Improvement In Flexural Strength Research Articles

Synergic effect of polyester fiber and nano silica on chemical resistance of geopolymer mortar.

The aim of this study is to evaluate the synergistic effect of polyester fiber-reinforced and nanoslica on the technical performance and durability of geopolymer mortar in terms of the chemical resistance. The study examined how the addition of polyester fiber and nanosilica affects the short-term severe durability of geopolymer mortar specimens made with fly ash (type F). The specimens were cured under ambient conditions. Different percentages (0.6%, 1.2%, and 1.8%) of polyester fiber were used, both with and without nanosilica. Additionally, a reference mixture containing only nanosilica was prepared.All mixtures had a liquid to binder ratio of 0.50, and the ratio of NaOH to Na2SiO3 solution was kept at 2.5:1 by weight. The produced mixes, after 28 days of ambient curing, were immersed for another 28 days in solutions containing 3.5%, 5%, and 5% of sodium chloride, magnesium sulphate and sulfuric acid, respectively. For comparison, control specimens which were not exposed to chemical attacks were tested at the same age of 56 days. Moreover, water absorption and sorptivity tests were conducted to explain the durability performance in a more detailed way. The test results express that the combination of both materials showed a synergistic effect and resulted in greater improvements in compressive and flexural strengths. Both materials can reduce the reduction in compressive strength caused by sulfuric acid exposure, but polyester fiber can increase mass loss. The presence of magnesium sulfate and sodium chloride can lead to a reduction in strength, but the addition of both polyester fiber and nanosilica can mitigate these effects. The addition of fibers creates a network of pores that can limit water absorption, and nanosilica can further enhance the microstructure and reduce water absorption. However, using polyester fiber beyond 1.2 percent can adversely affect the rate of water absorption.

Enset Fiber-Reinforced Polylactic Acid-Based Biocomposites for High-Performance Application

In recent years, there has been growing interest in using plant fibers to reinforce materials in modern manufacturing. This study focuses on the development of a novel biocomposite made from an enset fiber (EF) and polylactic acid (PLA) matrix using compression molding at a hot-pressing temperature of 170 °C and pressure of 7 MPa for 7 min. Before preparing the biocomposites, the fibers were chemically modified with different concentrations of sodium hydroxide (NaOH) and cut into shorter fibers with a 40 mm average length in size. Then, the extent of modifications on the mechanical properties, dynamic mechanical behavior, morphology, and water absorption were investigated. The tensile, flexural, and Charpy impact tests were carried out to evaluate the mechanical properties of the samples as per ASTM standards. Moreover, dynamic mechanical analysis (DMA) and the water absorbency of the biocomposites were investigated, and the results were graphically shown and explained. The results indicate that the biocomposite treated with 5% NaOH exhibited significant improvements in tensile strength, flexural strength, and impact strength compared to the untreated composite. The tensile modulus and flexural modulus of 5% NaOH-modified enset fiber biocomposite were also enhanced by 55.8% and 70.3% compared to untreated enset fiber biocomposite. The highest tensile strength, flexural strength, and impact strength found for the PLA composite reinforced by EF treated with 5% w/v NaOH solution were 20.16 MPa, 30.21 MPa, and 12.02 kJ/m2, respectively. In general, the modification of natural fibers improves adhesion at the interface and therefore decreases the water absorption and improves the dynamic mechanical properties of biocomposites.

ENHANCING CONCRETE PERFORMANCE BY UTILIZING CRUSHED GLASS AND WASTE BOTTLE PLASTIC FIBERS FOR IMPROVED STRENGTH AND FLEXURAL PROPERTIES

This research investigates the potential of using crushed glass and waste bottle plastic fibers as sustainable additives to enhance the performance of concrete in terms of strength and flexural properties. The study involves incorporating varying percentages of crushed glass (CG) and waste bottle plastic fibers (PE) fibers into concrete mixtures and assessing the changes in compressive and flexural strength across different curing periods, namely 7, 28, 56, and 90 days. The results reveal that the optimal combination for improved performance is 15% CG and 10% PE fibers, as it consistently demonstrates the highest percentage improvement in both compressive and flexural strength across all curing periods. The findings of this study have significant implications for sustainable construction practices, as incorporating crushed glass and waste bottle plastic fibers in concrete mixtures not only improves the material's performance but also promotes recycling and repurposing waste materials. Furthermore, the use of these recycled materials could lead to cost savings, reduced material volume, lower labor costs, and improved abrasion resistance in construction projects.

Synthesis of Pore-Size-Tunable Porous Silica Particles and Their Effects on Dental Resin Composites.

The filler/resin matrix interface interaction plays a vital role in the properties of dental resin composites (DRCs). Porous particles are promising fillers due to their potential in constructing micromechanical interlocking at filler/resin matrix interfaces, therefore improving the properties of the resulting DRCs, where the pore size is significantly important. However, how to control the pore size of porous particles via a simple synthesis method is still a challenge, and how their pore sizes affect the properties of resulting DRCs has not been studied. In this study, porous silica (DPS) with a dendritic structure and an adjustable pore size was synthesized by changing the amounts of catalyst in the initial microemulsion. These synthesized DPS particles were directly used as unimodal fillers and mixed with a resin matrix to formulate DRCs. The results showed that the DPS pore size affects the properties of DRCs, especially the mechanical property. Among various DPS particles with different pore sizes, DPS6 resulted in 19.5% and 31.4% improvement in flexural strength, and 24.4% and 30.7% enhancement in compression strength, respectively, compared to DPS1 and DPS9. These DPS particles could help to design novel dental restorative materials and have promising applications in biomedicine, catalysis, and adsorption.

Research on performance monitoring of binary nano modified concrete based on temperature variation

The use of concrete is widespread, but it poses challenges due to its high consumption of Earth's raw resources and difficulties in recycling and reclamation. Today, the pressing climate issues, including global warming and the emergence of a complex climate, continue to test cement-based polymers in the civil engineering industry. As a result, there is a growing demand for higher performance, renewable resources, and reduced carbon dioxide production, leading to a shift in the traditional industrial revolution. Composite nano concrete has emerged as an effective solution to address the challenges related to concrete mechanics and durability, aligning with the principles of sustainable development goals. The research focuses on utilizing composite nano-modified concrete to enhance the life cycle of structures. This nano-modified concrete incorporates Nano-SiO₂ (NS) and Nano-CaCO3 (NC) particles to create a new composite nano-concrete structure called NSC concrete. The research paper explores different dosages of composite nano concrete, specifically 2.5 %, 3.0 %, and 3.5 %, denoted as NSC25, NSC30, and NSC35, respectively. It examines the performance of the composite nano concrete under various temperature conditions, including 25 °C, 200 °C, 400 °C, and 600 °C, to simulate real-world scenarios and evaluate its value-based applications. The article analyzes multiple aspects, including mechanical properties, durability, visual appearance, and economic benefits of composite nano concrete. It also assesses NSC concrete's temperature dissipation capacity and insulation level and investigates the interfacial transition zone influenced by nanoparticles and temperature. The results indicate that the new composite nano concrete retains substantial enhancements in mechanical properties, with a maximum increase of 1.22 % in splitting strength and up to 45.69 % improvement in flexural strength at a temperature of 600 °C. Additionally, it demonstrates commendable durability and economic efficiency

Electromechanical properties of multi-reinforced self-sensing cement-based mortar with MWCNTs, CFs, and PPs

This experimental research examines the electromechanical properties of hybrid cement-mortar composites strengthened with different amounts of multi-walled carbon nanotubes (MWCNTs), carbon fibers (CFs), and polypropylene microfibers (PPs). The experimental program included optimal mechanical improvement at the nano and micro levels. The optimum micro-composite mortar derives from the finest mechanical response of the CFs and PPs micro-modified specimens in terms of flexural and compressive strength. Further, the electrical response of the mortars with the improved mechanical response was examined. The improved mechanical and electromechanical response of the optimum amounts of the two scales indicates the hybrid mortar with exceptional performance. This optimum amount in micro-scale in synergy with the optimum amount of MWCNTs constituted the hybrid-reinforced cement-based mortar. The optimized nano-, micro-, and hybrid-reinforced mortars were examined for their electrical properties in terms of electrical conductivity, impedance, and piezo-resistivity. These measurements in combination with the Nyquist plots of the resistance-reactance specified the sensing ability of the cementitious self-sensor. Results indicated that the optimum reinforcement in the nanoscale is 0.2 wt% MWCNT and in microscale 0.5% wt.% CFs exhibited improvement in flexural strength, compressive strength, and flexural toughness. The optimum nano- and micro-reinforced cement-based mortars presented much higher conductivity of about 867% and 633%, and lower impedance of about 89.4% and 86%, respectively, compared to the reference specimen, and a one-order-of-magnitude compared to the other contents. The excellence of the hybrid combination of 0.2 wt% MWCNΤs and 0.5% wt.% CFs occur with even more improved flexural strength of about 27%, flexural toughness of about 1607%, conductivity of 2617% more than the reference mortar, and lower impedance of about 96%, compared to the reference specimen. The piezoresistive response of the tested cement-mortar composites denotes the enhanced strain-sensing ability of the examined multi-reinforced mortars, highlighting the superiority of the hybrid one.

Balancing thermal conductivity and strength of hot-pressed AlN ceramics via pre-sintering and annealing process

The heat dissipation requirements of the new generation of semiconductors are placing higher demands on the overall performance of aluminum nitride (AlN) ceramics. This has led to an increasing emphasis on AlN ceramics that combine thermal conductivity and strength. AlN ceramics are often strengthened by hot-press sintering, but their thermal conductivity is typically modest. In this study, pre-sintering and annealing processes are introduced to optimize the thermal conductivity of hot-pressed AlN ceramics to avoid the detrimental effects of oxygen impurities in the AlN lattice. The effect of the oxide layer on the surface of commercial AlN particles is investigated, including density, phase composition, microstructure, and fracture behavior. The effect of annealing on the improvement of thermal conductivity and flexural strength is also verified. Electron paramagnetic resonance (EPR) analysis is performed to examine the concentration of intercrystalline defects under various conditions. Finally, AlN ceramics with a thermal conductivity of 204 W m−1 K−1 and a flexural strength of 376 MPa are obtained.

BioKnit: development of mycelium paste for use with permanent textile formwork.

This paper presents significant advances in mycelium biofabrication using permanent knitted textile formwork and a new substrate formulation to dramatically improve the mechanical properties of mycelium-textile biocomposites suitable for large-scale components for use in construction. The paper outlines the biofabrication process, detailing the composition of mycocrete, a viscous mycelium substrate developed for use with permanent knitted formwork, and the injection process required to regulate the filling of slender tubes of fabric with mycocrete. The use of a permanent integrated knitted formwork shows promise as a composite system for use with mycelium to improve mechanical performance and enable complex shapes to be fabricated for lightweight construction. Results of mechanical testing show dramatic improvements in tensile, compressive and flexural strength and stiffness compared to conventional mycelium composites. The testing demonstrates the importance of both the mycocrete paste recipe and the knitted textile formwork. In addition, the paper highlights the advantages of the proposed biofabrication system with reference to the BioKnit prototype: a 1.8m high freestanding arched dome composed of very slender biohybrid knit-mycelium tubes. This prototype demonstrates the opportunity to utilize the potential for lightweight construction and complex form offered by a textile formwork with low environmental impact mycelium biomaterials. The combination of textiles and mycelium present a compelling new class of textile biohybrid composite materials for new applications within the construction sector.

STUDY THE EFFECT OF DIFFERENT REINFORCEMENT RATIOS ON THE EXPANDED LIGHTWEIGHT GEOPOLYMER MORTAR PROPERTIES

Nowadays, the demand for the production of lightweight construction materials is increasing in order to reduce the cost, which is economically beneficial, as well as reducing the weight of the building as a whole. In this work, a lightweight geopolymer based on fly ash (type F) was developed using an alkaline activator at a concentration of 12 M and the ratio of the activator to the binder was (0.6). The natural sand was partially replaced with expanded perlite (EP), at replacement rates of 10, 30, and 50% by weight. Then the lightweight geopolymer (50% by volume of perlite) was reinforced with polypropylene fiber (PPF) with an addition ratio of (0.25, 0.5, 0.75, and 1%) of the total volume. Laboratory tests were carried out on the produced samples to determine the extent of the properties change after the addition of perlite. The density, insulating and absorbent properties of the lightweight geopolymer composite, which showed a decrease in unit weight with increased porosity and absorbency due to increased interstitial pores, were improved. A clear improvement in flexural strength was also observed when adding 1% polypropylene fibers. As for compressive strength, the improvement was slight. The lower density of the fibers also supports the weight of the unit.

Investigation of mechanical and thermal behavior of sisal fibre reinforced polymer biocomposites

In this study, biocomposites were developed with reinforced natural sisal (Agave sisalana) fibres by hand lay-up method. Sisal fibre loading was kept constant (30 wt%) with varying fibre lengths (5, 10, 15 and 20 mm) incorporated in epoxy composites to study their effects on mechanical and thermal properties. Mechanical testing (Tensile, Flexural and Impact) and thermal testing (Thermo-gravimetric analysis) were performed to identify mechanical properties and thermal stability. The specimens for tensile, flexural and impact test were taken as 165 mm × 20 mm × 3 mm, 80 mm × 13 mm × 3 mm and 65 mm × 13 mm × 3 mm respectively. A remarkable improvement in tensile, flexural and impact strength were noticed in composites incorporated with sisal fibres of 15 mm. The significant enhancement in tensile, flexural and impact strength was evaluated by 20.15%, 39.95% and 47.27% respectively as compared to neat epoxy composite. Higher thermal stability was also observed in 15 mm sisal fibre-reinforced composite.

Using waste poplar to replace nonrenewable MgO in cement-based composites

Waste poplar powders with dosage of 0%∼25% of MgO’s mass were mechanically mixed with magnesium oxysulfate cement to prepare new composites. The slurry fluidity, mechanical strength, water resistance and microstructure were studied. The optimal poplar powder dosage as 20% of MgO’s mass was determined based on seven indexes. The flexural strength and compressive strength of the optimal composite at 100d was 17.97 MPa and 62.51 MPa, with flexural strength improvement by 52% comparing to cement matrix. Softening coefficient of the optimal composite was 0.83, showing good water resistance. The optimal composite with 20% poplar powder presented maximum displacement of 0.514 mm and energy absorption capacity of 1.204 J before fracture, which improved by 153% and 209% comparing to cement matrix. The incorporation of poplar powder greatly reduced brittleness, due to the good bonding capability and compatibility of cement covering powders well. Overall, this study presents a feasible way of using waste poplar powders to reduce the consumption of MgO and prepare environmental-friendly composites.

Electrophoretically Deposited Multiscale Graphene Oxide/Carbon Nanotube Construct Mediated Interfacial Engineering in Carbon Fiber Epoxy Composites.

Fiber-reinforced polymer composites as a structural material have garnered tremendous interest over the past few decades. In particular, carbon fiber-reinforced epoxy (CFRE) laminates have seen extensive use in the aircraft and aerospace industry. The role of the interface between the matrix and fiber is critical and dictates the overall structural properties of the CFRE laminate. Herein, we attempt to use a commercially viable, green, and facile approach, electrophoretic deposition (EPD), to deposit covalently coupled multiscale graphene oxide (GO)/carbon nanotube (CNT) nanoconstructs onto carbon fiber (CF) fabric. The rationale behind using these hybrid conjugates is to exploit the positive synergistic effect of combining two-dimensional (2D) GO and one-dimensional (1D) CNT nanoparticles, which provide strengthening through different mechanisms resulting in a stronger matrix/fiber interface. The modified laminate with just 0.1 wt % GO/CNT content exhibited an improvement in flexural strength (FS) by 24% and interlaminar shear strength (ILSS) by 30% compared to the neat CFRE. Scanning electron microscope (SEM) micrographs confirmed uniform and homogeneous GO and GO/CNT deposition on CF. Raman, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses validate the successful functionalization of CNT and covalent coupling of GO and CNT. Atomic force microscope (AFM) and contact angle analyses indicate improved interaction between the CF and matrix. The deposition of the GO/CNT nanoconstruct on the CF improved the performance of CFREs owing to enhanced wettability, surface free energy, and surface roughness, leading to increased mechanical interlocking between the epoxy and CF at the interface. Dynamic mechanical analysis showed decreased segmental motion of epoxy chains due to improved interfacial adhesion following modification. Interesting observations were made in SEM fractography, which showed considerably different failure mechanisms in the modified CFREs. Electromagnetic interference (EMI) shielding effectiveness of -45 dB was achieved in the case of the GO/CNT-CFRE system. Electrothermal heating and de-icing performance of the modified system were also explored in this study. This versatile approach can open up new avenues for CFRE modification leading to considerably improved performance.

Chalcedonite aggregate in lime mortars: Assessment of strength, microstructure, and durability

The constructions of historic buildings are on ground and sub-ground level often affected by various salts leeching in the constructions from surrounding environment due to non-existent or non-functional ground-water insulation. The salts dissolved in water are transported through capillary system of masonry and cause severe problems at air-construction interface where the water evaporates into the environment and salts accumulate in the outer-most layer destroying it in the process by the crystallization. To improve the durability of repair mortars and their ability to accumulate salts lightweight porous aggregate is used. This study focuses on the use of chalcedonite aggregate in such materials. Mortars based on aerial and natural hydraulic lime are prepared and the siliceous aggregate is replaced by chalcedonite sand. Fresh state properties of mortars likely to affect microstructure and/or durability e.g. air content in fresh mortar are determined. Flexural and compressive strength are studied at the ages of 28, 56, 90, 180, and 365 days, additionally at 90 days microstructural characteristics, durability to freeze–thaw cycles and salt crystallization resistance are studied. The use of highly porous aggregate leads to significant increase in amount of mixing water needed to achieve the same workability, while air content in fresh mortar and water retention value are only mildly affected. The substitution of aggregate leads to improvement in flexural strength however, compressive strength is decreased. The incorporation of lightweight porous aggregate causes significant increase in total open porosity of the mortars, their water absorption as well as increase in capillary water transport. Even though the significant increase in hygric properties, the durability to freeze–thaw cycling also increases. The improvement in salt crystallization resistance is observed mainly in the case of sulfate attack with only minor improvements in the solutions of nitrates and chlorides. The mortars with chalcedonite aggregate show results favourable for their utility as repair mortars, mainly in damp buildings, where the fast capillary water transport is highly beneficial.

Milling route for the synthesis of nano-aluminium hydroxide for the development of low-density polymer composites

Abstract High loadings of coarse alumina trihydrate (ATH), commercially used in polymers as a fire-retardant filler, cause uneven dispersion and reduce workability and affect physicomechanical properties. Better tensile properties can be achieved by uniform dispersion of nanosize ATH in polymers while maintaining its flame-retardant properties. Consequently, mechanical milling, being a sustainable approach towards the creation of nano-size materials, was carried out to reduce the particle size of coarse ATH in a high-energy planetary ball mill. Investigations were carried out to optimize the milling parameters such as time, rotational speed, milling media size and feed size. During milling, some of the physical properties of ATH change. The energy profile was studied to get the desired product properties. Nano-ATH within the PP matrix reduces the loadings with improvement in tensile and flexural strength. Hence, lightweight PP/nano-ATH composites for suitable use can be developed.

Evaluation and Comparison of Mechanical Properties of Heat Polymerized Acrylic Resin After Reinforcement of Different Fibers in Different Patterns: An In Vitro Study.

Most denture fractures occur within the mouth due to resin flexural fatigue. For example, the deep labial notch at the high labial frenum causes denture breakage, as can deep scratches and generated processing stresses. The rising cost of annual prosthetic repairs is evidence that the problem of total denture fracture has not been solved. The purpose of this investigation was to evaluate the relative improvement in flexural strength between heat-cured polymethyl methacrylate (PMMA) resin reinforced with glass fibers (GF) and basalt fibers (BF) of varied orientations. A total of 150 heat-cured acrylic resin specimens of 65x10x3 mm dimension were prepared, 30 of which were left unreinforced (Group A), 30 of which were reinforced with GF in transverse pattern (Group B), 30 of which were reinforced with GF in meshwork pattern (Group C), 30 of which were reinforced with BF in transverse pattern (Group D), and 30 of which were reinforced with BF in meshwork pattern (Group E).All of the samples were put through flexural strength testing on the universal testing machine. One-way ANOVA and the Tukey-Kramer various correlation test (= 0.05) were used in SPSS for Windows to look at the facts. The mean flexural strength for Group A was 46.26±2.26 MPa, 64.98±1.53 MPa for Group B, 76.45±2.67 MPa for Group C, 54.22±2.24 MPa for Group D, and 59.02±2.38 MPa for Group E. Flexural strength was impacted by both the kind of BF and GF reinforcement (F = 768.316, P = 0.001). Within the limitation of the current research, BF reinforcement outperforms GF reinforcement and unreinforced heat-cured acrylic resin in terms of flexural strength.

Potential of Fe-Mn-Al-Ni Shape Memory Alloys for Internal Prestressing of Ultra-High Performance Concrete.

Prestressing of concrete is a commonly used technique in civil engineering to achieve long spans, reduced structural thicknesses, and resource savings. However, in terms of application, complex tensioning devices are necessary, and prestress losses due to shrinkage and creep of the concrete are unfavourable in terms of sustainability. In this work, a prestressing method using novel Fe-Mn-Al-Ni shape memory alloy rebars as a tensioning system in UHPC is investigated. A generated stress of about 130 MPa was measured for the shape memory alloy rebars. For the application in UHPC, the rebars are prestrained prior to the manufacturing process of the concrete samples. After sufficient hardening of the concrete, the specimens are heated inside an oven to activate the shape memory effect and, thus, to introduce the prestress into the surrounding UHPC. It is clearly shown that an improvement in maximum flexural strength and rigidity is achieved due to the thermal activation of the shape memory alloy rebars compared to non-activated rebars. Future research will have to focus on the design of the shape memory alloy rebars in relation to construction applications and the investigation of the long-term performance of the prestressing system.

Recycling of glass fibre reinforced polymer (GFRP) composite wastes in concrete: A critical review and cost benefit analysis

The application of fibre reinforced polymer (FRP) composites has increased substantially in recent years as a result of need for lighter and stronger materials. Currently, the reuse and/or recycling of composite wastes is very limited while most of wastes are disposed of in landfill or incinerated. Recently, mechanical recycling, fluidised bed, and pyrolysis has been developed to recycle FRP composites, but yet to be fully commercialised. As an alternative recycling strategy, incorporating glass fibre reinforced polymer (GFRP) into concrete has shown a great potential from both economic and environmental perspectives. This paper systematically reviews the performance of recycling of GFRP wastes into concrete with respect to fresh properties, mechanical properties, durability, environmental and financial aspects. Results show that the effect of recycled glass fibre reinforced polymer (rGFRP) on concrete mechanical strength is associated with the content of waste material (fibre or resin rich) and physical properties (shape, density, hydrophilicity) of GFRP recyclates, as well as the amount of recyclates. For rGFRP powder, the filler effect combined with the pozzolanic reaction can improve interfacial transition zone strength, increasing mechanical strength. Recycled glass fibre has reinforcing effect to restraint cracks and can provide extra slip resistance to strengthen the bond, resulting in improvement of flexural strength. Recycling of GFRP waste in concrete reduces water absorption of the concrete, improving durability properties. Furthermore, this research presents outcomes of cost-benefit analysis and benefit-cost ratio on five common GFRP recycling methods. The results show that repurposing rGFRP in concrete can reduce the total required investment and increase net profit. Recommendations and future perspectives are also provided to allow a wider adoption of rGFRP repurposing from industrial waste and the development of a more sustainable life cycle.

Mechanical, water absorption and tribological properties of epoxy composites filled with waste eggshell and fish scale particles

Egg shells and fish scales are two abundantly available by-products from food industries which can be used as filler materials to reinforce polymer composites. The bulk of discarded chicken eggshells and fish scales are disposed of in landfills, which cause environmental issues. The present research work focuses on the water absorption, mechanical and tribological properties of epoxy composites reinforced with chicken eggshells and catla fish scale particles. Hybrid composites incorporating both fillers were also made and evaluated. Results from the water absorption tests showed that the addition of fillers decreased the water absorption of the composites than neat epoxy. Tensile and impact tests revealed that the inclusion of fillers reduced the tensile and impact strength of the composites compared to neat epoxy, but improved the tensile modulus. The hybrid composite (EFREC) showed improvement in both flexural strength and modulus in comparison to neat epoxy. Also, the results from the wear tests revealed that the addition of fillers improved the wear resistance of the composites. Among all the mechanical and wear tested composite specimens, the hybrid composite (EFREC) showed the best performance. This was also validated from the SEM images of the fracture and wear surfaces of the composites.

Effect of treated Alfa fibers on hydration kinetics, mechanical, and adhesion properties of fiber cement composite

The addition of Alfa fibers into a cementitious matrix leads to a composite with improved mechanical properties – in particular, its flexural strength. However, Alfa fibers have been found to degrade over time, due to the highly alkaline environment of the cementitious medium. This study examined the effect of treatments applied to the Alfa fibers on the mechanical performances and adhesion of the cementitious composite. Treatments of the surface of the Alfa fibers (alkaline and hydrothermal treatments, coating with sulfoaluminate cement, ultrasound and enzymatic treatments) were applied, with the aim of improving the behavior in the long term. The raw and treated Alfa fibers were incorporated into cement mortars, at different lengths (10 and 20 mm), at an addition rate of 1% vol. After 90 days, an improvement in flexural strength was observed in the mortars with 1% vol. of treated fibers; contrary to untreated fibers. The alkaline and hydrothermal treatments are the most effective of the bunch. An increase in the strengths of 44% and 32% respectively was noted, in comparison to untreated fiber. This finding was confirmed by a modification in the hydration reactions of the composites. A compatibility factor between the fiber and mortar was determined, showing that composites with Alfa fibers having undergone alkaline and hydrothermal treatments are more compatible with the mortar. To measure the interactions (shear stress) between the Alfa fiber and the cement mortar, a specific measuring device, based on a fiber immersed in mortar, was put in place. An increase in shear stress with fibers after treatment, suggesting that the fiber/mortar adherence properties are improved.

Investigation on use of basalt fiber reinforced polymer for improvement in flexural strength of reinforcement concrete

Basalt fiber is a green, healthy and environmentally friendly high-tech fiber product without environmental pollution. It is widely used in military and civilian fields. It is not only of great theoretical significance but also of great strategic significance to strengthen the damage structures and members. The results show that, compared to glass fiber, carbon fiber and aramid fiber, basalt fiber, has good mechanical properties, acid-alkali resistance, excellent electrical properties, high wave permeability, non-conductive, and excellent sound insulation and insulation performance. This experimental study was conducted to determine the feasibility of using externally bonded BFRP fabrics to strengthen RC beams. Nine full-size specimens were tested. The following conclusions have been drawn from this research that of 4 types of different wrapping to the beam, beam with fully wrapped BFRP gained more flexural strength and load carrying capacity as compared to control beam.