Concrete Subject Research Articles

Calculating Dynamic Strengths of Concrete Subjected to Impact Load

The objective of this paper is to calculate the influential properties of concrete. These are the dynamic properties of sustainable concrete in the situation in which metal waste can found within its components. Growing the rate of pollution in the world, a fast decrease of the original resource, the requirement for utilization more areas of natural land, and increase the price of the newly available area are the reasons that make the researchers give great attention to the new concrete (green concrete) and destruction of unwanted material in the green mix. The concept of reuse aimed at sustainable structures was implemented within the current paper through consuming metal waste of cans and bottle caps in concrete. The waste materials were consumed in two modes; at 1stmode, it was applied in the role of fibres and mixed using 15% by weight of cement. On the 2ndmode, it was applied as coarse aggregate with 25% replaced by volume. The procedure includes testing 4 concrete mixes. The estimated properties were the flexural and compressive strengths, besides modulus of elasticity. Adding bottle caps (waste materials fibres) in concrete led to enhancement in strengths. The use of walls of cans (waste materials fibres) in concrete reduced the strengths. While in the case of compacted bottle caps plus pull-tab of cans (waste materials aggregate), concrete mechanical properties a little below the reference mix. The dynamic properties of concrete contain these types of waste under impact load were determined. As known, the dynamic properties are so helpful in the strategy that deals with civil constructions put in danger of impact loads like runways, gas explosion, etc. CEB-FIP (2010) code provides wide-ranging formulas to predict the strain change of concrete. The dynamic properties are determined by this code with consideration strain level between (10-2-100). In this range, dynamic loads in the civil constructions at the level of quasi-static strain were predicted.

Constitutive behavior of hybrid fiber reinforced concrete subject to uniaxial cyclic tension: Experimental study and analytical modeling

A reasonable cyclic tensile model is indispensable in the design and nonlinear analysis of fiber reinforced concrete structural members against repeated loads. This paper presents a systematic study on the constitutive behavior of hybrid steel-polypropylene fiber reinforced concrete material (HFRC) subject to uniaxial cyclic tension. A total of seven groups of cylindrical HFRC specimens were tested with influential factors in terms of fiber type, volume fraction and aspect ratio considered. The results show that HFRC specimens failed in a ductile manner due to the contributions of hybrid fiber on the cracking resistance at multiple length scales. It is noted that increasing the steel fiber (SF) content has a significant effect on the enhancement of the concrete cyclic tensile properties. Further improvements in the post-peak residual strength and toughness can be seen for the cases with a larger SF aspect ratio that also helps alleviate the stiffness degradation of the HFRC. Furthermore, an appropriate volume content of polypropylene fiber addition can improve the deformation and energy dissipation of the matrix. Finally, a semi-empirical constitutive model is proposed to describe the complete stress–strain relation and the damage accumulation of HFRC.

On the moisture migration of concrete subject to high temperature with different heating rates

A better understanding of moisture migration in concrete at high temperature can play an important role to improve the fire-resistance and radiation-shielding capability of concrete structures. In this regard, within the numerical framework of Multi-physics Lattice Discrete Particle Model, the moisture clog in concrete during heating is defined as the moisture-saturated region between the so-called “water front” and “water back” (isosurfaces of saturation = 1). The moisture migration in concrete subject to slow and fast heating has been investigated by simulating experimental tests in which moisture has been monitored via different techniques, namely 3D Neutron Tomography and Ground-Penetrating Radar. An overall consistency between experimental and numerical results has been observed, indirectly proving the effectiveness of numerical modelling and experimental monitoring of moisture migration.

Mixed Analysis of the Flipped Classroom in the Concrete and Steel Structures Subject in the Context of COVID-19 Crisis Outbreak. A Pilot Study

A sudden lockdown was declared on 14 March 2020 due to COVID-19 crisis, leading to an immediate change from face-to-face to online learning in all universities within Spanish jurisdiction. At La Salle School of Architecture, the Concrete and Steel Structures subject started online classes immediately after the lockdown law was published, using a methodology based on the flipped classroom approach and adapting the monitoring of the student to the virtual environment. This article presents a pilot study to analyze the adaptation of the model to the online format using a mixed approach in which qualitative and quantitative surveys were conducted at the end of the course with 48 participants. Responses from both surveys were organized according to six categories (teachers, assessment, methods, class development, students and documents) and 14 subcategories, as developed in an undergoing research project involving the subject since the academic year 2017/2018. Thus, the open responses of the students have been analyzed alongside with the quantitative data. The results demonstrate a proper adaptation of the model, as well as the negative perception of the students of the online format due to the loss of face-to-face benefits of the flipped classroom.

Influence of Cement Type on Deterioration of Sea Sand Concrete Subjected to Corrosion of Biological Sulfuric Acid

Influence of Cement Type on Deterioration of Sea Sand Concrete Subjected to Corrosion of Biological Sulfuric Acid

Bi-axial shear capacity of the tilted solid reinforced concrete beam subject to point loading

This paper concerns the biaxial shear capacity of reinforced concrete beams utilizing the “simple test method”. Applying the vertical shear force to the tilted beam. This loading condition simulated the response of the simply supported beams under biaxial shear applied corresponding to two main x and y axes. Three series of reinforced concrete beams have been tested. The main parameters of the present test are the tilting angle of the cross section simulating the ellipse formula of the JSCE recommendation to build reinforced concrete under biaxial shear, the shear reinforcement ratios from zero to 0.00377, 0.00502 and 0.00754, and three of ratios of longitudinal reinforcement were used (0.0276, 0.0426 and 0.0566). The ultimate capacity is discussed separately, based on the design approach using the ellipse interaction model, in terms of concrete contribution and shear reinforcement contribution (JSCE code 2010). By keeping the transverse steel ratio constant, it was found that the increase in the longitudinal ratio of reinforcement between 0.0276, to 0.0566 ‘respectively’ increased the diagonal cracking load (V c) by 22 % and 36.8 % and the ultimate load by 8 and 18 %.

Stress-Strain State of Rockfill Dam Concrete Face Due to Temperature Impact During Reservoir Impoundment

During the reservoir initial impoundment, a rockfill dam concrete face maybe subject to intensive thermal effect. Thermal stresses may considerably change the concrete face stress-strain state (SSS) and induce crack formation in it. With the aid of numerical modeling the author studied the concrete face thermal stresses and deformations for three alternatives of temperature distribution along the face thickness. It was shown that the character of temperature distribution plays an important role in formation of the face thermo-stressed state. At uniform cooling (or heating) due to rockfill low stiffness the face can partially compensate temperature deformations and thermal stresses. Thermal stresses makeup only 15÷30% of the potential ones in constrained conditions. More dangerous is the case of non-uniform distribution of stresses: it causes the face bending deformations. Stresses from bending deformations actually are not compensated. Combination of linear and bending deformations causes high thermal stresses in the face, which may become the reason of crack formation in the face. To provide the face favorable thermo-stressed state without impact from bending deformation sit is necessary to execute the impoundment of the reservoir during a long period. At designing rockfill dams with concrete faces it is necessary to take into account the fact that the less is the face thickness the more is the value of thermal stresses caused by uniform cooling (heating). It is reasonable to revise the recommendations for assigning the face thickness.

Influence of Fiber Content on Acoustic Emission Characteristics Related to Steel Fiber–Reinforced Concrete Subjected to Unconfined Uniaxial Compression

AbstractThis article reports the experimental study of the influence of the fiber volume content in steel fiber–reinforced concrete (SFRC) on the acoustic emission (AE) characteristics. Plain concr...

Incorporation of localizing gradient-enhanced damage model into layered membrane elements for reinforced concrete structures subject to in-plane loading

Implementation of the localizing gradient-enhanced concrete model and the Menegotto-Pinto steel model into eight-node quadrilateral layered membrane elements for reinforcement concrete (RC) members subject to in-plane quasi-static loading is presented and evaluated. This RC element circumvents the pathological mesh-sensitivity of continuum damage models and the spurious damage growth of standard gradient damage models. Drilling DOFs are adopted, which improve the smoothness of strain distributions and aid in numerical convergence. The layered cross-section consists of fully bonded/smeared steel reinforcement layers and concrete layers. Different properties over the thickness can be easily assigned to each layer to account for heterogeneity. Several benchmark tests are simulated to demonstrate the versatility and effectiveness of the RC element. It is highlighted that all analyses are performed with the fully implicit incremental-iterative Newton-Raphson algorithm. Consequently, the RC element is suitable for modeling quasi-static behaviors of RC members, especially those coupled with other physical processes (creep, shrinkage, corrosion, etc.).

A laboratory test on the effect of bugholes on surface degradation of tunnel lining concrete subject to freeze–thaw cycles

Bugholes are usually considered an aesthetic problem rather than a durability problem. Surface bugholes often appear on the sidewalls of a tunnel's lining concrete, which can be mitigated but never eliminated. However, the impact of surface bugholes on concrete durability is still unidentified. In cold regions, the lining concrete of a road tunnel is exposed to de-icer solutions splashed by traffic, and it is additionally exposed to freeze–thaw (F–T) cycles. This study focuses on the durability to F–T cycles of tunnel lining concrete with surface bugholes. For the objectives, the study was carried out on a laboratory-scale F–T test using large concrete blocks. An image analysis based on the RGB values of each pixel in the coloured photographic image was performed to detect and quantify deterioration of the concrete surface throughout the F–T cycles. Although severe scaling never occurred during the 300 F–T cycles, the concrete with bugholes indicated a significant local scaling at the edges of the bugholes. Some bugholes enlarged and some merged with existing bugholes, in accordance with such local scaling. The paper presents synergetic and negative effects of bugholes on the local scaling of tunnel lining concrete exposed to F–T cycles.

Theoretical foundations of the diagram method for calculating rod elements made of reinforced concrete

At the present stage of development, the diagram method for calculating rod elements made of reinforced concrete has a number of disadvantages, which is due to the lack of a single holistic theory. The paper attempts to propose its foundations. For this purpose, the most General structure of the theory has been developed, and a three-level computational model has been proposed, hierarchically built on the principle of the computational scheme discretization: level 1 - “element” - the rod design model, built according to the well-known rules of construction mechanics; level 2 – “cross” – enhanced non-linear (discrete) deformation model, adopted by BC 63.13330 with some significant author’s clarification; level 3 – material – the standard samples’ analysis model of concrete and rerod subject to the axial compressive action or tensile static short-term load or under static short-time load, pure shear (to describe proposed Jenny more deformation curve of concrete). A detailed algorithm for the relationship of models at all three levels is described.

Fragmentation Pattern and Removal Mechanism of Concrete Subjected to Abrasive Water Jet Impact

Abrasive water jet (AWJ) breaking technology is suitable for the maintenance and repair of concrete structures, generating minimal dust, low tool wear, and no vibrations or selective destruction. The failure features and mechanisms of concrete subjected to AWJ impact are fundamental issues of AWJ breaking technology, which are also related to the safety and quality of engineering construction. Based on computed tomography (CT), scanning electron microscopy (SEM), and image processing technology, this paper studied the fragmentation pattern and removal mechanism of concrete under AWJ impact. The general failure characteristics and crack propagation law of concrete subjected to AWJ impact were described through AWJ impact concrete tests. The spatial distribution of damage in concrete subjected to AWJ impact can be divided into the intensive action zone, the transition zone, and the weak action zone. The removal mechanism of AWJ was discussed by comparing the impact performance of a pure water jet (PWJ) system. The results indicate that abrasive particles can cause cliff‐shaped fracture and lip‐shaped distortion in the aggregate part and flat fracture surface in the matrix part. There is no obvious crack in the interfacial transition zone (ITZ) due to the weakening of the water wedge effect.

Semantic Characteristic of Nouns Formed with the Suffix -ost’ 
 in the Modern Russian Literary Language

The article aims to demonstrate the semantic diversity of the nouns formed with the suffix -ost, which have been considered as one of the most regular word-formation types in the modern Russian language. In order to give a semantic portray of the given word-formation type we have analysed all the nouns with the given suffix, included in the Shvedova Dictionary and the Russian Newspapers of the End of XX Century Corpus, developed by Laboratory for General and Computational Lexicology and Lexicography, Lomonosov Moscow State University. The analysis shows that nouns formed with the given suffix, while consisting a large percentage of deadjectival nominalisations in the modern Russian language, show rather diverse semantic features. The main subtypes of meanings, which consist the semantic paradigm of the given word-formation type, are transpositional (construction of nouns that name a quality), parametric (nouns that can be used as a parameter for measuring) and subject meaning (nouns that refer to a concrete subject in the extralinguistic reality). In addition, the last subtype subject meaning is also consistent of nearly 20 semantic classes, including substance, a person, a place, a type of documents, an event, a phenomenon and so on. The analysis of the corpus data shows that a large proportion of the most frequently used words in newspaper texts are the words that have rather concrete meanings. Hence their definitions in dictionaries are ought to be updated in accordance with their usages in the corpus. The results could be applied in the future study of deadjectival nominalisation in the modern Russian language

Denotazione, metafora e connotazione tra ekphrasis e mélophrasis

In classical rhetoric, the name ekphrasis designates the detailed verbal description of a concrete object or subject, i.e. the transposition into words of something that is intended to be seen by placing it under the eyes of the reader. The privileged field of application of this device are the visual arts, in which critics are expected to render both real and fantastic images through words, translating the fixedness of visual data into the temporal sequence of a verbal discourse. In the case of musical art, ekphrasis aims to render in words sequences of sounds that are in turn temporally oriented, and in this respect diverges from a verbal representation of the visual arts, which exist in a spatial dimension. In music, however, meanings exist but are generally not denoted according to a specific semantic system, and therefore require transcoding processes and lexical loans. Even in the poetic description of a work of visual art (e.g. the sonnets in which Marino describes the image of Daphne's metamorphosis into laurel in Bernini's marble group, animating and dramatizing it), ekphrasis can generate a flowering of poetic tropes that clearly enhance the semantic content. This enhancement of meaning is even more necessary in musical ekphrasis, which tends to shift the object of representation from physical-acoustic data, or from the specific semiographic system, to the sensations it produces in the listener. In fact, rather than insisting on the musical text, the melophrasis - as it has recently been renamed - is ultimately directed at the effect it causes, and therefore at viewers and their internalization processes. The result is a substantial shift from denotation to connotation, through extensive (but not uncontrolled) recourse to metaphorical procedures, applied to the sound images of the composition, to the proxemics and environmental components of performance, and finally to the specific sound symbolism contained in certain scores.

Effectiveness of Hybrid and Partially Confined Concrete Subjected to Axial Compressive Loading Using CFRP and GFRP Composite Materials

Abstract This paper presents the results of an experimental study that investigates the compression behavior of concrete and evaluates the effect of hybrid reinforcement by multiple geometries, and total and partial confinement, using CFRP and GFRP composite materials. A total of nine (09) variants of concrete cylindrical specimens, including one (01) variant of unconfined concrete and eight (08) variants of confined concrete with different geometries were subjected to axial load compression. The objectives of this study were to verify the applicability and effectiveness of partial and total confinement to improve the behavior of concrete, evaluate the effect of the hybrid confinement used, and obtain a typical reinforced model. The results obtained clearly show the effectiveness of the hybrid confinement and partially confined concrete in improving the compressive strength and deformation of the concrete, so it is possible to replace CFRP total confinement by partially confined concrete with two CFRP layers or by a hybrid confinement with a CFRP layer in the central zone and GFRP layers on the top and bottom of the specimen.

Da crítica à criatividade: reflexões sobre o realismo de Eugenio Raúl Zaffaroni diante dos desafios da criminologia crítica brasileira

O artigo discute a contribuição da dogmática de Eugenio Raúl Zaffaroni para as Ciências Criminais no Brasil, desde o processo de recepção da Criminologia na América Latina até sua versão crítica a partir da concepção funcional redutora. Contextualiza-se a contribuição do autor ao debate sobre raça nos campos criminológicos brasileiro e latino-americano, empreendendo esforços epistêmicos de não silenciar privilégios de branquitude, deixando de lado o sujeito abstrato – categoria alienante do branqueamento, própria da tradicional dogmática – para considerar o sujeito concreto, em suas dimensões individualizadas, a partir das experiências do controle penal latino-americano. O objetivo é discutir a contribuição de Zaffaroni para uma teoria crítica do exercício do poder punitivo. O texto aponta potencialidades do saber dogmático crítico desenhado pelo autor desde a década de 1980, quando indicava a necessidade da autorreflexão do saber criminológico-crítico, inaugurando uma perspectiva criativa de abordagem realista desde a margem latino-americana. Para tal análise, realiza-se revisão de literatura e uma análise teórica, a fim de a possibilidade de contenção do exercício do poder punitivo pela dogmática penal, com os olhos na Criminologia Crítica brasileira.

Chloride Transport in Cracked Concrete Subjected to Wetting – Drying Cycles: Numerical Simulations and Measurements on Bridges Exposed to De-Icing Salts

Although many models for service life predictions have been developed, their application to existing bridges is still not at a satisfactory level. The here presented coupled 3D chemo-hygro-thermo mechanical (CHTM) model can realistically simulate both corrosion phases: initiation and propagation. The focus of this research is the transport processes in cracked and un-cracked concrete before reinforcement depassivation. Realistic environmental conditions with the surface water and chloride contents variable in time are simulated based on the meteorological data for a mountain region where case studies bridges are located. Application of the large quantities of de-icing salts in combination with the poorly designed and executed details resulted in a high chloride content in concrete of the superstructure of both bridges: at the reinforcement level chloride content in cracked concrete elements exceeds the threshold value up to 10 times. Numerical results match well with the chloride content measured on the bridges after 11 and 14 years of service. Accounting for the realistic environmental conditions (wetting-drying cycles, application of de-icing salts only in the winter season, etc.) in the numerical simulations results in the continuous transport processes in concrete and higher chloride content in deeper concrete layers as opposed to the finite element models with the constant boundary conditions.

Response of a reinforced concrete cantilever beam subject to impulse impact loads

To study the response of a RC cantilever beam subjected to impulse excitations is based computational model. Static and dynamic analysis of the computational model was performed using a software product based on the Finite Element Method. Two numerical models have been builded for static analysis. In the first model, the concrete modelled with a linear - elastic material model and the reinforcement as deformable bars. In the second model, the concrete modelled using a nonlinear model of concrete - the material model of Willam and Warnke, and the reinforcement as deformable bars. For dynamic analysis, concrete modelled as a linearly elastic material and reinforcement as deformed bars. Under impulse loading, the applied force acts for a very short but limited time interval. This article presents five cases of impulse duration. The dynamic time-history analysis used to determine the dynamic response of the RC cantilever beam under the action of time variables. This type of analysis used to determine time-varying displacements, stresses, and internal forces caused by a combination of static and dynamic (pulse and harmonic) loads. A dynamic time-history analysis used to study the dynamic response to time-varying loads. The time-determined displacements, deformations, stresses and internal forces give the behaviour and reaction of the structure at any time in the studied interval.

Simultaneous determination of initial porosity and diffusivity of water-saturated reinforced concrete subject to chloride penetration by inverse problem

This paper proposes a protocol for the simultaneous determination of initial porosity and diffusivity of concretes from experimental data in the form of inverse problem. These are the fundamental parameters involved in the estimation of the first stage of the service life of reinforced concrete structures.The input data for the inverse problem are the free and bound chloride concentration measurements (with their inherent errors) made along a sample subjected to a diffusion process under known boundary conditions. From these data the coefficients of the selected isotherm, that relates the free and bound chloride concentration, are firstly adjusted to subsequently apply the proposed protocol to determine the initial porosity and diffusivity of the sample. The protocol actions include the start of the numerical simulations of each iteration, reading their partial solutions, the functionals calculation that allows programming the new simulations by establishing the new values of diffusivity and initial porosity by means of comparing the experimental and simulated values, etc. until the final solution is obtained.To verify the reliability of the proposed protocol, a concrete whose parameters are known a priori has been selected. First, the direct problem is solved to obtain the distribution of chloride concentrations in the sample. Subsequently, these concentrations are affected by random errors of 0.5, 1 and 5% to provide the input data for the inverse problem. In all cases, solutions have been obtained for the initial porosity and diffusivity that can be considered very precise in this field of engineering.

Poromechanical Microplane Model with Thermodynamics for Deterioration of Concrete Subjected to Freeze–Thaw Cycles

AbstractMechanical deterioration of concrete structures by freeze–thaw cycles has been widely spotted, mainly in temperate zones. In order to incorporate the icing-induced microdefects into global ...