Properties Of Concrete Structures Research Articles

Investigation on Effects and Properties of Concrete Structure after Exposed to Fire

Abstract: The integrity and strength of the materials used in reinforced concrete structures are highly influenced by their exposure environment. Exposing the building materials to high temperature changes their performance. The change in the performance is a result of the change in the material properties. When subjecting a building material to fire, the occurring damage depends on the severity of the fire in terms ofthe fire temperature and time of exposure. This study investigates the effects of fireexposure on the set of RC beams. Through controlled experiments, varyingtemperatures from 3000C to 7000C areapplied to RC beams, analyzing changes in compressive strength, spalling, andmicrostructure by using rebound hammer,UPV meter and applying two-point loading in UTM. Results indicate a significantreduction in compressive strength with increasing fire temperature, attributed to thermal degradation of cement paste and aggregate. Additionally, changes inmicrostructure, such as pore structure alterations and formation of cracks, are observed. Also, few of RC beams were strengthened using GFRP sheets as a U- shaped wrapping to entire beam and U- shaped wrapping at certain intervals. The strengthened specimens are again tested in UTM for two-point loading, the results of the tests showed the feasibility of rehabilitating RC beams exposed to fire using GFRP plates.U-shaped wrapping to entire beam showed the good performance

Calculation of embodied GHG emissions in early building design stages using BIM and NLP-based semantic model healing

To reach the goals of limiting global warming, the embodied greenhouse gas (GHG) emissions of new buildings need to be quantified and optimized in the very early design stages, during which design decisions significantly influence the success of projects in achieving their performance goals. Semantically rich building information models (BIM) enable to perform an automated quantity take-off of the relevant elements for calculating a whole building life cycle assessment (LCA). However, imprecise type and property information often found in today’s BIM practice hinders a seamless processing for downstream applications. At the same time, the early design stages are characterized by high uncertainty due to the lack of information and knowledge, making a holistic and consistent LCA for supporting design decisions and optimizing performance challenging. In assessing this often vague information, it is essential to consider different levels of element and material information for matching BIM to LCA data. For example, the structural properties of concrete are not yet defined in early design stages and should instead be considered as a range of material options due to different compressive strength classes.This paper presents a novel methodology for automatically matching the coarse information available in BIM models of the early design stages to the respective entries in LCA databases as a basis for a fully automated calculation process of the embodied GHG emissions of new buildings. This approach solves the existing gap in the automation process of manually enriching BIM models and adding information of LCA data and missing layers of vague models. In more detail, the proposed method is based on Natural Language Processing (NLP), using different strategies to increase performance in matching elements and materials from a BIM model to a knowledge database to enrich environmental indicators of commonly used elements’ materials. The knowledge database contains all missing information for LCAs and has different levels of information for a range of several potential design options of elements and materials, including their dependencies. Accordingly, this paper investigates multiple NLP techniques and evaluates the performance of state-of-the-art deep learning models such as GermaNet, SpaCy, or BERT. Following this, the most performant NLP approach is used to provide an automatic workflow for matching Industry Foundation Classes (IFC) elements to the knowledge database, facilitating a seamless LCA in the early stages of design. For five different case studies, the performances of the proposed matching method are analyzed. Finally, one case study is selected to compare the embodied emissions results to those of the conventional process.

Predicting Optimum Content of Eggshell Ash for Best Mechanical and Structural Properties of Concrete

Through an optimization procedure using Minitab software, the optimum waste eggshells-ash powder (WESP) content is used in reinforced concrete. The following percentages of WESP, 0%, 2.5%, 5%, 7.5%, 10%, 12.5%, and 15%, have partially replaced natural fine aggregate. With increasing WWESP, it was discovered that compressive strength, elastic modulus, impact-resisting, and bonding strength between steel bar and concrete increased for WWESP% up to 7.5%. The optimal WESP content was optimized using the Minitab software to be 3.64%.

Key Points for Construction Quality Control of Steel Bar Concrete Structure

In view of the good effect of steel bars in improving the elastic-plastic and flexural properties of concrete structures, combined with the good compressive strength of concrete, steel bars in the traditional reinforced concrete column and shear wall structures can greatly improve the performance of the main stress-bearing structures of super high-rise buildings. In order to clarify the key points of construction quality control of steel bar concrete structure, the control points are analyzed by theoretical analysis method combined with an engineering example. The results show that it is feasible to replace the traditional solid web section steel with the scattered steel bars to solve the difficult problem of the layout of the stirrups and longitudinal bars of the solid web section steel reinforced concrete column, and the ear plate connection of the steel bars is feasible; BIM Technology can realize the accurate positioning of steel bars and greatly improve the construction quality of steel bar concrete structures; During the construction process, it is very important to strictly control the verticality of steel bars, the spacing between steel bars, the spacing between steel bars, the distance from the outside of steel bars to the reinforcement at the column edge, and strictly control the quality of formwork installation and concrete pouring to ensure the quality of steel bar concrete structure.

Experimental Study on the Property and Mechanism of the Bonding Between Rubberized Concrete and Normal Concrete

Scholars have studied the impact of rubber particles (RPs) on the performance of the concrete and the research topics have covered all the mechanical properties and durability of normal concrete (NC). Recently, scholars have turned their research interest to the structural properties of concrete. However, there are few experimental studies on the bonding properties of RC to NC. The RPs have both positive and negative impacts on the bond performance. On one hand, RPs can reduce the shrinkage of concrete, resulting in reduced shear stress and tensile stress near the bonding boundary. On the other hand, RPs cause a reduction in the overall strength of concrete, resulting in the poor mechanical performance of the interface transition layer between the two concrete. The test results of this study show that the bonding splitting tensile strength between freshly mixed RC to aged NC first increases and then decreases with the rise of the RPs content in the RC, and the bonding splitting tensile strength reaches the peak when the RPs content is 10%. The bonding splitting tensile strength between the NC and the RC mixed with 3–5 mm RP is higher than that between the NC and the RC mixed with 1–3 mm RPs. When mixed with modified RPs, the bonding splitting tensile strength between the RC and the NC is improved. Applying an interfacial agent (a cement slurry or an epoxy) on the old concrete bonding surface can significantly improve the bonding splitting tensile strength. The results of non-repeated two-way ANOVA show that the content of the RPs and the type of the interfacial agent have significant effects on the bond splitting tensile strength, while the size and modification of the RPs have no significant effects on the bond splitting tensile strength.

Effect of Air Entrainment on the Properties of Concrete Structures Using Hydrogen per Oxide as an Admixture

Abstract: Air entrained concrete can be produced by introducing suitable air-entraining agent, one such commonly available material in India is hydrogen peroxide which is being used in my experimental work. The primary objective of this study to find the appropriate amount of hydrogen peroxide (3%) for strength and density, water absorption, other properties of concrete. For which the amount of H2O2 is varied from 0 %, 2.5%, 5%, and 7.5% H2O2 by weight of 100 kg of cement. The test which was carried out in the experimental work were density, workability, strength, water absorption, the slump of air-entrained concrete and aggression resistance of air-entrained concrete against an acid attack such as H2SO4, etc. Total 48 No. of the concrete cube was cast for the experimental work. The result of the experiment work shows if H2O2 is used in the range of 5-6% it will provide better workability, less water absorption and improved resistance against acid attack with acceptable 5-7% decrease in compressive strength

Effect of Concrete Admixtures on Structural Properties and Corrosion Resistance of Steel Reinforcements

Concrete structural properties are compromised largely due to corrosion susceptibility of steel reinforcements. This results in weakening and eventual failure of structures. Several strategies have been employed in past to control corrosion and increase mechanical strength of concretes, in particular for structural applications. In this study, fly ash and polypropylene fibers were utilized as the admixtures for preparation of concrete blocks with variable water-cement (w/c) ratios i.e. 0.45, 0.5 and 0.65. Three different grades of cements were selected in this study namely OPC 43, OPC 53 and sulfate resistant one. Also, two different steel alloys were used i.e. ASTM-615 and ASTM-706, since both of them are very common reinforcement materials (rebars). The curing time of 56 consecutive days was employed before testing and characterization. The results suggest remarkable improvement in the mechanical properties of blocks upon the incorporation of admixtures. However, rebars exhibited highest corrosion rate in the presence of OPC 43 cement at w/c ratio of 0.65.

Green Concrete: Environment Friendly Solution

Green concrete is a type of concrete. It is a sustainable material used for the construction of reinforced concrete structures. Green concrete is different compared to normal concrete. Nowadays, it plays a very good role in the construction of structures. It is subjected to very low energy consumption and low resource consumption. Green concrete is a very good material for sustainable development. Concrete is made from the replacement of substituent ingredients such as cement and aggregates. In this waste materials such as agricultural or industrial wastes are placed during manufacture to produce a new concrete. Green concrete is popular worldwide due to its extraordinary properties and applications. This paper mainly deals with the importance of green concrete and its applications, advantages, and disadvantages. The results are varying for based on different structures. So, we can get all characteristics and properties of concrete structures and know their strength.

Green Concrete: Environment Friendly Solution

Green concrete is a type of concrete. It is a sustainable material used for the construction of reinforced concrete structures. Green concrete is different compared to normal concrete. Nowadays, it plays a very good role in the construction of structures. It is subjected to very low energy consumption and low resource consumption. Green concrete is a very good material for sustainable development. Concrete is made from the replacement of substituent ingredients such as cement and aggregates. In this waste materials such as agricultural or industrial wastes are placed during manufacture to produce a new concrete. Green concrete is popular worldwide due to its extraordinary properties and applications. This paper mainly deals with the importance of green concrete and its applications, advantages, and disadvantages. The results are varying for based on different structures. So, we can get all characteristics and properties of concrete structures and know their strength.

Effect of Changing Cement Grade on the Properties of Structural Concrete

Many research efforts have been carried out, in a quest to produce mix design information that will guide the concrete and construction industry on how to achieve different concrete strengths, using the different grades of cement available. This is with a view to arresting the rampant collapse of buildings in Nigeria. The work presented in this paper is the result of investigation carried out to determine effects of changing cement grade, while casting a structural member, on the strength behaviour of the concrete. Two types of cement grades: 32.5 R and 42. 5 R were used for this research. In this investigation, the chemical and physical properties of the cement were determined. Consistency and setting times of mortar specimens from the two cement grades were also determined. Concrete samples made from the two cement grades 32.5 R and 42.5 R were evaluated for workability, density, compressive and tensile strengths at water/cement ratios of 0.40, 0.50 and 0.60. The results showed that the cement grade 42.5 consistently developed higher densities at all the water/cement ratios considered. This may be as a result of unforeseen additional dead load at the design stage, which would now amount to underestimation of dead load and thus design load. The results also showed that at higher water/cement ratios, the cement grade 42.5 R has densities exceeding the 2400 kg/m3 recommended by BS 8110. Furthermore, the concretes produced with cement grades of 32.5 R and 42.5 R have different strength development pattern and developed different 28-day compressive strength. Thus, it can be concluded that the action of changing the cement grade during concreting, for the same structural member is not supported by the national code, and will not result in safe and durable concrete.
 Keywords: Cement grades, Compressive strength, Density, Portland limestone cement, Tensile strength, Workability

Fire resistance of corroded high-strength structural concrete

Purpose The exposure of reinforced concrete structures such as high-rise residential buildings, bridges and piers to saline environments, including exposure to de-icing salts, increases their susceptibility to corrosion of the reinforcing steel. The exposure to fire can further deteriorate the structural integrity of corroded concrete structures. This combined effect of corrosion damage and fire exposure is not generally addressed in the structural concrete design codes. The synergistic combination of the effects of corrosion and fire forms the basis of this paper. Design/methodology/approach Concrete beam specimens with different strengths were prepared, moist-cured and corroded with impressed current. Later, they were “crack-scored” for corrosion evaluation, after which half were exposed to fire in a gas kiln. The fire damage was evaluated by nondestructive testing using ultrasonic pulse velocity. Next, all specimens were tested for residual flexural strength. They were then autopsied, and the level of corrosion was determined based on mass loss of the reinforcement. Findings For corroded specimens, the flexural capacity loss because of fire exposure increases as the compressive strength increases. In general, the higher the crack score, the higher the corresponding mass loss, unless some partial/segmental debonding of the reinforcement occurred. The degree of corrosion increases with decreasing compressive strength. The residual moment capacity, based on analytically determined capacities of uncorroded and nonfire-exposed beams, was significantly lower than those of uncorroded beams exposed to fire. Originality/value The combined effects of corrosion and fire on the mechanical properties of structural concrete are relatively unknown, and no guidance is available in the existing design codes to address this issue. Accordingly, the findings of the paper are expected to be valuable to both researchers and design engineers and can be regarded as the initial investigation on this topic.

Structural Properties of Concrete with the replacement of Natural Sand by Manufactured Sand

Structural Properties of Concrete with the replacement of Natural Sand by Manufactured Sand

Performance of concrete beams reinforced using banana fiber bars

This study aims to analyze the performance of using banana fiber bars on the mechanical properties of reinforced concrete beams. In order to achieve this aim, several experimental studies on the utilization of banana fibers to optimize the strength and properties of concrete structures are performed. The experimental studies are conducted based on a group of seven specimens of concrete beams with different aspects to: (1) determine the most critical factors affecting the performance of flexure behavior of reinforced concrete (RC) beams using banana fiber bars, (2) study the mix design aspects of the banana fiber bar in RC, (3) study the behavior of banana fiber bars on concrete behavior, (4) study the effect of banana fiber with different concrete grades. Results show that using banana bars as a reinforcement material can significantly increase the ability to resist cracking and spalling in concrete beams. Hence, using banana bars as a main reinforcement in concrete give more flexural strength with approximately 25 % compared to plain concrete.

OBJECTS OF TRANSPORT INFRASTRUCTURE: EXPERIENCE OF SCIENTIFIC SUPPORT IN CONSTRUCTION WITHIN THE “QUALITY” CONCEPT IMPLEMENTATION

Introduction. The paper deals with the issues related to the implementation of the “quality” concept in the construction of reinforced concrete transport facilities linked with the scientific support during design and construction. Nowadays this problem particularly relevant in the context of the modern construction solutions, combined with the need to obtain the required properties of concrete structures and ensure the economic feasibility of construction. The aim of the research is to generalize and systematize the main methods and techniques of concrete works, which minimize the defects and cracks while the construction of transport infrastructure.Materials and methods. On the example of different technologies used in the Russian construction over last 10 years, the authors demonstrated the developed methods of obtaining high quality concrete products taking into account tested and proved modern building materials.Results. The results of the research formed the basis of the projects, technological regulations for the production, specifications and standards of organizations, guidelines. Moreover, the results also allowed implementing the concept of “quality” in transport construction based on obtaining defect-free reinforced concrete structures with specified properties, taking into account the use of modern building materials.Discussion and conclusions. The research allows carrying out construction of various massiveness and extent. The obtained results form the basis of construction technology of other industrial and civil construction objects with reinforced concrete application. The paper is interesting and useful for specialists in providing defect-free construction of reinforced concrete building structures, for engineering and technical staff. The authors dedicate the research to the memory of Professor and Doctor of Technical Sciences, A.R. Solovyanchik (1938-2019).

Microbially Induced Calcium Carbonate Precipitation (MICP) and Its Potential in Bioconcrete: Microbiological and Molecular Concepts

In this review, microbiological and molecular concepts of Microbially induced Calcium Carbonate Precipitation (MICP) and their role in bioconcrete are discussed. MICP is a widespread biochemical process in soils, caves, freshwater, marine sediments and hypersaline habitats. MICP is an outcome of metabolic interactions between diverse microbial communities with organic and/or inorganic compounds present in environment. Some of the major metabolic processes involved in MICP at different levels are urea hydrolysis, denitrification, dissimilatory sulfate reduction and photosynthesis. Currently, MICP directed by urea hydrolysis, denitrification and dissimilatory sulfate reduction has been reported to aid in development of bioconcrete and demonstrated improvement in mechanical and structural properties of concrete. Bioconcrete is a promising sustainable technology in reducing the negative environmental impacts due to CO2 emission from construction sector and as well as in terms of economic benefits by way of promoting self-healing process of the concrete structures. Among the metabolic processes mentioned above, urea hydrolysis is the most applied in concrete repair mechanisms. MICP by urea hydrolysis is induced by a series of reactions driven by urease (Ur) and carbonic anhydrase (CA). Catalytic activity of these two enzymes depends on diverse parameters, which are currently being studied under laboratory conditions to understand the biochemical mechanisms involved and their regulation in microorganisms. It is clearly evident that microbiological and molecular components are essential to improve the process and performance of bioconcrete.

Investigation of the Role of Nano-Titanium on Corrosion and Thermal Performance of Structural Concrete with Macro-Encapsulated PCM.

The present study aims to investigate the impact of thermal energy storage aggregate (TESA) and nano-titanium (NT) on properties of structural concrete. TESA was made of scoria encapsulated with phase change materials (PCMs). Coarse aggregates were replaced by TESA at 100% by volume of aggregate and NT was added at 5% by weight of cement. Compressive strength, probability of corrosion, thermal performance, and microstructure properties were studied. The results indicated that the presence of TESA reduced the compressive strength of concrete, although the strength was still high enough to be used as structural concrete. The use of TESA significantly improved the thermal performance of concrete, and slightly improved the resistance of corrosion in concrete. The thermal test results showed that TESA concrete reduces the peak temperature by 2 °C compared to the control. The addition of NT changed the microstructure of concrete, which resulted in higher compressive strength. Additionally, the use of NT further enhanced the thermal performance of TESA concrete by reducing the probability of corrosion remarkably. These results confirmed the crucial role of NT in improving the permeability and the thermal conductivity of mixtures containing PCM. In other words, the charging and discharging of TESA was enhanced with the presence of NT in the mixture.

Effects of environmental temperature and age on the elastic modulus of concrete

Concrete mechanical properties change constantly with age, temperature, humidity and the other environmental factors. This research studies the effects of temperature and age on the development of concrete elastic modulus by a series of prism specimens. Elastic modulus test was conducted at various temperatures and ages in the laboratory to examine the effects of temperature and age on it. The experimental results reveal that the concrete elastic modulus decreases with the rise of temperature but increases with age. Then, a temperature coefficient K is proposed to describe the effects of temperature and validated by existing studies. Finally, on the basis of K, analytical models are proposed to determine the elastic modulus of concrete at a given temperature and age. The proposed models can offer designers an approach to obtain more accurate properties of concrete structures through the elastic modulus modification based on actual age and temperature, rather than using a value merely based on laboratory testing.

Partial Replacement of Cement Concreete with Biological Green Waste

Bagasse ash (BA), the residue obtained after the burning of sugarcane bagasse as a fuel, has pozzolanic properties with potential use as a supplementary binding material (SCM). Use of Bagasse ash (BA) as a mineral admixture needs to be established, especially in India, where sugarcane cultivation is widespread, to reduce land required for its disposal and cement consumption in construction industry. Hence, to encourage commercial use ofBA with minimum processing, an evaluation of the physical, chemical and morphological characteristics of a locally available BA and its effect, as SCM on properties of structural concrete was taken up.This research work describes the feasibility of using the Fly Ash (FA) Rice Husk Ash (RHA) and Sugarcane Bagasse Ash(SCBA) waste in concrete production as a partial replacement of cement. This present work deals with the effect on strength and mechanical properties of concrete using Triple blending of cement concrete using FA, RHA and SCBA instead of cement. The cement has been replaced by rice husk ash, accordingly in the range with 0%, 10%, 20% and 30% by weight. Concrete mixture of M20 and M25 and M30, were produced, tested and compared in terms of compressive strengths with the Conventional concrete. These tests were carried out to evaluate the mechanical properties for the test results of7, 14, 28, 56 and 90 days for Compressive strengths and Tensile & Flexural Strengths at 28 days. The durability aspect of the samples for Acid attack, Alkaline attack and Sulphate attack was also tested. The result indicates that the FA, RHA and SCBA improve the Compressive Strength and durability of concrete.

Corn steep liquor as a nutritional source for biocementation and its impact on concrete structural properties.

Microbial-induced carbonate precipitation (MICP) has a potential to improve the durability properties and remediate cracks in concrete. In the present study, the main emphasis is placed upon replacing the expensive laboratory nutrient broth (NB) with corn steep liquor (CSL), an industrial by-product, as an alternate nutrient medium during biocementation. The influence of organic nutrients (carbon and nitrogen content) of CSL and NB on the chemical and structural properties of concrete structures is studied. It has been observed that cement-setting properties were unaffected by CSL organic content, while NB medium influenced it. Carbon and nitrogen content in concrete structures was significantly lower in CSL-treated specimens than in NB-treated specimens. Decreased permeability and increased compressive strength were reported when NB is replaced with CSL in bacteria-treated specimens. The present study results suggest that CSL can be used as a replacement growth medium for MICP technology at commercial scale.

Study on concrete with rice husk ash

Rice husk ash (RHA) possesses high pozzolanic activities and very suitable as partial replacement of cement in concrete. This paper presents a comparative study on use of RHA as partial replacement of cement in concrete specimens. Review of the researches on physical, mechanical and structural properties of concrete containing RHA as partial replacement of ordinary Portland cement was included in this paper. Simultaneously, concrete specimens were tested with different percentages of RHA as replacement of cement content and with different w/c ratio. Compressive strength, flexural strength, tensile strength and slump test were carried out to evaluate the appropriateness of using RHA in concrete. The replacement of cement by RHA in structural concrete represents a good alternative in as economical as strength consideration of concrete, even without any kind of processing and found environmental benefits related to the disposal of waste. Review of researches shows that RHA-used concrete can resist chloride penetration more than normal ordinary Portland cement concrete.