Vol.4,No.3,2024-Table of Contents
- OPEN ACCESS ARTICLE
- Old residual mortar as a quality indicator of recycled brick aggregate
- Sustainable Structures Vol.4,No.3,2024 DOI:10.54113/j.sust.2024.000061 Online published:2024-12-1
- Abstract Old residual mortar (RM) on recycled aggregate surfaces is a major factor contributing to its lower quality. The present study aims to quantify the effect of old mortar on the properties of recycled brick aggregates (RBA) and recycled concrete (ReC) made with them. The process involves collecting and crushing discarded concrete blocks from seven sources to create recycled brick aggregates. A chemical-thermal combined process removes old mortar, and with varying RM contents, the aggregate properties are determined. C-25-grade concrete specimens are prepared using RBA with different RM content and tested for workability, compressive strength, splitting tensile strength, flexural strength, water absorption, bulk density, and voids in hardened concrete. Regression models expressing the change in properties with RM content are presented. The study reveals that the quality of RBA and concrete worsens with increasing RM, with a 20% RM value being considered a limiting value to maintain minimal variation in properties. The regression models suggest that every 10% increase in RM may result in an 11% increase in water absorption of RBA, an 8% increase in aggregate crushing value (ACV), a 3.6% increase in Los Angeles (LA) value, a 10% loss in compressive strength of ReC, a 7% loss in tensile strength, and a 9% loss in flexural strength, approximately. The developed models may be used to predict the expected quality of RBA and ReC based on their attached old RM, which would be helpful in deciding their usage for different applications.… More
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- Behaviour of post-tensioned benches made of high-content recycled aggregate concrete reinforced with racquet string fibres
- Sustainable Structures Vol.4,No.3,2024 DOI:10.54113/j.sust.2024.000060 Online published:2024-12-1
- Abstract This study investigates the serviceability and structural behaviour of a new type of recycled aggregate concrete (RAC) bench with waste badminton racquet fibres. Twenty-one cantilever benches were tested in two Series with different fibre volume fractions (Vf = 0%, 0.5%, 1.0% or 1.5%). The RAC had 100% of natural aggregates replaced with recycled concrete aggregate (RCA). The benches in Series II were post-tensioned in flexure using an innovative Post-Tensioned Metal Strapping (PTMS) technique using 1, 2 or 3 straps. Tests were carried out to evaluate 1) static loading behaviour, 2) long-term behaviour after 365 days of sustained loading, and 3) human-induced vibrations. The static test results show that benches with 100% RAC and PTMS had higher capacity (by about 25%) that counterpart benches without PTMS. Hence, the maximum flexural strength of the cantilever bench was improved by 5.7% for the cantilever bench with PTMS strengthening, which further enhanced the flexural behaviour compared to the bench with only 1.5% of fibres. The human-induced vibration test results confirmed that the maximum vibration of the benches met the code limits for floor buildings. Finite element analyses of the RAC benches with PTMS were carried out in Abaqus®, and the experimental deflections agreed well (errors <5%) with the FEM results. A simplified fatigue life analysis confirmed that the RAC benches with PTMS can have a potential service life of up to 20 years. The use of glow-in-the-dark (GID) features into the benches in Series II enhanced their night-time visibility and visual appeal by up to 8 h. This research contributes towards the development of new applications for RAC with waste badminton racquet fibres, which can offer more sustainable solutions for the construction of urban furniture.… More
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- Behaviour and design of extruded high-strength aluminium alloy SHS beam-columns
- Sustainable Structures Vol.4,No.3,2024 DOI:10.54113/j.sust.2024.000059 Online published:2024-12-1
- Abstract An extensive study of beam-columns made from 7A04-T6 aluminum alloy in a square hollow section (SHS) configuration is presented in this paper, integrating both experimental and numerical work to study their flexural buckling behaviour. Eight pin-ended SHS specimens with two extruded SHS profiles - 80×5 and 120 × 10 (in mm), were tested under eccentric compression, along with tests of material coupons and measurements of initial geometric imperfections. The experimental data were employed in the investigation to assess the validity of the numerical model, which was subsequently subjected to a series of parametric analyses aimed at expanding the existing results across a wider spectrum of slenderness ratios, cross-section dimensions, and load combinations. Both experimental and simulated datasets were employed to verify the precision of resistance forecasts for SHS beam-columns by design approaches outlined in European, Chinese and American standards. Findings indicated that both the European and Chinese standards tended to provide relatively conservative predictions for buckling resistances, while the American standard sometimes produced predictions leading to higher risk. Finally, a modification strategy for the design of AA7A04-T6 SHS beam-columns, utilizing modified interaction buckling factors that account for non-dimensional member slenderness and compression resistances, was suggested to enhance the precision and reliability of resistance forecasts.… More
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- Reinforcing the brittle resistance of high-strength concrete using agricultural waste fiber
- Sustainable Structures Vol.4,No.3,2024 DOI:10.54113/j.sust.2024.000058 Online published:2024-12-1
- Abstract The utilization of natural fiber wastes could be an ideal way to tackle two problems. Firstly, this may be a solution to the issue of environmental challenges related to agricultural wastes. Secondly, it can potentially fix high-strength concrete's (HSC) issue of unexpected (sudden) collapse. This study looked at the results of using two different kinds of natural fiber waste in HSC. Seven HSC mixtures were manufactured; three included rice straw fibers (RSF), three contained palm leaf sheath fibers (PLSF), and one was a control mix (without fibers). In this research, the volume fractions of RSF and PLSF ranged from 1% to 3% and had an aspect ratio equal to 100. Different tests, including slump test, compressive strength, modulus of elasticity, flexural strength and tensile strength were conducted to determine their various properties. There were no significant improvements on compressive strength due to use of natural fiber while its tensile and flexural strengths increased particularly when including 1% RSF. RSF improved the properties of HSC more significantly than PLSF.… More
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- An assessment of the pozzolanic potential and mechanical properties of Nigerian calcined clays for sustainable ternary cement blends
- Sustainable Structures Vol.4,No.3,2024 DOI:10.54113/j.sust.2024.000057 Online published:2024-12-1
- Abstract This study investigates the potential of calcined clays from Nigerian deposits as supplementary cementitious materials. Clay materials were obtained from three sites namely: Ikpeshi, Okpilla and Uzebba. The raw clay samples were then calcined at 700°C and 800°C. Chemical and mineralogical compositions were determined for the raw and calcined clay samples using XRF and XRD respectively. The chemical composition by XRF confirmed these clays as potential pozzolans with SiO2, Al2O3, and Fe2O3 collectively exceeding 70%. XRD analysis identified kaolinite and quartz as major mineral phases in the raw clays, which transformed into metakaolin upon calcination. Thermo Gravimetric Analysis (TGA) indicated varying lime consumption levels among the clays, with Ikpeshi clay displaying the highest pozzolanic reactivity and Uzebba clay the least. Compressive strength investigation on mortar cubes prepared with 50% substitution of Portland cement with the calcined clay and limestone, showed that Ikpeshi clay at 800°C had the best strength performance, with strength activity index of 0.92 (at age 28 days), demonstrating superior pozzolanic potential. Strength development was more significant between 7 and 28 days, indicating the pozzolanic reaction's contribution to long-term strength. However, initial strength at 3 days was lower than the reference Portland cement due to a delayed pozzolanic reaction. XRD analysis of blended pastes revealed typical phases of hydration like portlandite, calcium silicate hydrate phase, strätlingite, and ettringite, with the calcined clay blends showing reduced portlandite content, indicating absorption by the pozzolan's alumina phase.… More
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- Evaluating suitability of regression models in small data regimes using concrete with recycled copper tailings as a case study
- Sustainable Structures Vol.4,No.3,2024 DOI:10.54113/j.sust.2024.000056 Online published:2024-12-1
- Abstract The utilization of regression models for the prediction of construction material properties is well-established, yet their performance when applied to small datasets is still unclear. This study investigates the performance of different regression models combined with various data preprocessing techniques in contexts where data is limited. Specifically, the research focuses on evaluating the suitability of five regression models across nine different data processing scenarios using concrete with recycled copper tailing as a case study. This study aims to determine which combinations of regression models and preprocessing methods yield the most accurate predictions in small data regimes. This research is motivated by the necessity to enhance prediction reliability in the field of construction materials, where experimental data can often be scarce or costly to obtain. Within the study context, a dataset comprising 21 experimental specimens is used to evaluate the performance of the models on various concrete properties, including fresh density, compressive strength, flexural strength, pull-off strength, abrasion resistance, water penetration, rapid chloride ion permeability, and air permeability. Through rigorous evaluation involving a 10-fold cross-validation process to verify accuracy, the research demonstrates that selecting the optimal regression model and data preprocessing technique selection substantially improves prediction outcomes, even with limited data. The findings highlight the importance of this research, suggesting that even small datasets, when handled correctly, can provide robust insights.… More
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- Mechanical response of glass/kevlar hybrid composite jackets for steel containers carrying hazardous materials to enhance safety
- Sustainable Structures Vol.4,No.3,2024 DOI:10.54113/j.sust.2024.000055 Online published:2024-12-1
- Abstract Fiber reinforced (FRP) composite materials have high strength-to-weight ratios and excellent corrosion resistance. Cost reduction manufacturing through methods like Vacuum Assisted Resin Transfer Molding (VARTM) is impressive. This paper deals with composite materials reinforcement of railway tank cars via VARTM to enhance safety, improve fuel efficiency, and reduce adverse environmental impact during derailments aligning with industry goals for safer, sustainable solutions in relation to new railway tank car safety standards. This study investigates different performance aspects of various fiber/fabric configurations (glass, aramid) used as reinforcement with vinyl ester or epoxy. Additionally, core materials like polyurethane and polypropylene have been researched to enhance energy absorption. Effects of through-thickness stitching on mechanical integrity are evaluated for improved puncture resistance. Testing revealed that Kevlar fibers increased energy absorption by increasing strain to failure. Epoxy resin lowered maximum tensile strength by 22% compared to vinyl ester and increased the total energy absorption by 8%. Through-thickness stitching (z-direction) increased tensile strength by 13% and improved interlaminar shear strength.… More
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- Structural performance of additive manufactured wood-sodium silicate composite beams for sustainable construction
- Sustainable Structures Vol.4,No.3,2024 DOI:10.54113/j.sust.2024.000054 Online published:2024-12-1
- Abstract The current research examines the structural bending performance of additive manufactured wood-sodium silicate composite beams of various span-to-height proportions. Beams consisting of both a single layer as well as two layers of extruded wood-sodium silicate composite were considered. Both groups of beams exhibited a rise in maximum shear force (Vmax), maximum bending moment (Mmax), apparent modulus of elasticity (MOEapp), and modulus of rupture (MOR) when the span-to-height proportions rose. However, the amount of shear stress (τmax) decreased as the span-to-height proportion increased. Furthermore, the flexural and shear stress patterns for span-to-height proportions of 6 and 30 were calculated analytically using the transformed section methodology across the thickness of the beams at different positions of L/6, L/3, 5L/12, and L/2 of the beam span. The results demonstrated that the bending stress increased as the distances from the supports increased toward the middle of the beam. Compared to single-layer beams, two-layer beams displayed lower stress values overall. In particular, the bending stress was 4.85% lower in the two-layer beam with a span-to-height proportion of 6 than that of the single-layer beams. Furthermore, the single-layer beam's maximum shear stress was slightly greater than the two-layer beams. The greatest shear stress of the single-layer beams were computed 4.27% and 0.46% higher than those of the two-layer beams at span-to-height proportions of 6 and 30, respectively.… More
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