Strength Characteristics Of Concrete Research Articles

Experimental Investigations on Mineral Admixtures and Steel Fibers in High Strength Concrete

In the process of manufacturing of concrete sand is the most commonly used fine aggregate. The main sources for the natural sand are river beds. These characteristic assets are getting depleted because of over abuse and defilement by chemicals and waste from nearby industries. The waste generated from the demolition of existing structures for various reasons causes great concern and ecological issues. In this project our main objective is to study the influence of partial replacement of F.A with recycled fine aggregate and to compare it with the compressive strength and workability of high strength M60 concrete. We are also trying to replace the various percentages of recycled fine aggregate to study the tendency of the Characteristic strength of concrete.

Investigation on Interfacial Bond Strength Characteristics of Concrete Filled in Galvanized Steel Tubes Utilizing Statistical Analysis and Advanced Prediction Techniques

Investigation on Interfacial Bond Strength Characteristics of Concrete Filled in Galvanized Steel Tubes Utilizing Statistical Analysis and Advanced Prediction Techniques

Prediction of the Properties of Vibro-Centrifuged Variatropic Concrete in Aggressive Environments Using Machine Learning Methods

In recent years, one of the most promising areas in modern concrete science and the technology of reinforced concrete structures is the technology of vibro-centrifugation of concrete, which makes it possible to obtain reinforced concrete elements with a variatropic structure. However, this area is poorly studied and there is a serious deficiency in both scientific and practical terms, expressed in the absence of a systematic knowledge of the life cycle management processes of vibro-centrifuged variatropic concrete. Artificial intelligence methods are seen as one of the most promising methods for improving the process of managing the life cycle of such concrete in reinforced concrete structures. The purpose of the study is to develop and compare machine learning algorithms based on ridge regression, decision tree and extreme gradient boosting (XGBoost) for predicting the compressive strength of vibro-centrifuged variatropic concrete using a database of experimental values obtained under laboratory conditions. As a result of laboratory tests, a dataset of 664 samples was generated, describing the influence of aggressive environmental factors (freezing–thawing, chloride content, sulfate content and number of wetting–drying cycles) on the final strength characteristics of concrete. The use of analytical techniques to extract additional knowledge from data contributed to improving the resulting predictive properties of machine learning models. As a result, the average absolute percentage error (MAPE) for the best XGBoost algorithm was 2.72%, mean absolute error (MAE) = 1.134627, mean squared error (MSE) = 4.801390, root-mean-square error (RMSE) = 2.191208 and R2 = 0.93, which allows to conclude that it is possible to use “smart” algorithms to improve the life cycle management process of vibro-centrifuged variatropic concrete, by reducing the time required for the compressive strength assessment of new structures.

Experimental Study on Partial Replacement of Cement by PROSOPIS JULIFLORA in Concrete

In recent days, the prosopisjuliflora (seemaikaruvelam) develops in a haphazard way in our lands and acts as a major environmental pollutant. In this project our main objective is to study the influence of partial replacement of cement with prosopisjuliflora ash, and to compare it with the compressive strength and workability of ordinary M20 concrete. We are also trying to replace the various percentages like 10%, 15%, and 20% of prosopisjuliflora ash against cement to study the tendency of the Characteristic strength of concrete.

Probabilistic effect of non-potable mixing water on characteristic strength of concrete

Across the world, the acceptance criterion for concrete made with non-potable water (SA) is stipulated for mean strength with reference to similar concrete made with potable water (SP). The basis for the strength design of concrete is the characteristic strength. The effect of the acceptance criteria on the characteristic strength of SA and SP was examined using statistical simulations, for the first time. It was found that, compared with a two-sample set, using a three-sample set would improve the characteristic strength of SA. A higher allowable ratio between the means of SA and SP and a lower deviation of individual samples from the mean would improve the characteristic strength of SA. The effect of the coefficient of variation (CoV) of the original population on the characteristic strength of SA varied. On the one hand, a higher CoV reduced the characteristic strength of SP, thereby increasing the probability of SA strength being higher than SP strength. On the other, a higher CoV of SP meant a wider spread of the samples and that could increase the CoV of SA, thereby reducing the characteristic strength of SA. Probabilistic charts were developed for the characteristic strengths of SA and SP for different combinations of the aforementioned variables, with guidance for practical application.

ВЛИЯНИЕ МИКРОБНОЙ КАРБОНАТНОЙ БИОМИНЕРАЛИЗАЦИИ НА ПРОЧНОСТЬ ЦЕМЕНТНОГО КАМНЯ

An intensive urbanization, renovation of housing stock, emergencies and natural disasters lead to difficulties arise in the management of concrete waste. In this regard, recycling construction and demolition waste is an effective solution for saving material and energy resources in the construction field. The article discusses the possibility of optimizing the structure and increasing the strength characteristics of concrete by selecting the grain composition of the aggregate based on recycled concrete scrap and the use of microbial carbonate biomineralization. The distribution of aggregate grains (0.315–5 mm), which is crushed ordinary stone SKTs, into fractions has an impact on the nature of the formation of contact zones between the cement matrix and the aggregate. This determines a decrease in strength characteristics according to the following relationship: with a decrease in the size of the aggregate, the strength of cement concrete increases. The addition of a biomineralizing solution to the cement mixture leads to improved adhesion of the cement paste to the surface of the aggregate due to the formation of additional crystallization centers in the area of the contact layer, clogging of the pore space with induced new formations, which increases the strength of concrete, both at brand age and in the forecast period.

To Study the Strength Characteristics of Concrete Using Mineral Admixture

Aside from the combustion of fossil fuels, the cement making business emits carbon dioxide. The global cement industry accounts for around 7% of greenhouse gas emissions into the earth's atmosphere. To address the environmental impacts connected with cement manufacturing, alternative concrete binders must be developed. Another important environmental concern is the extraction of natural resources such as sand from river bottoms. As a result, substantial study into the use of cement substitutes, including several waste materials and industrial byproducts, is continuing. Bamboo leaf ash was utilised as a partial replacement for cement and fenugreek as an addition in this study, and it was compared to standard concrete. The considered bamboo leaf ash was 5%, 10%, 15% by weight of cement for M25 grade concrete and 5% of fenugreek powder as additive for every mix [1]. Additionally, an experimental investigation of the effects of using bamboo leaf ash in place of some of the cement and fenugreek powder as an additive on the performance of concrete in terms of compressive strength and flexure strength. Concrete is cast for the experimental study, and cement is partially substituted with bamboo leaf ash by weight of cement and fenugreek powder as an addition. Because the inclusion of bamboo leaf ash and fenugreek powder works as a binding ingredient in the concrete, the compressive and flexural strength increases. Finally, the compressive and flexural strengths for the combination of bamboo leaf ash as a partial replacement and fenugreek powder as an addition powder in concrete are investigated for the best results obtained from the aforementioned experiment.

Compressive Strength Characteristics of Concrete and Mortar According to Wood-Based Biochar Replacement Ratio

Compressive Strength Characteristics of Concrete and Mortar According to Wood-Based Biochar Replacement Ratio

Tensile Strength Characteristics of Concrete Blocks Using Abaca Fiber

The role of concrete as a material to strengthen buildings with long-term durability is an important goal of construction. Abaca fiber has the potential to strengthen concrete network materials. The purpose of this study was to identify the tensile strength characteristics of concrete using abaca fiber. The method used is through experimental studies in the laboratory to test the tensile strength of concrete blocks. This research was carried out in the Materials and Structures Laboratory using five stages. The results of this research have found that the potential of abaca fiber as a binder for cylindrical concrete aggregates with a certain fiber length and fiber volume allows the concrete to be stronger and have high resistance compared to ordinary concrete. In the split tensile strength section, the results obtained show that abaca fiber concrete provides stronger resistance than ordinary concrete if the fiber length is 50mm high and the fiber volume is at 0.15%. The same results are shown in the flexural strength of the beam without reinforcement, namely concrete with abaca fiber has strong toughness if the fiber length content used is 50mm and the fiber volume is at 0.15%. Overall, abaca fiber is very influential on the resistance of concrete if the fiber length and fiber volume are at a certain point, namely 50mm and 0.15%

Carbon-footprint based concrete proportion design using LSTM and MOPSO algorithms

Artificial intelligence can design more sustainable concrete mixtures to reduce costs and CO2 emissions. In this paper, a concrete mix ratio design method based on deep learning algorithm and meta-heuristic algorithm is proposed. The main parameters that control and affect the strength of the concrete were selected as input variables, including Cement, Fly ash, Blast furnace slag, Water, Superplasticizer, Coarse aggregate, and Fine aggregate of concrete per unit volume. The compressive strength of concrete as output variables, a long short-term memory network model was developed to predict and explain the compressive strength characteristics of concrete. Sensitivity analysis showed that cementitious material and concrete age are the most important factors affecting the compressive strength of concrete. This is in good agreement with the relevant theoretical research. Taking the trained prediction model as the objective function of compressive strength of concrete mix ratio design, combined with the concrete material cost and carbon emission from cradle to gate, the multi-objective particle swarm optimization algorithm is used to optimize the proportion of each component of concrete to find the optimal mix ratio under specific conditions. The results show that the long short-term memory network can predict the compressive strength of concrete with high accuracy, and replace the traditional explicit mathematical expression to simulate the complex nonlinear relationship of multiple parameters. The established algorithm can calculate the Pareto optimal solution set according to the objective function, and obtain the optimal mix ratio with the least material cost and carbon footprint while meeting the compressive strength required by the project. The results of this work provide an intelligent and efficient design method for determining concrete mix ratio design, which can provide a reference for practical engineering applications to a certain extent.

Microstructure Analysis of Concrete with Pulverized Used Foundry Sand as Mineral Admixture

There are several mineral admixtures used in concrete to enhance its properties. Pulverized used foundry sand (PUFS) is a recently introduced patented material into the mineral admixture category. The pulverized used foundry sand is made from the discarded waste foundry sand generated from the foundry operations. In this paper, an effort is made to investigate the different micro structure analysis methods employed in the elemental study of mineral compounds and to accentuate the strength enhancement mechanism of the pulverized used foundry sand in concrete. Representative samples obtained from concrete comprising pulverised used foundry sand content at 0%,5%,10%,15%, and 20% of the cement content by weight as per standard practice were tested with EDX (Energy Dispersive X-ray), SEM (Scanning Electron Microscope). EDX, SEM and XRD (X-Ray Diffraction) analysis were conducted on pulverized used foundry sand and silica fume for studying the various elements and its proportions. From the SEM images it is ascertained that the addition of PUFS increases the quantities of CSH (Calcium Silicate Hydrate) and Calcite in the concrete. As an outcome, the microstructure analysis of concrete having different proportions of PUFS portrays how the PUFS as a mineral additive affects the strength characteristics of concrete that contains it.

Soft computing techniques to predict the compressive strength of groundnut shell ash-blended concrete

Using groundnut shell ash (GSA) as a component in concrete mixtures is a viable approach to achieving sustainability in building practices. This particular kind of concrete has the potential to effectively mitigate the issues associated with high levels of CO2 emissions and embodied energy, which are primarily attributed to the excessive utilization of cement in conventional construction materials. When GSA is utilized as a partial replacement for cement, the strength characteristics of concrete are influenced not only by the quantity of GSA replacement but also by several other factors, including cement content, water-to-cement ratio, coarse aggregate content, fine aggregate content, and curing length. This work demonstrates a predictive model for the compressive strength (CS) of GSA mixed concrete using ML methods. The models were constructed with 297 datasets obtained from published literature. These datasets included various input variables such as cement content, GSA content, fine aggregate content, coarse aggregate content, water need, and curing duration. The output variable included in the models was the CS of concrete. In this study, a set of seven machine learning algorithms was utilized as statistical assessment tools to identify the most precise and reliable model for predicting the CS of GSA mixed concrete. These techniques included linear regression, full quadratic model, artificial neural network, boosted decision tree regression, random forest regression, K nearest neighbors, and support vector regression. The present study evaluated several machine learning models, and it was shown that the random forest regression model had superior performance in forecasting the CS of GSA mixed concrete. The train data’s R2 is 0.91, with RMSE of 2.48 MPa. Similarly, for the test data, the R2 value is 0.89, with an RMSE of 2.42 MPa. The sensitivity analysis results of the random forest regression model indicate that the cement content primarily drives the material’s CS. Subsequently, the curing period and GSA content significantly impact the CS. This work systematically evaluates the CS of GSA mixed concrete, contributing to the existing body of knowledge and practical implementation in this domain.

Experimental Investigation on Strength Characteristics of Concrete by Partial Replacement of Cement with Sodium Silicate

The basic material used for advancement in concrete is often composed of essential limiting materials such as concrete, fine aggregate, coarse aggregate, and water. Solid waste management is one of the most important tactics in today's total collection situation. As expected, an effort was made to decrease usual resources and conserve the environment. To increase the strength of concrete, Sodium Silicate (Na2SiO3) is added in the amounts of 5%, 10%, 15%, 20%, 30%, 35%, 40%, and 45% by weight of cement. The study entails investigating the effect of adding sodium silicate in various quantities on setting time, workability, and compressive strength. When sodium silicate is added to concrete, there is a significant increase in workability and durability, according to the literature. Setting time and compressive strength were studied, and it was shown that using sodium silicate as a substitute for cement improves workability and durability. When Sodium Silicate is added to concrete buildings, the content of calcium hydroxide drops while the content of calcium silicate hydrate (C-S-H gel) increases as compared to untreated concrete structures. Because the expansive and insoluble C-S-H gels partially fill the micro-pores, micro-voids, and micro fractures in the concrete structures, the sodium silicate-based concrete sealers are basically surface hydrophilic agents. Because of the production of C-S-H gel, the amount of water in the mix is reduced as compared to a traditional one, as is the initial setting time. Sodium Silicate is transformed into a binding agent as well as a superplasticizer after the reaction.

Method for identifying the strength characteristics of concrete of a reinforced concrete crossbar during heating under conditions of fire

This paper proposes a method that makes it possible to study the patterns of changes in the concrete strength of reinforced concrete crossbars depending on the heating temperature under fire conditions by interpreting the results of their standard fire tests. For the implementation of this method, it is proposed to use similar data obtained using mathematical modeling based on the finite element method and given material properties, including the curve of concrete strength reduction recommended by the guidelines, as data included in the set of measurement results during fire tests depending on temperature. Such data are time dependences of temperature indicators at individual cross-section points and time dependence of the maximum deflection of the crossbar. The article proposes an interpolation method that makes it possible to set the temperature at any point of the section based on the approximation of the isotherms by parabolas with a variable indicator of their power. A method based on the mathematical interpretation of temperature indicators obtained using the proposed interpolation method and the curve of the dependence of the maximum deflection on time using a deformation model for describing the stress-strain state is proposed to identify the dependence of the concrete strength of reinforced concrete crossbars. The work also shows that the results obtained using the proposed method of identifying concrete strength reduction coefficients are adequate as their relative error is on average no more than 7 %. Based on the results, the possibility of its application to study the regularities of the decrease in the strength of reinforced concrete crossbars under fire conditions has been proven

The comparison of the experimental investigations of strength characteristics of conventional and bacterial concrete

Conventional concrete (CC) is the greatest used construction material in the world, especially in aggressive environments. This is due to the element's size and shape. The world's consumption of concrete is on the order of 5.5 billion metric tons a year. The advancement of concrete technology, as well as the development of materials and mechanisms, has resulted in increased strength needs. Maintenance, repair, and rehabilitation of present concrete structures challenge a lot of difficulties, resulting in significant expenditure. Concrete is vulnerable to microcracks creation and has extremely undesirable pores. Hence, there is an urgent need to pay more attention to improving the properties of concrete in terms of strength. The effective remedy for the closure of cracks is Bacterial concrete (BC) which will constantly be in concrete and this phenomenon is called Microbiologically Induced Calcite Precipitation (MICP). The urease enzyme enables the deposition of calcium carbonate (CaCO3) with the advantage of bacteria. The bacterial remediation technique exceeds added techniques. The examinations were carried out with variety an of quantitative evaluations of the optimal concentration of bacterial cells to be collected in concrete. Based on the state-of-the-art evidence obtainable in the literature, in these existing soundings two different bacterial illustrations specifically Bacillus Megaterium (BM) and Bacillus Subtilis (BS) are measured in concentrations of 104, 105, and 106 cells/ml of mixing of water. The optimum amount of cell concentration of bacteria is created to be 104 cells/ml for BM and 105 cells/ml for BS based on the results of compressive strength. This investigation is carried out on strength-related properties such as compressive strength, splitting tensile strength, and flexural strength. It is determined that BM and BS bacteria can be firmly used for refining the performance and strength characteristics of concrete.

Prospects of the use of high-tension fiber concrete as the basis for the formation of protective shelters and fortification structures during the russian-ukrainian war

This article analyzes the current state of protective shelters and fortification structures, foresees the modern possibilities of using fastening and basalt-type structures to increase the stability of concrete fortifications both during the construction of buildings for the protection of the civilian population, and for the creation of dugouts, fortifications and fire structures for the protection of personnel in accordance.
 Studies of the physical and mechanical properties of fiber concrete modified with plasticizers and active mineral additives using basalt and polypropylene fibers have shown that their introduction has a positive effect on the strength characteristics of concrete. The compressive strength of fiber concrete at day 28 increases from 61.4 to 77.0 and 96.2 MPa, respectively, and the flexural strength from 7.4 to 12.7 and 13.8 MPa, respectively.
 For the production of reinforced concrete protective materials, it is more effective to create hybrid high-strength concrete using fibers of different nature, followed by the formation of a reinforced concrete slab of the appropriate size. At the same time, the standard provides for the manufacture of prefabricated reinforced concrete elements of fortification structures and platoon support points of wall panels of the SP-1, SP-2 type and floor slabs PP-1 with a thickness of at least 300 mm from heavy concrete of strength class C32/40 with the use of plasticizers and active chemical additives.
 However, when using the obtained hybrid fiber concrete with strength class C50/60 and using a reinforcing mesh according to the calculated data, it is possible to reduce the effective thickness of the fiber concrete slab to 27.5 cm installation of fortification.
 The use of a reinforcing mesh in a complex with basalt fiber provides increased resistance of fiber concrete to the action of a high-speed impact due to an increase in the density of the cementing matrix as a result of a decrease in water consumption, as well as due to spatial three-dimensional reinforcement with dispersed basalt fiber. As a result of the mutual combination of the strength characteristics of the concrete matrix at the micro- and macro-levels in hybrid fiber concrete, it is possible to reduce the thickness of reinforced concrete elements and reduce the weight of the protective structure while meeting the requirements of the standards for such fortifications. An increase in the strength of cement stone occurs due to a decrease in the concentration of stresses in places of local stresses and a redistribution of energy throughout the volume of the material.
 The conducted studies of modern hybrid high-strength concrete with basalt fiber create new opportunities for the creation of protective concrete fortifications and fortification structures.

In Situ Strength vs. Potential Strength of Concrete: Proposal of a New Procedure for the Assessment of Excess Voidage

Concrete cores extracted from the same structural element may show variations in strength resulting from a lack of homogeneity and variations in the grade of compactness. This paper, while accounting for such variability, introduces a new formulation to assess both in situ and the potential characteristic strength of concrete. The first part addresses the Concrete Society report 11 on formulations and the formulation introduced by the author that considers new coefficients that take into account the addition of water to the cement mixer and the influence of excess voidage. The second part describes a case study in that the procedures were applied to an experimental campaign carried out on two series of cores. The visual means method proposed by report 11 is applied for excess voidage assessment to the first series of cores, while a computed axial tomography (CAT) scan allowing a direct estimate of the percentage of voids in different sections is applied to the cores of the second series. Results show noticeable variations in the percentage of voids within the same drilling. Moreover, the proposed formulation can estimate the actual value of both the in situ and potential characteristic strengths of concrete with a reasonable degree of approximation. Finally, a computed axial tomography (CAT) scan leads to extremely precise results, making it possible to evaluate the percentage of voids in different sections of the same core.

THE INFLUENCE OF THE TECHNOLOGICAL MODE OF COMPACTION OF CONCRETE MIXTURE WITH FLY ASH AND MICROSILICA ADDITIVES ON THE STRENGTH OF CONCRETE

The aspects of expanding the scope of application of non-reinforced products, in particular, pipes with sufficient strength indicators, were considered, and the objective necessity of developing appropriate concrete compositions and compaction technology, as well as the nomenclature and parameters of additives, was confirmed. The article outlines the trends of increasing concrete strength characteristics due to the rationalization of methods of concrete compaction with the use of waste. It has been confirmed that for the material of the pipes it is necessary to ensure the increased tensile strength of the product. After compaction, it is necessary to remove the liquid from the concrete, which ensures maximum convergence and unification of the particles of the solid phase. The method of iterations was used to determine the influence of each of the factors of concrete strength research on tension. Considered methods of concrete mixture compaction, according to the features and rheological properties of which two principles are implemented during compaction: removal of excess entrapped air and excess water from low-mobility and rigid mixtures by external influence and removal of air from high-mobility mixtures. Special attention was paid to the technologies of compaction by pressing, vacuuming and vibrovacuuming. Samples of concrete compacted by pressing and vibrovacuum ensured the production of concrete of almost the same structure with compaction of all components. Test results, electron microscopy of cement stone, radiographs obtained with different methods of compaction are presented. An increase in the degree of crystallinity was recorded due to the higher speed of reaching the supersaturation of the liquid phase of the cement test during hydration. When processing the research results, a regression analysis was performed, and analytical models for predicting parameters were obtained. The results were obtained that the fine-grained concrete mixture when compacted by pressing provides an increase in strength under the condition of pressing in layers.

Application and validation of internally cured concrete strength characteristics by machine learning

Water is a precious resource, and the demand for potable water is high in many regions globally. Potable water is being used in the construction of buildings, and a substantial amount of water is required for curing concrete elements, which can be saved with modern construction practices like internal or self-curing concrete. The properties of concrete are usually identified through physical testing. Experiments become time-consuming, laborious and costly if multiple parameters in small proportions are to be modified and the results are to be predicted. Predicting nominal mix proportions becomes difficult; alternatively, utilising computational and predicting any specific or multiple outputs by analysing multiple input parameters with randomised data is feasible through machine learning. Considering this, an attempt is made to develop self-curing concrete of M30 grade utilising fractional replacement of 30% coarse aggregates with fly-ash aggregate as an internal curing agent. Different algorithms those that are processed in machine learning deal with prediction and validation of concrete characteristic strength parameters; 1) decision tree regression; 2) random forest regression, and 3) multiple layer perception regression analysis. In this study, the comparison found that the utmost successful machine learning strategy for prediction of concrete strength properties is the decision tree regressor method, with the least error fitting the regression curve.

Investigating the effect of hybrid nanomaterials on strength characteristics of concrete

Enhancing technologies and increasing population have resulted in a degradation of natural materials. This overconsumption of natural raw materials results in environmental degradation. Production of sustainable materials and limiting the use of natural materials is the need of today’s generation. This research study is an amalgam of both technologies and uses materials such as Nano Silica, a product of Nanotechnology, and waste elements like GGBFS and Fly ash which are a by-product of iron and coal production. Nano Silica (NS) with a replacement of 0.75%, 1%, and 1.25% and Ground Granulated Blast Furnace Slag (GGBFS) at 10%,20%, and 30% were used with cement while a constant rate of Fly Ash (FA) brick aggregates viz 50% replacement with coarse aggregate was done. The result obtained shows that, a 1% replacement of NS and 20% of GGBFS with 50% of FA brick aggregate gives significant results of overall strength and durability properties.