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This research paper aims to investigate reinforced concrete (RC) walls' behaviour under fire and identify the thermal and mechanical factors that affect their performance.

A three-dimensional (3D) finite element (FE) model is developed to predict the response of RC walls under fire and is validated through experimental tests on RC wall specimens subjected to fire conditions. The numerical model incorporates temperature-dependent properties of the constituent materials. Moreover, the validated model was used in a parametric study to inspect the effect of the fire scenario, reinforcement concrete cover, reinforcement ratio and configuration, and wall thickness on the thermal and structural behaviour of the walls subjected to fire.

The developed 3D FE model successfully predicted the response of experimentally tested RC walls under fire conditions. Results showed that the fire resistance of the walls was highly compromised under hydrocarbon fire. In addition, the minimum wall thickness specified by EC2 may not be sufficient to achieve the desired fire resistance under considered fire scenarios.

There is limited research on the performance of RC walls exposed to fire scenarios. The study contributed to the current state-of-the-art research on the behaviour of RC walls of different concrete types exposed to fire loading, and it also identified the factors affecting the fire resistance of RC walls. This guides the consideration and optimisation of design parameters to improve RC walls performance in the event of a fire.

Existing deterministic models that predict the capacity of corroded reinforced concrete (RC) beams have limited applicability because they were based on accelerated tests that induce general corrosion. This research gap was addressed by performing a combined numerical and statistical analysis on RC beams, subjected to natural corrosion, to achieve a much better forecast.

Data of 42 naturally corroded beams were collected from the literature and analyzed numerically. Four constitutive models and their combinations were considered: the elastic-semi-plastic and elastic-perfectly-plastic models for steel, and two tensile models for concrete with and without the post-cracking stresses. Meanwhile, Popovics’ model was used to describe the behavior of concrete under compression. Corrosion coefficients were developed as functions of corrosion degree and beam parameters through linear regression analysis to fit the theoretical moment capacities with test data. The performance of the coefficients derived from different combinations of constitutive laws was then compared and validated.

The results showed that the highest accuracy (R² = 0.90) was achieved when the tensile response of concrete was modeled without the residual stresses after cracking and the steel was analyzed as an elastic-perfectly-plastic material. The proposed procedure and regression model also showed reasonable agreement with experimental data, even performing better than the current models derived from accelerated tests and traditional procedures.

This study presents a simple but reliable approach for quantifying the capacity of RC beams under more realistic conditions than previously reported. This method is simple and requires only a few variables to be employed. Civil engineers can use it to obtain a quick and rough estimate of the structural condition of corroding RC beams.

Using coconut shell aggregates (CSA) in concrete benefits agricultural waste management and reduces the demand for mineral resources. Several studies have found that concrete containing CSA can achieve strengths that are comparable to regular concrete. The purpose of the present work is to evaluate the concrete’s durability-related properties to supplement these earlier findings.

Cylindrical specimens were prepared with a constant water–cement ratio of 0.50 and CSA content ranging from 0% to 50% (at 10% increment) by volume of the total coarse aggregates. The specimens were cured for 28 days and then tested for density, surface hardness, electrical resistivity and water sorptivity. The surface hardness was measured to describe the concrete resistance to surface wearing, while the resistivity and sorptivity were evaluated to describe the material’s resistance to fluid penetration.

The results showed that the surface hardness of concrete remained on average at 325 Leeb and did not change significantly with CSA addition. The distribution of surface hardness was also similar across all CSA groups, with the interquartile range averaging 59 Leeb. These results suggest that the cement paste and gravel stiffness had a more pronounced influence on the surface hardness than CSA. On the other hand, concrete became lighter by about 9%, had lower resistivity by 80% and had significantly higher initial sorptivity by up to 110%, when 50% of its natural gravel was replaced with CSA. Future work may be done to improve the durability of CSA when used as coarse aggregate.

The present study is the first to show the lack of correlation between CSA content and surface hardness. It would mean that the surface hardness test may not completely capture the porous nature of CSA-added concrete. The paper concludes that without additional treatment prior to mixing, CSA may be limited only to applications where concrete is not in constant contact with water or deleterious substances.

This review paper seeks to enhance knowledge of how pre-loading affects reinforced concrete (RC) beams under fire. It investigates key factors like deflection and load capacity to understand pre-loading's role in replicating RC beams' actual responses to fire, aiming to improve fire testing protocols and structural fire engineering design.

This review systematically aggregates data from existing literature on the fire response of RC beams, comparing scenarios with (WP) and without pre-loading (WOP). Through statistical tools like the two-tailed t-test and Mann–Whitney U-test, it assesses deflection extremes. The study further examines structural responses, including flexural and shear behavior, ultimate load capacity, post-yield behavior, stiffness degradation and failure modes. The approach concludes with a statistical forecast of ideal pre-load levels to elevate experimental precision and enhance fire safety standards.

The review concludes that pre-loading profoundly affects the fire response of RC beams, suggesting a 35%–65% structural capacity range for realistic simulations. The review also recommended the initial crack load as an alternative metric for determining the pre-loading impact. Crucially, it highlights that pre-loading not only influences the fire response but also significantly alters the overall structural behavior of the RC beams.

The review advances structural fire engineering with an in-depth analysis of pre-loading's impact on RC beams during fire exposure, establishing a validated pre-load range through thorough statistical analysis and examination of previous research. It refines experimental methodologies and structural design accuracy, ultimately bolstering fire safety protocols.

The design check regarding the fire resistance of concrete slabs can be easily performed using tabulated values. These tables are based on experimental results, but the level of safety, which is obtained by this approach, is not known. On the other hand, performance-based methods are more accepted, but require a target reliability as performance criterion. Hence, there is a need for calibration of the performance-based methods using the results of the “traditional” descriptive approach.

The calibration is performed for a single span concrete slab, where the axis distance of the reinforcement is chosen according to Eurocode 2 for a defined fire rating. A “standard” compartment is selected to cover typical fields of application. The opening factor is considered as parameter to obtain the maximum peak temperatures in the compartment. A Monte Carlo simulation, in combination with a response surface method, is set up to calculate the probabilities of failure.

The results indicate that the calculated reliability index for a standard is within the range, which has been used for the derivation of safety and combination factors in the Eurocodes. It can be observed that members designed for a fire rating R90 have a significant increase in the structural safety for natural fires compared to a design for a fire rating R30.

The level of safety, which is obtained by a design based on tabulated values, is quantified for concrete slabs. The results are a necessary input for the calibration of performance-based methods and could stimulate discussions among scientists and building authorities.

This study aims to determine the effect of replacing a portion of the cement in the concrete mixture with silica fume (SF) on the corrosion resistance of reinforcing bars, the compressive strength of concrete and the tensile strength of hook bars in both corroded and non-corroded external joints of structures. The external beam-column connection was studied because of its critical role in maintaining structural continuity in all three directions and providing resistance to rotation.

In external concrete joints, the bars at the end of the beams are often bent at 90° to form hooks that embed in columns. Owing to the importance of embedding distance and the need to understand its susceptibility to corrosion damage from chloride attack, a series of experiments were conducted on 12 specimens that accurately simulate real-site conditions in terms of dimensions, reinforcement and hook bars. SF was replaced with 10% and 15% of the weight of cement in the concrete mixture. To simulate corrosion, the specimens were subjected to accelerated corrosion in the laboratory by applying a low continuous current of 0.35 mA for 58 days.

The results revealed the effect of SF in improving the compressive strength of concrete, the pullout resistance of the hook bars and the corrosion resistance. In addition, it showed an apparent effect of the corrosion of reinforcing bars in reducing the bonding strength of hook bars with concrete and the effect of SF in improving this strength.

It was noted that the improvement of the results, achieved by replacing 10% of the weight of cement with SF, was significantly close to the results obtained by replacing 15% of the SF. It is recommended that an SF ratio of 10% be adopted to achieve the greatest economic savings.

Even though it is widely used, reinforced concrete (RC) is susceptible to damage from various environmental factors. The hazard of a fire attack is particularly severe because it may cause the whole structure to collapse. Furthermore, repairing and strengthening existing structures with high-performance concrete (HPC) has become essential from both technical and financial points of view. In particular, studying the postfire behavior of HPC with normal strength concrete substrate requires experimental and numerical investigations. Accordingly, this study aims to numerically investigate the post-fire behavior of reinforced composite RC slabs.

Consequently, in this study, a numerical analysis was carried out to ascertain the flexural behavior of simply supported RC slabs strengthened with HPC and exposed to a particularly high temperature of 600°C for 2 h. This behavior was investigated and analyzed in the presence of a number of parameters, such as HPC types (fiber-reinforced, 0.5% steel, polypropylene fibers [PPF], hybrid fibers), strengthening side (tension or compression), strengthening layer thickness, slab thickness, boundary conditions, reinforcement ratio and yield strength of reinforcement.

The results showed that traction-separation and full-bond models can achieve accuracy compared with experimental results. Also, the fiber type significantly affects the postfire performance of RC slab strengthened with HPC, where the inclusion of hybrid fiber recorded the highest ultimate load. While adding PPF to HPC showed a rapid decrease in the load-deflection curve after reaching the ultimate load.

The proposed model accurately predicted the thermomechanical behavior of RC slabs strengthened with HPC after being exposed to the fire regarding load-deflection response, crack pattern and failure mode. Moreover, the considered independent parametric variables significantly affect the composite slabs’ behavior.

In recent years, there has been growing interest in the use of stainless steel (SS) in reinforced concrete (RC) structures due to its distinctive corrosion resistance and excellent mechanical properties. To ensure effective synergy between SS and concrete, it is necessary to develop a time-saving approach to accurately determine the ultimate bond strength τ_u between the two materials in RC structures.

Three robust machine learning (ML) models, including support vector regression (SVR), random forest (RF) and extreme gradient boosting (XGBoost), are employed to predict τ_u between ribbed SS and concrete. Model hyperparameters are fine-tuned using Bayesian optimization (BO) with 10-fold cross-validation. The interpretable techniques including partial dependence plots (PDPs) and Shapley additive explanation (SHAP) are also utilized to figure out the relationship between input features and output for the best model.

Among the three ML models, BO-XGBoost exhibits the strongest generalization and highest accuracy in estimating τ_u. According to SHAP value-based feature importance, compressive strength of concrete f_c emerges as the most prominent feature, followed by concrete cover thickness c, while the embedment length to diameter ratio l/d, and the diameter d for SS are deemed less important features. Properly increasing c and f_c can enhance τ_u between ribbed SS and concrete.

An online graphical user interface (GUI) has been developed based on BO-XGBoost to estimate τ_u. This tool can be utilized in structural design of RC structures with ribbed SS as reinforcement.

The primary objective of this study is to produce one-way slabs made of LWFC with low density and sufficient compressive strength suitable for structural purpose then investigate their flexural behavior under various types of reinforcement and thickness of the slab and the influence of addition of PP fibers reinforcement on the mechanical behavior of reinforced concrete slabs. The specimens were tested using four-point loading. The results concerning load capacity, deflection and failure mode and crack pattern for each specimen were obtained. Also, an analytical investigation of PP fiber and GFG contribution on the flexural behavior of foamed concrete slabs is studied to investigate the significant role of PP fiber on the stress distribution in reinforced foam concrete and predict the flexural moment capacity.

The materials used in this study are cement, fine aggregate (sand), water, PP fibers, foaming agent, chemical additives if required, steel reinforcing rebars and glass fiber grid. The combination of these constituent materials will be used to produce foamed concrete in this research Then this study will present the experimental program of one-way foamed concrete slabs including slabs reinforced with GFR grids and another with steel reinforcements. The slabs will be tested in the laboratory under static loading conditions to investigate their ultimate capacities. The flexural behavior is to the interest of the slabs reinforced with GFR grids reinforcements in comparison with that of one with steel reinforcing rebars. Three groups are considered. (1) Group I: two slabs of PP fiber foamed concrete with minimum required reinforcements. (2) Group II: two slabs of PP fiber foamed concrete with glass fiber grids. (3) Group III: two slabs of PP fiber foamed concrete with the minimum required reinforcements and glass fiber grids.

The experimental results proved the effectiveness and efficiency of this the new system in producing a low density of concrete below 1900 kg/m³ had a corresponding strength of about 17 MPa at least. Besides, the presence of PP fibers had a noticeable improvement on the flexural strength values for all the examined slabs. It was found that the specimens reinforced with steel reinforcement mesh carried higher flexural capacity compared to these reinforced with GFG only. The specimens reinforced with GFG exhibited the lowest flexural capacity due to GFG separation from the concrete substrate. Also, an analytical investigation to predict the flexural strength of all tested specimens was carried out. The analytical results were agreed with the experimental results. Therefore, LWFC can be used as a substitute lightweight concrete material for the production of structural concrete applications in the construction industries today.

Foamed concrete is a wide field to discuss. To achieve the objectives of the project, the study is focused on the foamed concrete with the following limitations: (1) because the aim of this research is to produce foamed concrete suitable for structural purposes, it is decided to produce mixes within the density range 1300–1900 kg/m³. (2) Simply-supported slabs are of considered. (3) This study also looks out by using GFR and without it.

The main objectives of this study were producing structural foamed concrete slabs and investigate their flexural response for residential uses.

The durability of concrete containing recycled aggregates, sourced from concrete specimens that have been tested in laboratory testing facilities, remains understudied. This paper aims to present the results of experiments investigating the effect of incorporating such type of concrete waste on the strength and durability-related properties of concrete.

A total of 77 concrete cylinders sized Ø100 × 200 mm with varying amount of recycled concrete aggregate (RCA) (0%–100% by volume, at 25% increments) and maximum aggregate size (12.5, 19.0 and 25.0 mm) were fabricated and tested for slump, compressive strength, sorptivity and electrical resistivity. Disk-shaped specimens, 50-mm thick, were cut from the original cylinders for sorptivity and resistivity tests. Analysis of variance and post hoc test were conducted to detect statistical variability among the data.

Compared to regular concrete, a reduction of slump (by 18.6%), strength (15.1%), secondary sorptivity (31.5%) and resistivity (17.0%) were observed from concrete containing 100% RCA. Statistical analyses indicate that these differences are significant. In general, an aggregate size of 19 mm was found to produce the optimum value of slump, compressive strength and sorptivity in regular and RCA-added concrete.

The results of this study suggest that comparable properties of normal concrete were still achieved by replacing 25% of coarse aggregate volume with 19-mm RCA, which was processed from laboratory-tested concrete samples. Therefore, such material can be considered as a potential and sustainable alternative to crushed gravel for use in light or nonstructural concrete construction.