scholarly journals Porous Structure of Ultra-High-Performance Fibre-Reinforced Concretes

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1637
Author(s):  
Manuel Valcuende ◽  
Josep R. Lliso-Ferrando ◽  
Marta Roig-Flores ◽  
José M. Gandía-Romero
Keyword(s):  
Porous Structure ◽  
High Performance ◽  
Oxygen Permeability ◽  
High Strength ◽  
Fibre Volume ◽  
Curing Temperature ◽  
High Concentration ◽  
Curing Conditions ◽  
Very High ◽  
High Performance Fibre

The aim of this experimental work was to study the porous structure of Ultra-High-Performance Fibre-Reinforced Concretes (UH) made with different fibre volume contents (0%, 1%, 2%) under several curing conditions (laboratory environment, 20 °C, 60 °C, 90 °C), comparing the results with those recorded for ordinary, high strength and very high strength concretes. Scanning electron microscopy, mercury intrusion porosimetry, thermogravimetry, water absorption and oxygen permeability tests were carried out. The results showed a low portlandite content in UH (in the order of 75% lower than in concrete C50) and a low degree of hydration, but they rise with curing temperature. These concretes have a very fine porous structure, with a high concentration of pores on the nanoscale level, below 0.05 µm. Their porosity accessible to water is consequently around 7-fold lower than in conventional (C30), 6-fold lower than in high-strength (C50) and 4-fold lower than in very high-strength (C90) concretes. Their oxygen permeability is at least one order of magnitude lower than in C90, two orders of magnitude lower than in C50 and three orders of magnitude lower than in C30. The percentage of added steel fibre does not affect the UH porous structure.

Roof Structural System Study with Use of UHPC

2017 ◽  
Vol 259 ◽  
pp. 70-74
Author(s):  
Milan Holý
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Construction Materials ◽  
High Strength ◽  
Structural System ◽  
Total Load ◽  
Dominant Component ◽  
Industrial Buildings ◽  
Normal Strength ◽  
Very High

This paper deals with the roof structural system using prestressed girders made of ultra-high performance concrete (UHPC). One of the aims of this study is to verify whether the option of the UHPC girders could be under certain boundary conditions competitive with the commonly used construction materials. Due to its high strength, UHPC enables the design of the structural elements with the high load bearing capacity and with smaller slenderness compared to normal strength concrete elements. The price of UHPC is currently still very high compared to the normal strength concretes or steel. Therefore, its use for the usual designed structures does not recently seem too economically attractive. The effect of material savings is nonnegligible in the case, that a self-weight of the structure forms dominant component of the total load. In addition to the high strength, UHPC has very high resistance to environmental influences. It is therefore likely, that UHPC could be advantageously applied e.g. for the roofing of industrial buildings of chemical plants with high aggressive environments, because there are high demands on the life cycle of the structure.

scholarly journals Fibre Distribution Characterization of Ultra-High Performance Fibre-Reinforced Concrete (UHPFRC) Plates Using Magnetic Probes

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5064
Author(s):  
Lufan Li ◽  
Jun Xia ◽  
Chee Chin ◽  
Steve Jones
Keyword(s):  
Reinforced Concrete ◽  
Volume Content ◽  
High Performance ◽  
Fibre Orientation ◽  
Orientation Angle ◽  
Fibre Volume ◽  
Fibre Reinforced Concrete ◽  
Fibre Distribution ◽  
Fibre Orientation Angle ◽  
High Performance Fibre

Ultra-high performance fibre reinforced concrete (UHPFRC) is an innovative cement-based engineering material. The mechanical properties of UHPFRC not only depend on the properties of the concrete matrix and fibres, but also depend on the interaction between these two components. The fibre distribution is affected by many factors and previous researchers had developed different approaches to test the fibre distribution. This research adopted the non-destructive C-shape ferromagnetic probe inductive test and investigated the straight steel fibre distribution of the UHPFRC plate. A simplified characterization equation is introduced with an attenuation factor to consider the different plate thicknesses. The effective testing depth of this probe was tested to be 24 mm. By applying this method, fibre volume content and the fibre orientation angle can be calibrated for the entire plate. The fibre volume content generally fulfilled the design requirement. The fibre orientation angle followed a normal distribution, with a mean value of 45.60°. By testing small flexural specimens cut from the plates, it was found out that the mechanical performance (peak flexural strength) correlates with the product of fibre volume content and cosine fibre orientation angle.

Fabrication of Metallic Nanocomponents by Forging of Ni3Al-Nanoparticles.

2012 ◽  
Vol 1412 ◽  
Author(s):  
Landefeld Andreas ◽  
Rösler Joachim
Keyword(s):  
High Performance ◽  
High Strength ◽  
Complex Structures ◽  
Free Standing ◽  
Large Numbers ◽  
Upset Forging ◽  
Nanoscale Fabrication ◽  
The Individual ◽  
Near Future ◽  
Very High

ABSTRACTThe trend to manufacture components reduced in size at the micro- and nano-scale is obvious and is becoming more and more the state of art in designing actuators, sensors and chips. In recent years, nanoscale fabrication has developed considerably, but the fabrication of freestanding nanosize components is still a great challenge. The fabrication of metallic nanocomponents utilizing three basic steps is demonstrated here. First, metallic alloys are used as factories to produce a metallic raw stock of nano-objects/nanoparticles in large numbers. These objects are then isolated from the powder containing thousands of such objects inside a scanning electron microscope using manipulators, and placed on a micro-anvil or a die. Finally, the shape of the individual nano-object is changed by nanoforging using a microhammer to get specific geometries such as discs and more complex components such as gears and wheels in the near future. The almost cubic particles are essentially defect-free, therefore, provide very high strength (σ>2500MPa) in combination with excellent formability (|ϕ|>1,6). There are two approaches for forming these small particles. Upset forging is used to forge small discs (height<100nm) and to shape the nanoparticle in specific areas. Press forging into nano-dies is used to forge more complex structures. In this way free-standing, high-strength, metallic nanoobjects may be shaped into components with dimensions in the 100 nm range. By assembling such nano-components, high-performance microsystems can be fabricated, which are truly in the micrometre scale (the size ratio of a system to its component is typically 10:1).

scholarly journals Effect of Curing Temperature Histories on the Compressive Strength Development of High-Strength Concrete

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Keun-Hyeok Yang ◽  
Jae-Sung Mun ◽  
Myung-Sug Cho
Keyword(s):  
Compressive Strength ◽  
High Strength Concrete ◽  
High Strength ◽  
Relative Strength ◽  
Curing Temperature ◽  
Strength Development ◽  
Curing Conditions ◽  
Strength Concrete ◽  
Equivalent Age ◽  
Compressive Strength Development

This study examined the relative strength-maturity relationship of high-strength concrete (HSC) specifically developed for nuclear facility structures while considering the economic efficiency and durability of the concrete. Two types of mixture proportions with water-to-binder ratios of 0.4 and 0.28 were tested under different temperature histories including (1) isothermal curing conditions of 5°C, 20°C, and 40°C and (2) terraced temperature histories of 20°C for an initial age of individual 1, 3, or 7 days and a constant temperature of 5°C for the subsequent ages. On the basis of the test results, the traditional maturity function of an equivalent age was modified to consider the offset maturity and the insignificance of subsequent curing temperature after an age of 3 days on later strength of concrete. To determine the key parameters in the maturity function, the setting behavior, apparent activation energy, and rate constant of the prepared mixtures were also measured. This study reveals that the compressive strength development of HSC cured at the reference temperature for an early age of 3 days is insignificantly affected by the subsequent curing temperature histories. The proposed maturity approach with the modified equivalent age accurately predicts the strength development of HSC.

scholarly journals State of the Art: Mechanical Properties of Ultra-High Performance Concrete

2017 ◽  
Vol 3 (3) ◽  
pp. 190-198 ◽  
Author(s):  
Mohamadtaqi Baqersad ◽  
Ehsan Amir Sayyafi ◽  
Hamid Mortazavi Bak
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
High Performance Concrete ◽  
State Of The Art ◽  
High Strength ◽  
Structural Members ◽  
Ultra High Performance Concrete ◽  
Conventional Concrete ◽  
The Past ◽  
Very High

During the past decades, there has been an extensive attention in using Ultra-High Performance Concrete (UHPC) in the buildings and infrastructures construction. Due to that, defining comprehensive mechanical properties of UHPC required to design structural members is worthwhile. The main difference of UHPC with the conventional concrete is the very high strength of UHPC, resulting designing elements with less weight and smaller sizes.  However, there have been no globally accepted UHPC properties to be implemented in the designing process. Therefore, in the current study, the UHPC mechanical properties such as compressive and tensile strength, modulus of elasticity and development length for designing purposes are provided based on the reviewed literature. According to that, the best-recommended properties of UHPC that can be used in designing of UHPC members are summarized. Finally, different topics for future works and researches on UHPC’s mechanical properties are suggested.

scholarly journals A new congenital abnormal fibrinogen Ise characterized by the replacement of B beta glycine-15 by cysteine

Blood ◽  
1991 ◽  
Vol 77 (9) ◽  
pp. 1958-1963 ◽  
Author(s):  
N Yoshida ◽  
H Wada ◽  
K Morita ◽  
H Hirata ◽  
M Matsuda ◽  
...  
Keyword(s):  
Amino Acid ◽  
High Performance ◽  
Reversed Phase ◽  
Polymerization Reaction ◽  
Thrombin Time ◽  
Beta Chain ◽  
High Concentration ◽  
Elution Pattern ◽  
Peptide Peak ◽  
Very High

Abstract A new case of heterozygous dysfibrinogenemia characterized by the replacement of NH2-terminal amino acid of fibrin beta-chain was found in a 50-year-old man. Despite a prolonged thrombin time, the propositus' fibrinogen had a normal reptilase time with the normal release of fibrinopeptide A. Release of fibrinopeptide B by thrombin was strongly affected, but a very high concentration of thrombin almost completely released fibrinopeptide B with a normal elution pattern on reversed-phase high performance liquid chromatography (HPLC). Lysylendopeptidase-cleavage of purified B beta-chains analyzed on HPLC showed the decrease of one peptide compared with the normal and the appearance of an abnormal peptide peak. These peptides were treated with thrombin and further separated on HPLC. Amino acid sequence analysis of the abnormal peptide demonstrated that B beta glycine-15, NH2-terminus of the fibrin beta-chain, was replaced by cysteine. These findings will be of particular importance because they strongly support the hypothesis that the NH2-terminal portion of the fibrin beta-chain is involved in the polymerization reaction by thrombin. The propositus' daughter and two sisters had the same abnormal fibrinogen. This unique inherited abnormal fibrinogen was designated as fibrinogen Ise. During these studies, we found that a very high concentration of thrombin cleaves not only the A alpha Arg19-Val20 bond but also the COOH- terminal region of alpha-chains, which results in the generation of further degraded alpha-chains with apparent molecular weights of 44,000 or less.

scholarly journals A review of recent developments in geopolymer concrete

2018 ◽  
Vol 7 (4.5) ◽  
pp. 696 ◽  
Author(s):  
A. Chithambar Ganesh ◽  
Dr. M. Muthukannan
Keyword(s):  
High Performance ◽  
High Strength ◽  
Correct Choice ◽  
Curing Temperature ◽  
Geopolymer Concrete ◽  
Research Papers ◽  
Alkali Aggregate Reaction ◽  
Recent Developments ◽  
Alumino Silicate ◽  
Time Utilization

Geopolymer concrete is proved to have high strength, lesser shrinkage, resistance against reinforcement corrosion, acid and sulphate resistance, freeze-thaw resistance, fire resistance and resistance to alkali-aggregate reaction. There are many parameters which influence the strength characteristics of Geopolymer Concrete. They are types and fineness of Source alumino silicate material used, concentration and type of alkaline activators used, curing temperature and curing time, utilization of M-sand etc. High performance characteristics could be achieved through the correct choice of these parameters. This review paper focuses on the influence of different variables on the properties of geopolymer concrete and the progress in the field of geopolymer concrete. Consequently many research papers pertaining to the geopolymer have been reviewed in this state of art paper.  

scholarly journals ULTRA-HIGH-PERFORMANCE FIBRE-REINFORCED CONCRETE UNDER HIGH-VELOCITY PROJECTILE IMPACT. PART I. EXPERIMENTS

2018 ◽  
Vol 58 (4) ◽  
pp. 232 ◽  
Author(s):  
Sebastjan Kravanja ◽  
Radoslav Sovják
Keyword(s):  
Significant Influence ◽  
Impact Loading ◽  
High Velocity ◽  
High Performance ◽  
Fibre Volume ◽  
Fibre Reinforced Concrete ◽  
Volumetric Fraction ◽  
Projectile Impact ◽  
High Performance Fibre ◽  
Area And Volume

A series of cratering experiments were performed where the response of the Ultra-High-Performance Fibre-Reinforced Concretes with various fibre volume fractions to the high- velocity projectile impact loading was investigated. It was found that the increment of the fibre volumetric fraction did not have a significant influence on the depth of the penetration, but it was very effective in reducing the crater area and volume.

Preparation Experiment and Engineering Application of High Performance Concrete of Freezing Shaft in Deep Alluvium

2014 ◽  
Vol 584-586 ◽  
pp. 1407-1411
Author(s):  
Zhi Shu Yao ◽  
Zhen Xu ◽  
Hai Qing Song
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Raw Materials ◽  
Engineering Application ◽  
High Strength ◽  
Engineering Practice ◽  
Mixture Ratio ◽  
Curing Conditions ◽  
Remarkable Effect ◽  
Shaft Lining

According to the special construction environment and curing conditions of the freezing shaft inner and outer shaft lining in deep alluvium, first,configuration principle of high strength high performance concrete of freezing shaft in deep alluvium is proposed; Then raw materials are selected according to the preparation approach, and preparation experimental study of high strength high performance concrete is conducted with C60, C65, C70and C75 , and the optimum mixture ratio is obtained, and applied to the engineering practice, achieving remarkable effect.

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