Flexural Strength Research Articles

Bio-sourced flexible supramolecular glasses for dynamic and full-color phosphorescence

Glass, a diverse family of amorphous materials, has significantly advanced human society across various fields. The demand for flexible ultrathin glass, driven by modern optical displays and portable optoelectronics, presents challenges in energy consumption, fabrication complexity, and recycling. Here, we demonstrate flexibility and full-color luminescence in large-scale ultrathin glasses derived from readily available natural resources, specifically egg albumen (EA) and gelatin (GEL), via an evaporation-driven self-assembly process. The dynamic crosslinked networks formed through hydrogen bonding between EA and GEL impart both high hardness and flexibility to the glasses, with hardness and flexural strength values comparable to state-of-the-art inorganic and organic glasses. Additionally, the EA–GEL-based glasses exhibit excitation-dependent and time-gated chiral ultralong phosphorescence with color from blue and red, and a lifetime of up to 180.4 ms. With their easy processability and full-color emission, these biogenic glasses can be fabricated into anti-counterfeiting patterns and optical information codes.

From Waste to Strength: A Comprehensive Review on Using Fly Ash in Composites with Enhanced Mechanical Properties

This article explores the diverse applications of fly ash (FA), a by-product generated during the combustion of coal. The introductory segment thoroughly comprehends the origins, composition, and widespread occurrence of FA. FA, which comprises an estimated 38% of worldwide power generation, frequently encounters disposal and storage obstacles on account of its classification as non-hazardous waste in the majority of countries. The environmental issues linked to the dispersal of FA are underscored in the problem statement, which further emphasizes the urgency for sustainable alternatives. Due to the fugitive emissions and potential health hazards associated with metal melting in FA, it is critical to investigate novel applications and disposal techniques immediately. Environmental sustainability is a primary focus of research, with the development of synthetic FA composites being one such alternative. The analysis presents significant findings that underscore the wide-ranging applications of FA. These applications include its utilization as a filler in composites, as well as its incorporation into cement and geo-polymerization processes. Notably, (10-20) wt. % Nano-FA enhances epoxy-based composites, showcasing remarkable improvements in tensile strength, flexural strength, and impact resistance. In thermoplastic composites, substantial enhancements occur within the (5–10) wt. % FA range, but exceeding optimal ranges weakens matrix-fiber interaction, leading to diminishing returns. The article emphasizes the criticality of FA in improving the mechanical and thermodynamic characteristics of substances, specifically within the domain of composites. The investigation into FA nanoparticles, including their processing techniques and surface treatments, unveils encouraging prospects for enhancing material characteristics.

Optimizing mechanical properties and pioneering biodegradable polymer blends for superior energy-absorbing structures used in sport helmets

Replacing elements made of conventional plastics (like polystyrene) with biodegradable substitutes is part of the trend of sustainable development and waste reduction. The manuscript covers issues related to the design, manufacturing and testing of sports helmet protective inserts made of biodegradable material. The FEM numerical simulations carried out by the authors allowed to determine the optimal desirable mechanical properties (Re = 8.5–65 MPa, E = 500–8000 MPa for 30 × 30 mm inserts; Re = 10.5–60 MPa, E = 500–7500 MPa for 48 × 48 mm inserts; Re = 13–95 MPa, E = 400–8500 MPa for 55 × 55 mm inserts) and geometric parameters (wall thickness equal to 0.2–0.5 mm, height of 20 mm), ensuring the formation of a plastic fold, which is the most effective energy-absorbing mechanism. The conducted quasi-static compression, bending and dynamic tensile strength tests allowed to determine blends with appropriate proportions of durable PLA with more plastic PBAT, PBS and TPS that meet the established criteria: PLA50PBAT50, PLA30PBAT70 and PLA30TPS70.

Analysis of FS and Surface Roughness in Heat-Polymerized Poly Methyl Methacrylate Acrylic Resin Reinforced with Different Concentrations of Glass Fibers and Polypropylene Fibers: A Laboratory Study Using EDX and SEM

This study aimed to evaluate the flexural strength (FS) and surface roughness (Ra) of heat-polymerized poly methyl methacrylate (PMMA) acrylic resin reinforced with glass fibers (GF) and polypropylene fibers (PPF) in different concentrations. One hundred heat-cured PMMA resin samples were prepared and randomly allocated into five groups based on fiber reinforcement (n = 20). Group 1 had no fiber reinforcement, Group 2 had 0.5% silanized GF reinforcement, Group 3 had 1% silanized GF reinforcement, Group 4 had 0.5% silanized PPF reinforcement, and Group 5 had 1% silanized PPF reinforcement. Fatigue load was applied through artificial aging. FS testing of fifty samples was performed using a universal testing machine, and Ra was analyzed using an optical interferometric profilometer. Specimens were selected for SEM and EDX analysis. To find the differences among the studied groups, one-way analysis of variance and post hoc Tukey’s test were utilized. The results showed that Group 5 (1% PPF reinforcement) presented the highest fracture resistance (90.1±9.8 MPa), while the minimum FS scores were observed in Group 1 (no reinforcement) (59.2±7.1 MPa). Group 3 (1% GF reinforcement) exhibited the highest values of surface roughness (1.99±0.1992), whereas the lowest roughness scores were observed in Group 1. The study concluded that incorporating 0.5% PPF into the resin denture is a viable option for reinforcing the prosthesis without increasing surface roughness.

Study on the Engineering Properties of Lightweight Foamed Concrete Modified with Palm Stalk Fiber as an Additive

The escalation of agricultural waste in Malaysia has emerged as a significant focal point today. Agricultural trash is typically disposed of in landfills without regard for environmental considerations. Prior studies have demonstrated that highly reactive silica-containing debris can interact with calcium hydroxide in concrete, resulting in a thick microstructure. This study examines the possible application of palm stalk fibre (PSF) as an additive in lightweight foamed concrete (LFC) to enhance its engineering properties. The assessed engineering properties include compressive strength, flexural strength, splitting tensile strength, shrinkage and ultrasonic pulse velocity. Four distinct PSF percentages of 0.15, 0.30, 0.45 and 0.60 % were utilized as additions to the LFC mix. The findings indicated that incorporating 0.45 % PSF into LFC yielded optimal outcomes for compressive strength, flexural strength, splitting tensile strength, shrinkage and ultrasonic pulse velocity of LFC. The surface roughness of PSF enhances fiber-to-matrix interfacial bonding, since a rougher surface facilitates the interlocking of SBK fibre with the matrix within the LFC cementitious matrix.

Evaluation of the Mechanical Properties of Provisional 3DPrinted Resin After Repair with Different Materials: An In-Vitro Study.

To evaluate the mechanical properties of the 3D printed provisional restoration material that was repaired using different materials. The bar specimens have been manufactured using three-dimensional printing technology in accordance with the ISO 10477:2020 standards and divided into 5 groups randomly. For repair material application and replacement on the standardized silicone mold, the test specimens were ground at the center by 1x2x2 mm. No grinding was done on the control group specimens. Flowable composite, bis-acrylic composite resin, polymethyl methacrylate resin, and temporary 3D printing resin are utilized as repair materials (n=16). The specimens underwent a three-point-bending (3PB) test, with a cross-head speed of 1mm/min, in order to assess their flexural strength (FS) and flexural modulus (FM). The data received statistical analysis with one-way ANOVA and Tukey test. A Weibull analysis was performed, and the Weibull modulus of specimens was calculated. Control group specimens were showed the highest FS (142±12.6 MPa) and FM (4497±1205 MPa) values. Among the test groups, the utilization of temporary 3D printing resin as a repair material exhibited the greatest FS (67±33.3 MPa) values and showed statistical significance when compared to all other groups. Repairing 3D-printed provisional resin material weakens its mechanical properties. However, utilizing the own resin made of 3D-printed provisional resin material can be an effective choice for implementing minor modifications and additions.

Applicability of few layer graphene derived from annoni grass biomass on the mechanical properties of cement mortars

In this work, we report the potential applicability of few layer graphene (FLG) synthesized from annoni grass (AG) biomass (Eragrostis plana Nees) by investigating its impact on the flexural and compression strength of cement mortars. For this purpose the AG biomass was collected and burnt at the temperature of 400 °C per 60 min, obtaining the AG ash (AGA). For FLG production, the AGA was mixture with the chemical reagent potassium hydroxide (KOH) and burnt at the temperature and time of 850 °C and 60 min, respectively. For the mechanical properties analysis, a reference sample (A0-without FLG) and samples with different percentage of FLG were prepared, specifically 0.02 % (A1), 0.03 % (A2), 0.05 % (A3), 0.07 % (A4) and 0.1 % (A5). Statistical analysis (Analysis of Variance, ANOVA) of the mechanical properties demonstrates a maximum flexural and compression strength in sample A2. The flexural and compression strength increase 25.2 % and 10.1 % compared to the reference mortar. These results indicate that the FLG produced from AG not only improves the mechanical properties of mortars but also presents significant environmental benefits, because AG is considered an invasive pest of agricultural fields of the southern region of Brazil. Therefore, with its removal from the fields it would be contributing to environmental preservation.

Modification of Bamboo Fiber for Reinforcing Cement-based Composites and Durability Improvement

This study tackled the issue of inferior fiber-matrix adhesion in bamboo fiber (BF) reinforced cement-based composites, a critical factor impacting their performance and service life. Our approach introduces a novel application of silane coupling agents (SCAs) to improve the compatibility of BF with cement matrices. We utilized isocyanate propyl triethoxy silane (IPTS) in a pioneering manner, and used γ-glycidyl ether oxypropyl trimethoxysilane (KH560), respectively, to chemically modify the BFs. This modification strategy was designed to enhance the adhesion between BFs and the cement matrix through the SCAs' interaction with hydroxyl groups on the BF surface and their involvement in the cement hydration process. Our findings reveal that the modified BFs, when incorporated into cement composites, not only match the compressive strength of the control but also show a remarkable increase of over 20% in flexural strength and over 30% in tensile strength. Additionally, the modified BFs reduce drying shrinkage by more than 19% after 90-day curing, and similarly significant reductions are observed in chloride ion penetration and freeze−thaw cycle failure rates. Notably, IPTS outperforms KH560 in enhancing mechanical strengths and durability, likely due to the formation of more siloxane bonds on the fiber surface, leading to stronger cement matrix interaction. This research presents a cost-effective method to improve the performance of BF/cement composites, paving the way for broader utilization of BFs in sustainable construction materials.

A novel approach to accelerate the carbonation of γ-C2S under atmospheric pressure: Increasing CO2 dissolution and promoting calcium ion leaching via triethanolamine

An innovative approach to accelerate the carbonation of the γ-2CaO·SiO2 (γ-C2S) under atmospheric pressure was proposed by incorporating triethanolamine (TEA). The effect of TEA on the degree of carbonation (DOC) and the mechanical strength of γ-C2S were investigated, and the mechanism of carbonation accelerated by TEA under atmospheric pressure was analyzed. The results showed that as TEA concentration increased from 0.1 % to 5 %, the DOC initially increased and then decreased, with an optimal concentration of 1 %, where the DOC increased by 126.6 % compared to reference samples after 1 d of carbonation under atmospheric pressure, and this DOC was slightly higher than that of carbonated pastes without TEA under a CO2 pressure of 0.4 MPa. For γ-C2S mortar specimens, the flexural strength and compressive strength with 1 % TEA increased by 109.8 % and 99.3 %, respectively, and these values were slightly higher than those of specimens without TEA under CO2 carbonation pressure of 0.4 MPa. Additionally, at the optimal TEA concentration, CO2 solubility increased by 10.8 times and Ca2+ concentration increased by 94.7 %. This dual effect led to the carbonation rate under atmospheric pressure that could match or slightly exceed that under CO2 pressure of 0.4 MPa, which made this method a novel technique for accelerating carbonation.

Preparation of aragonite from calcium carbonate via wet carbonation to improve properties of steel slag building materials

Smelting in steel mills emitted large amounts of CO2 and produced the waste product steel slag (SS). Therefore, the use of SS to fix CO2 and produce value-added products could treat waste with waste and promote the effective use of resources. In this study, aragonite-type calcium carbonate was prepared by wet carbonation of SS, and the aragonite-rich SS (ASS) was pressed and moulded in the raw material of SS for semi-dry carbonation to obtain SS products. Through a series of experiments, the optimal conditions for the modulation and the formation mechanism of aragonite whiskers were investigated, and the effects of aragonite as a crystal seed on the properties and the degree of carbonation of SS products were also explored. In this experiment, the carbonation products were characterised microscopically by XRD, TGA, FT-IR and SEM, and the strength was tested by press machine. The results showed that aragonite phase was produced by wet carbonation of SS suspension containing 0.1M/L MgCl2 at 120 °C for 2h. The compressive strength, flexural strength, and secondary carbonation degree of the prepared SS products were increased when 5% ASS was added.

Predicting and optimizing maximum flexural strength of planar composite plate shear walls – concrete filled with the application of LR and RSM

Traditional theoretical models, while conservative, overlook the complex, nonlinear interactions between material and geometric parameters that influence wall flexural strength. Additionally, the extent to which these models maintain their conservative assumptions across varying parameters remains uncertain. This study aims to develop advanced predictive models for the flexural strength of planar composite plate shear walls—concrete filled (C-PSW/CF) by employing Linear Regression (LR) and Response Surface Methodology (RSM). Central Composite Design (CCD) was utilized to design numerical experiments to analyze the effects of varying parameters, including steel plate yield strength, concrete compressive strength, wall depth, depth-to-thickness ratio, and reinforcement ratio. A validated complex finite element modeling (FEM) procedure was used to analyze numerical experiments involving varying parameters of the selected variables. Both LR and RSM were applied to the generated dataset to formulate predictive equations for the maximum moment capacity of walls. Interaction plots were developed to reveal the nonlinear relationships between the variables and identify the most effective parameters influencing the wall strength. Comparisons between theoretical predictions, RSM, and LR models revealed that RSM provided the most accurate predictions, closely aligning with FEM results and effectively capturing the nonlinear interactions between wall parameters. The findings of this paper contribute to the development of more practical, accurate and optimized design methods for C-PSW/CF, ultimately improving both structural safety and efficiency.

Thermal and mechanical properties of high-performance polyester nanobiocomposites reinforced with pre-treated sunn hemp fiber for automotive applications

The objective of this study is to create high-performance nano biocomposites by utilizing unsaturated polyester resin (PE) reinforced with pre-treated short (2 cm) lengthened sunn hemp (SH) fibers and by incorporating 5 % nanoclay (hydrophilic bentonite) through the compression molding technique. The addition of 5 % nanoclay to the biocomposite significantly increased the flexural strength by approximately 165 % for H2O2-treated SH fiber and 148 % for KMnO4-treated SH fiber, when compared to untreated fibers. This enhancement was achieved through phase separation, intercalation, and exfoliation between the SH fibers, polyester resin (PE), and 5 % nanoclay. In particular, the H2O2-treated SH fiber nanobiocomposite exhibited a 43 % higher flexural strength compared to its corresponding biocomposite. The incorporation of nanoclay significantly decreased the water absorption of the bio-composites from 11.86 % in the untreated samples to a minimum of 2.76 % in the H2O2-treated SH/PE nanobiocomposite. The study suggests that short SH fiber/PE/nanoclay nanobiocomposites could be used as effective alternatives to synthetic composites in various applications, including the aerospace industry, household products, and automotive interior components such as side panels, seat frames, and central consoles. Additionally, they could be utilized in exterior parts like door panels and dashboards.

Mechanical characteristics and microscopic mechanism of polypropylene fiber modified recycled road solid waste fine aggregate mortar

Recycled fine aggregate (RFA) is a recycled building material obtained by crushing and screening waste concrete, which is the main raw material for producing recycled aggregate mortar (RAM). However, due to the defects of RFA such as many cracks, high porosity and large fragmentation index, RAM has problems such as low compressive strength and poor flexural strength, which limits its large-scale application in mortar engineering. In this paper, a series of experiments were carried out to verify that the addition of polypropylene fiber (PPF) improves the mechanical strength of RAM. Four lengths (3mm, 6mm, 9mm, 12mm) and three dosages (0.3%, 0.6%, 0.9%) of PPF were added, and their effects on the compressive strength and flexural strength of RAM were studied. The test results show that the addition of PPF can improve the compressive strength and flexural strength of RAM and increase the toughness of RAM. The addition of PPF with 0.6% dosage and 12mm length can increase the compressive strength of RAM by 57% and the residual strength by 73%. The addition of PPF with 0.9% dosage and 12mm length can increase the flexural strength of RAM by 58% and the fracture energy by 163%. Scanning electron microscopy (SEM) results show that PPF can improve the microstructure of RAM. The effective bonding between the matrix and PPF is observed, which increases the mechanical strength of RAM. In addition, PPF is pulled out and broken, proving that PPF effectively plays its bridging and stretching role in the matrix. Moreover, a prediction model for the effect of PPF length and dosage on the compressive strength and flexural strength of RAM is proposed, which can provide theoretical basis for practical engineering and reference for related researches. This study proposes a negative carbon method for applying road solid waste to engineering mortar, which can provide theoretical basis for practical engineering and reference for related research.

Functionalizing heavy metal contained incinerated sewage sludge ash in recycled glass-based alkali-activated materials for sewer environment

This study evaluates the performance of alkali-activated cement (AAC) mortars in an artificial sewage environment. The mortars, initially prepared with waste glass powder (GP) and ground granulated blast furnace slag (GGBS) in a 50:50 mass ratio, were modified by replacing 10 wt% of GGBS with incinerated sewage sludge ash (ISSA) with the goal of offering a biocidal effect. Comparisons were made with calcium aluminate cement (CAC), metakaolin (MK), and MK combined with zinc ferrite nanoparticles, each at a similar GGBS replacement level. The results showed that only incorporating CAC improved the strength development, achieving compressive and flexural strengths of 62.7 MPa and 7.4 MPa, respectively, at 28 days, while introducing ISSA or MK reduced the compressive strength to 47 MPa and flexural strength to 4.5 MPa. Although heavy metal ions from ISSA or zinc ferrite nanoparticles minimized biofilm thickness, they could not compensate for the reduced strength and increased alkalis leaching. Among all the tested mixtures, the 50GP40GGBS10CAC mixture exhibited superior biogenic acid resistance, possibly due to its Al-rich C-N-A-S-H gel phases (Ca/Si = 0.4, Na/Al = 0.8, Si/Al = 3.4) and refined pore structure (porosity = 3.4 %), making it the most microbial acid-resistant option for sewer rehabilitation.

Developing ultra-high performance concrete with different strength grade based on mix proportion sensitivity factor analysis

Abstract Owing to the excellent strength and durability, ultra-high-performance concrete (UHPC) has been used for fabricating large-scale and important infrastructures. However, mix proportion of UHPC is still the core factor influencing its workability, strength, cost and energy resource consumption. Based on this, the amount of cementitious materials, water-binder ratio, and the content of steel fibers were matched to obtain UHPC with required workability and strength according to three-factor five-level orthogonal range analysis considering the interaction of these three parameters. Experimental results show that the water-binder ratio and steel fiber content is the primary factor to guarantee the fluidity/compressive and flexural strength of UHPC, respectively. For developing UHPC with compressive strength grade of 150 MPa and flexural strength higher than 50 MPa, the amount of cementitious materials (including cement, silica fume, cenosphere, and fly ash) and the content of steel fibers should be higher than 1000 kg m−3 and 2.5 vol.%, and the corresponding water-binder ratio is equal to 0.16. When the aim is to fabricate UHPC with compressive strength grade of 120 MPa and flexural strength higher than 40 MPa, the water-binder ratio can be increased but should be lower than 0.20 with the increasing amount of cementitious material, and the volume fraction of steel fibers should be higher than 1.5 vol.%. High steel fiber content and water-binder ratio all easily coarsens the microstructure and pore structure of UHPC, and this phenomenon cannot be compensated by using high amount of cementitious materials. It should be adjusting the matching degree of amount of cementitious materials and water-binder ratio to obtain a slurry with appropriate fluidity and cohesiveness, and then content of steel fibers can be selected to perform without adverse effects.

Simultaneously enhancing the EMI shielding performances and mechanical properties of structure–function integrated CF/PEEK composites via chopped ultra-thin carbon fiber tapes and interfacial engineering with MXene

The functionalization of carbon fiber reinforced poly(ether-ether-ketone) (CF/PEEK) structural composites with high electromagnetic interference shielding efficiency (EMI SE) has important engineering application in the fields of aviation and aerospace. However, the simultaneous enhancement of interfacial properties and EMI SE in the CF/PEEK composite remains a significant concern. To address this issue, we have employed a continuous impregnation approach that involved synthesizing PFEEK as a binder and then utilizing mechanical spreading technology to prepare chopped ultra-thin CF tapes as the reinforcement phase. Subsequently, we deposited 2D MXene (Ti3C2Tx) on the CF tape surface to endow the interface properties and EMI SE for the CF/PEEK composites. As a result, when the MXene content was 1.0 mg/ml, the flexural strength, flexural modulus, and interlaminar shear strength (ILSS) of the obtained CF/PEEK composites achieved 17.6 %, 13.3 % and 36.6 % enhancement higher than that of the virgin CF/PEEK composites, respectively, which may be owing to the elevated interfacial properties via the hydrogen bonds, physical entanglement, π-π interactions, and mechanical interlocking with the incorporation of PFEEK and MXene. The optimal ILSS value and specific EMI SE/t value of the CF/PF-M1/PEEK composites can reach 113.7 MPa and 80.8 dB/mm, respectively. The enhancement in the EMI SE can be attributed to the enhancive reflection, the increased polarization losses, and multiple interlayer reflections of EM waves facilitated by the incorporation of MXene and multi ultra-thin CF/PF-MXene layers. This approach resulted in a structure–function integrated CF/PEEK composite, which holds promising application prospects across various cutting-edge domains.

Evaluation of the engineering properties and sustainability of solid masonry blocks produced with recycled concrete aggregates

The rapid expansion of global infrastructure has led to significant natural resource shortages and increasing environmental concerns related to construction and demolition (C&D) waste. Recycling C&D waste presents a viable solution to alleviate resource depletion and promote sustainability. This study explores the use of recycled concrete aggregates (RCAs) derived from C&D waste in producing solid masonry blocks (SMBs). RCAs were employed to replace both natural coarse and fine aggregates in these blocks. Physical and mechanical properties of SMBs were tested, including hardened density, compressive and flexural strengths, and water absorption. The findings showed that decreased strength and increased water absorption for cement-to-aggregate ratio (C: A) increased from 1:6 to 1:24; however, all produced SMBs satisfied the requirements specified by Indian and ASTM standards. The study concluded that using 100% RCAs in SMBs is structurally sound and environmentally beneficial, meeting international standards. Employing recycled aggregate concrete blocks lowers environmental impact and aids in sustainable development by facilitating the life-cycle closure of the building materials.

Machine Learning Based Prediction of Compressive and Flexural Strength of Recycled Plastic Waste Aggregate Concrete

In the last 50 years, the use of plastics has increased significantly due to advances in technology, population growth and increasing needs. However, this trend has led to the accumulation of large amounts of plastic waste. Numerous studies have been conducted on the use of recycled plastic materials in concrete production as a means of recycling and environmental protection. This study aims to predict the 28-day cylinder compressive and flexural strength of concretes using Polyethylene Terephthalate (PET), Phenolic Formaldehyde (PF), Polypropylene (PP), Polycarbonate (PC), Polyvinyl Chloride (PCV), High-Impact Polystyrene (HIPS) and High-Density Polyethylene (HDPE) plastic waste as aggregates. In this scope, a comprehensive database was created using experimental results obtained from the literature. Then, this study used six ML models, including Support Vector Regressor (SVR), Random Forest Regressor (RFR), Gradient Boosting Regressor (GBR), XGBoost Regressor (XGR), LightGBM Regressor (LGR), Bagged Decision Trees Regressor (BDTR), to predict the compressive and flexural strength of recycled plastic waste aggregate concrete (RPWAC). From the experimental database, 253 data points with strength between 6.00-70.05MPa were identified to estimate the compressive strength (CS) and 175 data points with strength between 1.21-7.96MPa were identified for flexural strength (FS). Cross-validation was used for six ML models and hyperparameter fine-tuning was performed. The results showed that six different ML models predicted the compressive and flexural strengths of RPWAC with high accuracy. The XGR model predicted CS and FS better than the other five different models with R2 values of 0.931 and 0.999, respectively. The three main properties effecting the CS of RPWAC were plastic waste content, water/cement ratio and concrete specific gravity, while the three main properties affecting the FS of RPWAC were cement specific gravity, plastic waste content and cement CS.

High-temperature behaviour of geopolymer composites containing carbon fibre and nano-silica: Mechanical, microstructure, and air-void characteristics

The fly ash–ground granulated blast-furnace slag-based geopolymer (FSG) represents a groundbreaking material, offering a sustainable and environmentally friendly alternative to conventional construction materials. This paper presents a systematic experimental study on FSG reinforced with carbon fibre (CF, 0%–1.0%) and nano-silica (NS, 1%–3%) at high temperatures (20, 200, 400, 600, 800, and 900 °C). Various tests concerning appearance, residual strength, uniaxial tension, XRD, FTIR, TGA, SEM, and air-void characteristics were conducted to analyse thermal effects. The findings show that as temperature increases, the colour of the geopolymer transitions from dark grey to yellow grey. Enhanced geopolymerisation during thermal solidification from 20 to 400 °C significantly increases the compressive, flexural, and tensile strengths of the geopolymer. The addition of CF and NS improves the residual strength of geopolymers at high temperatures, with optimal concentrations found to be 0.6% for CF and 2% for NS. CF maintains its bridging effect at high temperatures, enhancing fibre–matrix bonding, while NS promotes the formation of additional hydration products on CF surfaces, thereby strengthening the material further. After exposure to 800 °C, despite a weakening of the fibre–matrix interface, the modified geopolymers (FSGC0.6 and FSGC0.6N2) exhibit finer air bubble chord lengths and superior air-void characteristics than the control group. This supports the theory that the synergistic action of CF and NS not only enhances geopolymerisation but also fills pores, thus limiting crack propagation and densifying the pore structure.

Power ultrasound-assisted enhancement of granulated blast furnace slag reactivity in cement paste

The impact of the power ultrasound (PUS)-assisted preparation technique on the physicochemical and mechanical characteristics of cement-granulated blast furnace slag (GBFS) pastes was studied. Pastes containing GFBS with varying particle size fractions, partially replacing Portland cement, were tested using PUS in pulse mode in a sonoreactor with closed-circuit cooling. The best-performing cement-GBFS composite paste showed a notable increase in compressive and flexural 2-day strengths (132% and 58%, respectively), as well as Vickers hardness and modulus of elasticity (98% and 74%, respectively) when compared to conventional mixing procedures. Similarly, the BET surface area increased by about 111%, cumulative heat release increased by about 34% after 2 days, reduced substitute setting times (initial by about 32%, final by about 55%), and portlandite content decreased by about 29%. The power of this association is linked to C-S-H/C-A-S-H nucleation seeding, which can be formed via an interfacial mediator induced by PUS.