Self-compacting Concrete Mixtures Research Articles

Influence of mixing time and superplasticizer dosage on self-consolidating concrete properties

Self-compacting concrete (SCC) requires specific properties, such as fillability, flowability, and passability. It also needs to resist bleeding and segregation, which may be caused by increased water or superplasticizer (SP) content. In addition, long periods of mixing deteriorate the properties of fresh SCC and causes difficulty in filling structure sections. This study investigates the effect of different mixing periods (e.g., 15, 30, 60, and 90min from the addition of water to the mixture) and increased SP doses (e.g., 1.5%, 2%, 2.5%, and 3% of cement mass) on the properties of SCC mixtures. The properties of fresh concrete were assessed by seven tests, namely, slump flow, V-funnel, slump flow T50, V-funnel T5, L-box, bleeding, and segregation. Hardened concrete was assessed on the basis of compressive, indirect, and flexural strengths. Results showed that compared with the slump flow under 15min mixing time, the 30, 60, and 90min increase in mixing time reduced slump flow by 6%, 19%, and 27%, respectively. Findings also showed that results of SCC segregation and bleeding decreased when increased mixing time. The results also appeared that compressive strength of SCC slightly decreased compared with that under 15min mixing time. The increase in dosage of superplasticizer has mitigated the negative effect for long mixing periods on the properties of concrete.

Combined use of recycled powder and recycled coarse aggregate derived from construction and demolition waste in self-compacting concrete

This study aims to investigate the properties of self-compacting concrete (SCC) with a combined use of recycled coarse aggregate (RCA-0, 25%, 50% and 100% replacement by mass) and recycled powder (RP-10% and 20%), which were both derived from construction and demolition (C&D) waste. Fresh properties were conducted as per EFNARC and porosity was evaluated by using a non-destructive test technique micro X-ray Computer Tomography (X-ray CT). The results showed that SCC mixtures examined in this study all owed excellent flow-ability even when FA was fully replaced with RP. The compressive strength, splitting tensile strength and the resistance to chloride penetration of SCC generally weakened with an increase in the RCA replacement, and the rate of reduction was generally lower when RCA was used no more than 50%. X-ray CT results showed that a higher amount of RP can lead to agglomeration of particles that lead to higher porosity in concrete, which may attribute to the poor durability of SCC with RCA and RP.

РАЗРАБОТКА СОСТАВОВ САМОУПЛОТНЯЮЩЕГОСЯ БЕТОНА НА ОСНОВЕ БЕТОННОГО ЛОМА С ИСПОЛЬЗОВАНИЕМ СТРУКТУРНЫХ ХАРАКТЕРИСТИК

Abstract. Huge amount of recycled concrete is formed when dismantling of buildings. The paper describes an efficient application of recycled concrete aggregates and concrete grinding fines to obtain technological, economic and ecological benefits. The possibility of effective application as materials for self-compacting concrete with the use of crushed concrete and recycled concrete fines is shown. The use of filler in self-compacting concrete mixtures obtained by activation of concrete grinding fines with polycarboxylate-based superplasticizer is shown. This paper presents the results of research of self-compacting concrete produced with recycled concrete aggregates and activated filler. The physical and mechanical characteristics of coarse aggregate, grain distribution of aggregates and sand proportion in aggregate mix, design of self-compacting concrete mixture and its structure properties with use mathematical experiment planning method were carried out. This method applies in the design of the self-compacting concrete mixture by solving the system of equations. The equations obtained by corresponding mathematical models. The obtained mathematical models include argumentative characteristics defined by the end of structure formation. The optimal content of filler in self-compacting concrete mixture is determined. The optimal grinding mode of the equipment with specified specific surface area of the filler is obtained. The grain-size composition of mixture consisting of quartz sand and crushed concrete aggregate with fraction of 5-10 mm based on term of maximum approximation to the Fuller ideal gradation curve is designed.

Effect of Fly Ash and Un-crushed Coarse Aggregates on Characteristics of SCC

This research paper discusses the change in the workability and strength characteristics of Self Compacting Concrete (SCC) due to addition of fly-ash and use of un-crushed Coarse Aggregate (CA). Laboratory based experimental work was carried out by preparing 12 SCC mixtures among which six mixtures contained crushed aggregate and other six mixtures contained un-crushed coarse aggregate. A total of 550 kg/m3 binder content and fixed Water-Binder (W/B) ratio as 0.35 were used. Two mixtures were controlled by using Portland Cement (PC) and other ten mixtures contained PC and Fly Ash (FA). Slump flow time, slump flow diameter and J-ring height tests were conducted to study the fresh properties of SCC. Furthermore, compressive strength was calculated at 7, 14 and 28 days of curing. The outcomes indicated that the slump flow time, slump flow diameter and J-Ring height for all the mixes are within the limits specified by EFNARC guidelines. The compressive strength of SCCs depends upon dosage of fly ash. Compressive strength for SCCs with crushed CA was better than obtained in case of un-crushed CA. The maximum compressive-strengths were observed as 64.58 MPa and 58.05 MPa for SCC with crushed and un-crushed CA respectively.

Properties of steel fiber self-compacting concrete incorporating quarry dust fine powder

Self-compacting concrete (SCC) has great potentials as it offers several environmental, economic and technical benefits. Moreover, the use of fibers extends its possibilities since fibers arrest cracks and retard their propagation. Incorporation of Quarry Dust (QD) in SCC help to reduce environmental hazards during the production of QD. This study evaluated the fresh and hardened properties of steel fiber self-compacting concrete (SFSCC) incorporating QD. The optimum fiber and QD contents with no adverse effects on fresh and hardened properties were determined. A comparative study on behavior of SCC and SFSCC mixtures in terms of workability, compressive strength, compressive strength development ratio, tensile, flexural and energy absorption capacity was carried out. Test results showed that compressive strength increased with increase in QD contents at fixed fiber content by mass of Portland cement (PC) and then decreased. Strength development ratio (C28/C7) for SCC was 1.13, while it was 1.06, 1.08, 1.10 and 1.01 after reinforcing with 0.10, 0.20 and 0.30 contents of fiber. The compressive, tensile, flexural and energy absorption capacity or Toughness of SFSCC increased with the inclusion of the aforementioned contents of steel fiber up to 0.20 % volume of total binder at constant QD content and then decreased when compared with control SCC values. From these results, optimum value for the variables studied was obtained from mix QD20 + 0.2fr. Hence, steel fiber and QD could be successfully used in SCC production not minding the slight draw back on workability of SCC caused by inclusion of steel fiber, but with a modified dosage of super-plasticizer (SP), fresh and hardened properties, in accordance with specifications in relevant code(s) can be achieved.

Effect of side chain length change of polycarboxylate-ether based high range water reducing admixture on properties of self-compacting concrete

In this study, the effect of side chain length, molecular weights changes and adsorption amount of polycarboxylate ether-based high range water reducing admixtures having constant main chain length, free non-ionic amount and anionic/non-ionic ratio on fresh properties, early and advanced age compressive strength, water absorption capacity and ultrasonic pulse velocity value of self-compacting concretes (SCC) were investigated. FTIR (Fourier transform infrared) and GPC (Gel Permeation Chromatography) analyzes were carried out to characterize admixtures. According to the test results, all SCC mixtures produced within the scope of the study provided EFNARC criteria. If the admixture side chain length is higher or shorter than a certain value, the admixture requirement is increased for providing the desired target slump-flow value in SCC mixtures. This negative effect is thought to be due to the weakness of the steric hindrance effect for admixture with short side chain, the low adsorption amount and interlacing risk of side chains for admixture with the long side chain. On the other hand, the increase in the side chain length of the admixtures had a positive effect on the time-dependent fresh state performance of the mixtures. This positive effect is thought to be due to the low adsorption amount of the admixture, the increase in the side chain length and the increase of the non-adsorbed free polymer content in the mixture. While side chain length change of the water reducing admixture affected the 1 and 2-day compressive strength values of SCC mixtures, the 3, 7 and 28-day compressive strengths and the 28-day water absorption, ultrasound and dynamic elasticity modulus values did not significantly affect.

Performance evaluation of mechanical properties of self-compacting concrete using artificial neural network

This experimental study was undertaken to investigate the effects of using local materials (cement, fly ash, super-plasticizer, coarse aggre-gate, and sand) on the mechanical properties of Self-Compacting Concrete (SCC). For this purpose, a total of 31 mixtures of SCC were prepared by the neural network design methods. Furthermore, based on the experimental results, the neural network model-based clear for-mulations were developed to predict the mechanical properties of SCC. The test results have shown that mineral admixtures were very effective on hardened properties of SCC. In addition, it was found that the developed model by using neural network appeared to have a high predictive capacity of hardened properties of SCC with respect to regression and experimental. Â

Self-Compacting Concrete On The Basis Of Concrete Scrap Of Demolished Residential Buildings

When dismantling dilapidated buildings, a huge amount of concrete and reinforced concrete scrap is formed. The possibility of effective use of crushed concrete rubble and screening of its crushing as raw materials for self-compacting concrete is shown. The physical and mechanical properties of crushed concrete rubble are investigated. The use of a crushing dropout activated together with a polycarboxylate-based superplasticizer as a micro-filler in self-compacting concrete mixtures is also considered. The optimal content of the micro-filler in self-compacting concrete mixture is determined. The optimal grinding mode of the crushing dropout is set, due to the working conditions of the grinding equipment, to obtain the micro-filler of a given specific surface. The grain-size composition of mixture consisting of quartz sand and crushed concrete aggregate based on the maximum approximation condition to the reference Fuller's curve is designed. The mathematical-statistical method was used for the selection of the composition of self-compacting concrete with application of common structural argumentative characteristics determined by the end of the structure formation period. As these characteristics of self-compacting concrete, the volume concentration of the binder, which determines the macrostructure of concrete, and the true water-binder ratio, which has a decisive influence on the volume and nature of the pores in the cement stone, on the quality of the contact zone between the cement stone and the filler were adopted. Adequate polynomial mathematical models are obtained. They describe the properties of self-compacting concrete mix and concrete, and can also be used when designing their composition.

To the problem of forming the high-strength concrete dispersed composition and properties

Introduction. Significant disadvantages of currently used high-strength concrete are the high absolute consumption of binder as well as its low specific consumption per unit of strength. Including many components with the goal of multi-level optimization of the dispersed composition is one of the main methods for producing high-strength concretes with a minimum content of cement and high physical and mechanical properties. Obtaining such concretes can be connected with creating a dense high-aggregated solid phase of the constituents at various structural levels and low water-to-cement ratio.
 Materials and methods. he following components were used to study the properties and structure of the concrete: two fine aggregate fractions, granite-gabbro crushed stone of 5 to 10 mm fraction, portland cement of the CEM I 42.5N class, finely dispersed blast furnace granulated slag, metakaolin, silica fume, high-dispersed cement fraction, Glenium 430 superplasticizer, and high-valent hardening accelerator. The shape and size of the dispersed particles of the components were determined using a laser analyzer, the flowability of the concrete mixture was evaluated as per GOST 10181-2014 standard, while the concrete compressive strength following GOST 10180-2012 standard. The cement stone structure was studied using derivatographic analysis and x-ray phase analysis methods.
 Results. For concrete with an optimized dispersed composition, superplasticizer and high-valent hardening accelerator prepared using self-compacting concrete mixtures, the concrete strength at the age of 1 day after hardening was of 58,67 and 77 MPa and at the age of 28 days after hardening was of 150, 186 and 219 MPa under normal conditions and with cement consumption of 650, 710 and 770 kg/m3, respectively.
 Conclusions. Multi-level dispersion and granulometric modification in combination with chemical modification of the composition of self-compacting concrete mixtures is one of the most productive directions of research and synthesis of high-strength concrete with minimum consumption of Portland cement and high physical and mechanical properties. It is advisable to use several structural levels of the clinker component particles.

Effect of recycled aggregates on fresh and hardened properties of self compacting concrete

This article discusses the experimental investigation of fresh and hardened properties of Self Compacting Concrete (SCC) containing Recycled Aggregates (RA). In this study, Natural Coarse Aggregates (NCA) were replaced with Recycled Coarse Aggregates (RCA) at 0%, 50%, and 100% replacement levels. Similarly, Natural Fine Aggregates (NFA) were replaced with Recycled Fine Aggregates (RFA) at 0%, 25%, 50%, 75% and 100% replacement levels. In addition to Natural Aggregates (NA) replacement with RA, Fly Ash (FA) was partially substituted with Portland cement (PC), i.e., by 30% weight of cement for clean and sustainable development. The current study objective is to enumerate the significant usage of RCA and RFA for the SCC mixes and to evaluate their performance in their fresh and hardened state. The fresh properties of various SCC mixtures were examined using workability tests such as the Slump-flow test, T500 test, V: funnel test, and L: Box test. The Ultrasonic Pulse Velocity (UPV) test was performed for all SCC mixes in their hardened state. The compression strength of all SCC mixtures is also presented in contrast to the workability of concrete. It was concluded that with substitution of RCA and RFA with NCA and NFA respectively decline the workability properties due to high-water absorption and larger surface area of RCA and RFA than NCA and NFA respectively. The chemical admixtures were used in SCC mixtures with their varying dosage helps to maintain the workability and stability limits of all SCC mixes. It was observed that the UPV values of all SCC mixtures come in the excellent and good categories.

МНОГОКОМПОНЕНТНОСТЬ – ОСНОВНОЙ ФАКТОР ФОРМИРОВАНИЯ СТРУКТУРЫ И СВОЙСТВ ВЫСОКОПРОЧНЫХ БЕТОНОВ

The prospects and problems of multicomponent multilevel optimization of the dispersed composition of self-compacting concrete are considered with the aim of significantly increasing its construction and technical properties, with a minimum content of binder. Theoretical and practical principles have been developed for the design of disperse-particle size distribution of self-compacting concrete mixtures for high-strength concrete, in which various types of dispersed mineral modifiers (MM) are used, including fly ash of thermal power plants. Effective MMs for self-compacting concrete mixtures are differently dispersed granular blast furnace slag, fly ash of thermal power plants and silica fume, which create a dense packing structure of particles of a multicomponent binder with a low degree of disorder and ensure a decrease in the consumption of Portland cement in concrete up to 50% and higher. With such a choice of the type and parameters of MM, self-compacting concrete mixtures are characterized by lower water content, high viscosity and a low level of ultimate shear stress, ensuring its high-quality compaction. To study the properties and structure of concrete, quartz sand with Mk -2.58, granite crushed stone fr. 5-10 mm, Portland cement of class CEM I 52.5 N, finely dispersed granulated blast furnace slag, fly ash of thermal power plants, micro-silica and superplasticizer Glenium 430. For a uniform course of the pozzolanic reaction, a finely dispersed cement fraction was used in each micro-volume. Research methods: the shape and size of the dispersed particles of the components were determined by a laser analyzer, the mobility of the concrete mix in accordance with GOST 10181-2014, the compressive strength of concrete in accordance with GOST 10180-2012. The structure of the cement stone was studied by thermographic and X-ray phase analysis methods.

An Experimental Study of Self-Compacting Concrete Made with Filler from Construction and Demolition Waste

This study evaluated the influence of the Portland cement replacement by 0, 5%, 10%, 15% and 20% of Construction and Demolition Waste (CDW) filler contents in the production of self-compacting concrete (SCC). The SCC mixtures were evaluated on fresh state by slump flow, J-ring, resistance of segregation, specific gravity, and on hardened state by compressive and splitting tensile strength, specific gravity, air voids and absorption rate. The results indicated that all SCC produced with CDW filler met the limits established at any level of substitution without changes of the w/c ratio or superplasticizer content. It was possible to verify that the presence of CDW filler, in substitution of cement, by volume, improves the resistance to segregation and up to 5% of CDW filler decreases the loss of fluidity with time as compared to reference. It was found that all SCC mixtures, at 28 days, had the average compressive strength above 50 MPa, without showing significant loss with up to 20% of CDW filler. For splitting tensile strength, SCC recycled mixtures reached up to 92.5% of the SCC used as reference. Absorption rate and air voids index of SCC recycled mixtures had a maximum increase of 1.60%Compared to the reference one. So, it is possible to conclude that the use of the CDW filler up to 20% in substitution of cement, by volume, is feasible for SCC production.

Properties and Flexural Behavior of Self-Compacting Concrete with Added Coir Fiber And POFA

This paper presents the mechanical properties and flexural behavior of self-compacting concrete (SCC) with addition of 0.2%, 0.4% and 0.6% coir fiber (CF) as filler, and 10% palm oil fuel ash (POFA) as partial cement replacement. Fresh SCC-POFA-CF mixture was tested under slump flow and J-ring tests to determine its workability. SCC-POFA-CF cubes and cylinders were tested under compressive and tensile tests to determine its compressive strength, tensile strength, and flexural strength, while prisms were tested under four point bending load to determine its flexural behavior. It is found that workability of SCC-POFA-CF decreased when CF increased. The optimum percentage of CF in SCC mixture was found to be 0.4%. SCC-POFA-CF experienced less crack compared to the control specimen. This shows that CF in SCC prisms managed to control the crack propagation.

Mechanical and thermal charactristics of self-compacting concrete produced with blast furnace slag and fly ash

ABSTRACT One of the main by-products of the steel production is blast furnace slag (BFS). Self-compacting concrete (SCC) mixtures were produced, in which, the cement was partially replaced by BFS and fly ash (FA). Three different BFS ratios and three different FA ratios were used at 0.35 w/b ratio. SCC mixes were tested in its fresh state for flowability, passing ability and segregation resistance. In the hardened state, these mixes were examined for compression strength, splitting tensile strength, pore structure by scanning electron microscope (SEM), and heat of hydration was measured. The results concluded that, FA and BFS enhance the heat of hydration and durability properties of concrete leading to environmentally friendly concrete mixes.

Assessment of strength characteristics for experimental based workable self compacting concrete using artificial neural network

Self compacting concrete (SCC) is the concrete which can flow through reinforcement without the requirement of vibration. The proportioning of materials for workable SCC requires clear understanding of material properties and their behavior with one on one to apply it in construction site. Hence, an extensive experimentation is conducted based on empirical way and produced 123 workable SCC mixtures resulting for measuring the strength characteristics such as compressive strength (fc) and splitting tensile strength (fst). The workable SCC mixture is considered for strength characteristics only after passing the requirements of workability tests of SCC namely slump flow test, L-box test, V-funnel test and sieve segregation resistance test. The 123 workable SCC mixtures experimentally obtained fc ranging from 26.6 N/mm2 to 62.1 N/mm2 and fst ranging from 2.9 N/mm2 to 6.9 N/mm2. In this study, artificial neural network (ANN) had been used which was speedy and efficient for predicting output strength characteristics based on extensive experimental data investigated in laboratory. ANN is data modeling tool where relationship between inputs and output can be found out. In this work, after investigating all parameters for producing SCC, only important inputs considered in ANN model. Marquardt back propagation training algorithm had been used with inputs containing cement content, water cement ratio, type of mineral admixture, percentage of mineral admixture and type of chemical admixture. In this study, satisfactory mean square error and correlation coefficient had been obtained during training, validation and testing of ANN for predicting two outputs fc and fst separately.

ТЕХНОЛОГИЯ ПЕРЕРАБОТКИ БЕТОННОГО ЛОМА С ЦЕЛЬЮ ПОЛУЧЕНИЯ САМОУПЛОТНЯЮЩЕГОСЯ БЕТОНА

The article presents the recycling technology of reinforced concrete formed during the renovation program in Moscow city. It is shown that the part of concrete can be recycled to obtain raw materials for self-compacting concrete use, including products of recycling. The products include recycled concrete aggregate 5-10 mm fraction and the filler. It is indicated that the efficient concept of recycling process is sorting of various types of products and removal of contaminants. The sequence of technological operations for dismantling buildings, transportation and recycling of concrete, storing and quality control of the resulting product has been developed. Technological methods that allow to obtain self-compacting concrete mixtures with the use of recycled concrete in concrete plant are suggested.

Valorization of fly ash from a thermal power plant for producing high-performance self-compacting concrete

This study analyzes the feasibility of valorizing industrial by-product, fly ash from a thermal power plant as a partial replacement of mineral filler-limestone for the production of self-compacting concrete (SCC). Three types of SCC mixtures with different portions of fly ash and the reference mixture with limestone were designed. The synthesized SCCs in the fresh state were examined for density, entrained air content, flowability (Slump flow, Slump flow time (t500), V-funnel time (tv)), passing ability (L-box), and segregation resistance, while hardened state testing included: density, compressive and flexural strength, static modulus of elasticity, water permeability, resistance against freezing in the presence of de-icing salt, and SEM analysis. Taking into account the obtained results it can be concluded that the addition of fly ash has a positive impact on the concrete properties and that the optimal content of fly ash is 20 % with respect to the total filler mass.

Effect of fine fillers from industrial waste and various chemical additives on the placeability of self-compacting concrete

The premise for the study reflected in this article is the need to dispose of industrial waste, which is increasingly being used in the construction materials industry. Also, dynamically developing building industry demands attention of scientists and a direction of their works on improvement of the technology of carrying out construction works. Thus, the article is devoted to studying the influence of various chemical additives and fine fillers (industrial wastes) available in Kazakhstan on selfcompacting concrete (SCC) mixtures and its rheological, physical, and technical properties. According to the studies, revealed the most efficient type of fine-dispersed filler and the most optimal type of chemical additive to enable obtaining a high-quality SCC mixture based on local raw materials. As a result, the use of microsilica in comparison with other industrial wastes resulted in a conglomerate with high compressive strength of SCC at early terms of curing. In terms of economic efficiency and quality improvement, the results of study are of practical value for the manufacturers of ready-mixed concrete operating in Kazakhstan.

Assessing the quality of concrete – reinforcement interface in Self Compacting Concrete

Research has shown that even self-compacting concrete (SCC) mixtures can exhibit the so-called “top-bar effect” which impacts bond and anchorage. Several instances of conflicting results have nevertheless been published regarding interfacial bond between self-compacting concrete and steel reinforcement. The scope of this paper is to present an experimental methodology for assessing the quality of the interface between self-compacting concrete and ribbed reinforcement. For this purpose, seven different self-compacting and four normally vibrated concrete (NVC) mixtures with diverse rheological characteristics were examined. Digital Image Analysis of cut sections containing reinforcing bars at different cast-heights was used as a diagnostic tool. The study illustrates that the quality of the interface is strongly affected by the viscosity of the SCC mixtures and by the slump values in NVC. Self-compacting concrete mixtures show greater inherent robustness and cohesion at the steel–concrete interface compared to conventionally vibrated concretes.

Study of the influence of fine fillers from technogenic waste and chemical additives on the properties of self-compacting concrete

The article is devoted to the researches considering the influence of various chemical additives and fine fillers (industrial wastes) available in the Republic of Kazakhstan on concrete mixes and concrete rheological and physical-technical properties. The article provides laboratory studies results of some of self-compacting concrete (SCC) mixtures properties. There were identified the most efficient type of fine-dispersed filler and the most optimal type of chemical additive to be able to get a high-quality SCC mix and a concrete with the class of B25 based on local raw materials. There were enlisted compositions of SCC with a high strength in early terms. The research results are of practical value in the forms of economic efficiency and quality improvement in the production of SCC mixes for manufacturers of ready-mixed concrete operating in the Republic of Kazakhstan.