Editorial

8 pages, 221 KiB

Open AccessEditorial

Special Issue “Reinforced Concrete: Materials, Physical Properties and Applications”

by Alexey N. Beskopylny, Anatoly Lavrentyev, Evgenii M. Shcherban and Sergey A. Stel’makh

Appl. Sci. 2023, 13(3), 1826; https://doi.org/10.3390/app13031826 - 31 Jan 2023

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The Special Issue is devoted to reinforced concrete in terms of materials used, physical properties and application possibilities [...] Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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21 pages, 15925 KiB

Open AccessArticle

Time-Dependent Behavior of Reinforced Concrete Beams under High Sustained Loads

by Mohammed Shubaili, Ali Elawadi, Sarah Orton and Ying Tian

Appl. Sci. 2022, 12(8), 4015; https://doi.org/10.3390/app12084015 - 15 Apr 2022

Cited by 6 | Viewed by 2539

Abstract

High levels of sustained load can lead to time-dependent failure of reinforced concrete (RC) members. This in turn may lead to collapse of all or part of a building. Design errors, construction errors, and material deterioration may lead to concrete elements being subjected [...] Read more.

High levels of sustained load can lead to time-dependent failure of reinforced concrete (RC) members. This in turn may lead to collapse of all or part of a building. Design errors, construction errors, and material deterioration may lead to concrete elements being subjected to high levels of sustained loads well exceeding typical service loads. Plain concrete can experience compressive failure when subjected to a high sustained stress (over 75% of its short-term strength). However, there is a lack of knowledge about the time-dependent strength and stiffness characteristics of RC members under high sustained loads. This paper presents the results of experimental testing of simply supported shear-controlled RC beams under high sustained loads. Two series of beams, consisting of 4 and 5 beams, were tested at concrete ages of 67 to 543 days to represent in-service concrete structures. The applied sustained loads ranged from 82% to 98% of the short-term capacity and lasted for 24 to 52 days. Test results indicated that high sustained load may eventually lead to failure (collapse); however, the level of load needs to be very close (~98%) to the short-term capacity. Under sustained load, all specimens experienced increased deflection with over half of the deflection increase occurring in the first 24 h. The sustained load increased the deflection at shear failure by 190% on average. The increase in the beam deflection may allow for load redistribution in redundant structural systems. A sharp increase in deflection due to tertiary creep occurred in a short time (~2 min) before failure, indicating little warning of the impending failure. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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12 pages, 4548 KiB

Open AccessArticle

Assessment on the Properties of Biomass-Aggregate Geopolymer Concrete

by Haibao Liu, Qiuyi Li, Hongzhu Quan, Xiaolong Xu, Qianying Wang and Songyuan Ni

Appl. Sci. 2022, 12(7), 3561; https://doi.org/10.3390/app12073561 - 31 Mar 2022

Cited by 12 | Viewed by 1817

Abstract

Energy efficiency is one of the important indicators for the evaluation of green buildings, and it is also related to the sustainable development of the building industry and energy conservation. Using agricultural waste in concrete to produce biomass recycled aggregates can effectively utilize [...] Read more.

Energy efficiency is one of the important indicators for the evaluation of green buildings, and it is also related to the sustainable development of the building industry and energy conservation. Using agricultural waste in concrete to produce biomass recycled aggregates can effectively utilize agricultural solid waste to develop new wall materials with economic and energy-efficient properties. In this study, industrial wastes such as ground, granulated blast-furnace slag (GGBS) and fly ash (FA) were used to replace cement as cementitious material and coconut shell (CC) as lightweight coarse aggregate (LWA) in lightweight concrete. The lightweight coconut shell aggregate concrete with a density of less than 1950 kg/m³ was used as structural concrete. The thermal conductivity of synthesized biomass recycled aggregate concrete (SBRAC) was about 0.47 W/mK, which is 217% and 19% lower than that of natural aggregate concrete (NAC) and crushed coconut shell aggregate concrete (CCSAC), respectively. With the same volume, the costs of SBRAC and CCSAC are 25.1% and 4.9% lower than that of NAC, respectively. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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14 pages, 3703 KiB

Open AccessArticle

Research of Strength, Frost Resistance, Abrasion Resistance and Shrinkage of Steel Fiber Concrete for Rigid Highways and Airfields Pavement Repair

by Željko Kos, Sergii Kroviakov, Vitalii Kryzhanovskyi and Iryna Grynyova

Appl. Sci. 2022, 12(3), 1174; https://doi.org/10.3390/app12031174 - 23 Jan 2022

Cited by 13 | Viewed by 2285

Abstract

High-early strength fiber-reinforced concretes are effective materials for the full depth repair of rigid highway and airfield pavements. A comprehensive study was carried out on the influence of the amount of steel anchor fiber and hardening accelerator on properties that are important for [...] Read more.

High-early strength fiber-reinforced concretes are effective materials for the full depth repair of rigid highway and airfield pavements. A comprehensive study was carried out on the influence of the amount of steel anchor fiber and hardening accelerator on properties that are important for repairing concrete. A two-factor experiment was carried out, in which the influence of the hardening accelerator and fiber dosages on the strength, frost resistance, wear resistance and shrinkage of repaired steel-fiber-reinforced concrete for rigid pavements was studied. The investigated concretes contained 400 kg/m³ of cement and polycarboxylate plasticizer in the amount of 1.2% of the cement content. It has been established that the optimal concrete compositions are with the amount of Sika Rapid 3 hardening accelerator from 1 to 2% of the cement content and the steel fiber amount from 60 to 90 kg/m³. Optimal fiber-reinforced concrete compositions have a reduced shrinkage during hardening, and at the age of 2 days they have a compressive strength of at least 55 MPa and a flexural strength of at least 8.5 MPa. At the design age, the fiber-reinforced concrete compressive strength is 85–90 MPa, its flexural strength ranges from 15.5 to 17.5 MPa, it has a frost resistance of F200 and abrasion not higher than 0.24 g/cm². These properties ensure the high durability of the repair material. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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21 pages, 4075 KiB

Open AccessArticle

Bearing Capacity near Support Areas of Continuous Reinforced Concrete Beams and High Grillages

by Zeljko Kos, Yevhenii Klymenko, Irina Karpiuk and Iryna Grynyova

Appl. Sci. 2022, 12(2), 685; https://doi.org/10.3390/app12020685 - 11 Jan 2022

Cited by 6 | Viewed by 1342

Abstract

This work presents a proposed engineering method for calculating the bearing capacity of the supporting sections of continuous monolithic reinforced concrete tape beams, which combine pressed or driven reinforced concrete piles into a single foundation design. According to the mechanics of reinforced concrete, [...] Read more.

This work presents a proposed engineering method for calculating the bearing capacity of the supporting sections of continuous monolithic reinforced concrete tape beams, which combine pressed or driven reinforced concrete piles into a single foundation design. According to the mechanics of reinforced concrete, it is recommended to consider the grillage to be a continuous reinforced concrete beam, which, as a rule, collapses according to the punching scheme above the middle support (pile caps), with the possible formation of a plastic hinge above it. The justification for the proposed method included the results of experimental studies, comparisons of the experimental tensile shear force with the results of calculations according to the design standards of developed countries, and modeling of the stress-strain state of the continuous beam grillage in the extreme span and above the middle support-pile adverse transverse load in the form of concentrated forces. The work is important, as it reveals the physical essence of the phenomenon and significantly clarifies the physical model of the operation of inclined sections over the middle support. The authors assessed the influence of design factors in continuous research elements, and on the basis of this, the work of the investigated elements under a transverse load was simulated in the Lira-Sapr PC to clarify the stress-strain state and confirm the scheme of their destruction adopted in the physical model by the finite element method in nonlinear formulation. Based on the analysis and comparison of the experimental and simulation results, a design model was proposed for bearing capacity near the supporting sections of continuous reinforced concrete beams and high grillages that is capable of adequately determining their strength. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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20 pages, 4491 KiB

Open AccessArticle

The Influence of Composition and Recipe Dosage on the Strength Characteristics of New Geopolymer Concrete with the Use of Stone Flour

by Alexey N. Beskopylny, Evgenii M. Shcherban’, Sergey A. Stel’makh, Levon R. Mailyan, Besarion Meskhi and Diana El’shaeva

Appl. Sci. 2022, 12(2), 613; https://doi.org/10.3390/app12020613 - 09 Jan 2022

Cited by 19 | Viewed by 3135

Abstract

Currently, considering global trends and challenges, as well as the UN sustainable development goals and the ESG plan, the development of geopolymer binders for the production of geopolymer concrete has become an urgent area of construction science. This study aimed to reveal the [...] Read more.

Currently, considering global trends and challenges, as well as the UN sustainable development goals and the ESG plan, the development of geopolymer binders for the production of geopolymer concrete has become an urgent area of construction science. This study aimed to reveal the influence of the component composition and recipe dosage on the characteristics of fine-grained geopolymer concrete with the use of stone flour. Eleven compositions of geopolymer fine-grained concrete were made from which samples of the mixture were obtained for testing at the beginning and end of setting and models in the form of beams and cubes for testing the compressive strength tensile strength in bending. It was found that the considered types of stone flour can be successfully used as an additive in the manufacture of geopolymer concrete. An analysis of the setting time measurements showed that stone flour could accelerate the hardening of the geopolymer composite. It was found that the addition of stone waste significantly improves the compressive strength of geopolymers in comparison with a geopolymer composite containing only quartz sand. The maximum compressive strength of 52.2 MPa and the tensile strength in bending of 6.7 MPa provide the introduction of potassium feldspar in an amount of 15% of the binder mass. Microstructural analysis of the geopolymer composite was carried out, confirming the effectiveness of the recipe techniques implemented in this study. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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13 pages, 3638 KiB

Open AccessArticle

Influence of Concrete Strength Class on the Long-Term Static and Dynamic Elastic Moduli of Concrete

by Sergiu-Mihai Alexa-Stratulat, Petru Mihai, Ana-Maria Toma, George Taranu and Ionut-Ovidiu Toma

Appl. Sci. 2021, 11(24), 11671; https://doi.org/10.3390/app112411671 - 09 Dec 2021

Cited by 1 | Viewed by 1706

Abstract

Construction materials, among which concrete is by far the most used, have followed a trend of continuously increasing demand in real estate. A relatively small number of research works have been published on the long-term material properties of concrete in comparison to studies [...] Read more.

Construction materials, among which concrete is by far the most used, have followed a trend of continuously increasing demand in real estate. A relatively small number of research works have been published on the long-term material properties of concrete in comparison to studies reporting their findings at standard curing ages of 28 days. This is due, in part, to the length of time one must wait until the intended age of concrete is reached. The present paper contributes to filling this gap of information in terms of the strength and dynamic elastic properties of concrete. The dynamic modulus of elasticity may be used to assess the static modulus of elasticity (Young’s modulus), a key property used during the design stage of a structure, in a non-destructive manner. This paper presents the results obtained from laboratory tests on the long-term (6 years) characterization of concrete from the point of view of dynamic shear and longitudinal moduli of elasticity, dynamic Poisson’s ratio, static modulus of elasticity, compressive and tensile splitting strengths, and their change depending on the concrete strength class. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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16 pages, 6424 KiB

Open AccessArticle

Simplified 2D Finite Element Model for Calculation of the Bearing Capacity of Eccentrically Compressed Concrete-Filled Steel Tubular Columns

by Anton Chepurnenko, Batyr Yazyev, Besarion Meskhi, Alexey Beskopylny, Kazbek Khashkhozhev and Viacheslav Chepurnenko

Appl. Sci. 2021, 11(24), 11645; https://doi.org/10.3390/app112411645 - 08 Dec 2021

Cited by 5 | Viewed by 1859

Abstract

Concrete-filled steel tubular (CFST) columns are widely used in construction due to effective resistance to compression and bending joint action. However, currently, there is no generally accepted effective calculation method considering both nonlinearities of the materials and lateral compression. The article proposes the [...] Read more.

Concrete-filled steel tubular (CFST) columns are widely used in construction due to effective resistance to compression and bending joint action. However, currently, there is no generally accepted effective calculation method considering both nonlinearities of the materials and lateral compression. The article proposes the finite element analysis method of concrete-filled steel tubular columns in a physically nonlinear formulation by reducing a three-dimensional problem to a two-dimensional one based on the hypothesis of plane sections. The equations of Geniev’s concrete theory of plasticity are used as relations establishing the relationship between stresses and strains. The technique was tested by comparing the solution with the calculation in a three-dimensional formulation in the LIRA-SAPR software package and with the experimental data of A.L. Krishan and A.I. Sagadatov. It has been established that the effective area of operation of circular-section columns are small eccentricities of the longitudinal force. The proposed approach can be applied to analyzing the stress–strain state and bearing capacity of pipe-concrete columns of arbitrary cross-sections. There are no restrictions on the composition of concrete, and the shell material can be steel and fiberglass. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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17 pages, 6226 KiB

Open AccessArticle

Experimental Investigations on the Long Term Material Properties of Rubberized Portland Cement Concrete

by Ionut-Ovidiu Toma, Sergiu-Mihai Alexa-Stratulat, Petru Mihai, Ana-Maria Toma and George Taranu

Appl. Sci. 2021, 11(22), 10868; https://doi.org/10.3390/app112210868 - 17 Nov 2021

Cited by 4 | Viewed by 1494

Abstract

The paper presents the results of a research work aimed at assessing the long-term strength and elastic properties of rubberized concrete. The parameters of the research were the rubber replacement of fine aggregates and the age of testing the specimens. Compressive and splitting [...] Read more.

The paper presents the results of a research work aimed at assessing the long-term strength and elastic properties of rubberized concrete. The parameters of the research were the rubber replacement of fine aggregates and the age of testing the specimens. Compressive and splitting tensile strength of concrete cylinders were obtained at the age of 5 years, coupled with the static and dynamic modulus of elasticity of all concrete specimens. Additionally, the material damping coefficient was assessed by means of non-destructive tests. The density of the rubberized concrete decreases with the percentage replacement of natural sand by rubber aggregates. A significant drop in the values of density after 5 years was observed for specimens made with rubberized concrete. The static and the dynamic moduli of elasticity decrease with the increase in rubber content. A similar trend is observed for the compressive and tensile splitting strength. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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20 pages, 5658 KiB

Open AccessArticle

Influence of Mechanochemical Activation of Concrete Components on the Properties of Vibro-Centrifugated Heavy Concrete

by Evgenii M. Shcherban’, Sergey A. Stel’makh, Alexey Beskopylny, Levon R. Mailyan and Besarion Meskhi

Appl. Sci. 2021, 11(22), 10647; https://doi.org/10.3390/app112210647 - 11 Nov 2021

Cited by 22 | Viewed by 2720

Abstract

One of the crucial problems in current construction is energy, resource, and material efficient technologies in both industrial and civil engineering, associated with new material manufacturing and building construction. This article is devoted to developing comprehensive technology for activation effects on concrete made [...] Read more.

One of the crucial problems in current construction is energy, resource, and material efficient technologies in both industrial and civil engineering, associated with new material manufacturing and building construction. This article is devoted to developing comprehensive technology for activation effects on concrete made by various production techniques: vibration, centrifugation, and vibro-centrifugation. The possibility of a significant improvement in the microstructure of concrete and obtaining materials with increased specified characteristics, depending on its manufacturing technology, were studied during the complex activation effect exposed to this concrete and its components. Chemical activation of water and mechanical activation of cement were considered. The urgency and prospects of double, complex mechanochemical activation of concrete mixture components were substantiated. It was proven that the complex mechanochemical activation of the concrete mixture components gives a synergistic effect in obtaining concrete composition with an improved structure and improved characteristics. Furthermore, the relationship between concrete production technology and the technology of activation of its components was established. It was revealed that the most effective is the complex mechanochemical activation of vibro-centrifuged concrete, which gives an increase in strength up to 30%. The study results indicate a further direction of development associated with an increase in variatropic characteristics using both prescription and technological factors. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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18 pages, 4716 KiB

Open AccessArticle

Influence of Composition and Technological Factors on Variatropic Efficiency and Constructive Quality Coefficients of Lightweight Vibro-Centrifuged Concrete with Alkalized Mixing Water

by Sergey A. Stel’makh, Evgenii M. Shcherban’, Alexey N. Beskopylny, Levon R. Mailyan, Besarion Meskhi, Denis Butko and Alla S. Smolyanichenko

Appl. Sci. 2021, 11(19), 9293; https://doi.org/10.3390/app11199293 - 06 Oct 2021

Cited by 21 | Viewed by 3083

Abstract

Alkalization technology and its application to obtain high-performance concrete compositions is an urgent scientific problem that opens opportunities for improving building structures. The article is devoted to the new technology of manufacturing reinforced concrete structures with low energy consumption, resource, and labor intensity [...] Read more.

Alkalization technology and its application to obtain high-performance concrete compositions is an urgent scientific problem that opens opportunities for improving building structures. The article is devoted to the new technology of manufacturing reinforced concrete structures with low energy consumption, resource, and labor intensity based on the improved variatropic configuration of vibro-centrifuged concrete using activated water with high pH. The synergistic effect of the joint use of the proposed novel solutions has been theoretically and experimentally proved. Thus, growth in physical and mechanical characteristics of up to 15–20% was obtained, the structure and its operational ability were improved (the effectiveness of structural improvement, expressed as a percentage, reached values over 70%, concerning control samples). A positive effect on the properties of vibro-centrifuged concrete over the entire thickness of the annular section has been revealed. A method for controlling the integral characteristics of concrete has been obtained. The possibility of regulating the variatropic structure and controlling the differential characteristics of vibro-centrifuged concrete has been established. An assessment of the constructive quality and variatropic efficiency of vibro-centrifuged concrete was carried out, and new calculated dependencies were proposed, expressed in the form of relative coefficients. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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17 pages, 11172 KiB

Open AccessArticle

A Method for the Design of Concrete with Combined Steel and Basalt Fiber

by Leonid Dvorkin, Oleh Bordiuzhenko, Biruk Hailu Tekle and Yuri Ribakov

Appl. Sci. 2021, 11(19), 8850; https://doi.org/10.3390/app11198850 - 23 Sep 2021

Cited by 17 | Viewed by 2106

Abstract

Combining different fiber types may improve the mechanical properties of fiber reinforced concrete. The present study is focused on investigating hybrid fiber reinforced concrete (HFRC) with steel and basalt fiber. Mechanical properties of fiber reinforced fine-grained concrete are investigated. The results demonstrate that [...] Read more.

Combining different fiber types may improve the mechanical properties of fiber reinforced concrete. The present study is focused on investigating hybrid fiber reinforced concrete (HFRC) with steel and basalt fiber. Mechanical properties of fiber reinforced fine-grained concrete are investigated. The results demonstrate that using optimal steel and basalt fiber reinforcement ratios avoids concrete mixtures’ segregation and improves their homogeneity. Concrete with hybrid steel and basalt fiber reinforcement has higher strength. Effective methodology for proper design of HFRC compositions was proposed. It is based on the mathematical experiments planning method. The proposed method enables optimal mix proportioning of high-strength fine-grained concrete with hybrid steel and basalt fiber reinforcement. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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22 pages, 5936 KiB

Open AccessArticle

Ultimate Compressive Strains and Reserves of Bearing Capacity of Short RC Columns with Basalt Fiber

by Aleksandr V. Shilov, Alexey N. Beskopylny, Besarion Meskhi, Dmitry Mailyan, Dmitry Shilov and Oleg O. Polushkin

Appl. Sci. 2021, 11(16), 7634; https://doi.org/10.3390/app11167634 - 19 Aug 2021

Cited by 7 | Viewed by 4378

Abstract

Increasing the bearing capacity of reinforced concrete structures, reducing material consumption, and ensuring quality are critical in modern construction. The article presents an experimental study of the ultimate compressive strains of short fiber basalt reinforced concrete columns and provides recommendations for increasing the [...] Read more.

Increasing the bearing capacity of reinforced concrete structures, reducing material consumption, and ensuring quality are critical in modern construction. The article presents an experimental study of the ultimate compressive strains of short fiber basalt reinforced concrete columns and provides recommendations for increasing the bearing capacity using steel reinforcement bars with greater strength. The columns were tested in an upright position using a hydraulic press. Strains were measured with dial indicators and a strain gauge station. It was shown that the addition of 10% coarse basalt fiber increased the ultimate compressibility of concrete on ordinary crushed stone by 19.8%, and expanded clay concrete by 26.1%, which led to the strain hardening of concrete under compression by 9.0% and 12%, respectively. Ultimate compressive strains in fiber-reinforced concrete short columns with combined reinforcement increased 1.42 times in columns on a lightweight aggregate and 1.19 times on heavy aggregate. An increase in the ultimate compressibility of concrete makes it possible to use steel reinforcement with greater strength in compressed elements as the concrete crushing during compression occurs primarily due to the reaching of critical values by tensile stresses in the transverse direction. This makes it possible to manufacture structures with a higher load-bearing capacity and less material consumption. A practical example of the application of the proposed approach is given. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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19 pages, 6217 KiB

Open AccessArticle

Optimization of Composition and Technological Factors for the Lightweight Fiber-Reinforced Concrete Production on a Combined Aggregate with an Increased Coefficient of Structural Quality

by Levon R. Mailyan, Alexey N. Beskopylny, Besarion Meskhi, Sergey A. Stel’makh, Evgenii M. Shcherban and Oxana Ananova

Appl. Sci. 2021, 11(16), 7284; https://doi.org/10.3390/app11167284 - 08 Aug 2021

Cited by 23 | Viewed by 3757

Abstract

In recent years, developing lightweight concrete with both the necessary and sufficient strength characteristics is essential in the construction industry. This article studies the influence of the volumetric composition of lightweight fiber-reinforced concrete (LFRC) and the method of its distribution during the preparation [...] Read more.

In recent years, developing lightweight concrete with both the necessary and sufficient strength characteristics is essential in the construction industry. This article studies the influence of the volumetric composition of lightweight fiber-reinforced concrete (LFRC) and the method of its distribution during the preparation of the fiber–concrete mixture on the strength and deformation characteristics of LFRC on a combined aggregate. The optimal grain size of the porous filler was calculated by the mathematical planning method of the experiment. Regression models of the strength and deformation characteristics on the volumetric content of fiber and its distribution method were obtained. The most effective combination of these factors has been determined. The model shows that the increase in compressive strength was 12%, the value of the prismatic strength increased by 25%, the bending tensile strength increased by 34%, and the axial tensile strength increased by 11%. The ultimate strains during axial compression decreased by 10%, axial tension decreased by 12%, and the elasticity modulus increased by 11% compared to the test results of the control composition samples without fiber and pumice. The coefficient of constructive quality (CCQ) of the LFRC on a combined aggregate compared to concrete with the control composition without fiber and pumice showed an increase of more than 32%. It was also found that fiber reinforcement with basalt fibers with a combination of heavy and porous aggregates achieves a synergistic effect together. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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25 pages, 4075 KiB

Open AccessArticle

The Rapid Chloride Migration Test in Assessing the Chloride Penetration Resistance of Normal and Lightweight Concrete

by Jorge Pontes, José Alexandre Bogas, Sofia Real and André Silva

Appl. Sci. 2021, 11(16), 7251; https://doi.org/10.3390/app11167251 - 06 Aug 2021

Cited by 16 | Viewed by 4935

Abstract

Chloride-induced corrosion has been one of the main causes of reinforced concrete deterioration. One of the most used methods in assessing the chloride penetration resistance of concrete is the rapid chloride migration test (RCMT). This is an expeditious and simple method but may [...] Read more.

Chloride-induced corrosion has been one of the main causes of reinforced concrete deterioration. One of the most used methods in assessing the chloride penetration resistance of concrete is the rapid chloride migration test (RCMT). This is an expeditious and simple method but may not be representative of the chloride transport behaviour of concrete in real environment. Other methods, like immersion (IT) and wetting–drying tests (WDT), allow for a more accurate approach to reality, but are laborious and very time-consuming. This paper aims to analyse the capacity of RCMT in assessing the chloride penetration resistance of common concrete produced with different types of aggregate (normal and lightweight) and paste composition (variable type of binder and water/binder ratio). To this end, the RCMT results were compared with those obtained from the same concretes under long-term IT and WDT. A reasonable correlation between the RCMT and diffusion tests was found, when slow-reactive supplementary materials or porous lightweight aggregates surrounded by weak pastes were not considered. A poorer correlation was found when concrete was exposed under wetting–drying conditions. Nevertheless, the RCMT was able to sort concretes in different classes of chloride penetration resistance under distinct exposure conditions, regardless of the type of aggregate and water/binder ratio. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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21 pages, 7531 KiB

Open AccessArticle

Improving the Structural Characteristics of Heavy Concrete by Combined Disperse Reinforcement

by Levon R. Mailyan, Alexey N. Beskopylny, Besarion Meskhi, Aleksandr V. Shilov, Sergey A. Stel’makh, Evgenii M. Shcherban’, Alla S. Smolyanichenko and Diana El’shaeva

Appl. Sci. 2021, 11(13), 6031; https://doi.org/10.3390/app11136031 - 29 Jun 2021

Cited by 23 | Viewed by 5687

Abstract

The development of perspective concrete mixes capable of resisting the action of external loads is an important scientific problem in the modern construction industry. This article presents a study of the influence of steel, basalt, and polypropylene fiber materials on concrete’s strength and [...] Read more.

The development of perspective concrete mixes capable of resisting the action of external loads is an important scientific problem in the modern construction industry. This article presents a study of the influence of steel, basalt, and polypropylene fiber materials on concrete’s strength and deformation characteristics. A combination of various types of dispersed reinforcement is considered, and by methods of mathematical planning of the experiment, regression dependences of the strength and deformation characteristics on the combination of fibers and their volume fraction are obtained. It was shown that the increase in compressive strength was 35% in fiber-reinforced concretes made using a combination of steel and basalt fiber with a volume concentration of steel fiber of 2% and basalt fiber of 2%; tensile strength in bending increased by 79%, ultimate deformations during axial compression decreased by 52%, ultimate deformation under axial tension decreased by 39%, and elastic modulus increased by 33%. Similar results were obtained for other combinations of dispersed reinforcement. The studies carried out made it possible to determine the most effective combinations of fibers of various types of fibers with each other and their optimal volume concentration. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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17 pages, 2688 KiB

Open AccessArticle

Assessment of the Permeability to Aggressive Agents of Concrete with Recycled Cement and Mixed Recycled Aggregate

by Blas Cantero, Miguel Bravo, Jorge de Brito, Isabel Fuencisla Sáez del Bosque and César Medina

Appl. Sci. 2021, 11(9), 3856; https://doi.org/10.3390/app11093856 - 24 Apr 2021

Cited by 11 | Viewed by 2397

Abstract

Acceptance by the construction industry of recycled concrete as a sustainable alternative material is contingent upon a reliable assessment of its permeability to corrosive agents. This study analyses the transport mechanisms associated with chloride (Cl⁻), oxygen (O₂) and carbon [...] Read more.

Acceptance by the construction industry of recycled concrete as a sustainable alternative material is contingent upon a reliable assessment of its permeability to corrosive agents. This study analyses the transport mechanisms associated with chloride (Cl⁻), oxygen (O₂) and carbon dioxide (CO₂) ions in concrete with cement made with 10% or 25% ground recycled concrete (GRC) separately or in combination with 50% mixed recycled aggregate (MRA). The findings show that, irrespective of aggregate type, concrete with GRC exhibited lower resistance to ingress than conventional concrete due to its greater porosity. Nonetheless, O₂ permeability was consistently below 4.5 × 10⁻¹⁷ m² and CO₂ penetration, under 4 mm/year^0.5, indicative of concrete with high quality. Resistance to CO₂ and Cl⁻ penetration in the materials with 10% GRC was similar to the values observed in conventional concrete. On the other hand, the incorporation of 25% GRC increased the penetration of CO₂ and Cl^- by 106% and 38%, respectively. Further to those findings in normal carbonation environments, reinforcement passivity would be guaranteed in such recycled materials over a 100 year service life. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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13 pages, 2508 KiB

Open AccessArticle

Fracture Behaviour of Concrete with Reactive Magnesium Oxide as Alternative Binder

by J. A. Forero, M. Bravo, J. Pacheco, J. de Brito and L. Evangelista

Appl. Sci. 2021, 11(7), 2891; https://doi.org/10.3390/app11072891 - 24 Mar 2021

Cited by 7 | Viewed by 2018

Abstract

This research evaluates the fracture behavior of concrete with reactive magnesium oxide (MgO). Replacing cement with MgO is an attractive option for the concrete industry, mainly due to sustainability benefits and reduction of shrinkage. Four different MgO’s from Australia, Canada, and Spain were [...] Read more.

This research evaluates the fracture behavior of concrete with reactive magnesium oxide (MgO). Replacing cement with MgO is an attractive option for the concrete industry, mainly due to sustainability benefits and reduction of shrinkage. Four different MgO’s from Australia, Canada, and Spain were used in the concrete mixes, as a partial substitute of cement, at 5%, 10%, and 20% (by weight). The fracture toughness (K_I) intensity factor and the stress–strain softening parameters of the wedge split test were evaluated after 28 days. The experimental results showed that the replacement of cement with MgO reduced the fracture energy between 13% and 53%. Moreover, the fracture energy was found to be correlated with both compressive strength and modulus of elasticity. A well-defined relationship between these properties is important for an adequate prediction of the non-linear behavior of reinforced concrete structures made with partial replacement of cement with MgO. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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22 pages, 10214 KiB

Open AccessArticle

Investigation of the Behaviour of Steel-Concrete-Steel Sandwich Slabs with Bi-Directional Corrugated-Strip Connectors

by Mansour Ghalehnovi, Mehdi Yousefi, Arash Karimipour, Jorge de Brito and Mahdi Norooziyan

Appl. Sci. 2020, 10(23), 8647; https://doi.org/10.3390/app10238647 - 03 Dec 2020

Cited by 9 | Viewed by 2376

Abstract

The most researches on steel-concrete-steel (SCS) sandwich slabs are to control the cracking of concrete core along with losing weight, and shear connector type. In this study, the behaviour of SCS slabs with bi-directional corrugated-strip shear connectors (CSC) was investigated. One of the [...] Read more.

The most researches on steel-concrete-steel (SCS) sandwich slabs are to control the cracking of concrete core along with losing weight, and shear connector type. In this study, the behaviour of SCS slabs with bi-directional corrugated-strip shear connectors (CSC) was investigated. One of the most important practical problems of CSCs in SCS slabs is lack of access for another end welding to the second steel faceplate. In this research, plug weld was proposed to provide partial welding of the other end of CSCs to a steel plate. For this reason, three slabs were manufactured using the normal concrete core as a control sample and lightweight concrete (LWC) core with and without steel fibres. The behaviour of these slabs was compared with the behaviour of SCS slabs with J-hook and stud bolt connectors from previous researches. The specimens were tested under a concentrated block load as quasi-statically. Based on the load-displacement relationship at the centre, failure modes, loading capacity, energy absorption, and ductility showed acceptable behaviour for CSC system slabs. There was also a good agreement between the ultimate flexural strength based on experiments and previous research relationships. Full article

(This article belongs to the Special Issue Reinforced Concrete: Materials, Physical Properties and Applications)

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