A Qualitative Study of Reactive Powder Concrete using X-Ray Diffraction Technique

Basing on the basic preparation principle of reactive powder concrete, through mixing the new active component of slag, this thesis aims to confect new-type cement-based material with super high performance. As illustrated from the experiments of resistance to chlorine ion permeability, this type of concrete is with extremely compact structure and higher resistance to chlorine ion permeability compared with other cement-based materials. Silica fume presents the most important promotion effect on its resistance to chlorine ion permeability. Steel fiber and standard sand also help to enhance its impermeability. Through the analysis and the research on microstructure realized by X-ray Diffraction, mercury penetration experiment and SEM, all these views have been proved.

Download Full-text

Design and Evaluation of an Ultrahigh-Strength Coral Aggregate Concrete for Maritime and Reef Engineering

Materials ◽

10.3390/ma14195871 ◽

2021 ◽

Vol 14 (19) ◽

pp. 5871

Author(s):

Jinming Liu ◽

Boyu Ju ◽

Wei Xie ◽

Huang Yu ◽

Haiying Xiao ◽

...

Keyword(s):

Mechanical Performance ◽

Autogenous Shrinkage ◽

X Ray Diffraction ◽

Early Hydration ◽

X Ray ◽

Ultrahigh Strength ◽

Marine Concrete ◽

Marine Engineering ◽

Reactive Powder ◽

Economical Alternative

In this paper, an ultrahigh-strength marine concrete containing coral aggregates is developed. Concrete fabricated from marine sources is considered an effective and economical alternative for marine engineering and the construction of remote islands. To protect sea coral ecosystems, the coral aggregates used for construction are only efflorescent coral debris. To achieve the expected mechanical performance from the studied concrete, an optimal mixture design is conducted to determine the optimal proportions of components, in order to optimize the compressive strength. The mechanical properties and the autogenous shrinkage, as well as the heat flow of early hydration reactions, are measured. The hydration products fill up the pores of coral aggregates, endowing our concrete with flowability and self-compacting ability. The phases in the marine concrete are identified via X-ray diffraction analysis. The 28-day compressive and flexural strength of the developed marine concrete achieve 116.76 MPa and 18.24 MPa, respectively. On account of the lower cement content and the internal curing provided by coral aggregates, the volume change resulting from autogenous shrinkage is only 63.11% of that of ordinary reactive powder concrete.

Download Full-text

Agro Waste Sugarcane Bagasse as a Cementitious Material for Reactive Powder Concrete

Clean Technologies ◽

10.3390/cleantechnol2040030 ◽

2020 ◽

Vol 2 (4) ◽

pp. 476-491

Author(s):

Selvadurai Sebastin ◽

Arun Kumar Priya ◽

Alagar Karthick ◽

Ravishankar Sathyamurthy ◽

Aritra Ghosh

Keyword(s):

Construction Industry ◽

Reactive Powder Concrete ◽

Manufacturing Cost ◽

Quartz Powder ◽

X Ray ◽

Fine Powders ◽

Different Temperatures ◽

Reactive Powder ◽

Concrete Science ◽

Very High

In the field of advanced concrete science, the construction industry has risen to great heights. Due to its own characterisation, the manufacturing cost of reactive powder concrete (RPC) is very high. This can be minimised by substituting the components of the RPC with the aid of agro waste. Because of the production of sugar from the sugar cane industry, bagasse ash is abundantly available in India. It is not ideal for the direct replacement of ingredients in concrete because of the presence of carbon dioxide in bagasse ash. The study of bagasse ash’s actions under different temperatures and different exposure times is discussed in this paper. It is inferred from the findings obtained from the energy dispersive study of X-ray (EDAX) that the presence of reactive silica in bagasse ash could be substituted by RPC ingredients due to heat treatment. RPC is composed of exceptionally fine powders (cement, sand, quartz powder and silica smolder) and superplasticiser. The superplasticiser, utilised at its ideal dose, decreases the water to cement proportion (w/c) while enhancing the workability of the concrete. A thick matrix is accomplished by optimising the granular packing of the dry fine powders. This compactness gives RPC ultra-high quality and durability. Reactive powder concretes have compressive qualities extending from 200 to 800 MPa.

Download Full-text

Effect of Fibers on High-Temperature Mechanical Behavior and Microstructure of Reactive Powder Concrete

Materials ◽

10.3390/ma12020329 ◽

2019 ◽

Vol 12 (2) ◽

pp. 329 ◽

Cited By ~ 14

Author(s):

Muhammad Abid ◽

Xiaomeng Hou ◽

Wenzhong Zheng ◽

Raja Hussain

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Compressive Strength ◽

High Temperature ◽

Reactive Powder Concrete ◽

Peak Strain ◽

Fiber Reinforced ◽

Split Tensile Strength ◽

X Ray ◽

Reactive Powder

This study was aimed to investigate the effect of steel, polypropylene (PP), and hybrid (steel + PP) fibers on high-temperature mechanical properties of reactive powder concrete (RPC). The mechanical properties considered are cubic compressive strength, axial or prismatic compressive strength, split-tensile strength, flexural strength, elastic modulus, peak strain, and stress-strain behavior. The strength recession due to high temperature was investigated at micro level by scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction, mercury intrusion porosity, thermogravimetric, and differential scanning calorimetry analyses. The high-temperature tests were carried out at target temperatures of 120, 300, 500, 700, and 900 °C. The hot-state compressive strength of RPC started to decrease at 120 °C; however, a partial recovery at 300 °C and a gradual decrease above 300 °C were observed. The degradation of split-tensile strength, flexural strength, and elastic modulus were gradual with increasing temperature despite the effect of different fibers. Whereas, the peak strain was gradually increasing up to 700 °C. However, after 700 °C, it remained unchanged. Steel fiber reinforced RPC (SRPC) and hybrid fiber reinforced RPC (HRPC) showed a ductile behavior. PP fiber reinforced RPC (PRPC) showed a quite brittle behavior up to 300 °C; however, further heating made the microstructure porous and it became ductile too. Overall the performance of SRPC and HRPC were superior to PRPC because of higher modulus of elasticity, higher strength, and better fire resistance of steel fibers. Fiber reinforced RPC was found to have better fire resistance than traditional types of concrete based on comparative studies with the provisions of design codes and earlier research. The constitutive equations developed can be utilized in computer programs for structural design of RPC structures exposed to fire.

Download Full-text

High temperature oxidation resistance of porous Ni–Cr–Fe materials

International Journal of Materials Research (formerly Zeitschrift fuer Metallkunde) ◽

10.1515/ijmr-2020-1110412 ◽

2020 ◽

Vol 111 (4) ◽

pp. 356-359

Author(s):

Liang Wu ◽

Yifeng Xiao ◽

Xiuyan Xia ◽

Jinwen Qian ◽

Yuehui He

Keyword(s):

High Temperature ◽

Oxidation Resistance ◽

High Temperature Oxidation ◽

X Ray Diffraction ◽

Powder Synthesis ◽

Temperature Oxidation ◽

X Ray ◽

Mercury Intrusion ◽

Parabolic Law ◽

Reactive Powder

Abstract The oxidation behavior of porous Ni-Cr-Fe materials prepared by reactive powder synthesis with different open porosity was studied in air at 6008C, 800 8C and 1 0008C. The differences in surface morphology, phase and pore structure parameters between material oxidized and non-oxidized were characterized by means of scanning electron microscopy, X-ray diffraction analysis and mercury intrusion. The results show that the oxidation rate of the samples which were oxidized at 600 8C for 340 h, for 560 h at 800 8C and for 560 h at 1 000 8C were 0.00027%2 h-1, 0.0558%2 h-1, and 0.64412%2 h-1, respectively. All the oxidation kinetics curves obeyed the parabolic law, exhibiting excellent high temperature oxidation resistance.

Download Full-text

Mechanism Analysis of the Influence of Delay Period on Mechanical Properties of Reactive Powder Concrete

Frontiers in Materials ◽

10.3389/fmats.2020.563234 ◽

2021 ◽

Vol 7 ◽

Author(s):

Xiaohui Wang ◽

Qingxin Zhao ◽

Xiaojun He ◽

Shuang Zhang

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Delay Period ◽

Reactive Powder Concrete ◽

Hydration Products ◽

X Ray ◽

Significant Difference ◽

Calcium Silicon ◽

Reactive Powder

In order to analyze the influence mechanism of delay period on the mechanical properties of reactive powder concrete (RPC), the compressive strength of RPC with delay periods of 18, 24, and 30 h was tested at the age of 7, 28, and 90 days, respectively. The results show that compared with the RPC with delay period of 18 h, the compressive strength of the RPC with delay periods of 24 and 30 h increases by 3.2 and 4.2%, respectively, and the long-term strength reduction ratio decreases by 22.8 and 71.9%, respectively. The constitutive model curves of RPC under different delay period show that the initial elastic modulus E increases with the delay period and the strength and rigidity of RPC increase with the extension of delay period. According to the non-evaporation water quantity test, it could be speculated that the quantities of hydration products of the RPC with delay periods of 24 and 30 h slightly increase compared with the RPC with delay period of 18 h. X-ray diffraction (XRD) analysis show that the delay periods of 24 and 30 h consume more 3CaO·SiO2 (C3S) and 2CaO·SiO2 (C2S) compared with delay period of 18 h. Seen from the scanning electron microscope (SEM) image, the structures of the three groups of samples are relatively dense and have no significant difference. Through energy dispersive X-ray spectroscopy (EDS) analysis, the calcium-silicon ratios of hydration products of the RPC with delay periods of 18, 24, and 30 h are 1.81, 1.56, and 1.54, respectively. The existence of C-S-H gel and Ca(OH)2 in hydration products is confirmed by thermogravimetric-differential scanning calorimetry (DSC-TG) analysis. An appropriate delay period (30 h in this paper) generates more hydration products, then improves the compactness of the internal structure and reduces the calcium-silicon ratio of hydration products, and it is conducive to the growth of RPC compressive strength and the stability of long-term compressive strength.

Download Full-text

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071107 ◽

1973 ◽

Vol 31 ◽

pp. 132-133 ◽

Cited By ~ 1

Author(s):

R. E. Herfert

Keyword(s):

Surface Characterization ◽

Analytical Techniques ◽

X Ray Diffraction ◽

Depth Of Penetration ◽

X Ray ◽

The Past ◽

Transmission Electron ◽

Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

Download Full-text

Ribosome Structural Organization

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100051670 ◽

1974 ◽

Vol 32 ◽

pp. 332-333

Author(s):

James A. Lake

Keyword(s):

Ribosomal Proteins ◽

Structural Organization ◽

Three Dimensional ◽

Small Subunit ◽

Structural Studies ◽

X Ray Diffraction ◽

Specific Antibodies ◽

X Ray ◽

E Coli ◽

Complete Sequences

The understanding of ribosome structure has advanced considerably in the last several years. Biochemists have characterized the constituent proteins and rRNA's of ribosomes. Complete sequences have been determined for some ribosomal proteins and specific antibodies have been prepared against all E. coli small subunit proteins. In addition, a number of naturally occuring systems of three dimensional ribosome crystals which are suitable for structural studies have been observed in eukaryotes. Although the crystals are, in general, too small for X-ray diffraction, their size is ideal for electron microscopy.

Download Full-text

Electron Microscopy of Human Gallstones

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100065523 ◽

1971 ◽

Vol 29 ◽

pp. 296-297

Author(s):

C. Wolpers ◽

R. Blaschke

Keyword(s):

Electron Microscopy ◽

Room Temperature ◽

Bile Pigment ◽

X Ray Diffraction ◽

Triclinic Crystal System ◽

X Ray ◽

Follow Up Study ◽

Infra Red ◽

Main Components

Scanning microscopy was used to study the surface of human gallstones and the surface of fractures. The specimens were obtained by operation, washed with water, dried at room temperature and shadowcasted with carbon and aluminum. Most of the specimens belong to patients from a series of X-ray follow-up study, examined during the last twenty years. So it was possible to evaluate approximately the age of these gallstones and to get information on the intensity of growing and solving.Cholesterol, a group of bile pigment substances and different salts of calcium, are the main components of human gallstones. By X-ray diffraction technique, infra-red spectroscopy and by chemical analysis it was demonstrated that all three components can be found in any gallstone. In the presence of water cholesterol crystallizes in pane-like plates of the triclinic crystal system.

Download Full-text

High Resolution Replication of Organoclay Surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055126 ◽

1982 ◽

Vol 40 ◽

pp. 576-577

Author(s):

W. W. Barker ◽

W. E. Rigsby ◽

V. J. Hurst ◽

W. J. Humphreys

Keyword(s):

Clay Mineral ◽

Organic Molecule ◽

Organic Molecules ◽

X Ray Diffraction ◽

Xrd Pattern ◽

X Ray ◽

Naturally Occurring ◽

Silicate Layers ◽

Mineral Identification

Experimental clay mineral-organic molecule complexes long have been known and some of them have been extensively studied by X-ray diffraction methods. The organic molecules are adsorbed onto the surfaces of the clay minerals, or intercalated between the silicate layers. Natural organo-clays also are widely recognized but generally have not been well characterized. Widely used techniques for clay mineral identification involve treatment of the sample with H2 O2 or other oxidant to destroy any associated organics. This generally simplifies and intensifies the XRD pattern of the clay residue, but helps little with the characterization of the original organoclay. Adequate techniques for the direct observation of synthetic and naturally occurring organoclays are yet to be developed.

Download Full-text