Strength Of Concrete Structures Research Articles

Assessment of residual bonding performance for bimetallic steel bar-seawater concrete after exposure to high temperature

The bimetallic steel bar (BSB) is a new type of corrosion-resistant reinforcement material composed of carbon steel and stainless steel, which can effectively improve the durability of structures. Reinforced concrete structural strength depends on the bond between steel bars and concrete. This mechanism can be compromised after exposure to a fire, but it has been less considered in research, and is not addressed in concrete design codes. To evaluate the residual bearing capacity of BSB reinforced concrete structures after a fire, it is necessary to clarify the bonding performance between BSBs and concrete after exposure to high temperatures. In this study, 45 BSB-seawater concrete (BSBSC) pull-out specimens were prepared, and the bonding performance of BSBSC after high temperature was studied by heating treatment and pull-out tests. The results showed that the BSBSCs changed from bluish-gray to grayish-yellow with the increase in heat treatment temperature. After exposure to 400 °C, cracks appeared on the surface of BSBSCs. As the heat treatment temperature increased, the slope of the rising and descending stages for the bond stress-strain curve decreased gradually. In addition, as the thickness of the concrete cover increased, the bonding strength of BSBSCs also improved. The higher the heat treatment temperature, the less significant the improvement effect. Based on test results, a predictive model for the bonding performance characteristics of BSBSCs after high temperature was proposed, and a constitutive model for bonding stress-slip relationship was established.

The ways and mechanisms of using CFRP materials to strengthen the flexural performance of reinforced concrete beams

Due to the increasing demand for structural strengthening and retrofitting solutions, Fiber-reinforced plastic (FRP) materials has emerged as a promising technology to improve the performance of existing structures. FRP material is a composite material composed of fiber-reinforced plastics, known for its excellent strength and resistance to corrosion. The primary components of this material consists of various fibers, such as glass fiber, carbon fiber, or aramid fiber, along with a resin matrix, such as epoxy resin, polyester resin. FRP materials are commonly employed in construction engineering to enhance the flexural strength of concrete structures. This paper, through methods of literature review and building physical models, investigates the effectiveness of Carbon Fiber Reinforced Polymer (CFRP) materials in enhancing the bending strength of reinforced concrete beams. This study aims to examine the impact of carbon fiber reinforced polymer (CFRP) sheets on the flexural strength of reinforced concrete beams, which aims to establish calculation formulas based on the specific impacts observed. The findings of this study demonstrate the capacity of FRP materials, specifically CFRP materials, to improve the bending strength of reinforced concrete beams. The usage of FRP materials for structural reinforcement offers a durable, corrosion-resistant, and lightweight solution that can prolong the lifespan and improve the structural efficacy of existing infrastructure.

Nondestructive testing techniques for investigating mechanical property and porosity disparities in extrusion 3D printed concrete

ABSTRACT Three Dimensional Concrete printing (3DCP) stands at the forefront of modern construction methodologies, also named additive manufacturing, offering unparalleled time, cost, and labour savings compared to conventional approaches. The evaluation of fresh state parameters like extrudability and buildability through a specialised concrete extruder, combined with a methodical layer-by-layer deposition, ensures structural stability by precisely strengthening each layer. Mechanical strength evaluations highlight the printed material’s anisotropic nature, revealing extreme reductions of Fy = 27.94%, Fx = 19.07%, and Fy = 16.33% in compression, flexural, and split tensile strengths, respectively, compared to cast specimens. This emphasises the importance of direction-specific mechanical testing in understanding material behaviour completely. Non-destructive testing (NDT) methods, like Ultrasonic Pulse Velocity (UPV) testing, are crucial for the qualitative assessment of the integrity and mechanical strength of concrete structures, including both printed and cast specimens, by establishing a strong correlation with compressive strength without causing any damage. Limited research indicates that the microstructure of the material plays a significant role in its mechanical strength, particularly in printed specimens. This claim is reinforced by mercury intrusion porosimetry (MIP) results, which reveal that printed specimens have slightly higher overall porosity, concentrated between 1 µm and 0.1 µm, while cast specimens show higher porosity in pores smaller than 0.1 µm.

Sustainability-driven model for predicting compressive strength in concrete structures

Sustainability-driven model for predicting compressive strength in concrete structures

A Review on the Effects of Waste Textile Polymer Fiber on Concrete Strength: Exploring the Key Parameters

The construction industry is one of the largest users of natural resources and can, thus, lead to significant environmental issues. Therefore, there is elevated interest worldwide in developing sustainable construction materials and techniques that can reduce these associated environmental impacts. In this context, one substantial area of focus is the incorporation of textile waste in construction materials, such as concrete. Textile waste is generated in large quantities from the production stage through to the consumption and end-of-life disposal periods. Hence, it is prudent to devise effective ways of recycling this waste, which can, in turn, reduce the environmental implications of textile production and cut down the quantity of waste sent to landfills. Furthermore, fibers obtained from recycled textile waste can be used to reinforce concrete, thus replacing the need for synthetic fibers. This review focuses on the use and effects of incorporating polymer fibers from recycled textile waste in concrete and the use of textile polymer fiber in the construction of various structures, and challenges in the use of recycled fibers in concrete and the parameters affecting the resultant strength of concrete structures, such as stress transfer, crack control, bond strength, and spalling, etc., are discussed.

Synthesis of Eu3+-doped β-Ca2SiO4 phosphors and its utility as an indicator to visualize the distribution of grouting material

Grouting materials have been widely used in the engineering fields for filling the cracks and increasing the strength of concrete structures, etc. However, tracing the distribution of grouting material is still laborious and lack of efficient tools. In this study, a grouting material that could be used as an indicator to visualize the distribution of grouting material was proposed. Serial Eu3+-doped β-Ca2SiO4 phosphors were synthesized through a classical solid-state reaction method. The phase and crystallographic properties of the samples were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The hydration performance of the samples was studied by measuring the isothermal calorimetry and compressive strength. The luminescence properties were explored through photoluminescence spectroscopy and the visualizing of the distribution of grouting materials was realized in simulated grouting experiments. The results demonstrated that the inherent luminescence property of Eu3+-doped β-Ca2SiO4 endowed its capability as an indicator during grouting process and it could be adopted as a candidate to verify the accuracy of numerical simulation.

To study the effect of polypropylene fibre in concrete to increase the strength of concrete structures

The research project on the impact of polypropylene Fibercon on the strength of concrete structures will be beneficial in its potential application in conventional construction works as well as repair works, as the scarcity of conventional construction materials is causing many problems in construction practices like refurbishment or the construction of new structures. In the proposed effort, the use of polypropylene fibers as a reinforcing material for concrete buildings will be thoroughly examined. Flexural strength, tensile strength, and compressive strength are the parameters that will be examined in order to analyze the performance. Key Words: Compressive strength, Eco -friendly, Economical, Polypropylene fibre, seismic resistance.

Hybrid CFRP-BFRP Rebars for Prestress Concrete Slabs: Abaqus Analysis and Experimental Validation

This study utilizes Abaqus finite element software to analyze concrete slabs reinforced with a novel hybrid of Carbon Fiber Reinforced Polymers (CFRP) and Basalt Fiber Reinforced Polymers (BFRP) rebars known as CBRP rebars. The investigation focuses on assessing the structural performance of these slabs under varying prestressing levels (PL) and FRP reduction factors (FR), along with the prestress index level (PI). The study defines the FR factor as the reduction in the transverse reinforcement area of FRP compared to the control slab. The PI is the ratio of prestressed CBRP rebars to the total FRP reinforcement in the transverse direction, aiming to determine a lower FRP reduction factor without compromising the FRP slabs' design requirements. Three FR values (0.45, 0.37, and 0.29) are considered, with the CBRP tendon tensioned at 35% and 50% of the ultimate strength, including 0.5 and 0.6 of the PI, for validation against experimental test data. The numerical analysis incorporates advanced finite element modeling techniques, integrating material properties, load conditions, and structural parameters to detail the behavior of CBR-reinforced concrete slabs. Various loading scenarios are simulated to evaluate the performance of CBRP rebars under diverse conditions. Comparison with experimental data validates the hybrid reinforcement approach's reliability. The study's findings contribute significantly to understanding the structural performance of concrete slabs reinforced with CBRP rebars. The hybridization of CFRP and BFRP rebars offers a promising alternative for enhancing concrete structure strength while reducing the carbon footprint associated with traditional reinforcement materials. The versatility of CBRP rebars allows customization based on specific structural requirements. Based on the Abaqus numerical analysis and its alignment with experimental data, the study recommends optimizing the CFRP-BFRP ratio to meet structural demands, evaluating long-term performance, and exploring environmental benefits associated with sustainable reinforcement materials. This research advances knowledge in the hybrid fiber-reinforced polymers field, offering insights for engineers and researchers seeking innovative solutions for concrete structure enhancement using Abaqus as a powerful analytical tool.

Experimental Study on the Properties of Concrete with Partial Replacement of Sand by Plastic Pet Bottle Fiber

The use of plastic is increasing day by day, although steps were taken to reduce its consumption. The suitability of replacement of plastic pet bottle fiber as sand in concrete and its advantages are studied here. Plastic bottles are a major issue of solid waste disposal. Several things which were invented for our convenient life are responsible for polluting environment due to improper waste management technique. Polyethylene Terephthalate (PET) is used for carbonated beverage and water bottles. This is an environmental issue as waste plastic bottles are difficult to biodegrade and involve processes either to recycle or reuse. In the Modern world, the construction industry is searching for cost-effective materials for enhancing the strength of concrete structures. This study is carried out with the possibility of using the waste PET bottles as the partial replacement of fine aggregate in Ordinary Portland cement. The percentage substitution that gives higher compressive strength was used for determining the other properties such as flexural strength test.

Application of E-Glass Jute Hybrid Laminate Composite with Curved Shape on Compressive Strength of Cylindrical Column Concrete

This study provides a better understanding of reinforcing cylindrical concrete columns (CCC) using a hybrid laminated composite material (HLC) composed of jute and e-glass fibers, including the influence of layer quantity on strength and a comparison with previous research. The utilization of these alternative materials may lead to the development of novel and efficient solutions for constructing durable and robust structures. The primary objectives of this research are to assess the effects of employing HLC as a reinforcing layer on CCC compressive strength, optimize the reinforcement process by selecting appropriate layer sequences and types, and analyze the type of fiber damage in relation to the strength of HLC composite material. The materials utilized in this study encompass woven jute fabric sheets, e-glass fiber sheets, and epoxy resin. Compressive strength testing was conducted following ASTM C39 standards. Specimen variations were based on the number and type of reinforcing layers. The results revealed that CCC compressive strength increased by up to 100% with the application of up to three layers of jute compared to an unlayered specimen. Furthermore, CCC compressive strength experienced a remarkable enhancement of up to 150% with the incorporation of HLC composite. Hence, the implementation of HLC demonstrates significant potential for augmenting the strength of concrete structures.

Welding Bead Inspection Using Image and Multi-Sensor Fusion

Welding is a crucial manufacturing technique utilized in various industrial sectors, playing a vital role in production and safety aspects, particularly in shear reinforcement of dual-anchorage (SRD) applications, which are aimed at enhancing the strength of concrete structures, ensuring that their quality is of paramount importance to prevent welding defects. However, achieving only good products at all times is not feasible, necessitating quality inspection. To address this challenge, various inspection methods were studied. Nevertheless, finding an inspection method that combines a fast speed and a high accuracy remains a challenging task. In this paper, we proposed a welding bead quality inspection method that integrates sensor-based inspection using average current, average voltage, and mixed gas sensor data with 2D image inspection. Through this integration, we can overcome the limitations of sensor-based inspection, such as difficulty in identifying welding locations, and the accuracy and speed issues of 2D image inspection. Experimental results indicated that while sensor-based and image-based inspections individually resulted in misclassifications, the integrated approach accurately classified products as ‘good’ or ‘bad’. In comparison to other algorithms, our proposed method demonstrated a superior performance and computational speed.

Studying the rheological features, mechanical properties and flexural toughness of the WSFRSCC by varying the coarse aggregate volume

The low tensile strength of concrete structures requires studying the effects of fibers on the performance of fresh and hardened concretes where finding the right amount of coarse aggregates is a challenge in the concrete industry. This study has addressed the effects of increasing the volumes of wavy steel fibers (0.15, 0.3 and 0.45%) and coarse aggregates (30, 40, 50 and 60%) on fresh concrete parameters and Self-Compacting Concrete (SCC) strength and fracture characteristics. Results have shown that using wavy steel fibers has negative effects on the properties of the fresh SCC because its efficiency and flowability are reduced, and increasing the coarse aggregate volume has positive effects because the rheological properties are improved. On the other hand, increasing the wavy steel fiber volume will improve the compressive strength in concretes containing 50 and 60% coarse aggregates. Only in 60% coarse-aggregate concretes, increasing the fiber volume from 0.15 to 0.45% will slightly reduce the wavy steel fiber reinforced self-compacting concrete (WSFRSCC) tensile strength. Increasing the coarse aggregate volume (30% – 60%) will improve the elasticity modulus of specimens with fixed percent fiber. Comparison of ASTM C 1609, JSCE SF-4 and JG/T 472-2015 methods revealed that the latter could well provide a thorough understanding of the variations of the flexural toughness of the WSFRSCC due to the demarcation of the pre- and post-peak load areas.

Experimental Study on Concrete by Adding Polyester Fibres

Abstract There are increased innovations in the field of concrete because there are endless opportunities for innovative materials, techniques, applications, and design. Today’s construction industry is looking for cost-effective materials to improve the strength of concrete structures. As a result, an attempt has been made in the current research to investigate the impact of adding polyester fibres (Recron 3s) to concrete. Fibres improve concrete's tensile and flexural strength, fatigue properties, durability, shrinkage properties, impact and erosion resistance, and serviceability. Polyester fibres (Recron 3s) are micro fibres; they contribute to enhancing the resistance of concrete to shrinkage and cracking and also help to improve mechanical properties such as the flexural / split tensile and transverse strength of concrete along with improvements in abrasion and impact strength. An experimental study was done using a M30 mix design. Polyester fibres (Recron 3s) were used in the concrete with varying dosage rates of 0.50 kgs / cu.m – 2.00 kgs / cu.m. This study describes the enhancement in the strength of the M30 grade mix concrete by the addition of polyester fibres (Recron 3s) in the proportions of 0.5, 1, 1.5, 2.0kg/cu.m, and M30 concrete with varying dosages of the polyester fibres (Recron 3s) were mixed and cast.

A state-of-the-art review on reinforced concrete slabs strengthened by frp sheets under monotonic, impact and repeated loading

Composites made of fiber-reinforced polymer (FRP) have gained popularity as new high-performance material for concrete buildings in now days. The advantages of FRP composites include high strength, lightweight, and corrosion resistance. This paper’s primary objective is to assess the affect of FRP strips on the strengthening and repair of plain and reinforced concrete slabs. under the monotonic, impact, and repeated loading. According to studies’ observations, applying FRP strips to RC slabs significantly affects the final load and deflection. The number and positioning of FRP sheets improve the performance of slabs. The failure load magnitude of strengthened slabs would increase as slab thickness, concrete compressive strength, and sheet thickness increase. The ultimate load capacity was increased by (27-52%), depending on the FRP strengthening strategy used. GFRP sheets could be employed for improving or enhancing the impact strength of concrete structures. Externally attached GFRP sheets gave good resistance for reinforced concrete slabs against typical explosive blast.

An evolutionary functional link artificial neural network for assessment of compressive strength of concrete structures

Compressive strength (CS) has been considered as the utmost critical parameter while designing concrete structures. Usually, it is determined through laboratory tests, which are expensive, time consuming, and requires consumptions of materials. Therefore, correct prediction of CS before actual placement of concrete is highly desirable. The relationship among the constituent materials that forms concrete structures is highly nonlinear and necessitates application of intelligent methods. Though a few such methods like artificial neural network (ANN) based models are available in the literature; their performance in the context is limited to certain extent and they have their own merits and demerits. Hence, to address some of the limitations of ANN (non-higher order Neural Network) based models, this contribution proposed a hybrid model in which a flat network i.e., a type of higher order neural network- functional link artificial neural network (FLANN) is used as the base structure and genetic algorithm (GA) is employed to find out the optimal FLANN parameters (i.e., GA + FLANN). The training process comprises selection of connection weights, bias, as well as optimal number of basis functions of FLANN by GA rather fixing them earlier. Thus, an optimal FLANN is crafted on fly from exploitation of training data. The proposed model is used to assess the CS of concrete cements from datasets available in the literature considering samples of curing age at 3, 7, 14, 28, 56, and 91 days. A rolling window is used for input selection and five evaluation metrics are used for performance evaluation. On an average, the GA + FLANN obtained 0.477052 MAPE (mean absolute percentage of error), 0.598067 ARV (average relative variance), 0.593862 UT (U of Theil’s statistic), 0.551452 NMSE (normalized mean squared error), and 0.206135 SD (standard deviation) values which are the lowest compared to others. The superiority of the model is established through comparative studies and statistical significance tests.

Kajian Penggunaan Fly Ash Sebagai Pengganti Sebagian Semen Pada Beton Struktural

This study aims tofind out the effect of the use of fly ash as a substitute for part of cement onthe compressive strength and bending strength of structural concrete, as well as to find out the optimal composition of the use of fly ash so that maximum structural concrete strength is produced. The method used in this study is an experimental method. The study was designed with 5 treatments for concrete compressive strength test and 5 treatment for concrete bending strength test, each repeated 3 times. The treatment tested by beton with the use of fly ash as a substitute for cement as a substitute for cement 0%, 5%, 10%, 15% and 20%. The results showed that the use of fly ash as a substitute for part of cement affects thecompressive strength and bending strength of structural concrete, where there is an increase in compressive strength and bending strength in the use of fly ash 5% by producing a compressive strength of 5% 31.23Mpa and bending strength of 4.03 Mpa, there was also a decrease in compressive strength and bending strength in the use of fly ash of 10%, 15% and 20% by producing compressive strength of 29.74 Mpa, 28.15 Mpa and 26.78 Mpa, as well as producing concrete bending strength of 3.49 Mpa, 3.21 Mpa and 2.94 Mpa. The use of an optimum fly ash of 1.835% results in a maximum concrete compressive strength of 30.75 Mpa and a maximum concrete bending strength of 3.89 Mpa

CONCRETE CURING MONITORING SYSTEM

Monitoring the strength of concrete structures in their early stages is critical to avoid failure and determine readiness for use. Automatic curing is also important to minimize water waste, prevent cracks, and achieve a long-lasting structure.To facilitate automatic curing, a moisture sensor is utilized. Generally, the curing process takes 28 days, which is crucial for attaining the desired strength. This study developed a moisture sensor that automatically monitors the moisture content of concrete structures, even remotely.The strength and moisture values are presented in a graphical format, indicating that the beam achieved a strength of 26.5N/mm2 at 28 days and 30.8 N/mm2 at 56 days, demonstrating an increase in strength beyond the 28-day mark.

Corrosion inhibitors for enhanced strength, durability, and microstructure of coastal concrete structures

The prevalence of catastrophic structural member failure caused by steel corrosion in civil infrastructure underscores the importance of reducing reinforcement corrosion to enhance overall infrastructure costs, reliability, and sustainable development. The present research investigates the potential of corrosion inhibitors to enhance the durability and strength of concrete structures, with a focus on their long-term effectiveness in resisting corrosion in reinforced concrete structures. Multiple approaches such as inhibitors, repairing processes, and coatings have been explored to prevent concrete corrosion damage, with an emphasis on concrete corrosion performance in coastal and corrosive situations. This study investigates the effect of six different corrosion inhibitors (zinc oxide, magnesium oxide, urea, sodium nitrate, sodium molybdate, and diethyl ether) on the compressive strength and durability of concrete samples. The compressive strength is assessed using both destructive (28 days cube compressive strength) and non-destructive (Ultrasonic Pulse Velocity) test methods, while concrete durability is evaluated using the rapid chloride permeability test (RCPT). The compressive strength of the admixture incorporated samples are found to be higher than the control sample by almost 50% and above with excellent concrete quality. The RCPT values of inhibitor-incorporated samples are moderate and low with control samples having high permeability even in adverse conditions of freezing, thawing, and deicing. The samples incorporated with inhibitors also show less negative half-cell potential which is 1.43 times less than that of the control sample indicating the lesser probability of occurrence of corrosion. SEM imaging is also conducted to analyze the microstructure of each mix. The findings of this study highlight the importance of inhibitors in enhancing the durability of reinforced concrete structures.

Effects of Environmental Waste Plastic Bottle Cover (EWPBC) on Physical and Mechanical Properties of Concrete

The rapid industrialization and urbanization in many countries of the world is leading to great infrastructural development which in turns result to problems like shortage of construction materials and increased productivity of wastes – which has caused environmental issues due to inadequate recycling and disposal facilities. Construction industry is in need of materials which can increase the strength of concrete structures with low cost and less environmental impact. This research is aimed at addressing such issues by investigating the effect of environmental waste plastic bottle cover (EWPBC) on the physical and mechanical properties of concrete. EWPBC samples was collected within the environs and used at different percentage (0%, 12.5%, 25%, 50% and 100%) replacement for coarse aggregate. Physical properties of the materials were investigated and found to be in accordance with relevant specifications. Mechanical properties such as compressive strength and flexural strength tests were also carried out in line with relavant codes of practice. The compressive strenght increases with days of curring and at 12.5% EWPBC, the strength is 4.7% higher than the conventional concrete. The flexural stress is also higher than that of the conventional beam sample at 12.5% EWPBC. The flexural strain is 0.00248-0.0036 and within the specified acceptable limit (0.002-0.0035) for concrete with grade less than or equal to C50/C60. This shows a promising properties at 12.5% EWPBC replacement and also a reduction in cost. It was concluded that EWPBC can be used as substitute for aggregates and also a means of reducing environmental wastes and cost of disposal of such waste.

Research on detection method of concrete compressive strength based on dielectric properties

Compressive strength of concrete structures is a crucial quality parameter that determines their performance throughout lifespan. This study introduces an innovative approach of utilizing electromagnetic nondestructive testing to assess the compressive strength of mature concrete. The dielectric constant and compressive strength of standard specimens were tested by open coaxial probe and pressure testing machine, respectively, using ordinary Portland cement concrete with various water-cement ratios (0.4, 0.45, 0.5, 0.55, 0.6 and 0.65) as the research object. It has been discovered that increasing porosity reduces the number of polarized particles per unit volume of concrete, resulting in a decrease in polarization intensity. This decrease is manifested as a reduction in the dielectric constant in macro parameters. The relationship between porosity and dielectric constant was characterized using a series-parallel composite concrete dielectric model. Additionally, as porosity increases, the compressive strength of concrete decreases exponentially. By considering porosity as an intermediate variable, a concrete compressive strength model based on the dielectric constant was established. The model exhibits an average error of 3.62%, indicating the precise characterization of concrete's compressive strength using the dielectric constant. This model can serve as a theoretical basis for the implementation of electromagnetic nondestructive testing techniques in strength evaluation.