural strength. The four materials include PLA-CF, PAHT-CF, PETG-CF, and ABS-CF. The annealing methods involved heating the printed composites inside an oven in two different ways: placed on a tray and fluidized bed annealing with sharp sand. Annealing was conducted for a one-hour time interval at different annealing temperatures selected as per the glass transition temperatures of the four materials. The results showed that oven annealing provides better results under all scenarios except dimensional stability. PETG-CF and ABS-CF composites were significantly affected by oven annealing with expansion along the z-axis as high 8.42% and 18% being observed for PETG-CF and ABS-CF, respectively. Oven annealing showed better surface finish due to controlled and uniform heating, whereas the abrasive nature of sand and contact with sand grains caused inconsistencies on the surface of the composites. Sand annealing showed comparable hardness values to oven annealing. For tensile and flexural testing, sand annealing showed consistent values for all cases but lower than those obtained by oven annealing. However, oven annealing values started to decrease at elevated temperatures for PETG-CF and ABS-CF. This work offers a valuable comparison by highlighting the limitations of conventional oven annealing in achieving dimensional stability. It provides insights that can be leveraged to fine-tune designs for optimal results when working with different FFF-printed carbon-fiber-based composites, ensuring better accuracy and performance across various applications.

The Influence of Alkaline Treatment on Delamination resistance of Woven Flax Fiber-Reinforced Epoxy Composite Laminates

AbstractDelamination is one of the most typical failure modes of fiber-reinforced polymer composite laminates. Thus, investigating and improving the delamination behavior of these laminates are of vital importance. The present research discovers and investigates the role of the alkaline treatment of twill-woven flax fabric on the delamination resistance of flax fiber-reinforced epoxy composite laminates. Initially, flax fibers were treated with different sodium hydroxide solution concentrations (2–5–10%) for 2 h. The influence of alkaline treatment on fiber characteristics was evaluated by performing a single-yarn tensile test, scanning electron microscopy, and Fourier transform infrared spectroscopy analysis for treated and untreated flax fibers. The appropriate treatment condition was selected based on the properties obtained from the tests conducted on the fiber level. Subsequently, to discover the role of alkaline treatment on delamination resistance, flax fabric was treated with the selected treatment condition for further composite fabrication. The treated and untreated flax fiber-reinforced epoxy composites were fabricated using a hand lay-up technique followed by hot compression. Interlaminar shear strength, double cantilever beam, and end-notch flexural tests were carried out for treated and untreated composites to determine the effect of alkaline treatment on the delamination resistance. The results proved that the alkaline treatment of flax fabric significantly improved the delamination resistance of treated composite laminates compared to untreated ones. The interlaminar shear strength, the mode I interlaminar fracture toughness (propagation), and mode II interlaminar fracture toughness were improved by 27.3%, 14%, and 24.9%, respectively, for treated composite laminates compared to untreated ones.

Experimental study on flexural fatigue resistance of fiber-reinforced sustainable walnut shell ash mortar

In recent research on building materials, researchers have increasingly focused on replacing cement with agricultural waste. This approach offers significant advantages in terms of reducing global CO2 emissions and promoting the sustainability of building materials. In this paper, the use of the agricultural waste walnut shell ash (WSA) to partially replace cement in sustainable green mortars is explored. Specifically, equal amounts of WSA (5%, 10% and 15%) were used to replace cement. To offset the reduction in strength caused by the partial replacement of cement with WSA, basalt fibers were added to the mortar mixture. The effect of these fibers on the mechanical properties of the WSA-reinforced mortar was examined in compression tests, split tensile tests, and flexural fatigue cycle tests. In the flexural fatigue tests, the parameter and length of basalt fibers were varied and different stress levels (0.85, 0.8 and 0.75) were applied. The fatigue equations were developed using the Weibull model and p–s–n curves with a survival probability of 0.5 were derived. The results showed that the compressive strength and split tensile strength of the specimens increased with the addition of basalt fibers, with maximum values of 34.7 MPa and 3.8 MPa, respectively, and maximum increases of 8.78% and 21.95%, respectively. In addition, the average fatigue life of WSA mortar was 247,541 cycles, which increased by 139.26% when the stress level was 0.75, fiber length was 9 mm, and dosage was 0.3%. The linear regression fitting showed good correlation and provided valuable insights for practical engineering applications.

Influence of nano‐silica particles on fracture features of recycled aggregate concrete using boundary effect method: Experiments and prediction models

AbstractThe aim of this investigation is to assess the impact of using nano‐silica (Na) at varying weight percentages of 0%, 1.5%, 3%, 4.5%, and 6% as partial cement substitute on fracture parameters of recycled aggregate concrete (RAC). A servo‐controlled testing system was employed to carry out three‐point flexure tests on 90 notched beams. Boundary effect method was used in order to interpret the fracture features. The results illustrate that adding Na increases the size‐independent fracture energy, fracture toughness and initial fracture energy of RAC by 29%, 32%, and 24% compared to that without Na, respectively. The maximum values of these parameters occur at 4.5% Na. The reference crack length () decreases from 6% to 22% by adding 1.5% to 6% Na. This shows that the RAC gets more brittle by the addition of Na. Moreover, the RAC behavior moves towards linear elastic fracture mechanics criteria by adding Na. Finally, according to the mechanical properties and test variables, multivariable models were suggested for prediction of the fracture parameters of the RAC containing Na. The models predictions were compared with experimental findings of the previous research.

Durability of Two-Component Grout in Tunneling Applications: A Laboratory Test Campaign

Today, two-component grout is the most widely used backfilling technology in shielded mechanized tunneling. Despite its intensive use, however, very scant information pertaining to the durability of this material is available in the scientific literature. In this work, the aging of two-component grout is studied by curing grout samples using three different modalities. Furthermore, the action of air on two-component grout is studied by assessing the dehydration process, which is a phenomenon that occurs when the material is cured without being completely embedded in soil/rock. Uniaxial compression tests and three-point flexural tests have been carried out for mechanical characterization. The results reveal that in a curing environment made of sand, a moisture of 5% is sufficient to guarantee correct curing of the grout and extend the mechanical performance to three years, whereas the action of air is potentially dangerous, since the grout suffers strongly from dehydration. Despite this dehydration process, however, the mechanical performance of the grout also tends to increase for samples cured under the action of air until a very high level of cracking and shrinkage is reached. A discussion of the limitations on the uniaxial compression strength as the main mechanical parameter for the characterization of two-component grout concludes the work.

Structural Performance of GFRP-Wrapped Concrete Elements: Sustainable Solution for Coastal Protection

Protecting coastal regions is crucial due to high population density and significant economic value. While numerous strategies have been proposed to mitigate scouring and protect coastal structures, existing techniques have limitations. This paper introduces a novel approach, SEAHIVE®, which enhances the performance of engineered structures by utilizing hexagonal, hollow, and perforated concrete elements externally reinforced with glass fiber-reinforced polymer (GFRP). Unlike conventional steel bars, GFRP offers superior durability and requires less maintenance, making it a sustainable solution for any riverine and coastal environment. SEAHIVE® aims to provide robust structural capacity, effective energy dissipation, and preservation of natural habitats. Although some research has addressed energy dissipation and performance in riverine and coastal contexts, the structural performance of SEAHIVE® elements has not been extensively studied. This paper evaluates SEAHIVE® elements reinforced with externally bonded GFRP longitudinal strips and pretensioned GFRP transverse wraps. Testing full-size specimens under compression and flexure revealed that failure occurred when the pretensioned GFRP wraps failed in compression tests and when longitudinal GFRP strips slipped in flexure tests. Strength capacity was notably improved by anchoring the GFRP strips at both ends. These findings underscore the potential of the SEAHIVE® system to significantly enhance the durability and performance of coastal and riverine protection structures. FEM simulations provided critical insights into the failure mechanism and validated the experimental findings. In fact, by comparing FEM model results for cases before and after applying GFRP wraps under the same compression load, it was found that maximum stresses at crack locations were significantly reduced due to compression forces resulting from the presence of pretensioned GFRP wraps. Similarly, FEM model analysis on flexure samples showed that the most vulnerable regions corresponded to the locations where cracks started during testing.

Impact of Graphene Nano particles on static and dynamic mechanical properties of basalt-glass fibre reinforced epoxy polymer hybrid composites

ABSTRACT This paper investigates the structure-property relationships in basalt – glass fabric reinforced hybrid polymer composites doped with graphene nanoplatelets. Basalt Glass fabrics were reinforced with 0.2 wt.% − 0.8 wt.% graphene using hand layup and compression moulding to fabricate laminated plates. The mechanical, morphological, and thermomechanical properties were characterised using tensile, flexural, impact, SEM, FTIR, XRD, and DMA testing. Results showed that low graphene loadings of 0.2 wt.% − 0.4 wt.% led to small, isolated graphene platelets decorating the basalt fibres. At 0.8 wt.% loading, extensive wrinkling, folding, and stacking of graphene sheets on the basalt was observed. FTIR revealed increasing sp2 C=C vibrations and XRD showed rising graphene peak intensities with higher loadings. While tensile and flexural strengths improved up to 0.6 wt.% graphene due to efficient stress transfer, impact energy increased consistently until 0.8 wt.% graphene owing to reinforcement effects. DMA exhibited enhanced storage modulus and restricted mobility with more graphene. An optimum graphene loading of 0.6 wt.% was found to maximise the mechanical performance through uniform dispersion and strong interfacial adhesion. The results demonstrate that graphene incorporation can substantially augment the strength, toughness, and thermomechanical properties of the composites at appropriate compositions prior to aggregation.

Vertical z-axis discontinuous carbon fibers for improved lightning strike performance of continuous fiber-reinforced polymer composites

Effective lightning strike protection for critical aerospace and wind applications requires high electrical conductivity to dissipate current efficiently. However, polymer matrix composites face a challenge due to their inherently insulating nature. While conventional carbon fiber-reinforced composites (CFRP) exhibit electrical conductivity in the planar direction, achieving through-thickness conductivity remains an ongoing challenge. In this work, we have undertaken the fabrication of CFRP interleaved with vertically oriented carbon fibers (Z-fiber) to impart higher electrical conductivity along the thickness direction. Two Z-fiber composite variations are prepared: Z-1 with a single layer of Z-fiber and Z-5 with five interleaved layers and compared with no Z-fiber layer (Z-0) composite. The composite panels were subjected to lab-scale lightning strike tests with a current magnitude of 100 kA. To emulate real-world service conditions, an aerospace-grade paint coating was applied to the composite laminates. Comparative analysis shows Z-1 reduces damage diameter to ∼22 mm compared to Z-0 (∼26 mm), while Z-5 exhibits the least damage (∼16.7 mm), confirmed by optical microscopy. Z-5 demonstrates nine times higher through-thickness electrical conductivity than Z-0, reducing electrical anisotropy substantially. Thermal-electric finite element damage modeling predicts surface damage within 6% of experimental values for both Z-0 and Z-5 composites. Flexural tests post-lightning reveal Z-5 retains 66% flexural strength and 86% modulus, significantly better than Z-0, which retains less than 40% for both properties. This study highlights the efficacy of Z-fiber composites in lightning strike protection, offering improved through-thickness conductivity and mechanical property retention.

Properties of Steel Fiber Reinforced Desert Sand Concrete

To study the effect of steel fibers on the mechanical properties of desert sand concrete (DSC), three lengths (12 mm, 16 mm, and 20 mm) of steel fibers and five volumetric admixtures (0.4%, 0.8%, 1.2%, and 1.6%) of steel fibers were selected to make 13 groups of concrete specimens (78 cubic specimens and 39 prismatic specimens). Compressive test, splitting test and flexural test were carried out on the specimens of DSC after curing for 28 days. According to the test results, the influence law of each parameter on the mechanical properties of DSC was analyzed, and the working principle of steel fibers to improve the mechanical properties of DSC was described by combining macroscopic and microscopic methods. The results showed that the addition of steel fibers can effectively improve the damage pattern of DSC, and all the mechanical properties of DSC are improved; 12 mm steel fibers were relatively effective in enhancing the compressive strength of DSC and 20 mm steel fibers were relatively effective in enhancing the splitting and flexural strength of DSC; Both macroscopic and microscopic results showed that the addition of appropriate amount of steel fibers can effectively fill the internal pores of DSC. The results can provide theoretical basis and technical support for the engineering application of steel fiber reinforced DSC.

Analysis of aging effects on the mechanical and vibration properties of quasi-isotropic basalt fiber-reinforced polymer composites

Eco-friendly natural fiber composites, such as basalt fiber composites, are gaining traction in material science but remain vulnerable to environmental degradation. This study investigates the mechanical and vibrational properties of quasi-isotropic basalt fiber composites subjected to aging in two different environments: ambient (30 ºC) and subzero (-10 ºC), both in distilled water until moisture saturation. Aged specimens absorbed 8.66% and 5.44% moisture in ambient and subzero conditions, respectively. Mechanical testing revealed significant strength reductions in tensile, flexural, impact, and short beam shear tests, with ambient-aged specimens showing the largest decline (up to 31.7% in flexural strength). Vibrational analysis showed reduced natural frequencies, particularly under ambient conditions (27.27%). Sound absorption tests showed that pristine specimens had the highest transmission loss, while moisture-rich ambient-aged specimens had the lowest. SEM analysis confirmed surface degradation, with fiber pull-out and matrix debonding contributing to property loss. This research provides valuable insights into the environmental limitations of basalt fiber composites, emphasizing the need for enhanced durability in eco-friendly materials.

Evaluation of Admixture Silane Added into Cementitious Pastes

This manuscript evaluated the performance of silanes in cementitious matrices in the partial replacement of superplasticizers by silanes. For this, pastes with a water/cement ratio of 0.186 were produced and the superplasticizer admixture based on polycarboxylate esters was partially substituted by three types of silanes—vinyltriethoxysilane silanes (VTES), n-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS), and methacryloxypropyltrimethox-ysilane (MCPTMS)—in two substitutions levels (20% and 40%), and then tested in Portland cement pastes. Specific gravity, trapped air, mini-slump, and hydration kinetics (evaluated by isothermal calorimetry up to 48 h) of the pastes were determined in the fresh state. Thus, in the hardened state, the compressive and flexural strength tests (7 and 28 days), specific gravity, and absorption by immersion of the pastes were carried out. The results showed that the substitution of 20% and 40% of VTES and AEAPTMS considerably reduced the workability and increased the air content of the pastes in comparison to the reference sample. In contrast, the incorporation of 20% and 40% of MCPTMS did not significantly affect these properties. The presence of silane, for all analyzed samples, had a delaying effect on the hydration process: the maximum delay verified had a hydration peak in approximately 36 h for the 40% MCPTMS sample and the minimum delay verified had a hydration peak in approximately 11 h for the 20% VTES sample. The replacement of 20% and 40% by any of the silanes progressively reduced the flexural strength at both 7 and 28 days. In the compressive strength, as well as in the tensile strength in flexion, there was a decrease in the results when compared to the reference, except for the MCPTMS, at 7 and 28 days. In immersion absorption, all samples showed high percentages of absorption and void index when compared to the reference.

Evaluation of the thermomechanical properties of novel epoxy composites reinforced with Geonoma baculifera fibers

Natural lignocellulosic fibers (NLFs) have shown a great potential as reinforcements in composites in recent decades. Among other reasons, environmental concerns and the depletion of oil reserves justify research on natural composites as they offer an environmentally friendly alternative and align with the principles of sustainable development. Among the plethora of NLFs available in nature, the ubim fiber (Geonoma baculifera) has not yet been investigated as a reinforcement for composites in potential engineering applications. Therefore, this study evaluates, for the first time, the mechanical properties of epoxy composites with 10, 20, and 30 vol% of ubim fibers. These properties were assessed through Izod impact, tensile and flexural tests as well as dynamic mechanical analysis (DMA). The data were statistically analyzed using the ANOVA method. Scanning electron microscopy (SEM) analysis indicated a transition from a purely brittle fracture mechanism to a ductile-brittle combination as the fiber volume in the composite increased. Tensile tests of the composites demonstrated an increasing trend in strength and elastic modulus with fiber volume. The results of the flexural tests also displayed a similar trend in strength and elasticity modulus for the composites. The results of DMA tests showed that composite materials with a 30 vol% of ubim fibers exhibited a high glass transition temperature and a low tan δ value, suggesting higher stiffness of this composite compared to others. Overall, the results indicated that the incorporation of 30 vol% ubim fibers into the composites significantly improved their mechanical properties compared to other tested fiber fractions. Additionally, their functional characteristics, such as simplicity in the manufacturing process, low cost, and excellent strength-to-weight ratio, make these composites particularly suitable for applications in sectors such as the automotive industry, construction panels, and packaging. These factors contribute to the development of an efficient, sustainable, recyclable and environmentally friendly composite.

Investigation on piezoresistive properties of reduced graphene oxide treated glass textiles based multifunctional sensors

AbstractGlass fabric‐reinforced composites (GFRC) and other revolutionary engineered materials find extensive application in the aerospace, construction, and automobile sectors. It is challenging to predict damage under real‐time stresses due to the anisotropic behavior of composite materials. This study presents the development of a glass textile‐based multifunctional composite sensor and demonstrates its application as a change in resistance or gauge factor in structural health monitoring (SHM) systems. This sensor is coated with reduced graphene oxide (rGO) nanomaterial. Its electrical resistance is evaluated by examining the concentration of nanoparticles and varying geometrical parameters. A three‐point bending method assessed the piezoresistive behavior of the integrated sensor in the GFRC. The impact of sensor width and relative placements in the material's thickness direction within the composite samples is evaluated. Cyclic flexural testing was also performed to demonstrate real‐world applications. The research concludes that it can be utilized as a damage assessment technique for GFRC. The developed sensor can be used to provide an electrically conductive path or as a resistor in the field of E‐textiles. The developed piezoresistive sensor has the flexibility to be used as a multifunctional sensor for multiple purposes, such as force, torque, weight, pressure, flow, acceleration sensors, etc.Highlights Glass textile‐based multifunctional materials are reported as strain‐monitoring sensors. Tailored sensor resistance could be achieved through rGO current conduction paths. Glass textile‐based sensors could potentially be used in the field of E‐textile.

Enhanced Thermal and Flexural Properties of Alkalized Date Palm/Kenaf Fiber-Reinforced Epoxy Hybrid Composites: A Comparative Study of Untreated and Treated Fibers

ABSTRACT This study evaluates the thermal and mechanical behavior of hybrid composites made from date palm (DP) and kenaf fibers (KF) in an epoxy thermoset matrix. Both DP and KF fibers are abundant and renewable, reducing environmental impact. KF offers high tensile strength and stiffness, improving composite strength and rigidity, while DP fibers offer toughness and impact resistance, enhancing durability. The composites were developed in 30%, 50%, and 70% DP-KF compositions using layup and hot-pressing methods. Fiber treatment through alkalization was analyzed for its impact on mechanical and thermal properties to find the optimal fiber ratio. The hybrid composites were subjected to DMA, TGA, and flexural tests. The treated composites exhibited fewer impurities and increased cellulose content, resulting in enhanced flexural performance. This improvement was evident through higher storage modulus, lower loss modulus, and reduced tan δ when exposed to thermal stress. The 30% DP and 70% KF composites exhibited best performance. The treated 30DP-70KF exhibited improvement in the flexural strength and modulus by 13.8% and 2.7%, respectively. TGA demonstrated that treated 30DP-70KF composites had a higher glass transition temperature (Tg) and better thermal degradation resistance. These findings highlight the potential of natural fiber hybrids in creating sustainable, high-performance composite materials for construction and industrial applications.

Mechanical, Durability, and Microstructure Characterization of Pervious Concrete Incorporating Polypropylene Fibers and Fly Ash/Silica Fume

Pervious concrete, because of its high porosity, is a suitable material for reducing the effects of water precipitations and is primarily utilized in road pavements. In this study, the effects of binder-to-aggregate (B/A) ratios, as well as mineral admixtures with and without polypropylene fibers (PPFs) (0.2% by volume), including fly ash (FA) or silica fume (SF) (10% by substitution of cement), on the mechanical properties and durability of pervious concrete were experimentally observed. The experimental campaign included the following tests: permeability, porosity, compressive strength, splitting tensile strength, and flexural strength tests. The durability performance was evaluated by observing freeze–thaw cycles and abrasion resistance after 28 d curing. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA-DTA), and scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) were employed to investigate the phase composition and microstructure. The results revealed that, for an assigned B/A ratio identified as optimal, the incorporation of mineral admixtures and fibers mutually compensated for their respective negative effects, resulting in the effective enhancement of both mechanical/microstructural characteristics and durability properties. In general, pervious concrete developed with fly ash or silica fume achieved higher compressive strength (>35 MPA) and permeability of 4 mm/s, whereas the binary combination of fly ash or silica fume with 0.2% PPFs yielded a flexural strength greater than 6 MPA and a permeability of 6 mm/s. Silica fume-based pervious concrete exhibited excellent performance in terms of freeze–thaw (F-T) cycling and abrasion resistance, followed by fiber-reinforced pervious concrete, except fly ash-based pervious concrete. Microstructural analysis showed that the inclusion of fly ash or silica fume reduced the harmful capillary pores and refined the pore enlargement caused by PPFs in the cement interface matrix through micro-filling and a pozzolanic reaction, leading to improved mechanical and durability characteristics of pervious concrete.

Enhancement of Mechanical Properties of Geopolymer Ferrocement through Incorporation of a Novel Binder and through Optimization of Alkaline Activator Ratios

Geopolymer ferrocement is geopolymer mortar, reinforced with wire mesh. The ratios of binder composition and alkaline activator, with which the geopolymer has been prepared, have profound influence on the mechanical performance of geopolymer ferrocement. In this study the influence of a binder material Alccofine and variation in ratios of alkaline activators have been studied for their effect on mechanical properties of geopolymer ferrocement. Alccofine was replaced with varying proportions of Ground Granulated Blast-Furnace Slag (GGBS). The molarities of NaOH and NaOH/Na₂SiO₃ ratios were also variated to find their influence on strength and crack control of ferrocement, when combined with single, double, and triple-layers of ferro mesh configurations. Tests such as direct shear test, three-point bending, and four-point flexural tests were conducted to to measure shear strength, flexural strength and to estimate region of pure bending. It was observed that the mix with 20% Alccofine and 80% GGBS, an A/B ratio of 0.5, and a NaOH/Na₂SiO₃ ratio of 1.5 yielded a compressive strength of 50 MPa at 90 days of geopolymer ferrocement. Also the triple-layer mesh configuration exhibited the best results, achieving 10 N/mm² in shear strength and 12 N/mm² in flexural strength, compared with other configurations. These findings indicate that by incorporation of Alccofine, optimizing binder composition, activator ratios and reinforcement, the strength parameters of geopolymer ferrocement can be significantly improved.

Reuse of polyvinyl chloride residues—in powder and fiber forms—as potential components for green mortar pavers

Plastic wastes are considered a significant environmental pollution load because of their mostly non-biodegradable nature. Consequently, the need to lessen the environmental impact calls for employing eco-friendly strategies such as reusing materials in construction. The objective of this study is to analyze the mechanical behavior and environmental impacts of mortar elements, with a specific focus on pavers, by incorporating waste polyvinyl chloride (WPVC) as aggregate and partially replacing cement. Two distinct forms of this waste were considered in the investigation: (i) as it is generated in industrial processes, mainly in fiber form, WPVCf, and in the form of powder obtained by sieving the former, WPVCp. The ratio of conventional mortar materials replaced by WPVC and the final water-to-binder ratio changed based on waste type and mix workability. The experimental work involved preparing 84 pavers, each measuring 100 mm × 150 mm × 60 mm. For each type of paver, 12 samples were prepared, ensuring a minimum of 4 sets of test data for each curing period (7, 14, and 28 days). Flexural strength tests, conducted in accordance with the Colombian standard NTC 2017, utilized a standard flexural test machine with a 150 kN capacity. A specially designed steel tool applied a point load at the center of each paving block, maintaining a minimum distance of 10 millimeters from the edges. The findings demonstrated that pavers containing fiber plastic waste exhibited the requisite strength for paved walkways, even in the short term, when the weight ratio of WPVCf to sand (WPVCf/S) was 24 %. These results derive an eco-friendly solution for reusing PVC wastes currently deposited directly in landfills. Moreover, to analyze the environmental impacts of this solution, a Life Cycle Assessment (LCA) analysis was carried out in this research. The LCA results pointed out that dosing with a WPVCf/S ratio of 24 % emerges as the most ecologically responsible, manifesting substantial reductions across impact categories, such as a significant 23 % decrease in climate change, a 23 % reduction in Photochemical ozone formation, and a 22 % reduction in renewable energy consumption. This underscores the potential of WPVCf incorporation as a consequential step toward eco-friendly construction materials. Furthermore, this solution not only translates to diminished paving block costs by requiring less fine aggregate and cement but also contributes to reduced transportation expenses owing to the decreased weight of the pavers.