Properties Of Concrete Mixtures Research Articles

Experimental Analysis of Mechanical Properties on Concrete with Nano Silica Additive

In the current scenario nanotechnology and nanomaterials are emerging as key role in engineering and medical industries. The objective of this research is to increase the usage of fly ash in concrete to enhance the strength properties of concrete mixed with nano silica and to reduce the emission control caused by CO2discharged from cement manufacturing industries. The strength properties of concrete mixture is enhanced with nano size particles filled the voids amoung micron size cement particle, and hence a denser concrete mixture was being attained. Fly ash is used for partial replacement of cement to enhance the environmental sustainability and to reduce the cost. This research work focussed on preparation of nano silica mixed concrete with replacement of fly ash in concrete mixture. Nano silica was added in addition to the above by 1% and 2% to improve the overall strength properties. Different experimental analysis were carried out to obtained the results such as compression strength, ultimate divide tensile strength and elastic modulus of the enriched concrete mixture. From the observed results it was found that, compression strength was increased by adding 1% nano silica and 25% of fly ash and also increased the ultimate tensile strength by 28%. Scanning Electrom Microscope (SEM) results reveal that, the incorporation of the nano silica in concrete increases the mechanical properties and porosity was successfully minimized with enhancement of pore size distribution.

Enhancing technological processes in building construction and reconstruction by means of new technologies

This article covers three efficient technologies of construction operations, implementation of which would improve technological processes of building construction and reconstruction. Dealing with reconstruction and repair of enclosing structures in industrial buildings in very confined space due to the current production process, authors apply technology of craneless wall panels installation and dismounting of structures using existing funnel as a supporting element. While carrying out concrete works, the authors suggest using mixing technology on preliminarily processed water batched by electric field of soluble electrodes to improve physical and technological properties of concrete mixtures. For construction and reconstruction of residential buildings with sloping roofs, replacement or repair of metal roof, the authors propose to use sloping roof construction, heat-insulated with thermo panels, fastened to trusses by means of dowel system.

Impact of Added Chalcedonite Powder on Selected Concrete Properties

In recent times, the interest of scientists in new additives has increased, which can be modified by the properties of concrete mixtures and the parameters of hardened concrete. The PN-EN 197-1:2002 standard permits the use of mineral additives for cement, both as a main component (> 5.0% by weight) and as a secondary component (<5.0% by weight). Particular attention is paid to the problem of managing waste materials. The article discusses the results of laboratory tests on the effect of chalcedonite flour on the parameters of hardened concrete and rheological characteristics of the concrete mix. The addition to concrete mixtures was a chalcedonite meal with a diameter of less than 0.1 μm. It is a waste coming from the mine of broken chalcedonite aggregates. The main component of chalcedonite dust is silica. The rheological properties of concrete mixes, i.e. consistency, density, aeration degree and parameters of hardened concrete, including compressive strength, capillary rise and absorbability. The laboratory tests carried out indicate that the use of chalcedonite powder in the composition of a concrete mix has a positive effect on parameters such as capillary rising and water absorption. The addition of 15% of the meal results in a reduction of the compressive strength compared to the reference concrete by 10% on the 28th day of maturation. The use of a concrete additive in the form of chalcedonite powder can solve the problem of storing and managing waste in the production of broken chalcedonite aggregates. Concrete with chalcedonite meal can be used in places exposed to water, humidity and atmospheric conditions, where the compressive strength parameter is of secondary nature.

Properties of fibre-reinforced concrete made with discarded materials

This research paper investigates the physical, chemical and mechanical properties of steel slag aggregates (SSA), gravel aggregates (GLA), natural gabbro aggregates (NGA), and the different fresh and hardened properties of concrete mixtures prepared using SSA, GLA and NGA. Furthermore, this paper presents the compression and flexural test results of different concrete mixtures made with SSA or NGA combined with different volume fractions of basalt macro-fibre (BMF). The investigated parameters included the type of coarse aggregates, the replacement of the recycled aggregates (0, 25, 50, 75 and 100%) and the volume fraction of BMF (0·25% and 1·0%). Test results have shown that replacing NGA with GLA reduces both the compressive and tensile strength of the concrete. However, concrete made with SSA tends to result in a higher compressive strength than that made with NGA. In addition, the test results showed a considerable improvement in mechanical concrete properties with increasing BMF volume fractions.

Effects of elevated temperature on performance of recycled coarse aggregate concrete

This experimental program determines the influence of elevated temperature on the performance of concrete containing varying percentages of recycled coarse aggregates. Natural coarse aggregates were substituted by 30%, 60% and 100% recycled coarse aggregates obtained from concrete debris of a demolished building. Glass powder, marble powder and rice husk ash were used as binder to replace 20% of Ordinary Portland cement to enhance the strength related properties of concrete mixtures prepared with 100% recycled aggregates. Moreover, waste steel wires were used as a reinforcement to explore the possibility of improving the mechanical properties of recycled aggregate concrete. Cylindrical specimens of different mixtures were exposed to four different temperatures (i.e., 25, 200, 400 and 600 °C), and later on tested for mass loss, ultrasonic pulse velocity test, compressive strength test and splitting tensile strength test. Although the tested properties of concrete decreased with the increase of exposure temperature, the residual compressive strength of recycled aggregate concrete at elevated temperatures was satisfactory and comparable with the control mixture.

Modeling the weight and length changes of the concrete exposed to sulfate using artificial neural network

DOI: 10.7764/RDLC.17.3.337 This paper presents the modeling of an experimental investigation carried out to evaluate some mechanical and durability properties of concrete mixtures in which cement was partially replaced with Class C and Class F fly ash. A total of 39 mixtures with different mix designs were prepared. After compressive strength testing, the mixtures containing Class F and Class C fly ashes which had similar compressive strength values to control mixtures at 28 d for each series were used for sulfate resistance tests. The degree of sulfate attack was evaluated using expansion and weight loss. The test results indicated that Class C fly ash showed higher compressive strength than Class F fly ash. Moreover, the addition of fly ash significantly increased the resistance to sulfate attack when each amount of fly ash addition regardless of fly ash types was employed. In this paper, the Artificial Neural Network (ANNs) techniques were used to model the relative change in the weight and length of the concrete exposed to sulfate. The best algorithm for length changes of concrete exposed to sulfate is BFGS quasi-Newton backpropagation algorithm while the best algorithm for weight changes of concrete exposed to sulfate is the Levenberg-Marquardt backpropagation algorithm.

On the issue of expanding the base of mineral and complex additives for cement concrete

Modern materials science is characterized not only by the creation of high-strength building materials, but also by using a large number of raw materials and additives that improve the properties of concrete mixtures and concrete. The article considers the possibility of using both old and new generations of complex organomineral additives in concrete production. The nature of the effect of additives on the rheological behavior of cement systems and hydrate formation processes, as well as an assessment of the effect of mineral and organic additives on the composition of hydration products of cement systems, are revealed. Studies have shown that complex additives, which include hyper- and superplasticizers, lead to some slowdown in hydration and crystallization processes. The high efficiency of plasticizing additives helps to reduce water content, which in turn provides increased strength of cement concrete.

PROPERTIES OF MODIFIED CONCRETE FOR SPECIAL PURPOSE STRUCTURES

Purpose. The paper is aimed at developing the scientific fundamentals of new-generation monolithic concrete technology for special purpose structures by controlling the processes of structure formation of a modified cement system under natural hardening conditions. Methodology. The kinetics of interaction between the cement system and aggregates was evaluated by microcalorimetry. The measurements were carried out continuously for 24 hours after preparation of the mixture. The differential and integral characteristics of the heat release of the solidifying system were recorded. Investigation of the rheological properties of concrete mixtures was carried out on the mixtures with 10...15 cm consistency. The microhardness of contact layers was investigated on concrete cubes with dimensions from 20×20×20 to 50×50×50 mm. When determining the structural characteristics, x-ray phase and differential-thermal analyzes of the concrete cement matrix were used. Infrared spectroscopy was used to determine the effect of physicochemical modification on the cement system. Tensile creep was studied over a wide load range from 0.2 R t to 0.8 R t . Findings. It is determined that the reason for changing the concrete properties of natural hardening is the change in its hygrometric and thermal state, as well as the harmonic fluctuations of these environmental factors. The hygrometry of concrete depends on the thermal moisture conditions of the environment, the type and composition of concrete, the massiveness of concrete elements. An analysis of these factors and experimental data made it possible to establish the exponential dependence of the change in the hygrometric state of monolithic natural hardening concrete. The change in the moisture state of concrete makes it possible to predict its volumetric deformations. Originality . For the first time, the features of the structure formation of a modified cement system are established, consisting in the fact that magnesium chloride hydrate crystals grow rapidly in the space between hydrated clinker minerals, and the resulting mechanical cohesion defines the development of initial strength and rigidity. Since the free growth of crystals is hampered by a lack of space, the crystals mutually intergrow, forming a dense structure, contributing to the growth of strength. The developed organo-mineral modifying complex provides disperse reinforcement of the cement matrix of concrete. Practical value . The obtained dependences of structural concrete stresses make it possible to analyze their effect on the structure of modified concrete: to determine the probability of formation around the filler particles of the plastic flow zone, the material microcrack formation zone, the crack initiation period, the microcrack onset conditions, and the change of elasticity modulus of the material caused by microcracks in its structure. Disperous modification of cement matrix allows to obtain durable concrete of special purpose with design operational properties. The developed binder disperse modification technology, the established features of the structure formation mechanism for the modified cement system, as well as the use of the principle of congruence of a complex of technological influences to the physico-chemical processes of hydration of clinker minerals allowed developing the scientific fundamentals for the special purpose concrete technology. This helps to expand the use of modified concrete in various types of construction.

Effect of polypropylene fiber addition on mechanical properties of concrete based on portland cement

In this work results of poly(propylene) fibers (PP), from recycling process, added into concrete mixture based on portland cement was characterized. The main purpose of this research was to identify direct influence of the fibers addition on the concrete mechanical strength. The recipe of the concrete was prepared using three types of aggregates with different grain size: 0.125–0.250, 0.250–0.500 and 0.500–1.000 mm, deflocculant based on polycarboxylates, water and portland cement (42.5 MPa). To identify structures of the researched samples and fibers light microscopy (LM) observation was performed. Basic properties of concrete mixture were defined by slump cone test and setting time. Mechanical properties such as compressive strength and bending test after 1, 7, 14 and 28 days were characterized. Obtained results were compared with mixtures without fibers modifications. Study was proven that all chosen fibers from recycled origin revealed increased effect on final mechanical properties of concrete and are very perspective for future application in concrete technology.

ФИЗИКО-ХИМИЧЕСКИЕ ПОДХОДЫ К РАЗРАБОТКЕ ЭФФЕКТИВНЫХ ОРГАНОМИНЕРАЛЬНЫХ ДОБАВОК ДЛЯ БЕТОНА

Представлены физико-химические подходы к разработке эффективных органоминеральных добавок для регулирования свойств бетонных смесей. Углублены представления о влиянии свойств минеральных компонентов на структурообразование цементного камня. Установлена связь результатов физико-механических испытаний цементного камня с его микроструктурой и свойствами минеральных компонентов. Показана возможность сохранения эффективности пластифицирующих добавок за счет частичного замещения поликарбоксилатного пластификатора на более доступное химическое сырье. Разработанные комплексные органоминеральные добавки позволяют модифицировать структуру цементного камня и улучшать физико-технические свойства бетона.&#x0D; Работа выполнена при финансовой поддержке РФФИ, грант № 18-29-19033 мк

Predicting the compressive strength of silica fume concrete using hybrid artificial neural network with multi-objective grey wolves

The use of silica fume as a partial replacement for Ordinary Portland Cement provides a wide variety of benefits such as reduced pressure on natural resources, reduced CO2 footprint, and improved mechanical and durability properties. Compressive strength of concrete is one of the most important parameters in the design of concrete structures. Artificial Neural Network (ANN), as one of the powerful tools in the artificial intelligence field, has been widely used to predict various properties of concrete mixtures. One of the major drawbacks of the developed ANN models in predicting the concrete properties is their high complexity. In this study, estimating the compressive strength of silica fume concrete using the ANN method was considered as a two-objective optimization problem. These two objectives were the accuracy and the complexity of the developed ANN models. In this regard, a new multi-objective optimization method called Multi-Objective Grey Wolves Optimization (MOGWO) method was served to find a simple ANN model with acceptable error. After solving the optimization problem, a total number of 31 optimized ANN models were achieved. An ANN model with just one hidden layer with five neurons and the Pearson correlation coefficient of 0.9617 for all data was chosen as the final ANN model. Moreover, a sensitivity analysis was carried out to investigate the capability of the final ANN model in predicting the trend of the compressive strength of silica fume concrete with changing the effective variables on the compressive strength.

Use of recycled aggregates in road sub-base construction and concrete manufacturing

This paper investigates the use of construction and demolition waste in road embankment and concrete manufacturing. The aggregates are recycled from the demolition waste of a building and in particular from basalt, sandstone, structural concrete and vibrated concrete blocks. The main physical characteristics of recycled aggregates for road applications and the performance of road sub-base layers containing recycled components are determined and validated on the basis of the latest Italian specifications. The study demonstrates that recycled mixes have sufficient mechanical characteristics and are hence suitable in road sub-base construction, even if only limited to minor technical importance works. Moreover, the mechanical properties of concrete mixtures that use recycled aggregates as replacement for natural aggregates are evaluated and compared to those of standard concrete mixtures. Three types of recycled aggregates are considered (structural concrete, basalt, vibrated concrete blocks) at different replacement ratios. A higher percentage of recycled aggregates than the one prescribed by the current legislations can be effectively used in concrete preparation, especially in the case of aggregates derived from crushed basalt waste or from structural concrete manufactured using basaltic fine and coarse aggregates. The effect of natural fine aggregate replacement with recycled fine fractions on concrete is investigated. The results of the experimental program are significant and encourage the use of 100% recycled basalt aggregate in concrete. Therefore, in areas where the use of basalt stone as primary masonry building material is widespread, the reuse of demolition waste is highly recommended.

The Influence of Fine Particle Content (Cement Together with Sand Particles up to 0.25 mm) on Rheological Properties of Concrete Mixture

The influence of the fine particle content on the rheological properties of the fresh concrete mixture was studied. The change of cement together with sand particles up to 0.25 mm in mixture composition was taken into the consideration. The amount of fine particles in mixture composition varied in the range from 402 to 639 kg per one cubic meter of the concrete mixture. Technological properties of the concrete mixture were established according to the standardized requirements, rheological properties: yield stresses and viscosity of conventional concrete mixture were calculated based on analytical formulas. According to obtained test results, the increase of fine particle content from 481 to 520 kg in mixture reduced the yield stresses from about 557 to 132 Pa. Further increase of fine particle content from 600 to 639 kg showed the rise of yield stress by 3.87 times. On the other hand, the viscosity of concrete mixture gradually decreased (ca. 5.6 times). To sum up, the rheological properties of the concrete mixture were significantly influenced by the content, packing density, fineness, surface texture and particle size distribution of fine particles.

Testing of Rheological Properties of Concrete Mixtures Using a Special Vibroviscometer

AbstractThe rheological properties of concrete mixtures are presently important when new technologies for transporting, handling, placing, and compacting concrete are used in new concrete construct...

Metaheuristic-Based Machine Learning System for Prediction of Compressive Strength based on Concrete Mixture Properties and Early-Age Strength Test Results

Estimating the accurate concrete strength has become a critical issue in civil engi­neer­ing. The 28-day concrete cylinder test results depict the concrete's characteristic strength which was prepared and cast as part of the concrete work on the project. Waiting 28 days is important to guarantee the quality control of the procedure, even though it is a slow process. This research develops an advanced machine learning method to forecast the concrete compressive strength using the concrete mix proportion and early-age strength test results. Thirty-eight historical cases in total were used to create the intelligence prediction method. The results obtained indicate the effectiveness of the advanced hybrid machine learning strategy in forecasting the strength of the concrete with a comparatively high degree of accuracy calculated using 4 error indicators. As a result, the suggested study can provide a great advantage for construction project managers in decision-making procedures that depend on early strength results of the tests.

Radiation shielding and mechanical properties of steel fiber reinforced concrete (SFRC) produced with EAF slag aggregates

In this paper, the influence of Electric Arc Furnace (EAF) slag aggregates on the mechanical and gamma ray shielding properties of concrete mixtures were studied experimentally. EAF slag and crushed limestone were used as aggregates while steel fibers of different geometry were also incorporated into the concrete mixtures. Unit weight, ultrasonic pulse velocity, compressive strength, split tensile strength, flexural toughness and shielding properties in gamma energies 244, 344, 779, 964, 1112 and 1408 keV were measured and compared to the corresponding values of conventional concrete. The use of EAF slag aggregates results in the production of higher density concrete compared to conventional concrete with limestone aggregates with enhanced mechanical and shielding properties and adequate workability. Additionally, the inclusion of fibers improves the flexural behavior of concrete and slightly increases compressive strength and unit weight.

Fizikalno-mehanička svojstva betonskih mješavina za izradu kolnika na autobusnim stajalištima

Fizikalno-mehanička svojstva betonskih mješavina za izradu kolnika na autobusnim stajalištima

Using of Stone Flour from Some Mineral Rocks in Modern Concrete

There is shown the possibility of using mill ground rocks in SCC without deterioration of rheological properties of concrete mixtures. Obtained high-strength concrete of the new generation with high technical and economic indices and low unit costs per unit of cement strength.

The impact of coarse aggregate shape on the behavior of self-compacting high-performance concrete

Self-Compacting High Performance Concrete (SCHPC) presents a crucial step in the development of concrete technology. The most important features of self-consolidating concrete are flowability, segregation resistance and passing ability. Generally, the rheological properties are modified by effective superplasticisers and water to binder ratio. The aim of this study is to focus on the important aspect of the impact of shape of the coarse aggregate on fresh concrete mixture properties, strength and deformability of SCHPC. Coarse aggregate is a significant proportion of the concrete volume and therefore has a meaningful influence on its quality. By appropriate selection of the shape of the grain aggregate, it is possible to affect the rheological parameters of concrete. The results presented in this study indicated that the shape of the grains of coarse aggregate has an impact on the strength and stiffness of SCHPC. Moreover, the occurrence of irregular grains of coarse aggregate causes lower slump flow and higher plastic viscosity in comparison to concrete mixtures with regular grains only. The research presented in this article is part of the author's wider research devoted to this issue.

MULTILAYER CONCRETE INDUSTRIAL FLOORING SOLUTIONS ANALYSIS

The subject of the article is the presentation of European experience in the field of construction of industrial concrete floors. For the construction of the concrete slab floor to be prepared subsoil. Land stabilization can include mechanical stabilization, physical stabilization, and chemical stabilization. The most commonly used stabilization is mechanical stabilization. In order to determine the efficiency and effectiveness of the process, the treatment depends on the soil moisture for the soil type, so attention is paid to this material feature. Accordingly, the recipes from the French experience for the concrete stabilization layer are presented. For such prepared substrate the choice of material parameters and properties of concrete mixtures for concrete slabs for the concrete class in the strength of 10 to 35 MPa was presented.