Ardalan B. Hussein
58626117000
Publications - 16
Axial strength of back to back cold formed steel short channel sections with unstiffened and stiffened web holes
Publication Name: Scientific Reports
Publication Date: 2025-12-01
Volume: 15
Issue: 1
Page Range: Unknown
Description:
The increasing adoption of back-to-back built-up cold-formed steel (CFS) channel columns in construction is attributed to their lightweight nature, versatility in shape fabrication, ease of transportation, cost efficiency, and enhanced load-bearing capacity. Additionally, the incorporation of web openings facilitates the integration of electrical, plumbing, and heating systems. These built-up sections are widely utilized in wall studs, truss elements, and floor joists, with intermediate screw fasteners strategically positioned at regular intervals to prevent the independent buckling of channels. Based on 18 experimental tests, this study demonstrates an excellent correlation between finite element analysis and the experimental results, confirming the accuracy of geometrically and materially nonlinear finite element modeling in predicting the axial buckling strength of built-up short columns. Furthermore, the design standards of the American Iron and Steel Institute and Australian/New Zealand Standards were found to underestimate the axial load capacity by approximately 12.5%. The primary objective of this research is to investigate the influence of various hole configurations, both with and without stiffeners, on the axial performance of built-up short CFS channel columns. A total of 180 finite element models were developed, examining four different unstiffened and edge-stiffened hole configurations, validated against experimental results from plain webs. The findings reveal that web holes and edge stiffeners significantly impact axial load-bearing capacity, while the specific shape of the openings has a negligible effect. Specifically, introducing a hole at the centroid of each web results in an approximate 8.5% reduction in axial load capacity in the absence of edge stiffening. However, the incorporation of stiffeners around the perforations mitigates this reduction and enhances both structural efficiency and load-bearing capacity. These results highlight the critical role of edge stiffening in optimizing the structural performance of perforated built-up CFS columns.
Open Access: Yes
Structural behaviour of built-up I-shaped CFS columns
Publication Name: Scientific Reports
Publication Date: 2024-12-01
Volume: 14
Issue: 1
Page Range: Unknown
Description:
The utilization of cold-formed thin-walled members as structural members has gained significant popularity due to their advantages in fabrication, cost-effectiveness, and transportation convenience. However, the reduced thickness of the used sections poses challenges such as global, local, and distortional member buckling, leading to a decrease in their axial strength. This study focuses on addressing these challenges by connecting the channels together using screws as an alternative to welding, considering the cost, time, and ease of implementation. Conducting finite element analysis on structural columns built-up from cold-formed double C steel channels and subjected to axial loads, this paper verifies the numerical models used against experimental tests known from the literature. A comparison of experimental results with nonlinear FEA and AISI & AS/NZ standards reveals commendable agreement, particularly in predicting the buckling behavior of the built-up I-shaped CFS columns. While the results of the finite element analysis show an overestimation of approximately 3.6% compared to the experimental tests, the AISI and AS/NZS standards demonstrate a conservatism of about 3.0%. Furthermore, the current study investigates the influence of screw spacing on axial strength of built-up cold-formed steel columns. The findings are derived from 175 finite element experiments, evaluating seven different cross-sectional profiles with twelve distinct screw spacings. These spacings correspond to the half-wavelength of local, distortional, and global buckling, divided by values ranging from one to four. The screw spacing determined by half the local buckling half-wavelength along the webs’ centerline resulted in enhancements of 22%, 7%, 13%, and 11% in the critical elastic local, distortional, and global column buckling loads, as well as the nominal axial strength, respectively. These increases were even more pronounced for double-lane fasteners with the same spacing, yielding improvements of 25%, 46%, 17%, and 12%, respectively. For economic considerations, it is advisable to utilize single-lane fasteners with a half-wavelength equal to half the local buckling half-wavelength.
Open Access: Yes
Structural behavior of built-up I-shaped CFS beams
Publication Name: Results in Engineering
Publication Date: 2024-12-01
Volume: 24
Issue: Unknown
Page Range: Unknown
Description:
The use of back-to-back built-up C-section beams is becoming increasingly common in CFS construction due to their cost-effectiveness and enhanced load-carrying capacity, making them suitable for longer beam spans and convenient for transportation. These built-up sections are utilized in wall studs, truss components, and floor joists, with intermediate screw fasteners placed at specific intervals to prevent the separate bowing of channels. This study reveals a ratio of 1.003 between experimental findings and finite element analysis results, and 1.002 between experimental findings and direct strength method results, indicating a strong correlation between experimental data from nonlinear finite element analysis and predictions based on the American Iron and Steel Institute and Australian and New Zealand Standards, particularly in predicting the flexural buckling strength of beam specimens. Furthermore, ongoing research is investigating the impact of screw spacing on flexural strength. This study presents results from 175 finite element tests, evaluating seven distinct cross-sections with twelve unique screw spacings. These spacings correspond to the half wavelength of local, distortional, and global buckling, divided by values from one to four. It was found that screw spacing based on half the local buckling half-wavelength along the centerline of the webs increased the critical global buckling moment capacity and the nominal flexural strength by 56 % and 27 %, respectively. For double-lane screws with the same spacing, these increases were even more substantial, reaching 65 % and 31 %, respectively. Economically, the recommended spacing for single-lane screws is half the local buckling half-wavelength.
Open Access: Yes
Numerical Investigation of the Axial Load Capacity of Cold-Formed Steel Channel Sections: Effects of Eccentricity, Section Thickness, and Column Length
Publication Name: Infrastructures
Publication Date: 2024-09-01
Volume: 9
Issue: 9
Page Range: Unknown
Description:
Cold-formed steel channel (CFSC) sections have gained widespread adoption in building construction due to their advantageous properties, including superior energy efficiency, expedited construction timelines, environmental sustainability, material efficiency, and ease of transportation. This study presents a numerical investigation into the axial compressive behavior of CFSC section columns. A rigorously developed finite element model for CFSC sections was validated against existing experimental data from the literature. Upon validation, the model was employed for an extensive parametric analysis encompassing a dataset of 208 CFSC members. Furthermore, the efficacy of the design methodologies outlined in the AISI Specification and AS/NZS Standard were evaluated by comparing the axial load capacities obtained from the numerically generated data with the results of four previously conducted experimental tests. The findings reveal that the codified design equations, based on nominal compressive resistances determined using the current direct strength method, exhibit a conservative bias. On average, these equations underestimate the actual load capacities of CFSC section columns by approximately 11.5%. Additionally, this investigation explores the influence of eccentricity, cross-sectional dimensions, and the point-of-load application on the axial load capacity of CFSC columns. The results demonstrate that a decrease in section thickness, an increase in column length, and a higher degree of eccentricity significantly reduce the axial capacity of CFSC columns.
Open Access: Yes
Investigating the Factors Influencing the Strength of Cold-Formed Steel (CFS) Sections
Publication Name: Buildings
Publication Date: 2024-04-01
Volume: 14
Issue: 4
Page Range: Unknown
Description:
The utilization of cold-formed steel (CFS) sections in construction has become widespread due to their favorable attributes, including their lightweight properties, high strength, recyclability, and ease of assembly. To ensure their continued safe and efficient utilization, this review provides a comprehensive investigation into the factors influencing the strength of CFS members. This analysis encompasses design codes, prediction methodologies, material properties, and various structural configurations. This review uncovers discrepancies among existing design codes, particularly noting conservative predictions in AISI and AS/NZS standards for composite and built-up sections. Additionally, the effectiveness of prediction methods such as the direct strength method and effective width method varies based on specific structural configurations and loading conditions. Furthermore, this review delves into recent advancements aimed at enhancing fire resistance, connection design, and the composite behavior of CFS structures. The influence of factors such as eccentricity, sheathing materials, and bolt spacing on structural performance is also examined. This study underscores the crucial role of accurate prediction methods and robust design standards in ensuring the structural integrity and safety of CFS constructions. Through a comparative analysis, it is revealed that AISI and AS/NZS standards exhibit conservatism in predicting nominal buckling loads compared to experimental data. Conversely, a non-linear finite element analysis demonstrates a strong correlation with laboratory tests, offering a more accurate prediction of nominal buckling capacity. Overall, this review offers comprehensive insights aimed at optimizing CFS structural design practices. By identifying key areas for future research and development, this work contributes to the ongoing advancement of safe and efficient CFS construction applications.
Open Access: Yes
Effects of Lip Length and Inside Radius-to-Thickness Ratio on Buckling Behavior of Cold-Formed Steel C-Sections
Publication Name: Buildings
Publication Date: 2024-03-01
Volume: 14
Issue: 3
Page Range: Unknown
Description:
Cold-formed steel (CFS) sections constructed with high-strength steel have gained prominence in construction owing to their advantages, including a high strength-to-weight ratio, shape flexibility, availability in long spans, portability, cost-effectiveness, and design versatility. However, the thin thickness of CFS members makes them susceptible to various forms of buckling. This study focuses on addressing and mitigating different types of buckling in columns and beams by manipulating the lip length (d) and the ratio of inside radius to thickness (Ri/t) in CFS C-sections. To achieve this objective, a comprehensive analysis involving 176 models was conducted through the Finite Element Method (FEM). The findings reveal that an increase in lip length leads to a corresponding increase in critical elastic buckling load and moment ((Formula presented.), (Formula presented.), (Formula presented.), (Formula presented.), (Formula presented.), and (Formula presented.)). It is recommended to utilize a lip length greater than or equal to 15 mm for both columns and beams to mitigate various buckling types effectively. Conversely, an increase in the ratio of inside radius to thickness (Ri/t) results in an increase in critical elastic local buckling load ((Formula presented.)) and moment ((Formula presented.)). Thus, lip length (d) significantly influences column and beam buckling, whereas Ri/t exhibits a relatively impactful effect. Subsequently, the experimental test results were used to verify finite element models. These insights contribute significant knowledge for optimizing the design and performance of CFS C-sections in structural applications.
Open Access: Yes
State-of-the-Art: Integrating Fastener Technology and Design Guidelines for Enhanced Performance of Cold-Formed Steel Sections
Publication Name: Buildings
Publication Date: 2023-09-01
Volume: 13
Issue: 9
Page Range: Unknown
Description:
Cold-formed steel (CFS) elements have gained significant attention in the field of structural engineering due to their numerous advantages, including high strength-to-weight ratio, cost-effectiveness, and ease of assembly and prefabrication. This review paper presents a comprehensive state-of-the-art analysis of the design and analysis of CFS structures, with a specific focus on columns and beams. The primary objectives and aims of this review paper are to provide a detailed assessment of the factors influencing the behavior and performance of CFS elements, including partial composite action, fastener spacing, bolt arrangement, web aperture, stiffeners, and connection spacing, to propose and present various formulas and methodologies that accurately estimate critical buckling loads, strength, and moment resistance for CFS members, and to emphasize the significance of proper screw and bolt placement in preventing premature failure and enhancing the overall load-carrying capacity of CFS structures. Additionally, the impact of temperature on the mechanical properties and performance of CFS members is discussed. The review paper proposes different formulas and methodologies to accurately estimate critical buckling loads, strength, and moment resistance for CFS members. Moreover, the paper highlights the importance of proper screw and bolt placement to prevent early failure and improve the overall load-carrying capacity of CFS structures. The discussion also emphasizes the need for revisions in existing standards and codes to provide more practical guidelines for designers and engineers. Overall, this state-of-the-art review paper provides valuable insights and recommendations for researchers and practitioners involved in the design and analysis of CFS elements.
Open Access: Yes
Web crippling behavior of cold-formed steel built-up I-sections with stiffened and unstiffened perforated webs
Publication Name: Results in Engineering
Publication Date: 2025-12-01
Volume: 28
Issue: Unknown
Page Range: Unknown
Description:
This study investigates the web crippling behaviour of cold-formed steel (CFS) back-to-back built-up U-shaped sections with perforated webs. In this research, the web opening was positioned at the mid-height of the web directly beneath the bearing plate. Initially, the geometrically and materially nonlinear finite element (FE) models were validated against 24 experimental tests from the literature, demonstrating excellent agreement. Specifically, the mean FE-to-experimental strength ratios (PFE /PEXP ) were 1.002 and 1.001 for the Interior-Two-Flange (ITF) and Interior-Loading (IL) conditions, respectively. Subsequently, the verified nonlinear FEM models were employed to conduct an extensive parametric study comprising 198 built-up I-sections. Moreover, this extensive investigation systematically examined the effects of various parameters, including hole size, the presence of unstiffened and stiffened holes, as well as different hole shapes such as rectangular, slotted, circular, and square openings, on web crippling performance. Furthermore, the results indicate that unstiffened holes can reduce the web crippling strength by as much as 54 % compared to plain webs. In contrast, edge-stiffened holes can enhance the web crippling strength by up to 42 % relative to plain webs. These findings highlight the significant impact of web perforation geometry and stiffening on the web-crippling behaviour of CFS built-up sections.
Open Access: Yes
Structural behavior of built-up I-shaped cold-formed steel beams with edge-stiffened holes, unstiffened holes, plain webs, and batten reinforcement
Publication Name: Results in Engineering
Publication Date: 2025-12-01
Volume: 28
Issue: Unknown
Page Range: Unknown
Description:
Perforated cold-formed steel (PCFS) back-to-back channel beams are increasingly gaining popularity in the building sector due to their numerous advantages and economic benefits. Notably, their lightweight nature allows for easier handling and installation, while the holes in PCFS beams facilitate the accommodation of utilities such as electrical and plumbing installations. In this study, a geometrically and materially nonlinear finite element model (FEM) was developed and validated using experimental data from existing literature. The validation results indicated a strong correlation, with the ratios of FEM and Direct Strength Method (DSM) predictions to experimental outcomes being 1.007 and 0.945, respectively. This demonstrates a significant agreement among experimental data, FEM analysis, and moment capacity estimations based on American Iron and Steel Institute (AISI) Standards, although AISI predictions were found to underestimate moment capacities by approximately 5.5 %. Following model validation, an extensive parametric study involving 192 FEM simulations was conducted to evaluate the influence of hole size, hole geometry, edge stiffeners, and batten reinforcements on the moment-carrying capacity of built-up I-shaped CFS beams. The findings indicate that, in comparison with beams having plain webs, the presence of web openings leads to a reduction in moment capacity of approximately 10 %, 9 %, 9 %, and 6 % for circular, slotted, square, and rectangular holes, respectively. Furthermore, the results demonstrate that the inclusion of stiffeners around web openings, together with batten reinforcement, markedly improves the structural performance of PCFS built-up beams. In particular, the maximum enhancement in moment capacity of beams with batten reinforcement and edge-stiffened holes, relative to those with unstiffened holes, is about 9 %, 10 %, 13 %, and 14 % for circular, rectangular, square, and slotted holes, respectively. Overall, the findings offer valuable insights into the structural behavior of perforated built-up CFS beams and emphasize the effectiveness of web hole stiffening and batten reinforcement strategies in mitigating strength reductions caused by web perforations.
Open Access: Yes
Structural behavior of built-up I-shaped high-strength cold-formed steel columns with edge-stiffened holes, unstiffened holes, plain webs, and batten reinforcement
Publication Name: Thin Walled Structures
Publication Date: 2026-01-01
Volume: 218
Issue: Unknown
Page Range: Unknown
Description:
Cold-formed steel (CFS) back-to-back channel sections are widely employed as load-bearing structural components due to their high strength-to-weight ratio and ease of fabrication. These sections are often perforated to facilitate service installations; however, the presence of holes alters stress distribution, reduces axial load capacity, and increases the complexity of structural analysis. To investigate these effects, a geometrically and materially nonlinear finite element (FE) model was developed and validated against experimental data from existing literature. Specifically, the validation results demonstrated a strong correlation, with the ratios of Finite Element Analysis (FEA) and Direct Strength Method (DSM) predictions to experimental findings being 1.001 and 1.003, respectively. These results indicate a high level of agreement between experimental data, FE analysis, and strength predictions according to the American Iron and Steel Institute (AISI) and the Australian/New Zealand Standards (AS/NZS). Subsequently, the validated FE model was utilized to perform an extensive parametric study involving 130 simulations to examine the influence of hole geometry, edge stiffeners, and batten reinforcement plates on the axial capacity of built-up CFS columns. The results indicate that unstiffened slotted holes lead to an approximate 10.3% reduction in strength, whereas edge-stiffened square holes contribute to a 2.7% increase in axial capacity. Additionally, batten-reinforced unstiffened rectangular holes and edge-stiffened rectangular holes were found to enhance strength by approximately 7.5% and 15.5%, respectively. Moreover, incorporating batten plate reinforcements in plain columns improved axial capacity by approximately 6%. These findings provide valuable insights into the structural behavior of perforated CFS built-up columns and highlight the effectiveness of hole stiffeners and batten reinforcements in mitigating strength reductions caused by perforations.
Open Access: Yes
Ant Colony Optimization-Driven Ensemble Learning for Carbon Emission Modelling in Fly Ash–Slag Geopolymer Concrete
Publication Name: Materials
Publication Date: 2026-05-01
Volume: 19
Issue: 10
Page Range: Unknown
Description:
This study investigates the prediction of carbon emissions from fly ash and ground granulated blast furnace slag-based geopolymer concrete (GPC) using advanced ensemble machine learning (ML) techniques. Although ML has been extensively utilized to model GPC’s mechanical performance, its application in estimating environmental impacts, specifically carbon emissions, is limited. The research employs six ensemble ML models, such as random forest, gradient boosting, extreme gradient boosting (XGB), CatBoost, and light gradient boosting machine (LGBM), including versions optimized using ant colony optimization (ACO). Among them, the ACO-enhanced XGB model demonstrated the highest predictive accuracy with a coefficient of determination (R2) of 0.97, with low prediction errors (MAE = 3.92, RMSE = 6.17). However, cross-validation and uncertainty analyses indicate that the performance differences among top models are relatively small. Conversely, LGBM exhibited the least predictive reliability. Feature importance analysis revealed that curing parameters, specifically initial curing time, curing temperature, and the dosage of dry sodium hydroxide, had the most influence on carbon emissions. To evaluate model robustness and interpretability, Monte Carlo simulation and Gaussian white noise analyses were conducted. Results confirmed that CatBoost and ACO–gradient boosting (ACO-GB) demonstrated greater stability under varying and noisy conditions, whereas XGB-based models, although highly accurate, were comparatively more sensitive to input variability. Overall, the research establishes a data-driven, efficient framework for quantifying carbon emissions in GPC, highlighting the importance of evaluating both predictive accuracy and model robustness, advancing sustainable material design through intelligent modelling.
Open Access: Yes
DOI: 10.3390/ma19102168
The Development and Optimization of Machine Learning Models for Predicting the Shear Capacity of Corroded Reinforced Concrete Beams
Publication Name: Buildings
Publication Date: 2026-05-01
Volume: 16
Issue: 10
Page Range: Unknown
Description:
The deterioration of steel reinforcement through corrosion triggers cracking and loss of concrete cover, ultimately weakening the structure’s strength and ductility. In practical design and assessment, it is vital to precisely quantify the shear capacity of corroded reinforced concrete beams (CRCBs). In this paper, machine learning (ML) models are developed to predict the shear capacity of CRCBs, including kernel ridge regression (KRR), K-nearest neighbors (KNN), decision trees (DT), random forest (RF), gradient-boosted regression trees (GBRT), and extreme gradient boosting (XGBoost). A total of 408 data entries on the shear strength of CRCBs under different corrosion conditions were collected to establish an extensive database. The reliability of the proposed ML models is examined by contrasting their outputs with the experimental data. The XGBoost model demonstrated superior predictive capability, achieving an R2 value of 0.994 and outperforming all other tested models, including RF, GBRT, and DT. The Shapley Additive Explanations (SHAP) algorithm is adopted to reveal the contribution of each input feature to the predicted shear capacity of CRCBs. The interpretive SHAP results show that the ultimate shear capacity of CRCBs is most influenced by beam depth (h), with the shear span-to-depth ratio (λ) and concrete compressive strength ((Formula presented.)) being the subsequent key contributors. A comparative assessment between the XGBoost model and traditional analytical models was carried out to estimate the shear strength of CRCBs. Results demonstrate that the XGBoost model delivers enhanced predictive accuracy and improved performance. A parametric investigation examined its robustness under variations in geometry and material properties, while a user-friendly interface was created to support its practical use.
Open Access: Yes
Experimental and Artificial Intelligence-Based Framework for Performance Prediction of Rubberized Concrete Incorporating Waste Tyre Rubber
Publication Name: Sustainability Switzerland
Publication Date: 2026-07-01
Volume: 18
Issue: 13
Page Range: Unknown
Description:
The accumulation of waste tyres presents a significant environmental challenge owing to their non-biodegradable nature and limited recycling options. The incorporation of tyre-derived rubber into concrete offers a promising strategy to reduce landfill waste and lower the consumption of natural aggregates. This study presents an integrated experimental and machine learning-based framework for evaluating and predicting the performance of rubberized concrete. M25-grade concrete mixtures were prepared with partial replacement of coarse aggregates by waste tyre rubber at proportions of 0%, 10%, 20%, and 30% by volume. Mechanical performance was assessed through compressive and split-tensile strength tests, whereas durability was evaluated using water absorption measurements. Microstructural characterization was conducted using scanning electron microscopy and X-ray diffraction analysis. In parallel, predictive models based on artificial neural networks, adaptive neuro-fuzzy inference systems, and fuzzy logic were developed and validated using statistical measures. The results showed that increasing rubber content reduced mechanical strength and increased water absorption due to weaker interfacial bonding and higher porosity. Nevertheless, concrete containing a 10% rubber replacement retained approximately 90% of the control strength while maintaining satisfactory durability. The machine learning models demonstrated strong predictive accuracy for estimating concrete properties. Overall, the findings suggest that limited incorporation of waste tyre rubber can contribute to the development of sustainable and low-carbon concrete materials with reduced embodied energy and environmental impact.
Open Access: Yes
DOI: 10.3390/su18136634
Sustainable Development of Paver Blocks Using Fly Ash and Plastic Waste: Strength, Durability, and Cost Analysis
Publication Name: Sustainability Switzerland
Publication Date: 2026-07-01
Volume: 18
Issue: 13
Page Range: Unknown
Description:
This study investigates the combined use of fly ash (FA) and plastic waste (PW) as partial replacements for cement and coarse aggregates in the production of paver blocks. Experimental mixes were developed with a substitution level of FA (10% to 30%) and PW (3% to 15%). The performance of the modified concrete block was evaluated in terms of compressive strength (CS), flexural strength (FS), ultrasonic pulse velocity (UPV), water absorption (WA), Cantabro abrasion resistance (CAR), and rapid chloride permeability test (RCPT). Experimental results revealed that the optimal mixture, containing 25% FA and 12% PW (M4), exhibited superior performance. Compared with the control mix, the 56-day compressive and flexural strengths increased by 14.1% and 15.3%, respectively. The UPV value increased to 5.1 km/s, indicating improved concrete quality and matrix densification. Durability performance was significantly enhanced, with water absorption reduced by 25.4%, Cantabro abrasion mass loss decreased by 23.7%, and chloride ion penetrability reduced by 50.0% at 56 days. Statistical analysis using two-way ANOVA confirmed that FA and PW contents significantly influenced paver block performance (p < 0.05). The economic assessment further demonstrated cost savings of up to 3.0% compared with conventional concrete paver blocks. The study demonstrates that FA and PW can be effectively valorized in paver block production, offering both economic and environmental benefits. This green approach supports sustainable construction practices and promotes efficient waste management.
Open Access: Yes
DOI: 10.3390/su18136632
Mechanical, Durability and Microstructural Performance of OPC–GGBFS–FGD Gypsum Ternary Concrete: Identification of an Operational Sulfate Activation Threshold
Publication Name: Materials
Publication Date: 2026-07-01
Volume: 19
Issue: 14
Page Range: Unknown
Description:
Ordinary Portland cement (OPC) production contributes approximately 7–8% of global anthropogenic CO2 emissions, driving urgent demand for clinker-efficient binders utilizing industrial by-products. Flue gas desulfurization (FGD) gypsum and ground granulated blast-furnace slag (GGBFS) represent underutilized industrial by-products with documented potential as supplementary cementitious materials. This study investigates the mechanical, durability and microstructural performance of OPC–GGBFS–FGD gypsum ternary concrete mixtures incorporating untreated flue gas desulfurization (FGD) gypsum at 0–20% of total binder mass and ground granulated blast-furnace slag (GGBFS) at 25–50% of total binder mass in M30 structural concrete (w/b = 0.45). Compressive, split tensile and flexural strengths were evaluated at 7–90 days alongside rapid chloride penetration (RCPT), water absorption, strength efficiency index (SEI) and SEM–EDX analyses. Binary GGBFS replacement progressively enhanced long-term compressive strength, with T35F0 attaining 55.6 N/mm2 at 90 days (+33.7% relative to the OPC control). Moderate FGD gypsum contents (5–10%) further enhanced overall performance. Among all mixtures, T50F10 exhibited the best overall performance on the mechanical and durability indicators evaluated, achieving 54.2 N/mm2 compressive strength at 90 days together with a rapid chloride permeability value of 410 C, corresponding to ‘Very Low’ chloride ion penetrability. Beyond 10% FGD gypsum, progressive multi-parameter deterioration was observed, and mixtures containing 20% FGD gypsum failed to meet the M30 design requirement at 28 days. SEM–EDX confirmed that optimum sulfate activation produced a dense C–(A)–S–H-rich matrix, while excess sulfate caused matrix disruption. The findings establish 10% FGD gypsum by total binder mass as the optimum sulfate activation threshold for the investigated GGBFS and FGD gypsum sources at w/b = 0.45, and demonstrate the potential of untreated industrial FGD gypsum to produce durable, low-clinker structural concrete.
Open Access: Yes
DOI: 10.3390/ma19142962
Utilisation of Oil-Contaminated Sand in 3D-Printed Concrete: Rheological, Mechanical, and Microstructural Assessment
Publication Name: Buildings
Publication Date: 2026-07-01
Volume: 16
Issue: 14
Page Range: Unknown
Description:
The growing demand for construction materials has intensified concerns regarding natural sand depletion and the accumulation of industrial waste. Among these wastes, oil-contaminated sand (OCS) generated from petroleum-related activities presents environmental challenges while also offering potential for beneficial reuse. Previous studies have reported that low OCS contents can enhance workability and improve mechanical properties, highlighting its potential as a sustainable construction material. This study investigates the feasibility of incorporating OCS as a partial replacement for natural sand in 3D concrete printing (3DCP). Three mixes containing 0%, 0.5%, and 1% OCS were evaluated in terms of flowability, setting behaviour, printability, rheological response, hydration behaviour, mechanical performance, anisotropic response, and microstructural characteristics. The results showed that OCS incorporation had only a limited influence on flowability, while both the initial and final setting times exhibited noticeable delays. The maximum printable layers reached from 19 for the control mixture to 22 and 26 layers for the 0.5% and 1% OCS mixes, respectively, accompanied by reduced settlement and structural deformation. Rheological analysis revealed higher static yield stress and structuration rates for the OCS-modified mixes, contributing to enhanced buildability and geometric stability. Hydration calorimetry showed comparable heat-flow behaviour between the control and OCS-modified mixes, suggesting only a limited influence of OCS on cement hydration kinetics. The incorporation of OCS improved the compressive strength of the printed mixes and reduced compressive anisotropy, while SEM observations revealed a denser and more homogeneous microstructure, particularly for the 0.5% OCS mix. Thus, the findings indicate that low-level incorporation of oil-contaminated sand is a viable strategy for improving the printability and performance of 3D-printed concrete, promoting the sustainable reuse of contaminated industrial waste.
Open Access: Yes
