High Fluidity Concrete Research Articles

Mechanical properties of natural fiber-reinforced normal strength and high-fluidity concretes

An experimental investigation of mechanical properties of jute fiber-reinforced concrete (JFRC) has been reported for making a suitable construction material in terms of fiber reinforcement. Two jute fiber reinforced concretes, called jute fiber reinforced normal strength concrete (JFRNSC) and jute fiber- reinforced high-fluidity concrete (JFRHFC), were tested in compression, flexure and splitting tension. Compressive, flexural and splitting tensile strengths of specimens were investigated to four levels of jute fiber contents by volume fraction. From the test results, Jute fiber can be successfully used for normal strength concrete (NSC) and high-fluidity concrete (HFC). Particularly, HFC with jute fibers shows relatively higher improvement of strength property than that of normal strength concrete.

フレッシュコンクリートのレオロジー的性状に関する理論的研究

Modeling fresh concrete's rheological behaviors is basically needed for flow simulation and establishing indexes of quality control and test method, which are indispensable to workability design of concrete. In this study, the author proposed a microscopic approach to rheological performance clarification of fresh concrete based on a series of past studies on viscosity mechanism, granular characteristic, shear resistance-particle fabric relationship, shear deformation-particle movement, etc. This approach treats with fresh concrete as a kind of particle assembly containing water, of which deformation resulted from particles' movement can be induced following by analyzing the probability of moving particles, and variation of mean particle contact angle and distance of particles. Using this approach, constitutive laws of fresh concrete before and after yielded were investigated theoretically. The obtained constitutive laws are applied to not only high fluidity concrete but also stiff concrete, and can express the characteristics of shear deformation/flow of fresh concrete: non-linear, and vertical pressure, stress history, and loading elapsed time-dependent.

Recycling of tailings from Korea Molybdenum Corporation as admixture for high-fluidity concrete

The main objective of this study is to develop an eco-friendly and a large recycling technique of flotation Tailings from korea (TK) from metal mines as construction materials such as admixtures for high-fluidity concrete (HFC). TK used in this study was obtained from the Korea Molybdenum Corporation in operation. TK was used as the alternative material to adjust flowability and viscosity of HFC in the form of powder agent which enables adjustment of concrete compressive strength. In this study, we have performed concrete rheological tests and concrete flowability tests to obtain the quality characteristics of TK for using as the admixture in producing HFC. The results indicated that the adequate mix ratio of cement to TK should be 8:2 (vol%). It is more effective to use the TK as admixture to control flowability, viscosity and strength of HFC than the normal concrete. It was found that TK could be recycled construction materials in bulk such as admixture for HFC, in terms of the economic and eco-friendly aspects.

모의실험체에 의한 다성분계 고유동 콘크리트의 시공성능 평가에 관한 연구

건설산업이 대형화, 초고층화, 다양화되면서 우수한 기술과 Know-how가 요구되고 있고, 또한 건설기술자의 부족, 특수환경 하에서의 건설공사의 증가 및 구조물의 고성능화 등의 요구에 따라 콘크리트 분야 기술력을 개발하고 실용화하는 것이 필요하다. 이를 위하여 고성능 콘크리트에 대한 성능규정 및 기술개발에 많은 노력을 기울여 왔으며 한 가지 방안으로 신뢰성이 높은 고유동 콘크리트를 적용하면 시공의 제약조건을 극복할 수 있으며, 작업인원의 절감 및 공기단축의 효과를 얻을 수 있을 것으로 기대된다. 고유동 콘크리트를 현장에 적용하기 위해서 실제 건설현장에서 대용량의 배치플랜트에서 생산할 경우에도 시공성을 만족시킬 수 있는지를 평가하기 위하여 현장 모의시험을 실시하였다. 시험결과로부터 다성분계 고유동 콘크리트는 실제 구조물에서도 양호한 충전성능을 가진 것을 확인할 수 있었고, 수화열로 인한 콘크리트 내부온도 상승도 양호한 범위 값을 나타내었다. 향후 시공조건에 따라 전련산업관련 구조물 등에 유용하게 활용될 수 있을 것이다. As structures become larger, taller, and more diverse, a high degree of technology and expertise are required in the construction industry. However, it has been becoming difficult to construct under severe conditions and to fulfill the high performance needs of structures due to a lack of skilled construction engineers. To compensate for these weak points, high-performance concrete and performance specifications have been developed. The application of reliable high-fluidity concrete, which is one of these efforts, is expected to be effective in terms of overcoming severe conditions, reducing the number of workers required, and shortening the construction period. In order to apply high fluidity concrete in the field, practical mock-up tests were carried out to estimate whether self-compaction concrete could satisfy constructability needs. From the results, it was verified that the multi-component high fluidity concrete has excellent flowability in practical structures. In addition, it was shown that the temperature distribution in the concrete due to hydration heat is satisfactory. As a result, it is judged that multi-component high fluidity concrete can be utilized as an effective building material for various structures, including structures related to the electric power industry.

An Experimental Study on Properties of High Fluidity Concrete with Large Maximum Size of Aggregate

An Experimental Study on Properties of High Fluidity Concrete with Large Maximum Size of Aggregate

Behavior of composite segment for shield tunnel

Composite segment has been developed for obtaining high capacity in lining of shield tunnel subject to high hydraulic pressure and earth pressure in deep underground, which is made of steel plates connected to an infill of high fluidity concrete with shear connectors. However, a rational design method for composite segments can not be established, because the behavior of composite segments is not clarified. The purpose of this paper is to study the behavior of the most complicated composite segment with six steel plates using finite element method and the four-point bending tests. The effects of the shear studs and the thicknesses of steel plates were verified and estimated quantitatively. Meanwhile, the failure modes of composite segments were investigated. Comparisons show that the finite element model is suitable for composite segments and predicts the behavior of composite segments accurately.

フライアッシュを大量混合したコンクリートの実大模擬部材試験体による検証

The concretes containing large quantity of fly ash with constant portland cement content were produced at the ready-mixed concrete plants, and placed into full scale formworks. Their fresh and hardened properties were measured and discussed.1.At various fly ash content per unit volume, for example 455kg/m3, the concretes which have various flowability, such as medium or high fluidity concrete, were produced easily. And they could be filled smoothly into narrow space of wall formworks with reinforcements.2.The fly ash concretes appeared higher compressive strength from the early age and carbonation resistance than those of the concrete without fly ash.

高流動コンクリートを流動させた実大柱壁部材の品質と小径コアによる単位セメント量に関する一考察

Small-sized core method by sodium gluconate can be used in determining the unit cement content of concrete.Applicability of this method to quality control of concrete in structures was examined.A full-scale model structure with a high fluidity concrete, whose extent of segregation was intentionally increased, were built and relationship between concrete quality and the unit cement content determined with the small-sized core method by sodium gluconate was studied.It was shown that the relationship was correlative and application of small-sized core method by sodium gluconate to the quality control of concrete in structures was found to be reasonable.

Properties of High Fluidity Concrete with Combination of Fine Powder of Slowly Cooled Blast Furnace Slag and Granulated Blast Furnace Slag

The properties of high fluidity concrete with a combination of the fine powder of slowly cooled blast furnace slag and granulated blast furnace slag were examined. The change of slump flow value with time decreased when a specified ratio or more of slowly cooled blast furnace slag was used. The concrete with various levels of compressive strength can be prepared by changing the mixing ratio of these powders. It has been clarified that close relations exist between adiabatic temperature rise and the unit weight of binder, as well as between autogenous shrinkage and water binder ratio, and that mix proportion design suited to required performance is possible. By the use of this high fluidity concrete, it is possible to suppress both CO2 emission and limestone consumption per unit of concrete, which suggests that this concrete is useful from the viewpoint of reduction in environmental burden.

Relationships between Rheological Constant of Cement Paste and Fluidity of High-Fluidity Concrete

In order to develop a method for evaluating the fluidity of high-fluidity concrete using cement paste, the relationships between the rheological properties of cement paste and the slump flow of the concrete were investigated, using several commercial Portland cements. The rheological constants of the cement paste were measured with a rotating viscometer changing the mixing procedure, dosage of superplasticizer, and the operation conditions of the viscometer. The yield values of cement pastes measured with a parallel-plate type rotating viscometer were found to show good correlation with the slump flows of concretes.

A study on the applicability of vibration in fresh high fluidity concrete

The introduction of superplasticizers (Sp) in the production of concrete has produced highly flowable mixtures with enhanced viscosity. In cases of optimum flowability and viscosity, for example self-compacting concrete (SCC), no vibration is necessary for placement. However, such ideal conditions are not practically easy to achieve and deviations are possible. This paper reviews the results of a study to investigate the vibration of such high fluidity concrete. Two criteria were used to characterize the fresh mix, that is, slump flow and V-funnel time (V-time). Firstly, the feasibility of vibration on such mixes was studied. Then, the significance of flowability and viscosity was determined. Next, the relationship between workability and its segregation tendency was investigated. Finally, concrete mixes that missed SCC criteria were vibrated. Three different scenarios of vibration were concluded: namely, mix that accept vibration freely, mix that required controlled vibration and mix that needed prior treatment of viscosity enhancing agent (VEA) before vibration.

Flow Performance of High-Fluidity Concrete

In this paper a particle assembly model was proposed for high fluidity concrete in the fresh state. This particle assembly is composed of cohesionless particles (aggregates grains) and cohesive particles (cement grains) surrounded by mixing water membranes. By using a microscopic approach and expanding Eyring’s rate process viscosity theory, the flow mechanism of high fluidity concrete having interfriction was clarified, and its flow curve was examined. Furthermore, the effects of normal stress and environmental temperature on the flow behavior of high fluidity concrete were investigated quantitatively. Finally, a shear test apparatus was developed and a series of shear tests were performed to verify the obtained theoretical results.

유동화공법에 의해 제조한 고유동 콘크리트의 시공 및 원가분석

High fluidity concrete(HFC) requires high dosage of superplasticizer to acquire sufficient fluidity, and high contents of fine powder and viscosity enhancing admixtures to resist segregation. The use of high amount of admixtures to make HFC at batcher plant in ready mixed concrete company is one of the reasons to raise the manufacturing cost of HFC. For this reason, new type of manufacturing method of HFC are described using both flowing concrete method and segregation reducing superplasticizer(SRS) in order to gain economical profit and offer the convenience for quality control.. As dosage of melamine based superplasticizer increases, it shows that fluidity and bleeding increase, while air contents and ratio of segregation resistance decrease. It also shows that addition of viscosity agent into superplasticizer reduce bleeding and improve segregation resistance of concrete. Dosage of AE agent into superplasticizer containing viscosity agent recovers loss of air contents during flowing procedure. Combination of proper contents of superplasticizer, viscosity agent and AE agent make possible to develope segregation reducing type superplasticizer. Compressive strength of high fluidity concrete applying flowing method with it is higher than that of base concrete. No differences of compressive strength between compacting methods are found. For the estimation of construction cost of high fluidity concreting using segregation reducing type superplasicizer, under same strength levels, although material cost of high fluidity concrete is somewhat higher than that of plain concrete due to segregation reducing type superplasticizer cost, labor cost and equipment cost of high fluidity concrete is cheaper than that of plain concrete. However, based on the strength differences, high fluidity concrete shows lower material cost, labor cost and equipment cost than that of plain concrete due to decreasing in size of member and re-bar caused by high strength development of concrete.

Yield Model of High Fluidity Concrete in Fresh State

This paper presents a microscopic approach to model the yield condition of high fluidity concrete in the fresh state for the rheological evaluation and the numerical flow simulation to optimize its workability and composition. Based on considering fresh concrete as a type of particle assembly containing water, cohesive particles (cement grains), and cohesionless particles (aggregate grains), the directions and magnitudes of inter-particle forces are examined, the shear deformation resistance of fresh concrete is investigated. Then, an equation of yield condition is derived, and a yield model is proposed for high fluidity concrete in fresh concrete. Furthermore, the dependence of the yield stress on interparticle friction, temperature, normal stress on the shear plane, etc., is clarified on the basis of the obtained yield condition equation.

Theoretical Analysis of Time-Dependence and Thixotropy of Fluidity for High Fluidity Concrete

This paper deals with the time dependence of fluidity and thixotropy of high fluidity concrete containing polycarboxylate-based superplasticizer. Taking the effects of both hydration and physical flocculation of cement particles into consideration, the increases in apparent viscosity and Bingham constants with the elapsed time of the stationary state, and the time dependence of the apparent viscosity in agitated state, are theoretically investigated. Moreover, the effects of the number, peak value, and durations of applied stepwise stresses, etc., on the shape and the area surrounded by the hysteresis loop of shear rate versus shear stress are discussed quantitatively.

寒中時養生方法が各種混和材料を用いた高流動コンクリートの諸性状に及ぼす影響

It is important to understand the curing methods of the high fluidity concrete and various properties in winter from the point of the plan as the construction. Therefore, we examined the high fluidity concrete that used admixtures such as binding agents, segregation reducing agent by using the large model test specimen. As results, the heat curing is effective means to obtain prescribed strength at the early age in the winter concrete construction. However, attention is required for the curing period and the state of moist at the heat curing. The freezing and thawing resistance decreases according to an initial the curing methods occasionally. The finding obtained by the experiment can be reflected in the construction plan.

無収縮高流動コンクリートで一体化した逆打ちコンクリートの打継ぎ部の力学性状に関する研究

Shrinkage compensating high fluidity concrete is a new type of concrete for construction joints which enables the joint to bond firmly in the inverse placing construction method. With the aim of examining mechanical behavior in horizontal joint inversely cast with shrinkage compensating high fluidity concrete, the bending test and shear test were conducted. As the result, it has become clear that the flexural strength and shearing strength of horizontal joint inversely cast with shrinkage compensating high fluidity concrete is equal to the strength of the construction joint of normal placing method.

The segregation tendency in the vibration of high fluidity concrete

The introduction of superplasticizer (Sp) has produced concrete that could flow easily under its own weight. In balancing the concrete's ability to flow at the same time maintaining the coarse aggregate distribution, the viscosity of concrete must be enhanced. This study aimed to investigate the effect of vibration on such flowable yet viscous concrete. Concrete flowability and viscosity are quantified by the standard slump cone and V-funnel test, respectively. Despite being flowable, the study concluded that concrete viscosity is an important parameter in determining the tendency for coarse aggregates to segregate. Large-sized coarse aggregates are affected more by the vibration process than the small-sized ones.

高流動コンクリートのせん断流動挙動に関する理論的考察

This paper presents a theoretical study on the shear flowing behavior of high fluidity concrete in fresh state. The yield stress and the flow curve are investigated by the microscopic approach, that is, it is thought that fresh concrete is a kind of particle assembly constituted by cement particles and aggregate particles, and the time-dependence of its deformation and flow is caused by the movements of cement particles. The effects of temperature, normal stress and time point of shear rate measurement on the yield stress and the flow curve of high fluidity concrete are also discussed quantitatively. And the dependence of measured Bingham constants on the level and distribution range of shear rates applied in measurement is clarified.

フライアッシュを使用した高流動コンクリートの調合要因が流動特性に及ぼす効果

This paper is intended to study the effects of the mix proportion on the theological figures of the high-fluidity concrete using fly ash. The relationship between the mix proportion and the fluidity of the concrete was investigated regarding several experimental factors such as the kind of fly ash, the mixing ratio of fly ash to the normal cement, the mixing ratio of super plasticizer and viscosity agent, and sand aggregate ratio, etc. The rheological characteristics of the high-fluidity concrete such as plastic viscosity and yield value were measured by using the J shaped flow test. The main results are as follows. 1) In case of increasing the mixing ratio of Type I fly ash and Type II fly ash, the plastic viscosity and the yield value decrease. In case of increasing the mixing ratio of Type IV fly ash, these values increase. 2) The plastic viscosity of the concrete using Type I fly ash is smaller than that of the concrete using Type II fly ash. 3) The yield value of the concrete using Type I fly ash is nearly the same as that of the concrete using Type II fly ash.