High Fluidity Concrete Research Articles

Influence of mortar thickness on the dynamic segregation of high-fluidity concrete

The properties of concrete are related to the mesostructure decided by the constituents. This study aims to establish a quantitative relationship between the dynamic stability of fresh concrete and the mesoscopic parameters. A novel method named the declined table test is used to evaluate the dynamic segregation tendency of fresh concrete continuously. With the VSI method provided by ASTM C1611 in contrast, it is demonstrated that using the ratio of the flow angle of mortar to the flow angle of concrete (Am/Ac) obtained from the declined table test is credible as the dynamic segregation index. The concrete with an Am/Ac ratio lower than 1.5 is regarded to be in a stable state. According to the mortar filming ability test, the mortar in concrete can be divided into stable mortar and free mortar. Stable mortar saturation degree is proposed to reveal the mechanism of dynamic stability from the mesoscopic view, which is defined as the specific value of the volume fraction of stable mortar and total mortar (SDv) or the specific value of stable mortar thickness and mortar thickness between coarse aggregate particles (SDt). In contrast, SDt has a better correlation to the Am/Ac ratio and the SDt value should be higher than 1.14 to guarantee enough stability of fresh concrete.

Test Method of Segregation Resistance of High Fluidity Concrete Based on Numerical Simulation of Dynamic Segregation of Coarse Aggregate

Test Method of Segregation Resistance of High Fluidity Concrete Based on Numerical Simulation of Dynamic Segregation of Coarse Aggregate

Experimental and analytical study on compressive bearing capacity of steel shell-concrete composite bridge tower

To improve the mechanical performance and construction convenience of the bridge towers, a steel shell-concrete composite tower (SSC structures) was proposed. The steel shell consists of outer and inner steel plates, diaphragms, and stud connectors inside the cells. Then the high fluidity concrete is poured into the steel shell to form the composite tower. Through the uniaxial compressive tests of the specimens with different concrete strength and the nonlinear finite element parametric analyses, the force transfer mechanism of the steel shell, the infilled concrete, and the stud connectors at the steel–concrete interface were revealed. The results show that the proposed steel shell-concrete composite tower has a higher bearing capacity than the conventional concrete-filled steel tube tower, in which the bearing capacity of concrete was increased by about 20% from the test results due to the composite effect between steel and concrete. Diagonal breakage bands were formed when the specimens finally failed, on which the concrete was crushed, and the steel plates had large out-of-plane deformation and weld cracking. Through finite element calculation, it was found that the increase of stud forces mainly occurred after the yield of the steel wall plates, and the maximum values of the shear forces and tension forces were 3.6 kN and 4.7 kN, respectively. The results also show that the multiple-cell section has better mechanical performance than the double steel section, which is suitable for the section form of the composite bridge tower.

Concrete Interface Feature Extraction and Stability Analysis Based on PCA Model

With the rise of concrete pumping construction technology, high-mobility concrete has been more and more widely used. However, high fluidity concrete is prepared with high sand ratio and small stones, which weakens the volume stability of aggregate as a skeleton. Therefore, instability often appears in the practical application of large concrete. At present, the research on the stability of concrete interface feature extraction is still relatively scarce. In this paper, through a large number of experiments, the law of the main performance of concrete is systematically studied, and the characteristics of concrete interface are extracted using the principal component analysis (PCA) model. On this basis, the influence of different factors on the stability of concrete is studied, especially the compressive strength, volume stability, and durability of concrete. The experimental results will have a good reference value and far-reaching significance for improving the application status of high fluidity concrete.

Evaluations of All-in-One, Polycarboxylate-Based Superplasticizer with Viscosity Modifying Agents for the Application of Normal-Strength, High-Fluidity Concrete

High fluidity concrete exhibits an excellent self-compacting property. However, the application of typical high-fluidity concrete is limited in the normal strength range (18~35 MPa) due to the large amount of binder. Therefore, it is important to solve these problems by adding a viscosity modifying agent (VMA) with a superplasticizer (PCE), which helps to improve the fluidity of the concrete. In addition, the rheology and stability of the concrete with VMA can be improved by preventing bleeding and segregation issues. Current studies focused on the physical phenomena of concrete such as the fluidity, rheological properties, and compressive strength of normal-strength, high-fluidity concrete (NSHFC) with different types of a polycarboxylate-based superplasticizer (NPCE). The obtained results suggested that the combinations of all-in-one polycarboxylate-based superplasticizers (NPCE) did not cause any cohesion or sedimentation even stored for a long time. The combination of three types of VMA showed the best fluidity (initial slump flow of 595~630 mm) without any segregation and bleeding, and the compressive strength at 28 days was also found to be the highest: 34–37 MPa. From these results, the combination of PCE (2.0%) + HPMC (0.3%) + WG (0.1%) + ST (0.1%) showed an 18% higher plastic viscosity and -4.4% lower yield stress than Plain.

Numerical method for predicting flow and segregation behaviors of fresh concrete

Current meshless particle methods are able to simulate the flow of fresh concrete, but fail to predict the segregation since fresh concrete is regarded as homogeneous fluid. This study aims to develop a numerical approach to predict the segregation of coarse aggregate (CA) in fresh concrete together with the flow behavior. A double-phase & multi-particle (DPMP) model was proposed to describe fresh concrete, which treats fresh concrete as a double-phase fluid composed of matrix mortar and the CA particles that had random shapes, size distribution, and different density from matrix mortar. Each CA particle was formed by the element particles, of which number was dependent on the size and shape of described CA particle. Three types of inter-particle interaction, including CA-CA particles, CA-mortar particles, and two mortar particles, were investigated, respectively. Then, based on the complete implicit MPS (I-MPS) method and the DPMP model, the L-box flow of two series of high fluidity concrete were simulated. The ability of the proposed numerical approach to simultaneously simulate the flow and segregation behaviors of fresh concrete was confirmed. Moreover, this numerical method can analyze the changes of localized rheological parameters of segregated concrete.

An experimental study on the flowability and strength properties of normal strength - high fluidity concrete by combination of polycarboxylate superplasticizer and viscosity modifying admixtures

An experimental study on the flowability and strength properties of normal strength - high fluidity concrete by combination of polycarboxylate superplasticizer and viscosity modifying admixtures

Ductile Evaluation and Mechanical Performance of Recycled Aggregate Concrete Using PVA and Steel Fibers

In recent years, a high toughness cement composite material (HTCCM) has been developed, which has far more performance than existing fiber reinforced concrete. HTCCM is a composite material made by reinforcing cement-based materials with fibers. It exhibits multiple crack characteristics under bending stress and greatly improves toughness during flexural, tensile, and compressive fracture. In this study, it is examined the mechanical properties of high fluidity and high toughness concrete (HFHTC) using fly ash as an admixture and recycled fine and coarse aggregate as an aggregate. From the standpoint of durability, it is necessary to fully examine the long-term properties of HFHTC using recycled fine and coarse aggregate, therefore, it is examined the strength and shrinkage of HFHTC using recycled fine and coarse aggregates.

Study of concrete shrinkage behaviour using the restrained squared eccentric ring test method

Four types of cement-based concrete specimens were analysed in this study – high-fluidity concrete, semi-dry concrete, high-fluidity crumb rubber concrete with a rubber content of 110 kg/m3 and semi-dry crumb rubber concrete with a rubber content of 110 kg/m3. The restrained squared eccentric ring test method was applied to measure the restrained shrinkage strains at early age (first 5 d) in the 0, 90 and 180° zone of the specimens, as well as the time when the specimens cracked. All 12 specimens cracked near the 0° zone, and the values of restrained shrinkage strains in the 0, 90 and 180° zones showed a decreasing sequence. Compared with the ordinary concretes without crumb rubber, the restrained shrinkage of the crumb rubber concretes was reduced and the cracking time was prolonged. The restrained shrinkage strains in the 0, 90 and 180° zone plotted against time showed a linear growth pattern. The ratio of shrinkage strain between the 0° zone and the 90° zone and that between the 0° zone and the 180° zone were practically invariable over time, suggesting that restrained shrinkage strains may be expressed mathematically by a product of a time-dependent function and a spatially dependent function, as postulated in a number of analytical studies.

Outline of the Activities of the Research Group for Promoting the Use of High-Fluidity Concrete in Buildings

建築物の耐震性向上や大規模化に伴い，従来のスランプ管理のコンクリートでは充填が困難になるケースが増加している。そこで流動性の高いコンクリートの利用促進によるコンクリート工事における生産性向上，不具合低減，高品質化を図ることを目的とし，日本建設業連合会では，「建築分野における高流動性コンクリートの普及に関する研究会」を発足し，20社が参加し，3つのワーキンググループで活動を行った。本報では，本研究会の活動概要，各WGの活動成果および本研究会の成果物として「現場添加型高流動性コンクリートの製造要領書」と「高流動性コンクリートの利用ガイドライン」について紹介する。

Preparation for polyacrylic acid modified by ester group in side chain and its application as viscosity enhancing agent in polycarboxylate superplasticizer system

The problem of bleeding and segregation in high fluidity concrete can be eliminated by the addition of viscosity-enhancing agents (VEA). However, the dispersion capacity of PCE would be perturbed by the addition of VEA. In most cases, this negative impact was due to competitive adsorption between VEA and PCE. In order to mitigate the negative impact, ester groups were introduced to reduce the adsorption capacity, and one new kind of viscosity-enhancing agents was designed; the polymers were copolymerized of acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA), with 1:1 and 1:8 M ratios of AA and HEA. And then, the effect of these two VEAs on rheology of cement paste plasticized by PCE at 5 min and 30 min were studied. Adsorption behavior was analyzed by total organic carbon (TOC), and the zeta potential was also measured. The conformation of the polymers in liquid phase were analyzed by dynamic light scattering (DLS). And the decomposition of ester group under alkaline condition was verified by FTIR and 1HNMR. The results indicated that the synthesized VEA could plasticize cement paste, and the reason was that VEA could be adsorbed by cement grains and act as the same role as the first-generation superplasticizer. The plasticizing capacity was increased over time, because the adsorption capacity was enhanced due to the released carboxyl groups from the decomposition of ester groups. Furthermore, from 5 min to 30 min, the decomposition of ester group could increase the conformation size of VEA by producing crosslinking in the presence of Ca2+, and the crosslinking act as positive role in increasing viscosity and resist the bleeding and segregation. Moreover, it was observed that VEA had negative impact on dispersion capacity of PCE, and the higher density of ester group resulted in lower negative impact at the beginning; one reason for this was because the higher density of ester group showed lower competitive adsorption capacity. Such results offered one new type of VEA available for superplasticizer system.

骨料分布的均匀性对大流动性混凝土强度和耐久性的影响

骨料分布的均匀性对大流动性混凝土强度和耐久性的影响

Effect of Sodium Tripolyphosphate on Clay Tolerance of Polycarboxylate Superplasticizer

High fluidity concrete has been widely used in modern civil engineering project to ensure that the highly efficient construction process can be achieved. Generally, the fluidity can be obtained with the incorporation of superplasticizer system composed of polymers and retarders. Sodium tripolyphosphate (STPP), a commonly used retarder in cement-based material, can obviously increase the dispersion of polycarboxylate superplasticizer (PCE), and this has been widely employed in real concrete. However, the effect of STPP on clay tolerance of PCE has not been confirmed until now, and it is still uncertain whether STPP in PCE system has positive or negative effect on workability of fresh concrete with poor-quality aggregates containing montmorillonite (Mt) which is one of the most harmful clay minerals. In this study, the effect of STPP on fluidity of cement-Mt paste with PCE has been investigated. The fluidity was tested with mini slump to assess the clay tolerance of PCE. The adsorption amount of PCE and STPP in Mt suspension was tested with total organic carbon analyzer and inductive coupled plasma emission spectrometer to characterize the adsorption behavior. The interlayer spacing was evaluated with X-ray Diffractometer and the structure of intercalated Mt by PCE was characterized with Fourier-transform infrared spectrometer and thermo gravimetric analyzer, and these results were used to illustrate the effect of STPP on intercalation of PCE. Finally, the dispersion model was proposed to reveal the mechanism behind. The results show that STPP can disperse the Mt particles and increase adsorption amount of PCE in Mt suspension, thereby accelerating rather than hindering the intercalation of PCE into Mt. The fluidity of cement-Mt paste with PCE-STPP system is depended on the added dosage of STPP: with the dosage less than 0.20%, the contribution of STPP to dispersing the cement particles predominates, hence increasing the fluidity of the paste and improving the clay tolerance; while with the dosage more than 0.20%, the acceleration of the intercalation of PCE resulting from STPP becomes predominant, thereby reducing the fluidity of the paste. This result can provide useful experience for the improvement in clay tolerance of PCE in real concrete with poor aggregate containing Mt.

Effects of curing conditions and addition of fine blast furnace slag powder on the initial performance of concrete using expanding material

In this study was investigated the effect of steam curing in the case of adding expandable material to powdery high fluidity concrete containing blast furnace slag fine powder on two kinds of expansive materials, ettringite type inflation material and lime type expansion material. As a result, the constraint expansion strain increases with the ettringite type due to the increase in the steam curing temperature. However, it was confirmed that it decreased with the lime type expansion material.

A Study on the Properties of High-Fluidity Concrete with Low Binders Using Viscosity Agent

기존의 고유동 콘크리트는 높은 분체계로 인해 수화열과 수축의 증대, 비경제적인 강도발현 등의 문제점이 발생하여 일반강도 범위의 콘크리트에는 사용범위가 제한하고 있다. 그러나 공사품질의 향상과 더불어 공사비 절감, 공기단축 등의 이점으로 일반강도 수준의 고유동 콘크리트의 필요성이 대두되고 있다. 이를 위해 본 연구에서는 점성을 최소화하고 재료분 리...

The performance of high fluidity concrete for normal strength structures

Self-compacting concrete (SCC) represents high quality concrete with exceptional workability and enables the easy production of heavily reinforced concrete structures of complex geometry. In spite of its obvious advantages, the high cost of SCC prevents its wider use. For normal strength concrete structures, the performance of high fluidity concrete would be sufficient, providing an affordable and more cost-effective solution than SCC for the construction market. The objective of the current research was to explore the properties of fresh and hardened high fluidity concrete composed of a high amount of fine fillers from industrial by-products (ground limestone filler and fly ash filler) and polycarboxylic ether polymers. The enhanced performances of the resulting concrete mixtures are discussed in terms of the mechanisms involved and the implications of their application in construction.

고압송용 고유동콘크리트 개발을 위한 가압에 따른 굵은골재의 흡수 특성

Abstract: In this study, we developed a pressing device which can reproduce the pressure of concrete inside the conveying pipe as a part of the basic study to development of high fluidity concrete under high pressure pumping. Using this pressing device, we evaluated a absorption properties of aggregate that are crushed coarse aggregate, river gravel and lightweight coarse aggregate according to pressure of coarse aggr egate and aggregate inside a high fluidity concrete, focused on the reduction of unit water quantity by pressure. In addition, it was evaluated the compressive strength of high fluidity concrete about before and after of pressive. Test a result, case of condition under the high pressure of 250 bar, absorption ratio of crushed coarse aggregate and river gravel were not increased above the surface absorption, absorption ratio of lightweight coarse aggre gate was increased than the surface absorption.Keywords: High Pressure Pumping, High Fluidity Concrete, Pressurization, Coarse Aggregate, Absorption

일라이트 미분말을 혼입한 고유동 콘크리트의 유동성 및 충전성에 관한 연구

This study is to be investigate properties of workability, compacting and compressive strength replaced by the illite powder in high fluidity concrete. For this purpose, illite powder has replaced the binder of high fluidity concrete of 5%, 10%, 15%, 20%. After concrete mixing, slump flow test, reach time slump flow 500mm, O-lot test were conducted on fresh high fluidity concrete. And compressive strength was determined 28 days for the hardened high fluidity concrete specimens. According to the test results, the workability, filling height of high fluidity concrete were increased in 10% replacement of illite powder. Furthermore, the compressive strength of high fluidity concrete was increased in 10% replacement of illite powder.. It was possible to confirm that optimal mixture ratio of illite powder seems to exist, and it is shown to be 10% according to our experimental results.

폐 대리석 분말을 혼입한 고유동 콘크리트의 기초적 특성에 대한 실험적 연구

본 연구는 대리석가공과정에 발생하는 부산물인 폐 대리석 분말을 고유동 콘크리트의 유동성, 충전성 및 강도특성에 어떠한 영향을 주는지를 분석하였다. 실험결과, 폐 대리석 분말을 혼입한 굳지 않은 고유동 콘크리트 특성을 살펴보면 유동성이 증가하였고, 재료분리 저항성, 충전성이 우수하였다. 또한 경화한 고유동 콘크리트에서 압축강도는 폐 대리석 분말의 치환율 15%까지 모든 재령에서 압축강도가 증가하여 폐 대리석 분말의 최적 치환율은 15% 이내가 적정할 것으로 판단된다. 이상의 실험결과를 바탕으로 폐 대리석 분말을 고유동 콘크리트의 충전재로 활용하면 산업부산을 활용할 수 있어 환경오염방지와 콘크리트 제조시 원가절감의 이점을 동시에 달성할 수 있을 것으로 판단된다. The marble powder is a by-product that can be freely collected during the manufacturing process of marble, such as sawing, shaping, and polishing. Disposal of this waste powder is one of the environmental problems worldwide today. Therefore, this study investigated to solve this problem by consuming the waste marble powder in high fluidity concrete, as a pore filler. For this purpose, the waste marble powder was used as a binder replacing 5%, 10%, 15%, and 20% of cement in high fluidity concrete. After mixing, slump flow test, time-to-reach the slump flow of 500mm test, O-lot test and U-box test were conducted with fresh concrete. For the hardened concrete, compressive strength was determined at the age of 28 days. According to the test results, the workability of high fluidity concrete increased with the powder of 15% replacement, and the compressive strength of high fluidity concrete also increased with the same amount of powder.

A Study on the Evaluation of Field Application of High-Fluidity Concrete Containing High Volume Fly Ash

In the recent concrete industry, high-fluidity concrete is being widely used for the pouring of dense reinforced concrete. Normally, in the case of high-fluidity concrete, it includes high binder contents, so it is necessary to replace part of the cement through admixtures such as fly ash to procure economic feasibility and durability. This study shows the mechanical properties and field applicability of high-fluidity concrete using mass of fly ash as alternative materials of cement. The high-fluidity concrete mixed with 50% fly ash was measured to manufacture concrete that applies low water/binder ratio to measure the mechanical characteristics as compressive strength and elastic modulus. Also, in order to evaluate the field applicability, high-fluidity concrete containing high volume fly ash was evaluated for fluidity, compressive strength, heat of hydration, and drying shrinkage of concrete.