Use Of Concrete Structures Research Articles

Chemical interference between graphene oxide and polycarboxylate superplasticizer, and the resulting impact on the concrete strength, workability, and microstructure

Graphene oxide (GO) nanoreinforcement is shown to significantly improve the strength and durability of concrete at the expense of mix workability. While polycarboxylate superplasticizers (PCSP) addition has improved GO-cement/mortar strength and workability in existing literature, this article examines if this improvement is translated to concrete with lower cement and water contents. PCSP and GO showed colloidal instability and particulate aggregation through surface charge measurements, presumably caused by divalent Ca 2 + ion interbridging between the GO and PCSP. This chemical interference results in a 26% reduction in 28-day compressive strength and a 20% decrease in the workability of PCSP-treated GO-concrete. Microstructural examination reveals significantly larger pores in PCSP+GO cement than in GO-cement or PCSP-only cement due to the chemical interference induced by PCSP-GO interactions in cement and concrete. Hence, PCSP and GO interactions must be further researched for practical use in concrete structures.

Mechanical properties and fracture behavior of seawater-mixed sea sand recycled aggregate concrete

Despite their undeniable potential for promoting sustainability in construction materials, the characteristics of recycled aggregates (RCA), seawater, and sea sand may vary significantly, thereby affecting their use in structural concrete. This study exploits these materials to investigate their performance in producing sustainable concrete and establishing its mechanical and fracture behavior. The so produced material, referred to as seawater sea sand recycled aggregate concrete (SSRAC) could lend a hand in widening the usage of RCA and sea sand in a variety of applications where the use of ever-depleting natural materials as concrete constituents becomes an issue. Consequently, the variables of the study include the type of water (fresh versus seawater), type of coarse aggregate (RCA versus natural coarse aggregate, NCA), and the type of fine aggregate (dune sand versus sea sand). For each water type, three concrete mixtures are produced using NCA-dune sand, RCA-dune sand, and RCA-sea sand combinations. Analyses of the mechanical characteristics of the concrete, including compressive strength, flexural strength, modulus of elasticity, and fracture toughness, were conducted based on experimental tests. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analyses were also conducted on the designed specimens to investigate their microstructure. In terms of fracture characteristics, the use of seawater resulted in improvement in the fracture toughness. The use of recycled aggregate along with seawater resulted in improved compressive strength. However, natural aggregate concrete (NAC) showed higher flexural strengths than recycled aggregate concrete (RAC). The results also revealed that the addition of sea sand had a detrimental impact on all mechanical characteristics. Thus, optimizing the concrete composition in which the investigated materials partially replace the conventional concrete constituents is required in order to consider alternative constituents to generate sustainable concrete for practical applications.

Deep learning techniques in concrete powder mix designing

Abstract The water-cement ratio is multiple phases procedure in which we aim to determine the most optimal combination for producing high-performing concrete. In modern literature and business practice, there are various methods for designing concrete mixes, although the Three Equation Method-inspired procedures are by far the most widely used. Concrete compressive strength is one of the fundamental properties that determines its class. Foreseeable compressive strength concrete is necessary to promote the use of concrete structures. The primary feature of its durability and safety is. Deep learning has recently received a lot of attention, and the prospects for this technology are even brighter. Machine learning algorithms have advanced to the point that they can recognize patterns, which are difficult for humans to recognize. This has sparked interest in data mining on enormous datasets. In this research, we aim to utilize cutting-edge developments in machine learning techniques for the production of concrete mixes. To provide the ideal structure of a synthetic neural network that has been chosen, we compiled a comprehensive dataset of concrete mixtures, complete with laboratory destructive test results. A mathematical formula that may be used in practical applications has been developed from the creation of an artificial neural network.

Prediction of sound and vibration levels from heavy-hard impacts in a cross laminated timber—Concrete hybrid building

Heavy-hard weight impacts in fitness spaces often result in elevated noise and vibration levels, which can lead to complaints in sensitive adjacencies. Previous works have demonstrated a method to predict the resulting noise and vibration levels in fitness space adjacencies. This method involves the analysis of an in situ transfer function in combination with laboratory force data and sound pressure level measurements from a shotput dropped on a calibrated reference rubber impact sheet. It was originally developed for use in concrete structures, which are typical for large multi-residential, commercial, and mixed-use buildings that commonly feature fitness amenity rooms or commercial gyms. The growing popularity of mass timber as a sustainable building material provides an opportunity to expand upon the previous research by examining the validity of the prediction method in another structural type. This paper serves as a case study of heavy-hard impacts in a residential hybrid mass timber structure, where weight drops from a fitness center at the top level of the concrete podium were disturbing apartment residents occupying the first CLT level directly above.

An Innovative Approach for Evaluating the Quality of Recycled Concrete Aggregate Mixes

The objective of this research is to develop an innovative methodology for evaluating the quality of coarse aggregate mixes that incorporate recycled concrete aggregate for use in structural concrete. The proposed approach consists of three steps: measuring the packing density, quantifying the adhered mortar, and characterizing the mechanical resistance of the aggregate mixes containing both natural and recycled concrete aggregate. Comprehensive practical recommendations for each step are discussed in detail to facilitate the broader future utilization of recycled concrete aggregate in structural concrete. The mechanical resistance of aggregate mixes is significantly influenced by both packing density and the quantity of adhered mortar. Predictive models are used to illustrate the mechanical resistance of aggregate mixes based on packing density and adhered mortar amount, recognizing the direct correlation between these properties.

The effect of type of mechanical anchors on bond behavior of ribbed-surface GFRP bars embedded in concrete

The deficiency in the bond between concrete and fiber-reinforced polymer (FRP) bars is a major hindrance to their widespread use in concrete structures. One effective solution to this problem is to use mechanical anchors along the bar. This research investigates the effect of mechanical anchors on the bond behavior of glass fiber-reinforced polymer (GFRP) bars embedded in concrete. In the first phase, eight beam specimens were constructed and tested in flexure, in which the FRP bars contained no anchors or anchors made of polyethylene, aluminum, or steel. The increase in maximum tensile stress in the bar was 43 %, 17 %, and 12 % for specimens with steel, aluminum, and polyethylene anchors, respectively. Steel anchors were identified as the most effective option with the greatest maximum stress and greatest initial stiffness in the stress-slip curve. In the study's second phase, an additional set of 16 beam specimens was tested to investigate the effect of the number of steel anchors. The results showed that the tensile stress developed in the GFRP bar increases at a higher rate with a greater number of steel anchors. Compared to the specimen without anchors, the bar stresses increased by 20–25 % for one and 52–59 % for two steel anchors.

Durable Structural Concrete Produced with Coarse and Fine Recycled Aggregates Using Different Cement Types

The durability properties of structural recycled aggregate concrete (RAC) produced with 50% coarse recycled concrete aggregates and up to 20% fine recycled concrete aggregates were analysed and compared to those of conventional concrete (NAC). Both the RAC and NAC mixtures achieved the same compressive strength when using an effective water–cement ratio of 0.47 and 0.51, respectively. All the concretes were produced using three types of cement: CEM II A/L 42.5 R, CEM II A/S 42.5 N/SRC and CEM III/B 42.5 N-LH/SR. The properties of drying shrinkage, chloride permeability, and accelerated carbonation coefficient of the concretes were determined experimentally, and the obtained results were compared with the values estimated by specific standards of exposure to XC1–XC4 (corrosion induced by carbonation can happen due to the presence of humidity) and XS1 (corrosion caused by chlorides from seawater) environments. The results showed that all the concretes achieved maximum drying shrinkage for use in structural concrete. Any concretes produced with CEM IIIB, including the RAC-C50-F20 concrete, achieved very low chloride ion penetrability, ranging between 500 to 740 Coulombs. In addition, all concretes manufactured with CEM IIAL and CEM IIAS, including RAC-C50-F20, were suitable for use in XC3 and XC4 exposure environments, both with 50- and 100-year lifespans.

Crack Resistance of Prestressed Reinforced Concrete Beams with Wire Rope Reinforcement.

One of the main objectives of capital construction worldwide is to increase the efficiency of construction. To achieve this, a significant improvement in the quality of concrete and reinforced concrete is required. Nowadays, in developed countries, one of the key directions for enhancing the efficiency of concrete and reinforced concrete is reducing their density by using inexpensive and high-quality local porous fillers. In recent years, the use of concrete structures with porous fillers based on ceramporite in load-bearing reinforced concrete structures has allowed for the improvement of their technical and economic indicators and the reduction in their own weight by up to 35%. This, in turn, is considered an essential factor in seismic zones, and therefore, special attention is paid to these issues. This article presents the data of experimental and theoretical studies obtained from investigating the crack resistance of prestressed lightweight reinforced concrete flexural elements with wire rope reinforcement. The main factors influencing crack resistance were considered, including the effects of two types of porous filler (ceramporite), two types of concrete, concrete strength, percentage of reinforcement, and level of precompression. The tests were conducted using short-term and repeated loadings. Based on the analysis of the obtained data, some refinements have been made to the methodology for calculating the crack resistance of such structures according to current design standards.

Thermodynamic Effect of High-Rise Reinforced Concrete Typology on Asian Cities: Effect of Socioeconomic Obsolescence Factors on Thermodynamic Complexity

The construction of reinforced concrete (RC) apartments played a crucial role in accommodating the substantial increase in urban populations during the post-war period in Asian cities. However, the RC process in these regions exhibits limitations in terms of the building’s life cycle duration. These limitations arise due to two main factors: the inherent hybrid nature of RC and the insufficient measures for addressing inner rebar corrosion, as well as the lack of adequate control over the management of the “structural class” amid rapid economic expansion. This study examines the impact of rapid urbanization and economic growth on the construction industry, with a specific focus on the utilization of concrete buildings. Drawing on Odum’s urban energetics theory, macroeconomic data are analyzed to investigate the patterns and implications of widespread concrete construction during the late 20th century, particularly in Asian countries. The findings are then compared with earlier periods of economic expansion in other countries, aiming to provide a comprehensive understanding of the interplay between urbanization, economic growth, and the use of concrete structures. The application of Odum’s theory enhances the analytical process, offering valuable insights into the dynamics of the macro urban energy system. In this assessment, four countries are selected based on the stage of their urban economic expansion. The selection is determined using the recent changes observed in three key factors: (1) urban concentration, (2) GDP growth rate, and (3) gross fixed capital formation (GFCF) on housing volume. The assessment identifies the point in time when production, represented by the GDP growth rate, surpasses consumption, represented by GFCF on housing volume. Through this assessment, it becomes possible to make macro-scaled predictions about the urban energy system, even with limited archival data available.

SELECTION OF THE RATIONAL PARAMETERS OF THREE-LAYER REINFORCED CONCRETE STRUCTURES WITH MONOLITHIC BONDING LAYERS BY THE METHOD OF COMPUTER MODELING

For the selection of the rational physical, mechanical and geometric parameters of three-layer reinforced concrete structures with monolithic bonding layers, it is necessary to have numerous data on the stress field and patterns of their deformation upon loading, changes in the energy parameters of the strength of concrete and the thickness of the layers. The important condition for the analysis of the stress-strain state by computer simulation is verification with experimental studies. This research is a confirmation of the reliability of the partitioning of the model into finite elements, the choice of their size and configuration. Modeling of three-layered enclosing structures with overall dimensions of attic overlappings allows obtaining strains and deformations in the outer and middle layers at different levels of loads and performing their comparison with limiting values. Due to the high rigidity of the three-layered enclosing structures with a monolithic bond of the layers and the use of structural concrete in the outer layers, the strength of which is more than 10 times higher than that of the middle layer, there are no cracks in the operating loads. In order to recommend considering the stress-strain state, there are more dimensional three-layer coating plates with monolithically bonded layers with different geometric and strength parameters, with different degrees of reinforcement and levels.

Superelastic Nickel-Titanium (NiTi)-Based Smart Alloys for Enhancing the Performance of Concrete Structures.

Recent advances in materials science have led to the development of smart materials that can continuously adapt to different loading conditions and changing environment to meet the growing demand for smart structural systems. The unique characteristics of superelastic NiTi shape memory alloys (SMAs) have attracted the attention of structural engineers worldwide. SMAs are metallic materials that can retrieve their original shape upon exposure to various temperatures or loading/unloading conditions with minimal residual deformation. SMAs have found increasing applications in the building industry because of their high strength, high actuation and damping capacities, good durability, and superior fatigue resistance. Despite the research conducted on the structural applications of SMAs during the previous decades, the existing literature lacks reviews on their recent uses in building industry such as prestressing concrete beams, seismic strengthening of footing-column connections, and fiber-reinforced concrete. Furthermore, scarce research exists on their performance under corrosive environments, elevated temperatures, and intensive fires. Moreover, the high manufacturing cost of SMA and the lack of knowledge transfer from research to practice are the main obstacles behind their limited use in concrete structures. This paper sheds light on the latest progress made in the applications of SMA in reinforced concrete structures during the last two decades. In addition, the paper concludes with the recommendations and future opportunities associated with expanding the use of SMA in civil infrastructures.

Evaluation of Characteristics and Building Applications of Multi-Recycled Concrete Aggregates from Precast Concrete Rejects.

The construction industry must meet current environmental requirements, mostly those pertaining to the reduction in construction and demolition waste and the consumption of raw materials. The use of recycled concrete aggregates can be part of the solution, but one question that arises is how many times recyclables can be recycled. This unknown involves other related queries regarding the properties and possible uses of repeated recycled concrete aggregates. This research is derived from the precast concrete industry, where multi-recycling is a pressing need. From good-quality parent concretes, three cycles of recycled concrete aggregates were produced and analysed. The final results are promising due to the good quality of the recycled and multi-recycled concrete aggregates obtained. Not only can they be used in low-level applications (backfilling) as usual, but they can also be used for more demanding purposes, such as graded aggregates, cement-treated road bases and concrete pavements. Their use in structural concrete is feasible, but it will be dependent on the water absorption level and the amount of recycled aggregate substitution. This research proves the viability of multi-recycled concrete aggregates with all of the associated environmental benefits.

Insights on the Corrosion Resistance of Reinforced Recycled Aggregate Concrete

Recycled aggregate produced from crushed waste concrete is suitable for use in structural concrete. It reduces the demand for non-renewable resources and also for energy in general. However, RA is more porous than most natural aggregates. The porosity of the concrete cover defines the corrosion resistance of reinforced concrete, and it is therefore disputed how the use of recycled aggregate may affect the durability of reinforced concrete. This paper describes the corrosion-related performance of reinforced concrete with recycled aggregates in the initiation stage (determined by the carbonation and chloride ingress) and propagation stage (determined by the electrical resistivity and cracking) of corrosion. The aspects of interest are not only the porosity of RA but also its effects on the chloride binding, carbonation, electrochemical properties and corrosion cracking development.

Conformity assessment model for mechanical coupling devices and anchors for reinforcing steel for use in concrete structure

The use of mechanical coupling devices and anchors for reinforcing steel for use in concrete structures can simplify the design and construction of reinforced concrete and reduce the amount of reinforcement required. Technical Approvals of these products by suitably qualified organisations are acceptable under Building Regulations and by major specifiers as the appropriate way of assessing non-standard or new and innovative products. Specifiers, manufacturers, traders, and customers increasingly demand certainty in the quality management of mechanical coupling devices and anchors entering the supply chain. The supply chain is extremely complex. The weak traceability systems and pressure on the supply chain to reduce cost have created the environment where risks increase. This unique and comprehensive model describes the technical and assessment requirements for the conformity of mechanical coupling devices and anchors. It covers all stages in the supply chain from the production, assembly, product performance and evaluation of mechanical properties including tensile strength, ductility, permanent elongation (slip), cyclic loading performance and fatigue performance. The essential elements of the quality management system combined with additional requirements on process control, product testing and robust installation methodology are essential and agreed by all relevant sectors of industry.

Behavior of steel clamp confined brick aggregate concrete circular columns subjected to axial compression

Re-use of recycled aggregates in concrete has become a very sustainable solution owing to its environment-friendly and cost-effective nature. Clay bricks are most widely used in construction all over the world. Subsequently, waste generated from the demolition of clay-brick structures is most troublesome. Inherent porosity of bricks compromises the compressive strength of concrete with clay brick aggregates (C-CBA) that has rendered its use in structural concrete for quite some time. With some external clamping pressures, this deficiency can be countered. This study presents an experimental investigation into the use of steel clamps as a strengthening material for C-CBA. Steel clamps are cost-effective, readily available, and very easy to use. C-CBA were tested in two groups depending upon compressive strength: 15 & 35 MPa. Further, 3, 5, and 11 steel clamps were used in each group. Results suggested that steel clamps can effectively be used in enhancing the compressive strength of C-CBA to a level that is acceptable to be used in structural concrete. Increase in peak compressive strength of C-CBA was found to be proportional with the number of steel clamps employed. Three analytical concrete models were used to predict the compressive strength of C-CBA after strengthening. It was concluded that all three analytical models predicted well C-CBA compressive strength for 3-clamp specimens. However, their pre-diction accuracy was highly compromised as the number of steel clamps were increased.

The Relationship between Bond Strength and Critical Penetration Depth of Rust in Reinforced Concrete Structures

Bond strength and critical penetration depth of rust are major factors that affect the service life of reinforced concrete structures. This research endevoured to establish a relationship between the bond strength and critical penetration depth of rust for reinforced concrete structures. There are 7 brands of Cem 1 cement in Kenya available for use in concrete structures. To achieve the desired objective, three Cem 1 cement brands (Cem A, B and C), fine aggregates, coarse aggregates and steel were obtained from the local Kenyan market. The chemical and physical properties of the materials were investigated. For a selected design strength of 25N/mm2, concrete materials were batched by weight and mixed by an electric pan mixer. For each brand of cement 9 cubes of size 150mm * 150mm * 150mm for a compression test, 9 cylinders of 150mm * 300mm for tensile strength and 9 cylinders of 150mm * 300mm for bond strength were cast. After 24 hours, the cast specimens were demoulded and immersed in curing tanks for 27 days. Specimens for compression, split tensile and bond strength were tested at 7,14 and 28 days. From the results, it was observed that the chemical composition of Cem 1 brands in the Kenyan market vary, which affects the hardening properties of concrete. A model for the critical penetration depth of rust in reinforced concrete was proposed by establishing a correlation between the spilt tensile and bond strength and substituting it in the Xu and Shayan model. The proposed and published models compared well. From the proposed model, a relationship between the critical penetration depth and bond strength was established. It was noted that the critical penetration depth increased with an increase in the bond strength of reinforced concrete. The results of this research are expected to contribute to the modeling of the service life of reinforced concrete structures.

Influence of Nanomaterials on Physical Mechanics and Durability of Concrete Composite Piers

Concrete is one of the most widely used engineering materials in the field of civil engineering. With the extensive use of concrete structures, people have paid more and more attention to the durability of concrete structures. Nowadays, the research on the durability of concrete structures has become a hotspot in the field of civil engineering academics.The purpose of this article is to study the influence of nanomaterials on the physical mechanics and durability of concrete composite bridge piers, and to prepare nano-concrete by mixing appropriate number of nanomaterials (nanoSiO2, liquid nanoSiO2 and nanoFe2O3) into the concrete composite bridge piers. The physical mechanics and durability of nano-concrete under the combined action of CO2 erosion and AAR. The results show that the 28-day compressive strength test of nano-concrete is carried out to analyze the effect of the type and amount of nano-materials on the 28-day compressive strength of concrete. The test results show that the concrete has the highest compressive strength when the content of nano-SiO2, liquid nano-SiO2 and nano-Fe2O3 is 2%, 2% and 1%, respectively. The effect of nano-SiO2 on the durability of concrete under the effect of AAR is better than that of liquid nano-SiO2. Therefore, nanomaterials can effectively improve the pore structure of concrete, and participate in the hydration of concrete, thereby improving the durability of concrete such as frost resistance, impermeability, erosion resistance, and corrosion resistance.

Tensile and compressive behavior of self-compacting concrete incorporating PET as fine aggregate substitution after thermal exposure: Experiments and modeling

Examining the response of self-compacting concrete (SCC) to high temperatures contributes greatly to better understand how structures made with this concrete behave in the fire. On the other hand, the use of waste materials in concrete to produce eco-friendly concretes requires knowing and specifying the mechanical features of these concretes for use in concrete structures. Therefore, this research focused on the impact of using polyethylene terephthalate (PET) particles as a substitution for different fractions of fine aggregate (0, 5, 10, and 15%) on the compressive and tensile performance of SCCs for the two cases of no thermal exposure and thermal exposure at 200, 400, and 600 °C. The impact of the volume percentage of PET particles on the freshly mixed SCCs was investigated using the slump flow, flow time, V-funnel, and L-box tests. Afterward, various mechanical features (compression and tension strengths, failure strain, elastic modulus, toughness, strain at peak stress, and stress–strain graph) following thermal exposure were assessed, and some empirical formulas were derived for predicting them. Moreover, the empirical findings of the current work were evaluated against the values estimated by the prediction relationships of different codes, namely ASCE, EN 1994-1-2, and ACI 216. In general, there was proper consistency for lower thermal exposures, while there were underestimations of the empirical values for higher thermal exposures. Based on observations, for the higher exposure temperatures and higher PET substitution level, drops in the mechanical features were more considerable, so that the compressive strength, tensile strength, and elastic modulus decreased by about 60% in the SCC specimen with a PET substitution level of 15% after thermal treatment at 600 °C compared with SCC without PET and heat (reference). At last, based on empirical relationships derived for the mechanical features, a stress–strain relationship was presented to capture the compressive response of SCCs incorporating waste PET particles following exposure to high temperatures. This model has an appropriate correlation with the empirical findings.

DESIGN MODELS OF THE BEARING CAPACITY OF THE SUPPORT SECTIONS OF BASALT-CONCRETE BEAM STRUCTURES

Abstract. In the past decade, structures with non-metallic composite reinforcement (FRP) find more and more widespread use in construction practice, especially in buildings and structures for special purposes. Due to its high strength, resistance to chemical and physical corrosion, dielectric and diamagnetic properties, low weight and low thermal conductivity, FRP is increasingly replacing steel reinforcement. However, the wider use of concrete structures with FRP is constrained by insufficient knowledge of the features of their work, insufficient regulatory support and little experience in operating these facilities. Practice has shown the promise and economic feasibility of using FRP in road, hydraulic engineering, transport construction, in the construction of bridge spans, treatment facilities, chemical and food industry facilities, and foundations in an aggressive soil environment. At the same time, the prospects for using basalt-plastic reinforcement (BFRP) are primarily due to the low cost of the main raw material, basalt fibers, due to the presence of significant reserves of basalt in the world. The basic principles of calculation of bending structures reinforced with FRP, in all foreign standards, as well as in the domestic Manual, are the same as for elements with steel reinforcement. The design models of the bearing capacity of the bearing sections of concrete beams reinforced with BFRP are considered. The bearing capacity of inclined sections of elements with large and medium shear spans should be determined by an inclined crack using variable coefficients , taking into account the real length of a dangerous inclined crack , a significant reduction in tensile stresses in transverse reinforcement to . The bearing capacity of the support sections with small shear spans must be determined as for short cantilevers along an inclined compressed strip between the concentrated force and the support using a variable coefficient . This approach provides satisfactory convergence between the calculated and experimental values of the bearing capacity of inclined sections (coefficient of variation BFRP.

Acid Resistance of Ternary Blended Nanosilica Concrete Incorporating Fly Ash and Alccofine

The use of industrial waste or byproducts as a replacement of cement leads to cost reduction, energy-saving, and is also eco-friendly. Studies reveal that the quaternary and ternary blended concrete may be superior in durability properties when compared with conventional concrete. With the expansion of the use of concrete structures in the sewage system, the corrosion effects of aggressive acid attacks on cement-based construction have gained more significance. The present study aims to investigate the acid resistance of M30 and M60 grades of concrete and the influence of the combination of fly ash, alccofine, and nanosilica in it. The combination of 25% fly ash, 10% alccofine and various percentages of nanosilica (0.5%, 1%, 2%, 3%) have been tested for 28, 56, 90,180 days for acid resistance. From the result, it is seen that the concrete with a combination of fly ash, alccofine, and nanosilica showed better performance in resisting the acid attack on M30 and M60 grades of concrete based on percentage weight loss of specimens over different curing periods.