Search Results (38)

Currently, the visual study of the structure of building materials and products is gradually supplemented by intelligent algorithms based on computer vision technologies. These algorithms are powerful tools for the visual diagnostic analysis of materials and are of great importance in analyzing the quality of production processes and predicting their mechanical properties. This paper considers the process of analyzing the visual structure of non-autoclaved aerated concrete products, namely their porosity, using the YOLOv11 convolutional neural network, with a subsequent prediction of one of the most important properties—thermal conductivity. The object of this study is a database of images of aerated concrete samples obtained under laboratory conditions and under the same photography conditions, supplemented by using the author’s augmentation algorithm (up to 100 photographs). The results of the porosity analysis, obtained in the form of a log-normal distribution of pore sizes, show that the developed computer vision model has a high accuracy of analyzing the porous structure of the material under study: Precision = 0.86 and Recall = 0.88 for detection; precision = 0.86 and recall = 0.91 for segmentation. The Hellinger and Kolmogorov–Smirnov statistical criteria, for determining the belonging of the real distribution and the one obtained using the intelligent algorithm to the same general population show high significance. Subsequent modeling of the material using the ANSYS 2024 R2 Material Designer module, taking into account the stochastic nature of the pore size, allowed us to predict the main characteristics—thermal conductivity and density. Comparison of the predicted results with real data showed an error less than 7%. Full article

Strengthening lapped spliced reinforced concrete (RC) beams using tiny-diameter steel wires as near-surface-mounted (NSM) rods has not been carried out previously. Thus, the purpose of this work is to examine the behavior of RC beams with insufficient lap splices that are strengthened by NSM steel wires with different schemes to improve durability, efficiency, and effectiveness. At the middle of the beam, a splice length equal to 25 times the diameter of the rebar was used to join two tension bars. Many different schemes were implemented in strengthening the splice region, such as attaching longitudinal wires to the sides and/or bottom of the beam in different quantities with/without end anchorage, placing perpendicular and inclined U-shaped wires at the splice region in different quantities, and implementing a network of intersecting and opposite wires in two different directions. The effect of variables on the behavior of strengthened beams was studied. The findings proved that when the longitudinal wire reinforcement-to-lapped rebars area ratio was 9.4%, 18.7%, and 28%, the ultimate load of the beams was improved by 15.71%, 71.43%, and 104.57%, respectively. When the transverse U-shaped wire reinforcement ratio was 0.036, 0.051, 0.064, 0.075, and 0.150, the ultimate load of the beams was improved by 3.7%, 20%, 31.4%, 50%, and 80%, respectively, and the ultimate deflection was enhanced by 2%, 32%, 19%, 67%, and 62.4% compared to the unstrengthened beam. Full article

This review examines the impact of recycled aggregates (RAs) on the fresh and mechanical properties of high-strength concrete (HSC). The results revealed that incorporating RAs can reduce the compressive strength of HSC by up to 25%, with strength values ranging from 40 to 70 MPa depending on the RA content. The addition of supplementary materials like silica fume, fly ash, and polycarboxylate ether significantly mitigated these negative effects, enhancing the compressive strength by approximately 15–20% compared with the control mixes without additives. Furthermore, the tensile strength was observed to decrease by up to 18% with increasing RA content, but fiber reinforcement improved this by 10%, demonstrating the potential of additives to offset mechanical weaknesses. The modulus of elasticity also declined by up to 30% with higher RA dosages, highlighting the critical impact of the adhered mortar quality on the overall stiffness of the concrete. According to the literature, it was noticed that, when the dosage of RCAs is increased, there is a drop in the strength activity index (SAI). When the substitute dosage exceeded 50%, the SAI decreased. These findings underscore the importance of using optimized additive combinations to improve the mechanical performance of RA concrete, making it a viable option for sustainable construction. Overall, the findings suggest that, although RAs may negatively affect certain physical traits of HSC, the use of appropriate additives can optimize its performance, making it a viable option for sustainable construction practices. Full article

An investigation was conducted to assess the efficacy of using waste rubber as a substitute for a portion of an aggregate to enhance concrete’s sustainability. For the purpose of accomplishing this objective, a total of 12 specimens were constructed and then subjected to a series of tests to investigate their bending behavior. The samples were constructed with the following dimensions: 1000 mm length and a 100 mm by 150 mm cross-sectional area. A few factors were selected, including the impacts of the longitudinal reinforcement ratio and the waste rubber ratio. Based on the volume of aggregates, rubber replacement rates of 0%, 5%, 10%, and 15% were investigated in this study. To assess the beam bending behavior, the stirrup width and spacing were kept constant at ∅6/10. The longitudinal reinforcement was composed of three diameters: ∅6 at the top (for all beams) and ∅8, ∅10, and ∅12 at the bottom. The experimental results demonstrated that the effects of varying amounts of waste rubber and tension reinforcement on the bending and cracking of reinforced concrete beams (RCBs) were varied. The findings indicate that the incorporation of waste rubber into concrete results in a reduction in both the load-carrying capacity and the level of deformation of the material. Additionally, it was shown that as the amount of waste rubber in the RCB increased, the energy absorption capacity and ultimate load decreased. There was a reduction in energy dissipation of 53.71%, 51.69%, and 40.55% for ∅8 when longitudinal reinforcement was applied at 5%, 10%, and 15% replacement, respectively. Additionally, there were reductions of 25.35%, 9.31%, and 58.15% for ∅10, and 38.69%, 57.79%, and 62.44% for ∅12, respectively. Full article

An actual scientific problem in current concrete science is poor knowledge of the problem of modifying concrete with plant waste. At the same time, plant waste benefits from other types of waste because it is a recycled raw material. A promising technological approach to modifying concrete with plant waste is the introduction of components based on the processing of coffee production waste into concrete. This study aims to investigate the use of biochar additives from spent coffee grounds (biochar spent coffee grounds—BSCG) in the technology of cement composites and to identify rational formulations. A biochar-modifying additive was produced from waste coffee grounds by heat treatment of these wastes and additional mechanical grinding after pyrolysis. The phase composition of the manufactured BSCG additive was determined, which is characterized by the presence of phases such as quartz, cristobalite, and amorphous carbon. The results showed that the use of BSCG increases the water demand for cement pastes and reduces the cone slump of concrete mixtures. Rational dosages of BSCG have been determined to improve the properties of cement pastes and concrete. As a result of the tests, it was determined that the ideal situation is for the BSCG ratio to be at a maximum of 8% in the concrete and not to exceed this rate. For cement pastes, the most effective BSCG content was 3% for concrete (3%–4%). The compressive and flexural strengths of the cement pastes were 6.06% and 6.32%, respectively. Concrete’s compressive strength increased by 5.85%, and water absorption decreased by 6.58%. The obtained results prove the feasibility of using BSCG in cement composite technology to reduce cement consumption and solve the environmental problem of recycling plant waste. Full article

The study conducted axial tensile strength tests on concrete samples that replaced conventional aggregates with recycled aggregates. In Series I, using FNG instead of FNA resulted in a reduction in compressive strength by 12.8–49.8% and tensile strength by 14.5–44.6%. If the proportion of FNG exceeds 50%, compressive strength decreases by more than 24.5% and tensile strength by more than 27.5%. In Series II, replacing CNA with CRG reduced compressive and tensile strengths by 18.4–32.8% and 5.1–24.9%, respectively; exceeding 40% CRG results in a compressive strength reduction of more than 32.8% and a tensile strength reduction of more than 24.9%. In Series III, samples made with RCA, CNA, and 20% CRG showed a compressive strength decrease of 8.8–22% and a tensile strength decrease of 10.7–26%; RCA80 samples showed maximum reductions. In Series IV, replacing CNA with RCA resulted in compressive and tensile strength reductions of 15.4–34.7% and 13.9–24.3%, respectively; RCA80 samples again showed maximum reductions. Maximum stress unit deformation values (ε_o) increased by 3–58.4% in Series I, 9–80% in Series II, 10–44.9% in Series III, and 9–32% in Series IV. Tensile toughness values showed the highest increase of 35.15% in the CRG40 sample and the lowest of 0.13% in the RCA40-20 sample. The use of glass aggregates in concrete is feasible, but exceeding certain ratios can significantly reduce strength. Concrete can effectively use waste glass as a partial substitute for cement, fine aggregates, or as a filler material, potentially enhancing compressive strength. Full article

During the process of cutting andesite stones, the waste mud is kept in powder form once fully dried. It is difficult to store the waste that is produced as a consequence of the extensive utilization area and consumption of andesite. Thus, eliminating waste storage challenges and incorporating these wastes into the economy are crucial. For this reason, this study examined the effects of waste andesite dust (WAD) on the flexural behavior of reinforced-concrete beams (RCBs) using experimental testing and 3D finite-element modeling (FEM) via ANSYS. Thus, different rates of WAD up to 40% were used to investigate the influence of the WAD rate on the fracture and bending behavior of RCBs. While the RCB with 10% WAD had a slightly lower load-bearing and ductility capacities, ductility capacities significantly drop after 10% WAD. At 40% WAD, both the load-bearing capacity and ductility significantly reduced. Based on the experimental findings, using 10% WAD as a replacement for cement is a reasonable choice to obtain eco-friendly concrete. Moreover, the outcomes of 3D FEM were also compared with those of experiments conducted using ANSYS v19 software. The displacement values between the test and FEM findings are quite similar. Full article

Over the last decades, cement has been observed to be the most adaptive material for global development in the construction industry. The use of ordinary concrete primarily requires the addition of cement. According to the record, there has been an increase in the direct carbon footprint during cement production. The International Energy Agency, IEA, is working toward net zero emissions by 2050. To achieve this target, there should be a decline in the clinker-to-cement ratio. Also, the deployment of innovative technologies is required in the production of cement. The use of alternative binding materials can be an easy solution. There are several options for a substitute to cement as a binding agent, which are available commercially. Non-crystalline alkali-aluminosilicate geopolymers have gained the attention of researchers over time. Geopolymer concrete uses byproduct waste to reduce direct carbon dioxide emissions during production. Despite being this advantageous, its utilization is still limited as it shows the quasi-brittle behavior. Using different fibers has been started to overcome this weakness. This article emphasizes and reviews various mechanical properties of fiber-reinforced geopolymer concrete, focusing on its development and implementation in a wide range of applications. This study concludes that the use of fiber-reinforced geopolymer concrete should be commercialized after the establishment of proper standards for manufacturing. Full article

The performance of self-compacting concrete (SCC) is gaining popularity in construction due to its exceptional strength and durability. However, the properties of combined steel and concrete at elevated temperatures lack experimental data from previous research. This study aimed to investigate the behavior of the SCC core with a steel tube at ambient and elevated temperatures varying from 100 °C to 800 °C with 100 °C intervals for each test specimen. Tests were conducted on circular steel tubes filled with SCC for different grades (M25, M30, and M40) under compression at elevated temperatures. Experimental observations revealed that the stress–strain curve increased with increasing the cross-sectional area and grade of concrete. However, increasing the temperature and length-to-diameter ratio reduced the stress–strain curve. At elevated temperatures, confined SCC experienced a smaller decrease in the overall modulus of elasticity when compared to unconfined concrete. Within the compressive elastic region (from 30 °C to 400 °C), there was a significant relationship between lateral strain and longitudinal strain, which was followed by a sudden increase beyond 400 °C. Equations for various design parameters were proposed based on the peak load and confinement factor of confined SCC-filled steel tubes (SCCFSTs) via multiple regression. Moreover, this study developed load–axial shortening curves, identifying significant properties such as the yield strength of confined SCCFSTs, including the load-carrying capacity. The predicted numerical analysis results were well aligned with the experimental results, and the findings contributed valuable insights for designing resilient and durable combined SCC and steel tube infrastructures. Full article

The building and construction industry’s demand for steel reinforcement bars has increased with the rapid growth and development in the world. However, steel production contributes to harmful waste and emissions that cause environmental pollution and climate change-related problems. In light of sustainable construction practices, bamboo, a readily accessible and eco-friendly building material, is suggested as a viable replacement for steel rebars. Its cost-effectiveness, environmental sustainability, and considerable tensile strength make it a promising option. In this research, hybrid beams underwent analysis through the use of thoroughly validated finite element models (FEMs), wherein the replacement of steel rebars with bamboo was explored as an alternative reinforcement material. The standard-size beams were subjected to three-point loading using FEMs to study parameters such as the load–deflection response, energy absorption, maximum capacity, and failure patterns. Then, gene expression programming was integrated to aid in developing a more straightforward equation for predicting the flexural strength of bamboo-reinforced concrete beams. The results of this study support the conclusion that the replacement of a portion of flexural steel with bamboo in reinforced concrete beams does not have a detrimental impact on the overall load-bearing capacity and energy absorption of the structure. Furthermore, it may offer a cost-effective and feasible alternative. Full article

Asphalt is widely employed in road construction due to its durability and ability to withstand heavy traffic. However, the disposal of waste polymers has emerged as a significant environmental concern. Recently, researchers have used polymer waste to modify asphalt pavements as a new approach. This approach aims to improve pavement performance and address the environmental concerns of polymer waste. Researchers have demonstrated that incorporating polymeric waste into asphalt mixtures can lead to performance improvements in asphalt pavements, particularly in mitigating common distresses including permanent deformation and thermal and fatigue cracking. The current comprehensive review aims to summarize the recent knowledge on the usage of waste polymers in asphalt mixtures, encompassing their impact on performance properties and mixture design. The review also addresses different types of waste polymers, their potential benefits, challenges, and future research directions. By analyzing various studies, this review offers insights into the feasibility, effectiveness, and limitations of incorporating waste polymers into asphalt mixtures. Ultimately, this contributes to the advancement of sustainable and environmentally friendly road construction practices. Full article

This study investigates the potential of two bitumen modifiers, high-density polyethylene (HDPE) and nano clay (NC), to enhance the rutting resistance of asphalt mixture. Four HDPE asphalt binders were prepared by mixing the HDPE at percentages of 2%, 4%, 6%, and 8% with the virgin binder, while four NC asphalt binders were produced by mixing the NC at percentages of 1%, 2%, 3%, and 4%. The consistency and flow of virgin binder, HDPE binders, and NC binders were evaluated by penetration, softening point, and viscosity tests. The results show a gradual increment in the binder stiffness by increasing the percentage of both modifiers. The static creep test was conducted at a temperature of 40 °C to evaluate the rutting resistance. The results confirm that both modifiers can greatly improve the rutting resistance of the asphalt mixture, where 8% HDPE and 3% NC modifications reduce the strains provoked in the asphalt mixture under loading by about 50%. According to the correlation analysis, the mixture rutting performance is highly attributed to the binder stiffness, where the lower the penetration value of the asphalt binder, the lower the strains in the asphalt mixture and the higher the stiffness modulus of the asphalt mixture. Full article

Reinforced concrete infilled frames have been studied over the years along with the infilled openings. To resist the lateral loads that are applied on the frames, stress is transferred from the reinforced concrete (RC) to infill, which leads to brittle collapse. The conventional interface medium, which was considered by researchers and recent studies, was prepared by changing the interface materials between the RC frame and infill panels to different elastic materials. This study focuses on optimizing the interface pressure using a butyl rubber tube, which reduces the stress distribution to the infill panel from the RC frame. A 50% window opening was adopted in this study, which is the optimized size from previous research. The optimization patterns followed linear and nonlinear patterns, such as the same pressures in all stories and varying pressures in all stories. The third story had a 8 PSI pattern and the other stories had a 2 PSI pattern; all stories with 8 PSI patterns achieved the least displacement when compared to other variations. A monotonic static analysis was performed for both the experimental and analytical study. The boundary conditions were pinned, and coupling interfaces were made for the master and slave surfaces. The pressure conditions were applied in various linear and nonlinear patterns to optimize the pressure. A comparative study was performed on the displacement, stiffness, and drift ratio for the critical position of the interface pressure in both the analytical and experimental studies. The difference was approximately 0.53% in the analytical study and 0.37% in the experimental work. The optimization was performed using both an experimental model and an analytical model, which had an error percentage of 0.61%. Full article

Reinforced concrete corbels were examined in this study for the cracking behavior and strength evaluation, focusing on defects typically found in these structures. A total of 11 corbel specimens were tested, including healthy specimens (HS), specimens with lower concrete strength (LC), specimens with less reinforcement ratio (LR), and specimens with more concrete cover than specifications (MC). The HS specimens were designed using the ACI conventional method. The specimens were tested under static loading conditions, and the actual strengths along with the crack patterns were determined. In the experimental tests, the shear capacity of the HS specimens was 28.18% and 57.95% higher than the LR and LC specimens, respectively. Similarly, the moment capacity of the HS specimens was 25% and 57.52% greater than the LR and LC specimens, respectively. However, in the case of the built-up sections, the shear capacity of the HS specimens was 9.91% and 37.51% higher than the LR and LC specimens, respectively. Likewise, the moment capacity of the HS specimens was 39.91% and 14.30% higher than the LR and LC specimens, respectively. Moreover, a detailed nonlinear finite element model (FEM) was developed using ABAQUS, and a more user-friendly strut and tie model (STM) was investigated toward its suitability to assess the strengths of the corbels with construction defects. The results from FEM and STM were compared. It was found that the FEM results were in close agreement with their experimental counterparts. Full article

Industrial waste usage in the technology of construction materials is currently in a relevant and promising direction. Materials made of industrial waste have a lower cost and are highly environmentally friendly. The objective of this study is to develop effective compositions of sulfur concrete based on the maximum possible number of various wastes of the local industry for this and to investigate the characteristics of this composite. Test samples of sulfur concrete were made from sulfur, fly ash, mineral aggregates and bitumen additive. The dosages of fly ash, sand and bitumen varied, while the content of sulfur and crushed stone remained constant. The following main characteristics of sulfur concrete were determined: density; compressive strength; and water absorption. Tests of sulfur concrete were carried out after 1 day and 28 days of hardening. The best values of compressive strength (24.8 MPa) and water absorption (0.9%) were recorded for the composition of sulfur concrete at the age of 28 days with the following content of components: sulfur—25%, modified with 4% bitumen of its mass; fly ash—10%; crushed stone—40%; and sand—25%. The optimal composition of modified sulfur concrete showed compressive strength up to 78% more and water absorption up to 53% less than the control composition. The characteristics of the sulfur concrete samples after 28 days of hardening differ slightly from the values after 1 day of hardening (up to 1.8%). An analysis of the structure confirmed the effectiveness of the developed composition of sulfur concrete in comparison with the control. Full article