Introduction/Objective Saltwater intrusion can significantly alter the geotechnical properties of coastal soils, with implications for infrastructure stability and environmental management. This study investigated the effects of salinity on the shear strength parameters of coastal soils in Ikot Abasi Local Government Area, Nigeria. Methods Laboratory tests, including triaxial, direct shear, Atterberg limits, and compaction tests, were conducted on soil samples subjected to different salinity levels. Samples were collected from four locations within the coastal zone and designated as Points A, B, C, and D for identification. Results Grain-size analysis classified soils from Points A, B, and C as clayey sand (SC), while Point D was classified as well-graded sand with silt (SW-SM) according to the Unified Soil Classification System (USCS). Accordingly, Points A–C exhibited cohesive behavior, whereas Point D was predominantly non-cohesive. Saltwater intrusion was simulated using NaCl solutions prepared with distilled water. Increasing salinity reduced the liquid limit of Points A–C by 23.2–32.0% and the plastic limit by 7.02–14.6%. Similarly, OMC decreased while MDD increased with increasing salt concentration. Cohesion increased progressively with salinity, from 34% to 48% at Point A, 42% to 58% at Point B, and 17.3% to 26.0% at Point C, whereas the corresponding variations in the angle of internal friction (ϕ) were nonlinear. At Point D, ϕ decreased progressively from 31.34° to 24.86° with increasing salinity. Discussion Increasing salinity reduced the liquid limit and the plasticity index of soils from Points A, B, and C, whereas Point D remained non-plastic. The reduction in PI indicates a narrower plasticity range and reduced susceptibility to shrink–swell behavior. The observed decrease in OMC and increase in MDD with increased salinity may be associated with salinity-induced changes in clay-particle interaction and soil fabric. Triaxial tests further showed that cohesion increased with salinity for the cohesive soils at Points A, B, and C, although the corresponding variations in friction angle (ϕ) were nonlinear. In contrast, Point D exhibited a progressive decline in ϕ, with a reduction of approximately 6.48° between distilled water and 15% saline water. The failure-envelope intercepts (−0.10 to +0.04 kPa) were close to zero, indicating negligible cohesion and confirming that shear strength at Point D was governed mainly by friction. Conclusion The results of this study demonstrate that increasing salinity was associated with the changes observed in the shear strength parameters and mechanical behavior of coastal soils. These findings highlight the need to account for salinity-induced changes in geotechnical design and assessment of coastal infrastructure.
Introduction/Objective The study presents an augmented form of Abrams’ law that describes the relationship between the strength and water-binder ratio of concrete. This augmentation permits the prediction of the compressive strength of concrete containing fly ash regardless of the mass substitutions of cement by fly ash and the testing age within the ranges of 14-120 days. Methods In the modified Abrams’ law, the (apparent) water-binder ratio is replaced by the effective one in which the reactivity of fly ash is considered, and the substitution ratio of fly ash is included. The empirical parameters in the augmented formula have been determined with multi-linear regression analysis based on experimental data. Results The goodness of the curve fitting to this renewed strength formula is excellent. The compressive strength predicted from the augmentation coincides with its measured counterpart in the literature. Discussion Abrams’ law is augmented by introducing effective water-binder ratio and fly ash replacement rate, and verifies it through regression analysis of experimental and literature data. This topic has practical significance and contributes to the mixture design of sustainable concrete. Conclusion The Abrams’ formula is basically simple but has restricted limits of validity. The proposed augmentation improves the accuracy of the strength estimation of sustainable concrete mixtures batched with mineral admixtures such as fly ash.
Introduction This study investigates the effectiveness of rehabilitating fire-damaged reinforced concrete (RC) short columns by removing the deteriorated concrete cover, replacing it with normal concrete (NC), and strengthening the columns using carbon fiber reinforced polymer (CFRP) sheets. Methods An experimental program was conducted on nine small-scale RC column specimens subjected to eccentric axial loading with an eccentricity of 45 mm. The columns were exposed to fire temperatures of 500 °C and 700 °C for durations of 60 min and 120 min using a specially designed furnace, while sustaining a constant axial load equal to 50% Pu. An unexposed control specimen was tested for comparison. After fire exposure, the damaged concrete cover was removed and replaced with NC, followed by full wrapping using CFRP sheets. Results The results showed a significant reduction in ultimate load capacity with increasing fire temperature and exposure duration. Fire-exposed specimens exhibited noticeable strength degradation compared to the control specimen. After rehabilitation using NC replacement and CFRP wrapping, the columns demonstrated substantial recovery and enhancement in load-carrying capacity. Discussion The improvement in structural performance is attributed to the confinement effect provided by CFRP sheets combined with the restored concrete cover. The results also highlight the influence of fire severity on residual strength and confirm the effectiveness of the proposed rehabilitation technique under eccentric loading conditions. Conclusion Replacing the damaged concrete cover with NC and strengthening with CFRP sheets proved to be an effective rehabilitation technique for fire-damaged RC columns. The proposed method significantly restored and enhanced load-carrying capacity, supporting its practical application for post-fire strengthening under sustained eccentric loads.
Introduction/ObjectiveThis study investigates the combined influence of Recycled Coarse Aggregates (RCA) and Hooked Steel Fibers (HSF) on the fresh and mechanical properties of concrete, aiming to achieve a balance between sustainability and structural performance. MethodsConcrete mixes were prepared with RCA replacement levels of 0%, 25%, 50%, and 75%, while HSF was incorporated at volume fractions ranging from 0.0% to 1.0%. Fresh properties were assessed using slump tests, whereas compressive, flexural, and splitting tensile strengths were evaluated after 28 days to examine hardened behavior. ResultsRCA incorporation resulted in notable reductions in mechanical strength due to increased porosity and weaker interfacial bonding; however, the addition of HSF effectively compensated for these losses. An HSF dosage of 0.4–0.6% was sufficient to recover compressive and flexural strength losses at 25–50% RCA, whereas 1.0% HSF was required to restore or surpass tensile and flexural properties at 75% RCA replacement. Slump values decreased with increasing fiber content, indicating reduced workability, but remained within manageable limits with the use of admixtures. DiscussionThe findings highlight the potential of HSF to mitigate the strength reductions associated with RCA, thereby offering a balance between performance and sustainability suitable for practical applications. ConclusionWith optimized HSF dosages, the mechanical drawbacks associated with RCA can be effectively offset, enabling the production of structurally sound and eco-friendly concrete for diverse construction applications.
Introduction/ObjectiveReinforced Concrete (RC) frames with masonry infills represent a widely adopted structural typology in Algeria. The present study aims to predict the fundamental period of this type of structure using various machine learning algorithms. MethodsSeveral machine learning models, including Gaussian Process Regression (GPR) applied for the first time to this problem, are employed to assess their performance in predicting the fundamental period of masonry-infilled reinforced concrete frames, using statistical metrics such as the coefficient of determination R2 and the Root Mean Square Error (RMSE). An uncertainty propagation analysis is subsequently conducted using the GPR model to evaluate the sources of uncertainty associated with the prediction of the fundamental period of structures. ResultsThe results indicate that the GPR model achieves a coefficient of determination R2 = 0.9999 on the test data, outperforming all models previously proposed in the literature. The uncertainty analysis reveals that model-related uncertainty accounts for 7.8% of the total uncertainty, whilst input data uncertainty accounts for 92.2%. DiscussionThis study highlights the relevance of using GPR models to predict the fundamental period of reinforced concrete frames. It also addresses one of the key limitations of purely data-driven models and demonstrates the benefits of resorting to physics-informed machine learning models. ConclusionThis study demonstrates the superiority of the GPR model over other machine learning models, whilst also outperforming the models previously proposed in the literature. An analysis of the influence of the input variables reveals that their relationships are predominantly non-linear.
Introduction Local scour downstream of sluice gates poses significant risks to the safety and performance of hydraulic control structures. This study investigates the hydraulic behavior of a stepped stilling basin incorporating various combinations of negative and positive steps, with and without baffle blocks, to control scour under submerged hydraulic-jump conditions. Methods A total of 16 basin configurations were tested across 96 experimental runs to examine the effects of step arrangement, block shape, and block height on scour depth, scour geometry, and energy dissipation downstream of the sluice gate. Multiple linear regression analysis was applied to develop empirical equations for predicting scour characteristics under limited flow conditions. Results Positive steps were more effective than negative steps in reducing maximum scour depth. The configuration C 1 (two negative steps followed by four positive steps) achieved a 48% reduction in scour depth compared to the flat basin. Adding a single row of baffle blocks further improved performance. Maximum scour depth reductions at a Froude number of 1.91 and relative block height h/K = 1.5 were: square blocks 54%, cylindrical 47%, and rectangular 44%. Energy dissipation increased modestly (3–24%), while scour reduction was more pronounced (20–54%), highlighting the sensitivity of scour behavior to geometric modifications rather than total energy loss. Discussion These findings demonstrate that geometric modifications, especially positive steps and appropriately sized baffle blocks, effectively stabilize hydraulic jumps and weaken near-bed velocities. The study provides practical guidance for designing stilling basins to mitigate scour in sluice gate applications. Conclusion Properly designed negative–positive step combinations with square baffle blocks (h/K = 1.5) can significantly reduce scour depth while maintaining efficient energy dissipation. The empirical equations developed offer a predictive tool for engineering design under similar flow conditions.
IntroductionThe accelerating growth of urban and industrial activities has led to mounting volumes of nonbiodegradable waste, posing urgent environmental challenges for modern societies. Recycling these wastes in stone matrix asphalt (SMA) mixtures helps reduce environmental impact while improving pavement performance. This study investigates the use of shredded cigarette filters (SCF) as fiber stabilizers and recycled medicine blister packs (RMBP) as aggregate replacement in SMA mixtures to enhance performance and support waste management. Methods Laboratory testing included Superpave volumetric analysis, assessment of moisture susceptibility in terms of tensile strength ratio test (TSR), fatigue life evaluation, determination of rutting behavior in terms of Hamburg wheel-tracking test (HWTT), and service life modeling, to assess the effect of SCF and RMBP. ResultsThe recycled SMA mixture showed improvements compared to the control mix, including lower air voids, higher binder retention, enhanced moisture resistance (TSR of 86.7%), and improvements in stiffness and fatigue life (up to 20%). HWTT results revealed rut depth reductions of 19-31%, and service life modeling predicted an extension from 18.0 years for the control to 24.3 years for the recycled mixture under heavy traffic. DiscussionIncorporating SCF and RMBP into SMA mixtures demonstrated strong potential for enhancing pavement sustainability and aligned with ongoing advancements in waste-based asphalt technologies. The findings highlighted the broader value of recycled materials in improving mixture performance, although the work remains limited by the absence of certain durability tests and the reliance on controlled laboratory conditions. ConclusionThe findings suggested that incorporating SCF and RMBP into SMA mixtures can improve durability, moisture resistance, and service life, while supporting environmental sustainability through the recycling of postconsumer waste.
Introduction This research investigated the effects of incorporating Styrofoam grains (Expanded Polystyrene, EPS) into Boubyan clay (Kuwait) to develop a lightweight, sustainable geotechnical material. Materials and Methods The soil was classified as CL (lean clay) based on the Unified Soil Classification System (USCS). Samples were mixed with 0%, 10%, 15%, 20%, and 25% Styrofoam (2–5 mm grains) by volume. Standard Proctor compaction tests were used to determine maximum dry unit weights and optimum moisture contents. consolidation tests measured swelling pressures and displacements. Coefficients of volume compressibility (m_v) and consolidation (c_v) were calculated. Finally, consolidated-undrained triaxial tests assessed shear strength parameters (cohesion C′ and friction angle φ′). Results The addition of EPS reduced the maximum dry unit weight and increased the optimum water content. Swelling pressures and displacements decreased with higher EPS content; m_v and c_v both declined, indicating reduced compressibility and slower consolidation. Void ratios decreased, while final settlements and strains increased with Styrofoam. Triaxial tests showed a decrease in cohesion (C′) and an increase in friction angle (φ′) as the Styrofoam content increased, resulting in lower maximum shear and normal stresses. Discussion Introducing EPS into Boubyan clay improved its strength-to-weight ratio by reducing compressibility and slowing consolidation, though at the expense of increased settlements and reduced cohesion. These trade-offs suggest an optimal EPS content (around 10–15%) and point to future work, such as adding bonding agents (e.g., cement), to mitigate strength losses. Conclusion Integrating Styrofoam grains into Boubyan clay offers a viable method for producing a lightweight additive by reducing compressibility, aiding densification, and modifying strength parameters for specialized civil engineering applications.
Introduction This study investigated the effect of using eco-friendly materials such as silica fume, crumb rubber, and waste plastic fiber in ferrocement mortar. It is also compared with their performance against traditional mortals. The effect of using two types of reinforcement, welded wire mesh and glass fiber mesh, in ferrocement to retrofit beams with full or U-shape wrapping was also studied. Methods The experimental program consists of casting ten reinforced concrete beams with dimensions of 150×250×1800 mm. Two beams served as reference beams. The other eight beams were preloaded to 70% of the failure load, then retrofitted using ferrocement with two layers of mesh and a thickness of 25 mm. Results The results showed that the highest increase in ultimate load was 13.6% for the beam retrofitted using traditional mortar and reinforced with welded wire mesh in full wrapping. For eco-friendly mortar, the highest increase was 7.7% for the beam retrofitted with welded wire mesh and 6.2% with glass fiber mesh, both in U-shaped wrapping. Beams retrofitted using eco-friendly mortar exhibited higher ductility than those with traditional mortar, by 3.6% with welded wire mesh and 5.4% with glass fiber mesh in full wrapping. However, their stiffness was lower compared to traditional mortar. Discusion The increase in ultimate load for welded wire mesh is due to higher tensile strength compared to glass fiber mesh. Eco-friendly mortar causes an increase in ductility and reduces stiffness due to weak bonding between materials, resulting in more deformation. Conclusion Ferrocement is an effective method for retrofitting RC beams due to its availability, low cost, and effectiveness in improving beam behavior.
Introduction The use of geotextiles is now well established in the field of civil engineering, particularly in geotechnics, where they serve a range of functions including drainage, filtration, separation, reinforcement, protection, and erosion control. For over three decades, these materials have played a key role in the design and long-term performance of infrastructure. The development of geotextiles made from natural plant fibers, especially those derived from kenaf, represents a promising advancement that offers both economic and environmental benefits. This study aims to evaluate the mechanical and hydraulic properties of woven geotextiles made from kenaf fibers sourced from Nérékourosso, as well as their effectiveness in reinforcing road foundation layers. Methods Two types of geotextiles were produced by weaving, with mesh openings of 0 mm and 5 mm, respectively. Mechanical characterization tests were carried out, along with static puncture resistance and normal-to-plane permeability tests. CBR load-bearing tests were performed to evaluate reinforcement efficiency depending on the geotextile’s position in the foundation layer. Mechanical tests showed higher tensile strength in the cross direction for the geotextile with no mesh opening (17.19 kN/m) compared to the 5 mm mesh type (2.90 kN/m). Results The closed-mesh geotextile withstood a maximum puncture load of 1170 N, versus 540 N for the open-mesh variant. The 0 mm mesh geotextile exhibited a surface flow rate of 2200 L/min/m 2 . CBR tests indicated better performance for the 5 mm mesh geotextile, especially when placed at mid-height within the reinforced layer. Discussion These results suggest that while the closed-mesh geotextile offers superior intrinsic mechanical properties due to its dense structure, the open-mesh variant performs better in soil reinforcement applications, likely because its structure allows better interaction with surrounding materials and more effective stress distribution. Conclusion Kenaf-based woven geotextiles show promising potential for road foundation reinforcement, with mesh configuration significantly influencing performance.
Introduction This study aimed to apply flood management at Kinunang River, focusing on evaluating and designing the most suitable river channel geometry that will effectively mitigate destruction due to moderate to extreme flood events. Kinunang is a river located within the Likupang Special Economic Zone for ecotourism. Consequently, the river area’s precondition is flood-free, and any developments herein should adhere to eco-friendly and aesthetic principles. Methods Hydrological analysis of local rainfall data was carried out using HEC-HMS to predict the amount of flood discharge. Hydraulic analysis using HEC-RAS was applied to predict channel storage capacity, to simulate flow profile, and to assess the flow speed with the intention of minimizing scouring. Eco-hydraulic property of the designed channel cross-section was examined by simulating the effect of placing 3 different plants along the channel. Results Re-dimensioning of the river cross-section resulted in a multi-stage trapezoid channel with an upper width (La), lower width (Lb), and depth (h) of 2 m, respectively. The use of vetiver grass was able to reduce the flow velocity by 29%. Discussion The multi-stage trapezoidal cross-section was selected because it can drain the design flood discharge and facilitate the use of plants to meet the eco-hydraulic property. Vetiver grass was chosen due to its maximum amount of velocity reduction. Conclusion The Kinunang River does indeed require channel re-dimensioning. A multi-stage trapezoid channel and the planting of vetiver grass will diminish the impact of the design flood, prevent river bank erosion, and display an attractive green river bank.
Efficiently updating construction schedules is vital for managing dynamic workflows. Traditional methods like Gantt charts rely on manual updates, but newer approaches, such as Chronographic Modelling and Dynamic Modelling of Occupancy Rate Scheduling (DMORS), require tracking spatial positioning and occupancy rates of teams and resources. Given the complexity of these tasks, emerging technologies are being adopted to enhance data collection. This study reviews recent advancements in tracking construction site occupancy and spatial positioning. It categorizes these technologies into three main types: image and video capture, 3D point cloud generation, and sensor-based tracking systems. Each method is evaluated based on seven essential criteria: data collection speed, portability, accuracy, worksite impact, post-processing time, accessibility, and technology maturity. The research provides a selection framework for contractors, helping them choose the most suitable tools based on project size and complexity. High-precision tools like LiDAR and laser scanning are ideal for large contractors requiring detailed modelling, while smaller firms may prefer cost-effective solutions such as manual data collection with photos or videos. This research highlights that no single technology meets all needs for tracking construction site occupancy. High-precision tools offer accuracy but may disrupt work, while simpler methods are easier to use but less detailed. So, depending on the size of the contractor or the project, the best technology may vary. Ultimately, this paper supports the integration of space planning schedules in construction management by offering a structured approach to implementing modern data capture technologies. The study also highlights future trends, advocating for multi-technology integration to improve accuracy and exploring the potential of artificial intelligence for automated data analysis.
The existing Minangkabau traditional wooden buildings that are more than 100 years old are commonly found in Tanah Datar Regency, West Sumatra Province, Indonesia. However, it is necessary to assess the residual strength of the wood to evaluate the main structural members, such as beams and main columns, which may have experienced a decrease in strength. The aim of this research is to carry out non-destructive testing to obtain the dynamic elastic moduli of the existing buildings. Non-destructive testing was conducted using ultrasound technology specifically designed for wood. The members studied were the main columns and beams of the existing buildings. This study focused on the two existing Minangkabau wooden buildings located in Tanah Datar Regency. The test results for the first building yielded a dynamic elastic modulus (MoEd) of 14,600.8 MPa, with a standard deviation of 1,803.1 MPa and a coefficient of variation of 12.35% (0.1235). In comparison, the second building showed a dynamic elastic modulus of 11,108.52 MPa, with a standard deviation of 1,720.14 MPa and a coefficient of variation of 15.48% (0.1548). Additionally, the elastic modulus for the first building was 10,282.25 MPa, while the second building had an elastic modulus of 7,822.90 MPa. The results from this study indicated that the elastic modulus of the first existing building showed a trend of no significant decrease in strength. These results matched with visual observation that the tested columns and beams did not experience damage. In contrast, the test results for the second building indicated that the tested main beams experienced a decrease in strength due to damage, which ranged from 28.23% to 35.18%. The non-destructive testing of existing timber buildings offers benefits, including providing recommendations for repairs and assessing structural members that need to be replaced due to strength degradation using the same quality or the same species of timber. This study suggests a non-destructive testing method for evaluating existing timber buildings.
Construction projects in mountainous regions are increasingly confronted with challenges posed by rockfall hazards, which have become more severe due to environmental changes, including deforestation and landslides.These risks threaten infrastructure integrity and human safety, necessitating the integration of impact-resistant features into structural designs. In this context, enhancing the structural response of post-tensioned slabs under impact loads is a critical area of study. This research investigates the effectiveness of incorporating Forta-Ferro fibers into concrete mixes to improve the impact resistance of post-tensioned slabs. The aim is to evaluate whether fiber-reinforced concrete offers better structural performance under dynamic loading conditions, thereby contributing to safer and more resilient construction in hazard-prone areas. Two geometrically identical slabs (1.5 m × 3.3 m × 0.18 m) were prepared. The first slab was cast using conventional concrete, while the second was cast using the same mix with an addition of 0.4% by volume Forta-Ferro fibers. Both slabs were subjected to a central impact using a 600 kg steel ball dropped freely from a height of 8 meters. Additionally, three-dimensional finite element models were developed to simulate the slabs’ behavior under the same loading conditions. Experimental results demonstrated that the slab incorporating Forta-Ferro fibers exhibited enhanced performance, including reduced displacement, improved crack distribution, and less overall damage. Comparison with finite element simulations confirmed the accuracy of the numerical model in capturing the real behavior of the slabs. The inclusion of Forta-Ferro fibers significantly improves the impact resistance of post-tensioned slabs. The proposed fiber-reinforced design provides a viable solution for enhancing structural response under dynamic loading, with experimental and numerical results in strong agreement.
Despite developments in the construction industry and construction projects, performance optimisation remains a critical need. Accurately estimating and measuring performance is essential for effective planning and cost forecasting. This study addresses the significant housing shortage in Iraq by assessing the performance and productivity of construction teams on residential housing projects. Two machine learning techniques were applied—multiple linear regression (MLR) and support vector regression (SVR). Sixty datasets from different housing projects in Baghdad and central Iraq were analysed. Seven datasets were allocated for validation. Models were evaluated using measures including mean square error (MSE), root mean square error (RMSE), mean absolute error (MAE), correlation coefficient (R), and coefficient of determination (R2). Multiple linear regression outperformed support vector regression, showing lower prediction errors and stronger correlations with actual values. These results provide valuable insights into construction productivity, expressed in labour hours per square metre of built area. They enable experts to accurately estimate task duration, supporting accurate cost estimation and effective project planning. This contributes significantly to meeting the demand for housing units due to population growth.
Concrete slabs are critical components in structural applications but are inherently limited by their brittleness and low tensile capacity, which can lead to failure under torsional loads. Traditional steel reinforcement provides some resistance but introduces issues, such as increased weight and susceptibility to corrosion. Carbon Fiber-reinforced Polymer (CFRP) materials present a promising alternative due to their high tensile strength, nonmagnetic properties, and resistance to corrosion. This research employed finite element analysis (FEA) through ABAQUS software to investigate the torsional performance of concrete slabs reinforced with CFRP. A total of 24 square slabs were modeled, comprising 21 CFRP-reinforced slabs and 3 steel-reinforced slabs. The analysis focused on the effects of varying CFRP bar sizes (8 mm, 10 mm, and 12 mm) and compressive strength of concrete (21 MPa to 50 MPa) on the torsional behavior of the slabs. The results revealed that increasing CFRP bar size and concrete compressive strength significantly enhanced torsional cracking and ultimate moments. The largest increases in torsional cracking and ultimate moments were 4% and 21%, respectively, when the bar size was increased from 8 mm to 12 mm. Similarly, the highest increases in these moments were 53% and 42%, respectively, when the compressive strength increased from 21 MPa to 50 MPa. These insights are crucial for optimizing the design of CFRP-reinforced slabs in torsional applications.
Background Artificial Neural Networks (ANN) can be a useful tool to assist in the design of reinforced concrete structures. The aim of this paper is to develop artificial neural network models for predicting the required diameter of eccentrically compressed concrete-filled steel tubular (CFST) columns and the wall thickness of the steel pipe. Methods Within the framework of the set goal, three models of ANN were developed. The first model predicts the required cross-sectional diameter for the minimum pipe wall thickness. The second model solves the same problem for the maximum possible wall thickness. The input parameters of the first two models are the axial force, bending moment, strength characteristics of steel and concrete, column length, and a coefficient characterizing the share of constant and long-term loads in the total load. The third model predicts the required wall thickness based on the listed parameters, as well as the column diameter. Synthetic data, including more than 2 million samples, was generated to train the models. The ANN architecture is a feedforward neural network with 2 hidden layers containing 16 neurons each. Machine learning models are implemented in the MATLAB environment. Results The trained models showed high performance in terms of mean squared error and correlation coefficient between the target and predicted values of the output parameter. The importance of features was also assessed using the variable fixation method. It has been established that the required value of the column diameter is most significantly influenced by the magnitude of the bending moment, axial force and column length. The required pipe wall thickness is most influenced by the magnitude of internal forces and the diameter of the column. Conclusion The developed models of artificial neural networks are an effective and reliable tool that can help a civil engineer in the design of buildings and structures that include CFST elements.
This work evaluates the potential of locally obtained moderate-grade kaolinitic clay from Tabelbala, Algeria, for manufacturing metakaolin-based geopolymer mortar with improved mechanical and thermal properties in hot-arid conditions. Urban heat islands and environmental concerns related to cement production drive the search for sustainable alternatives. Geopolymer binders can substitute for Portland cement with lower carbon emissions and better thermal performance. The low reactivity of local materials like Tabelbala clay requires enhancement. This study aimed to optimize the geopolymerization process by enhancing the reactivity of Tabelbala clay by using silica fume and alkaline activators. Additionally, it evaluated the impact of curing conditions on its mechanical and thermal properties. Kaolinitic clay was calcined at 900 °C to produce metakaolin, and the activation was performed using sodium hydroxide, potassium hydroxide, and silica fume or sodium silicate solution. Using ambient and solar curing techniques, geopolymer mortars were analyzed for their compressive and flexural strengths, shrinkage, bulk density, porosity, and thermal conductivity. Solar curing significantly enhanced compressive strength (up to 37.4 MPa) and flexural strength (up to 12 MPa) at 28 days. Adding silica fume also reduced drying shrinkage and thermal conductivity with a marked improvement in density. Even though the Tabelbala clay is of moderate quality when combined with silica fume and cured optimally, it can produce geopolymer mortars with excellent mechanical and thermal properties, demonstrating their suitability as sustainable construction materials for arid climates.
The anchorage zone, where the prestressing force is transmitted to the concrete, represents a critical component of prestressed girders. This research investigates the behavior of eccentric anchorage zones in prestressed girders constructed with fiber-reinforced concrete (FRC) using finite element analysis (FEA). The study specifically examines the impact of steel fiber volume ratio, bar size of the spiral in the local zone and bar size of the reinforcement in the general zone on the behavior of the anchorage zone. A three-dimensional solid element model was created in ABAQUS software, employing non-linear analysis to replicate the structural behavior and strength characteristics of the eccentric anchorage zone when incorporating fiber-reinforced concrete. The analysis included different configurations of fiber volume ratios, the quantity of reinforcement in the local zone, and the quantity of reinforcement in the general zone. The results indicate that using steel fibers with a volume ratio of 1%-1.5% can replace either spiral or tie reinforcement but cannot substitute the entire reinforcement system. Using 2% steel fibers results in an ultimate load increase of 30%-50%. Specimens with fibers demonstrate more ductile failure modes. A spiral bar size of 20 mm increases ultimate load between 21% and 31%. Tie bar size of 10 mm increases ultimate load between 24% and 32%, with greater ductile behavior observed in specimens with tie reinforcement.
Background The continuous use of cement has been on the rise. This increase has a significant detrimental effect on the ecosystem. Many studies are being carried out in an effort to find materials that can replace cement in mortar, either fully or partially. These investigations should have solutions that will be able to produce a higher strength and durable mortar than conventional mortar. Aim This study aims to present a sustainable structural cement-based material with lower cement content that provides better mechanical and physical properties. Objective The goals of this study were to determine the cement-wood ash replacement percentage that resulted in the best compressive and flexural strength on cubes and rectangular beams, respectively, as well as to examine and evaluate the physicomechanical characteristics of the cement-wood ash mortar with and without scattered basalt fiber reinforcement. Methods A variety of mortar mixtures were created, each with a different amount (20%, 40%, 60%, 80%, and 100%) of wood ash replacing cement in part or entirely by volume. The effects of scattered chopped basalt fiber and wood ash/cement substitution were tested for strength after 7 and 28 days of cure. On the mortar, tests for density, slump, and water absorption rate were performed. Results The result of this research revealed that mortar reinforced with chopped basalt fiber had an improved compressive and flexural strength at defined mixes at 28 days of curing with a maximum compressive strength of 12.58 N/mm2. The experimental results suggest 20-40% replacement as the optimum range for cement-wood ash partial replacement. An average increase in density with an increase in sample age as well as the addition of basalt reinforcement was observed with a sample B1 containing 20 percent partial replacement of cement with ash and in the presence of basalt fiber reinforcement, exhibiting the highest density of 2272kg/m3 at 28 days of age contrasting with sample A5, containing 80 percent partial replacement of cement with wood ash. Moreover, sample A5 showed a density of 1824 kg/ m3, the lowest value at 28 days of age. Conclusion The study showed improvement in the flexural and compressive strength of the mortar when reinforced with micro basalt fiber. The partial replacement of cement with wood ash in mortar showed an impact on the water absorption rate and strength of the mortar. Hence, this cement-wood ash mortar reinforced with micro basalt fiber can be used in plastering walls or for flooring to improve the properties of the concrete structural members. Additionally, it can also be used in concrete repairs.
