Definition of rheological characteristics of self-compacting concretes in Russian and foreign regulatory documents

2019 ◽  
pp. 39-45
Keyword(s):  
Water Content ◽  
The Self ◽  
National Standard ◽  
Rheological Characteristics ◽  
Use Of Self ◽  
Self Compacting Concrete ◽  
Regulatory Documents ◽  
Regulatory Frameworks ◽  
Concrete Mix ◽  
Definition Of

The article is devoted to the comparison of acting domestic and foreign regulatory frameworks for assessing properties of the self-compacting concrete. Advantages of the self-compacting concrete mix such as improved flowability and high density at low water content due to what this material has been widely used abroad are presented. In addition, the main rheological characteristics of self-compacting concretes concerning the mobility of the mix, viscosity and segregation, as well as methods for their evaluation with the use of a cone flow diameter, V-shaped funnel, L-shaped box, blocking J-ring are considered. Visual indexes of stability and possibilities of their use are shown. It is noted that when producing concretes it is necessary to provide for possible shrinkage by compensating it due to the use of self-stressing concretes, self-stressing cements and expanding additives, especially when using self-compacting concretes, which exclude forced compaction (vibration). The article reveals the need to develop the national standard and its harmonization with foreign analogs and modification of the Sets of rules existing in Russia.

The Influence of Fiber Reinforcement on the Properties of the Self-Compacting Concrete Mix and Concrete

2020 ◽  
Vol 299 ◽  
pp. 112-117
Author(s):  
Margarita A. Goncharova ◽  
Vladimir V. Krokhotin ◽  
Alexander N. Ivashkin
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Fiber Reinforcement ◽  
The Self ◽  
Rheological Characteristics ◽  
Self Compacting Concrete ◽  
Stress Strain ◽  
Concrete Mix ◽  
Technological Effectiveness

The paper considers the influence of fiberglass on the rheological and stress-strain properties of self-compacting concretes. The use of fiberglass in self-compacting concrete compositions makes it possible to achieve a sufficient coefficient of grain separation in coarse and fine fillers, which significantly influences the mobility and technological effectiveness of self-compacting mixes. Optimum compositions of self-compacting concretes are obtained, rational volumes of the hyper-plasticizing additive and of fiberglass are determined. The components were selected experimentally, in order to optimize the composition according to rheological characteristics. It is established that the use of fiberglass positively influences the stress-strain characteristics of concrete: it raises the compressive strength, as well as the bending tensile strength without deteriorating the workability and spreadabilityof the self-compacting concrete mix.

Influence of concrete mix proportions on axial performance of concrete-filled steel tubes made with self-compacting concrete

2019 ◽  
Vol 23 (5) ◽  
pp. 835-846 ◽  
Author(s):  
Y Ouyang ◽  
JJ Zeng ◽  
LG Li ◽  
AKH Kwan
Keyword(s):  
Steel Tube ◽  
The Self ◽  
Use Of Self ◽  
Self Compacting Concrete ◽  
Steel Tubes ◽  
Concrete Filled Steel Tube ◽  
Concrete Mix ◽  
Key Factor ◽  
Air Void ◽  
Concrete Filled Steel Tubes

Self-compacting concrete is quite commonly used in concrete-filled steel tube structures, but the compaction level of the self-compacting concrete, that is, the percentage of volume occupied by materials other than air void, within the steel tube is seldom investigated. The authors are of the view that the concrete mix proportions of the self-compacting concrete may have significant effects on the compaction level of the self-compacting concrete, which will be quantified by the ‘compaction index’ proposed in this study and thus the performance of the concrete-filled steel tube. Moreover, the mix proportions would also influence the performance of the concrete-filled steel tube by affecting the aggregate–aggregate and aggregate–paste interactions of the concrete, albeit this important issue is rarely addressed in previous studies either. Herein, a pilot study is conducted to investigate the influences of the self-compacting concrete mix proportions on the axial performance of concrete-filled steel tube. Four groups of concrete-filled steel tube specimens made with different self-compacting concrete were tested, and the investigated concrete mix parameters included the paste volume, fine to coarse aggregate ratio, and 9.5–19.0 mm aggregate ratio. It was found that the compaction index of the self-compacting concrete is a key factor enabling the successful use of self-compacting concrete in concrete-filled steel tube. Moreover, the paste volume and aggregate proportions of the concrete mix have certain effects on the post-peak behaviour and ductility of concrete-filled steel tube.

scholarly journals Saturation Point of Superplasticizers Determined by Rheological Tests for Self Compacting Concrete

2017 ◽  
Author(s):  
Mehena Oualit ◽  
Amar Irekti ◽  
Yannick Melinge
Keyword(s):  
Experimental Research ◽  
Coaxial Cylinder ◽  
Mix Design ◽  
Saturation Point ◽  
Self Compacting Concrete ◽  
Mix Proportioning ◽  
Concrete Mix ◽  
Final Adjustment ◽  
Definition Of

The dosage of superplasticizer is first determined in mortar mixtures and it is after adjusted in concrete mix trials. Other self compacting concrete (SCC) mix proportioning methods rely on the definition of the superplasticizer saturation dosage in pastes. These approaches to mix design have advantages over the ones based exclusively on concrete batching because it is less expensive and material demanding to perform tests in mortar and paste than in concrete. This paper presents the results of an experimental research carried out to investigate the use of tests performed in paste to define the optimum dosage of superplasticizer for self-compacting concrete. The materials employed were Portland cement, pozzolana and three types of superplasticizers: poly naphthalene sulfonate (PNS), poly melamine sulfonate (PMS) and a polycarboxylate. The saturation point of each superplasticizer was determined in pastes by rheological tests using a coaxial cylinder rheometer AR2000. Self-compacting concretes were prepared using the superplasticizer contents found. The results obtained led to the conclusion that in SCC mixture proportioning methods, the determination of the superplasticizer content in the paste phase is paramount. Nevertheless, final adjustment of w/c+f ratio was always needed in order to produce SCC.

Modelling of Formwork Pressure Using Self-Compacting Concrete by Numerical Methods for Attaining Environmental Sustainability

2016 ◽  
Vol 692 ◽  
pp. 119-128
Author(s):  
Shini Shanmughan ◽  
Ramesh Kannan
Keyword(s):  
Theoretical Model ◽  
Numerical Methods ◽  
Pore Structure ◽  
Environmental Sustainability ◽  
The Self ◽  
Self Compacting Concrete ◽  
Proposed Model ◽  
Concrete Mix ◽  
Cast Concrete ◽  
Formwork Pressure

Self-Compacting Concrete does not require any kind of external vibration for its placing and compaction. It possesses the ability to flow under its own weight and to fill the formwork completely which will result in full compaction even in the case of congested reinforcement. The pore structure of the self-compacting concrete is different that of traditional concrete which results in changes in durability behavior. The pressure exerted by the concrete mix has its own significance in defining the durability aspects of the self-compacting concrete. This research includes a brief review how efficient modelling of SCC can be used to achieve sustainability. The prevision of the theoretical model are compared with the pressure value obtained at the end of casting carried out on a formwork along with the readings of the progression of probable yield stress of the cast concrete. After this the assumptions of the model during casting phase are compared to the results from the available literature and explain the validity of the proposed model to explain and forecast the experimental review.

scholarly journals ANTI-FOAMING ADMIXTURE (AFA) AND ITS INFLUENCES ON THE PROPERTIES OF A FRESH SELF-COMPACTING CONCRETE MIX / PRIEŠPUČIO (AFA) ĮTAKA SUSITANKINANČIO BETONO MIŠINIO SAVYBĖMS

2012 ◽  
Vol 18 (2) ◽  
pp. 151-157 ◽  
Author(s):  
Beata Łaźniewska-Piekarczyk ◽  
Janusz Szwabowski
Keyword(s):  
Flow Time ◽  
The Self ◽  
Air Bubbles ◽  
Self Compacting Concrete ◽  
Air Content ◽  
Air Volume ◽  
Concrete Mix ◽  
High Flowability

The properties of a concrete mix should secure the self-elimination of needless air bubbles from its volume. What is interesting, these properties are not taken into consideration in commonly used self-compacting tests. On the basis of different tests concerning self-compacting concrete mixes, it has been discovered that too high air content in their volume was a result of a superplasticiser, in spite of meeting the self-compactibility criteria. To decrease too high air volume in SCC, the use of an anti-foaming admixture (AFA) is proposed by the authors. Because of an AFA introduced into a self-compacting mix, air-content in this mix is decreased, mix flow diameter is increased and flow time is decreased. In case of a mix incorporating an AFA, its high flowability does not cause segregation of the mix, which is possible in case of SCC incorporating only a superplasticiser. However, time of introduction of an AFA is essential to get higher flowability degree, but is not important in achieving low air volume in SCC. Moreover, the workability of a self-compacting mix with an AFA keeps the same level for a longer period of time. Santrauka Betono mišinio sudėtis turi būti tokių savybių, kad užtikrintų nereikalingo oro kiekio pasišalinimą. Įdomu, kad į šias savybes dažniausiai nėra atsižvelgiama atliekant susitankinančio betono bandymus. Remiantis įvairiais susitankinančio betono mišinio tyrimais, buvo nustatyta, kad per dideliam oro kiekiui įtakos turi superplastikliai, nepaisant to, kad jie turi tankinančių savybių. Norint susitankinančio betono mišinyje (SCC) sumažinti per didelį oro kiekį, siūloma naudoti priešputį (AFA). Kadangi AFA įterpimas į susitankinančio betono mišinį sumažina oro kiekį, padidėja mišinio pasklidimo skersmuo ir sumažėja pasklidimo trukmė. Jeigu mišinio sudėtyje yra AFA, mišinio takumas neskatina išsisluoksniavimo, o tai gali atsitikti naudojant SCC tik superplastiklį. Tačiau AFA įterpimo trukmė turi poveikį mišinio takumo laipsniui, bet nėra reikšminga pasiektam mažam oro kiekiui SCC. Be to, susitankinančio betono mišinio su AFA klojumas ilgesnį laiką išlieka to paties lygmens.

Delving into Horror

2019 ◽  
Vol 29 (5) ◽  
pp. 135-150
Keyword(s):  
The Self ◽  
Time And Space ◽  
The Third ◽  
The World ◽  
The Subject ◽  
Perception Of Time ◽  
Definition Of

The springboard for this essay is the author’s encounter with the feeling of horror and her attempts to understand what place horror has in philosophy. The inquiry relies upon Leonid Lipavsky’s “Investigation of Horror” and on various textual plunges into the fanged and clawed (and possibly noumenal) abyss of Nick Land’s work. Various experiences of horror are examined in order to build something of a typology, while also distilling the elements characteristic of the experience of horror in general. The essay’s overall hypothesis is that horror arises from a disruption of the usual ways of determining the boundaries between external things and the self, and this leads to a distinction between three subtypes of horror. In the first subtype, horror begins with the indeterminacy at the boundaries of things, a confrontation with something that defeats attempts to define it and thereby calls into question the definition of the self. In the second subtype, horror springs from the inability to determine one’s own boundaries, a process opposed by the crushing determinacy of the world. In the third subtype, horror unfolds by means of a substitution of one determinacy by another which is unexpected and ungrounded. In all three subtypes of horror, the disturbance of determinacy deprives the subject, the thinking entity, of its customary foundation for thought, and even of an explanation of how that foundation was lost; at times this can lead to impairment of the perception of time and space. Understood this way, horror comes within a hair’s breadth of madness - and may well cross over into it.

scholarly journals Functional Method of Designing Self-Compacting Concrete

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 267
Author(s):  
Tomasz Rudnicki
Keyword(s):  
Coarse Aggregate ◽  
Cement Mortar ◽  
Experimental Studies ◽  
Functional Method ◽  
Structural Viscosity ◽  
Self Compacting Concrete ◽  
Theoretical Assumptions ◽  
Concrete Mix ◽  
Selection Of ◽  
Double Coating

The article presents a new functional method of designing self-compacting concrete (SCC). The assumptions of the functional method of designing self-compacting concrete were based on the double coating assumption (i.e., it was assumed that the grains of coarse aggregate were coated with a layer of cement mortar, whereas the grains of sand with cement paste). The proposed method is composed of four stages, each of which is responsible for the selection of a different component of the concrete mix. The proposed designing procedure takes into consideration such a selection of the mineral skeleton in terms of the volumetric saturation of the mineral skeleton, which prevents the blocking of aggregate grains, and the designed liquid phase demonstrated high structural viscosity and low yield stress. The performed experimental studies, the simulation of the elaborated mathematical model fully allowed for the verification of the theoretical assumptions that are the basis for the development of the method of designing self-compacting concrete.

scholarly journals A Comparison of Two Sensory Panels Trained with Different Feedback Calibration Range Specifications via Sensory Description of Five Beers

Foods ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 534 ◽  
Author(s):  
Line Elgaard ◽  
Line A. Mielby ◽  
Helene Hopfer ◽  
Derek V. Byrne
Keyword(s):  
Average Distance ◽  
Calibration Method ◽  
The Self ◽  
Use Of Self ◽  
Fixed Target ◽  
Immediate Feedback ◽  
Leader Following ◽  
Novel Method ◽  
Standard Deviations ◽  
Sensory Profiles

Feedback on panel performance is traditionally provided by the panel leader, following an evaluation session. However, a novel method for providing immediate feedback to panelists was proposed, the Feedback Calibration Method (FCM). The aim of the current study was to compare the performance of two panels trained by using FCM with two different approaches for ranges calibration, namely self-calibrated and fixed ranges. Both panels were trained using FCM for nine one-hour sessions, followed by a sensory evaluation of five beer samples (in replicates). Results showed no difference in sample positioning in the sensory space by the two panels. Furthermore, the panels’ discriminability was also similar, while the self-calibrated panel had the highest repeatability. The results from the average distance from target and standard deviations showed that the self-calibrated panel had the lowest distance from target and standard deviation throughout all sessions. However, the decrease in average distance from target and standard deviations over training sessions was similar among panels, meaning that the increase in performance was similar. The fact that both panels had a similar increase in performance and yielded similar sensory profiles indicates that the choice of target value calibration method is unimportant. However, the use of self-calibrated ranges could introduce an issue with the progression of the target scores over session, which is why the fixed target ranges should be applied, if available.

scholarly journals Co-evolving with self-tracking technologies

2018 ◽  
Vol 20 (10) ◽  
pp. 3624-3640 ◽  
Author(s):  
Dorthe Brogård Kristensen ◽  
Minna Ruckenstein
Keyword(s):  
Political Economy ◽  
Digital Technology ◽  
The Self ◽  
Quantified Self ◽  
Use Of Self ◽  
Technology Market

Seen in a longitudinal perspective, Quantified Self-inspired self-tracking sets up “a laboratory of the self,” where people co-evolve with technologies. By exploring ways in which self-tracking technologies energize everyday aims or are experienced as limiting, we demonstrate how some aspects of the self are amplified while others become reduced and restricted. We suggest that further developing the concept of the laboratory of the self renews the conversation about the role of metrics and technologies by facilitating comparison between different realms of the digital, and demonstrating how services and devices enlarge aspects of the self at the expense of others. The use of self-tracking technologies is inscribed in, but also runs counter to, the larger political-economy landscape. Personal laboratories can aid the exploration of how the techno-mediated selves fit into larger structures of the digital technology market and the role that metrics play in defining them.

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