Showing papers on "Flexural strength published in 2022"

Constructing hierarchical structure based on LDH anchored boron-doped g-C3N4 assembled with MnO2 nanosheets towards reducing toxicants generation and fire hazard of epoxy resin

Abstract: High fire hazard of releasing considerable toxicants and heat is regarded as a notorious issue for hindering the further application of epoxy resin (EP). Hence, a hierarchical structure (MLBCN) based on LDH anchored boron-doped g-C3N4 assembled with MnO2 nanosheets is rationally constructed as flame retardant additive for EP. Concretely, the incorporation of 1.0 wt% MLBCN leads to the decreases of 31.9% and 25.3% in peak heat release rate and total heat release, separately, reflecting the impeded heat release. Meanwhile, the peak smoke production rate and total smoke release are reduced by 37.1% and 33.4%, respectively, corroborating the hindered fire toxicity. The clear evidence for inhibited emissions of toxic CO and NO gases can be acquired from TG-IR spectra. These results collectively confirm the efficacy of MLBCN in reducing the toxicants generation and fire hazard of EP, deriving from its physical barrier, chemical catalyzing and charring promotion actions. Besides, the tensile and flexural strength are improved by 43.9% and 10.6%, by adding 1.0 wt% MLBCN, demonstrating the promoted mechanical performance. Overall, using MLBCN achieves the simultaneous enhancements in fire safety and mechanical capability of polymer. This work may provide valuable inspirations for constructing multicomponent hierarchical structure, optimizing their prospects in polymer-matrix composite and other areas.

Constructing hierarchical structure based on LDH anchored boron-doped g-C3N4 assembled with MnO2 nanosheets towards reducing toxicants generation and fire hazard of epoxy resin

Abstract: High fire hazard of releasing considerable toxicants and heat is regarded as a notorious issue for hindering the further application of epoxy resin (EP). Hence, a hierarchical structure (MLBCN) based on LDH anchored boron-doped g-C3N4 assembled with MnO2 nanosheets is rationally constructed as flame retardant additive for EP. Concretely, the incorporation of 1.0 wt% MLBCN leads to the decreases of 31.9% and 25.3% in peak heat release rate and total heat release, separately, reflecting the impeded heat release. Meanwhile, the peak smoke production rate and total smoke release are reduced by 37.1% and 33.4%, respectively, corroborating the hindered fire toxicity. The clear evidence for inhibited emissions of toxic CO and NO gases can be acquired from TG-IR spectra. These results collectively confirm the efficacy of MLBCN in reducing the toxicants generation and fire hazard of EP, deriving from its physical barrier, chemical catalyzing and charring promotion actions. Besides, the tensile and flexural strength are improved by 43.9% and 10.6%, by adding 1.0 wt% MLBCN, demonstrating the promoted mechanical performance. Overall, using MLBCN achieves the simultaneous enhancements in fire safety and mechanical capability of polymer. This work may provide valuable inspirations for constructing multicomponent hierarchical structure, optimizing their prospects in polymer-matrix composite and other areas.

Influence of Replacing Cement with Waste Glass on Mechanical Properties of Concrete

Abstract: In this study, the effect of waste glass on the mechanical properties of concrete was examined by conducting a series of compressive strength, splitting tensile strength and flexural strength tests. According to this aim, waste glass powder (WGP) was first used as a partial replacement for cement and six different ratios of WGP were utilized in concrete production: 0%, 10%, 20%, 30%, 40%, and 50%. To examine the combined effect of different ratios of WGP on concrete performance, mixed samples (10%, 20%, 30%) were then prepared by replacing cement, and fine and coarse aggregates with both WGP and crashed glass particles. Workability and slump values of concrete produced with different amounts of waste glass were determined on the fresh state of concrete, and these properties were compared with those of plain concrete. For the hardened concrete, 150 mm × 150 mm × 150 mm cubic specimens and cylindrical specimens with a diameter of 100 mm and a height of 200 mm were tested to identify the compressive strength and splitting tensile strength of the concrete produced with waste glass. Next, a three-point bending test was carried out on samples with dimensions of 100 × 100 × 400 mm, and a span length of 300 mm to obtain the flexure behavior of different mixtures. According to the results obtained, a 20% substitution of WGP as cement can be considered the optimum dose. On the other hand, for concrete produced with combined WGP and crashed glass particles, mechanical properties increased up to a certain limit and then decreased owing to poor workability. Thus, 10% can be considered the optimum replacement level, as combined waste glass shows considerably higher strength and better workability properties. Furthermore, scanning electron microscope (SEM) analysis was performed to investigate the microstructure of the composition. Good adhesion was observed between the waste glass and cementitious concrete. Lastly, practical empirical equations have been developed to determine the compressive strength, splitting tensile strength, and flexure strength of concrete with different amounts of waste glass. Instead of conducting an experiment, these strength values of the concrete produced with glass powder can be easily estimated at the design stage with the help of proposed expressions.

Mechanical properties of oil palm fibre-reinforced polymer composites: a review

Abstract: In recent years, serious reduction in petroleum resources and concerns about the usage of synthetic plastics have prompted global communities to accept the use of natural fibres and biopolymers in many products. Lignocellulosic fibre polymer biocomposites have attracted the attention of scientists and engineers because of their wide availability, low carbon emission and biodegradability. Currently, oil palm is one of the main crops cultivated in Malaysia and Indonesia and is regarded as a potential source of lignocellulosic fibres for biocomposites. The cellulosic content of oil palm fibres (OPFs) enhances the mechanical properties of composites. Ensuring the compatibility of OPFs as main constituents with other materials in composites for a specific applications is essential. Mechanical performance in terms of tensile, flexural and impact strength determines an OPF's compatibility. However, no comprehensive reviews focusing on the mechanical properties of OPF biocomposites have been published, and factors influencing mechanical performance, such as interfacial adhesion, stacking sequence, additive, type of polymer and fibre size have not been explored. Some studies have identified the research gaps and deduced that the potential applications of OPFs as reinforcement materials in composites have not been explored.

Mechanical Behavior of Crushed Waste Glass as Replacement of Aggregates

Abstract: In this study, ground glass powder and crushed waste glass were used to replace coarse and fine aggregates. Within the scope of the study, fine aggregate (FA) and coarse aggregate (CA) were changed separately with proportions of 10%, 20%, 40%, and 50%. According to the mechanical test, including compression, splitting tensile, and flexural tests, the waste glass powder creates a better pozzolanic effect and increases the strength, while the glass particles tend to decrease the strength when they are swapped with aggregates. As observed in the splitting tensile test, noteworthy progress in the tensile strength of the concrete was achieved by 14%, while the waste glass used as a fractional replacement for the fine aggregate. In samples where glass particles were swapped with CA, the tensile strength tended to decrease. It was noticed that with the adding of waste glass at 10%, 20%, 40%, and 50% of FA swapped, the increase in flexural strength was 3.2%, 6.3%, 11.1%, and 4.8%, respectively, in amount to the reference one (6.3 MPa). Scanning electron microscope (SEM) analysis consequences also confirm the strength consequences obtained from the experimental study. While it is seen that glass powder provides better bonding with cement with its pozzolanic effect and this has a positive effect on strength consequences, it is seen that voids are formed in the samples where large glass pieces are swapped with aggregate and this affects the strength negatively. Furthermore, simple equations using existing data in the literature and the consequences obtained from the current study were also developed to predict mechanical properties of the concrete with recycled glass for practical applications. Based on findings obtained from our study, 20% replacement for FA and CA with waste glass is recommended.

Hydration, reinforcing mechanism, and macro performance of multi-layer graphene-modified cement composites

Abstract: Multi-layer graphene (MLG) has excellent mechanical properties and a unique stacked structure. In this paper, sulphoaluminate cement replaced ordinary portland cement to prepare low-carbon ecological ultra-high-performance-concrete (UHPC); the effects of MLG on the hydration, microstructure, and mechanical properties of UHPC were investigated, revealing the hydration mechanism and reinforcing mechanism of MLG on UHPC. Results show that adding MLG can significantly enhance the macro performance of UHPC. When the MLG content is 0.08%, UHPC has better macro performance. Compared with the M0 group, the flexural strength and compressive strength of the M3 group increased by 31.6%, 35.3%, 43.3%, 50.9%, and 9.5%, 13.5%, 22.2%, 21.7% after curing for 1 d, 7 d, 28 d, and 56 d, respectively. We quantitatively characterized the content of hydration product changes in UHPC. Various characterization analyses showed that the adsorption effect and nucleation effect of MLG promoted the hydrolysis and ions exchange of Ca2+ and Al3+, which provided sites for the growth of hydration products and accelerated the hydration process of cement, forming more hydration products, including AFt (ettringite) and AH3 (gibbsite). AFt, AH3, and MLG are closely connected, filling the pores and reducing the porosity of the matrix, optimizing the pore structure, and the medium and large pores transformed into micro-nano pores. Revealing the multi-level reinforcing mechanism, namely hydration products (AFt, AH3) and MLG filling the pores; MLG prevented the extension of micro-cracks and changed micro-cracks development path through filling effect, deflection effect, pulling out, and bridging effect.

Performance of Self-Compacting Mortars Modified with Nanoparticles: A Systematic Review and Modeling

Abstract: During the transition of one material from macro- to nano-range size, considerable changes occur in the electron conductivity, optical absorption, mechanical properties, chemical reacting activity, and surface morphology. These changes can be advantageous in the production of new mixture composites. Due to the need for developing improved infrastructure, new and high-performance materials should also be developed. In this regard, to improve the performance of concrete mixtures, several methods have been investigated, including using nanoparticles (NPs) to enhance various characteristics of the concrete composite like improving fresh and mechanical properties of self-compacting concrete (SCC) as well as improving permeability and absorption capacity of the composite by providing extremely fine particles to fill micro-pores and voids. In this paper, a state-of-the-art review was carried out on the influence of various NPs inclusion on the fresh, mechanical, and durability properties of self-compacting mortars (SCM). So that current and most recent studies previously published were investigated to highlight the influences of different NPs on the slump flow diameter, V-funnel flow time, compression and flexural strengths, water absorption, chloride penetration, and electrical resistivity. Moreover, the main section of this study was devoted to proposing different models, including nonlinear model (NLR), multi-logistic model (MLR), and artificial neural network (ANN), to predict the compressive strength (CS) of SCMs modified with NPs. Based on the analyzed data, it was illustrated that the addition of NPs into SCMs significantly enhances the fresh, mechanical, and durability performance of SCMs. Moreover, the microstructure of SCMs was considerably improved due to the higher specific surface area of NPs and their reaction with undesirable C–H which present in the cement paste matrix to produce additional C-S-H gel.

Use of recycled coal bottom ash in reinforced concrete beams as replacement for aggregate

Abstract: In this research, it is studied the crack and flexural behavior of reinforced concrete beams with various bottom ash ratios (BARs) considered as fine aggregate in an experimental and numerical investigation. For experimental purposes, different concrete series are considered varying aggregate sizes ranging from 0 to 25 mm. To supplement concrete, bottom ash is put to use in conjunction with material from 0–5 mm in size aggregate particles as replacement for fine aggregates with ratios of 25%, 50%, 75%, and 100%. Experiments were done to investigate the behavior of the beams and how flexural and fracture behaviors are represented. 75% BARs gave optimum results in terms of displacement capacity. Increasing BAR to 100% decrease deflection capacity of the beam. Also, ANSYS software is used to build 3D finite element models (FEMs) of beams to compare with experiment data. Experimental and 3D numerical tests show exceptionally tight flexural and fracture behaviors. Following this, a computer-generated structure is made by running SAP 2000, and the strength of the beams is then utilised in an RC structural model. Every stage of the building’s construction is thoroughly assessed utilizing multiple types of seismic testing, employing the SAP2000 program, with the resulting analysis providing significant findings on how the seismic force of 75% BAR affects horizontal displacement of each floor. The results showed that the weight of the structure dramatically decreases as the number of columns and RCBs are raised while also increasing the number of BARs. Moreover, the magnitude of earthquake and BAR have a significant effect on the horizontal displacement behavior of reinforced concrete structures. The strength of the concrete structure varies between close- and far-fault earthquakes, and for close-fault earthquakes, concrete strength is stronger than for far-fault earthquakes. This brings us to the second disadvantage of BAR which is the 75% strain produces a severe displacement of reinforced concrete structures. Besides, it was seen that the simulations and experiments yield tiny cracks with very identical configurations.

Effect of different burning degrees of sugarcane leaf ash on the properties of ultrahigh-strength concrete

Abstract: The global expansion of agricultural production increases agricultural waste ash (AWA). Accordingly, AWA should be disposed to preserve the environment. This study focuses on using AWA as a partial substitute for cement to produce ultrahigh-strength concrete (UHSC). This research investigated the effect of using sugarcane leaf ash (SLA) as a pozzolanic material on the properties of UHSC. The cement replacement rates by SLA were 10%, 20% and 30% by weight. SLA was heat-treated at 400, 500, 600, 700 and 800 °C for 2 h to improve its physical and chemical properties. The effects of the heat-treated SLA on UHSC mechanical properties such as, compressive strength, split tensile strength, flexural strength and modulus of elasticity, were studied. The effects of heat-treated SLA on UHSC durability such as, water permeability, chloride penetration and sorptivity of UHSC were also investigated. In addition to, microstructure analysis of several UHSC mixtures was presented. Results showed the efficiency of SLA as a partial substitute of the 20% of cement weight with mechanical properties and durability higher than the mechanical properties and durability of the reference mixture. Compared with the reference mixture, the heat-treated SLA used as a partial substitute generally improved all properties. The UHSC containing SLA heat-treated at 700 °C and a 20% substitution rate achieved the best results of 162.5, 17.78, 24.05 and 55,820 MPa for compressive strength, tensile strength, bending strength and modulus of elasticity at test age of 28 days.

Fiber-reinforced alkali-activated concrete: A review

Abstract: Alkali-activated materials (AAMs) received broad recognition from numerous researchers worldwide and may have potential applications in modern construction. The combined use of AAM and steel fibers are superior to typical binder systems because the matrix and fibers exhibit superior bond strength. The results obtained by various authors have shown that good dispersion of the fibers ensures good interaction between the fibers and the AAM matrix. The tensile strength of FR-AAC is superior to that of Ordinary Portland cement (OPC)-based materials, with the addition of silica fume (SF) being particularly remarkable. However, the tensile strength of fiber-reinforced alkali-activated concrete (FR-AAC) decreases with increasing fiber length. The bond strength increases with the increasing grade of concrete, the roughness of interface, and the solution's strength activated by alkalis. Regardless of fiber type, AAC's modulus of elasticity is linearly correlated with compressive strength. Fibers can affect the modulus of concrete due to the stiffness of the fiber and the porosity of the composite. Poisson's ratio for AAC corresponded to the ASTM C469-14 standard (about 0.22) and decreased to about 0.15–0.21 with silica fume addition. There are limited resources for the experimental Poisson's ratio and it is only estimated using the predictive equations available. Therefore, it is necessary to conduct additional experimental studies to estimate Poisson's ratios for FR-AAC composites. Retention of 59% and 44% in flexural strength during exposure at 800 °C and 1050 °C was observed in the FR-AAC stainless steel composite, and the chopped alumina fibers achieved higher yield strength at these temperatures. For FA-based AAC mortars with 1% SF with a hooked end, activated with a solution of NaOH and sodium silicate, an increase in the number of bends increased the bond strength, load pull-out and maximum pull-out strength. Autogenous shrinkage and drying shrinkage increase with higher silicate content, while shrinkage decreases with higher NaOH concentration. Relatively little research has been completed on FR-AAC in terms of durability or different environmental conditions. In addition, trends of development research toward the broad understanding regarding the application possibilities of FR-AAC as appropriate concrete materials for developing robust and green concrete composites for modern construction were extensively reviewed.

Characterization of prickly pear short fiber and red onion peel biocarbon nanosheets toughened epoxy composites

Abstract: In this research, the role of prickly pear short fiber and red onion peel wrinkled biocarbon nanosheets toughened epoxy resin composite was investigated. The main aim of this research was to find the effectiveness of adding biocarbon along with prickly pear fiber in the load-bearing, thermal and electrical conductivity behavior of the epoxy resin composite. The biocarbon nanosheets were prepared for this present investigation from red onion peel waste using the pyrolysis process. The composites were characterized by American society of testing and materials (ASTM) standards and compared with previous results. The highest tensile strength and flexural strength were observed for 3 vol.% of biocarbon nanosheets up to 60% and 40% respectively than pure epoxy. Izod impact toughness and hardness values also increased with the inclusion of reinforcements by 5 vol.% around 93% and 90% correspondingly. Similarly, relative permittivity and dielectric loss enhanced about to 6.4 and 0.74 for 5 vol.% of biocarbon nanosheets. The thermal conductivity also improved with the addition of biocarbon nanosheets and maximum values up to 0.42 W/mK. This enhanced dielectric, mechanical, and thermally active composites might be employed as a microwave shielding material in electronic devices, automotive, and industrial applications for communications equipment that require shielding material with good mechanical properties.

Effect of Aluminium Tetrahydrate Nanofiller Addition on the Mechanical and Thermal Behaviour of Luffa Fibre-Based Polyester Composites under Cryogenic Environment

Abstract: In recent times, research has shifted away from conventional materials and alloys and more towards nanocomposites to create lighter, more efficient materials for specific applications. The major goal of this research is to see how successful adding aluminium tetrahydride (ATH) filler to a luffa fibre/polyester-based hybrid composite is. The compression moulding process was used to create the nanocomposite. The following limitations were used to achieve the goals mentioned above: (i) weight percent of ATH, (ii) weight percent of luffa fibres, and (iii) cryogenic treatment hours. The mechanical properties of the materials, such as flexural, tensile, and impact, were examined. The scanning electron microscope observed the morphology pictures, revealing flaws such as interface behaviour, fibre pullouts, voids, and interior cracks. As a result, the current study found that adding nanofiller to a natural fibre composite can improve its mechanical properties, because it established a strong link between the matrix and its reinforcements, which would aid in the effective transmission of stress in the hybrid system. It also improved moisture resistance, which might be useful in construction and commercial industries. The composite with 1 wt.% of ATH, 24 wt.% of luffa fibres, and 30 minutes of cryogenic treatment showed better mechanical strength. Cryogenic treatment reduces compressive interface stresses, which helps maintain fibre and matrix in contact and improve adhesion, resulting in superior results. TGA analysis was used to confirm it.

Flexural behavior of reinforced concrete beams using waste marble powder towards application of sustainable concrete

Abstract: The performance of waste marble powder as a partial replacement for cement is examined with the aim to achieve more sustainable concrete. Pursuant to this goal, a total of 15 specimens were manufactured and then tested to examine the bending behavior. The effects of longitudinal reinforcement ratio and waste marble powder ratio were selected as variables. The experimental results showed that different proportions of tension reinforcement and waste marble powder had different crack and bending impacts on reinforced concrete beams. As the waste marble powder amount in the concrete mixture is increased from 0% to 40%, it was detected that the crack type changes from a shear crack from to a flexural crack as the amount of waste marble powder increases in the mixing ratio. The experimental findings revealed that the waste marble powder can be successfully used as 10% of the partial replacement of cement. Increasing the waste marble powder ratio by more than 10% can significantly decrease the capacity of the beams, especially when longitudinal reinforcement ratio is high. The influence of waste marble as partial replacement on the capacity decreases as the longitudinal reinforcement ratio decreases. Therefore, 10%–20% marble waste can be utilized as a replacement for cement when the longitudinal reinforcement ratio is close to the balanced ratio and more than 20% waste marble ratio should be avoided for any cases.

Utilization of fibers in ultra-high performance concrete: A review

Abstract: Fibers are essential in reinforcing the mechanical properties of ultra-high performance concrete (UHPC), particularly the tensile and flexural strength. This paper conducts a systematic review on the effect of fibers with different textures and geometry on the properties of UHPC from the following aspects: (1) the bond mechanism of steel fibers with the UHPC matrix; (2) the effect of fiber shape, fiber orientation and hybridization of steel fibers on the microstructure, failure mode, mechanical properties, autogenous shrinkage and durability of UHPC; (3) the reinforcing mechanism of synthetic fibers (polyvinyl alcohol fibers (PVA), polypropylene fiber (PP), polyethylene fibers (PE)), mineral fibers (basalt fibers, wollastonite fibers) and carbon fibers in UHPC and their effect on the performance of UHPC; (4) the use of hybrid fibers and their synergetic effect on the mechanical performance and shrinkage of UHPC. Finally, this paper discussed the further research trends of fibers in UHPC.

Understanding the role of unzipped carbon nanotubes in cement pastes

Abstract: Carbon nanotubes (CNTs) and graphene oxide (GO) are the most studied carbon-based materials for the modification of cementitious materials. Prior studies have shown that CNTs (due to high bending stiffness) can improve flexural strength more efficiently than GO, whereas GO (due to active surface groups) performs better in improving the compressive strength of cementitious composites. This laboratory study investigates the role of unzipped CNTs (UCNTs) in cement pates. All three types of UCNTs have a similar C/O atomic ratio as GO, without any wrinkles to be observed under transmission electron microscope. The UNCTs admixed at 0.1% by weight of cement improved the compressive and flexural strengths of a cement paste (w/c of 0.38) by 22% and 51%, respectively, greatly outperforming CNTs and GO, respectively. Such outstanding reinforcement efficiency of UCNTs resulted from their abundant surface chemistry (similar to GO) as well as one-dimensionality and bending stiffness (similar to pristine CNTs).

Effect of aggregate and fibre types on ultra-high-performance concrete designed for radiation shielding

Abstract: This research examines the properties of ultra-high-performance (UHPC) and heavyweight radiation shielding concrete (UHPHSC). Several types of heavy-weight fine aggregates (sand, magnetite, hematite ilmenite and barite) were used to achieve these properties. In addition, the different types of fibres (steel fibre, lead fibre and basalt fibre) with a volume fraction of 2% were used. The fresh properties of workability and density, and hardened properties of compressive strength, splitting tensile strength, flexural strength, and water permeability were studied. Radiation attenuation was measured at two different gamma-ray energies at 137Cs0.662 and 60Co 1.173 (MeV) sources. Linear attenuation coefficient, half-value layer and tenth-value layer were evaluated. UHPHSCs were exposed to different temperatures at 22 °C, 250 °C, 500 °C and 750 °C to study their effect on the compressive strength and the mechanical shielding properties of gamma rays. The highest density of concrete, 3850 kg/m3, was achieved using magnetite aggregate and steel fibre. Although the highest compressive strength of 180.6 MPa was achieved using Ilmenite aggregate and steel fibre, the best radiation protection properties were achieved using lead fibre and magnetite aggregates.

Calcined Attapulgite Clay as Supplementary Cementing Material: Thermal Treatment, Hydration Activity and Mechanical Properties

Abstract: Abstract The present paper studied the effects of calcination temperatures (200–800 °C) on the appearance, mineral composition, and active SiO 2 content in attapulgite and investigated the effects of attapulgite before and after calcination on the chemically bonded water content, the degree of reaction of cement paste, and the mechanical properties such as the flexural strength, compressive strength, and splitting-tensile strength of cement mortar. The results indicate that the calcination temperature changes the mineral composition of attapulgite, thereby affecting the hydration activity of cement-based materials. The attapulgite calcined at 500 °C (AT500) has the best enhancement on the hydration activity of cement-based materials. The calcination at 500 °C is most beneficial to the dissolution of SiO 2 , and the content of SiO 2 reaches 20.96%. The contents of chemically bonded water in the samples incorporated with calcined attapulgite reduced and that of the samples incorporated with AT500 at 28 d is the same as that of the control group. The reaction degree of AT500 is 78.61% at 28 days. Calcined attapulgite clay can reduce the energy consumption of the cement industry and promote the sustainable development of attapulgite clay.

The Impact of Nano Clay on Normal and High-Performance Concrete Characteristics: A Review

Abstract: The use of nano clay to improve the qualities of construction materials and engineering applications has attracted a lot of discussion in recent years. This review article summarizes the influence of nano clay as a cement substitute and supplement on the performance of conventional and high-performance concrete. The addition of nano clay to high performance concrete revealed an increase in compressive and flexural strength, as well as durability attributes such as resistance to elevated temperatures and sulfate attack, while simultaneously decreasing porosity, permeability, and water absorption. This enhancement is a result of nano clay’s roles as nano reinforcements, nanofillers, nucleation sites, and reactive pozzolans, which promote hydration and increase material characteristics.