Scanning Electron Microscopy in the Studies of Hydrated Cementitious Materials Microstructure Formed in the Presence of some Heavy Metals Containing Admixtures

2015 ◽  
Vol 231 ◽  
pp. 145-153 ◽  
Author(s):  
Wiesława Nocuń-Wczelik ◽  
Barbara Trybalska
Keyword(s):  
Electron Microscopy ◽  
Cement Hydration ◽  
Cementitious Materials ◽  
Early Age ◽  
Silicate Phase ◽  
Small Individual ◽  
Calorimetric Measurements ◽  
Individual Particles ◽  
Scanning Electron ◽  
Nitrate Solutions

The calorimetric measurements together with microscopic observations and analyses relating to the interaction of cement paste with sulfate and nitrate solutions of various concentration were carried out. These salts modify the rate of cement hydration at early age. In the presence of sulfates the formation of some well crystallized calcium sulfates or calcium sulfoaluminates can be found. In case of nitrates there is no additional products. However, one can observe that the calcium silicate phase becomes less fibrous but more compact, with very small individual particles, as the nucleation from the liquid phase is disturbed. There are the accompanying cations incorporated in this product.

scholarly journals Effect of nano-SnO2 on early-age hydration of Portland cement paste

2019 ◽  
Vol 11 (6) ◽  
pp. 168781401985194 ◽  
Author(s):  
Jianping Zhu ◽  
Genshen Li ◽  
Ruijie Xia ◽  
Huanhuan Hou ◽  
Haibin Yin ◽  
...  
Keyword(s):  
Portland Cement ◽  
Cement Paste ◽  
Cement Hydration ◽  
Cementitious Materials ◽  
Hydration Process ◽  
Strength Development ◽  
Early Age ◽  
Test Machine ◽  
Portland Cement Paste ◽  
Scanning Electron

Nanomaterial, as a new emerging material in the field of civil engineering, has been widely utilized to enhance the mechanical properties of cementitious material. Nano-SnO2 has presented high hardness characteristics, but there is little study of the application of nano-SnO2 in the cementitious materials. This study mainly investigated the hydration characteristics and strength development of Portland cement paste incorporating nano-SnO2 powders with 0%, 0.08%, and 0.20% dosage. It was found that the early-age compressive strength of cement paste could be greatly improved when nano-SnO2 was incorporated with 0.08% dosage. The hydration process and microstructure were then measured by hydraulic test machine, calorimeter, nanoindentation, X-ray diffraction, scanning electron microscope, and mercury intrusion porosimetry. It was found that the cement hydration process was promoted by the addition of nano-SnO2, and the total amount of heat released from cement hydration is also increased. In addition, the addition of nano-SnO2 can promote the generations of high density C-S-H and reduce the generations of low density C-S-H indicating the nucleation effect of nano-SnO2 in the crystal growth process. The porosity and probable pore diameter of cement paste with 0.08% nano-SnO2 were decreased, and the scanning electron microscopic results also show that the cement paste with 0.08% nano-SnO2 promotes the densification of cement microstructure, which are consistent with the strength performance.

Evaluation of computer-controlled SEM in the study of metal-contaminated soils

2003 ◽  
Vol 67 (2) ◽  
pp. 219-231 ◽  
Author(s):  
H. W. Langmi ◽  
J. Watt
Keyword(s):  
Electron Microscopy ◽  
Heavy Metals ◽  
Contaminated Soils ◽  
X Ray ◽  
Computer Controlled ◽  
Weathering Crusts ◽  
Individual Particles ◽  
Element Mapping ◽  
Scanning Electron

Computer-controlled scanning electron microscopy (CCSEM) has been assessed for the determination of form and size distribution of heavy metals in urban contaminated soils. Metal distributions within individual particles were determined using X-ray element mapping. The sites selected for study were (1) around a landfill site, previously a colliery in Wolverhampton, UK and (2) a private garden adjacent to a railway in Nottingham, UK. Backscattered thresholding techniques were used to isolate the Pb-containing categories. The classification results for both Wolverhampton and Nottingham soils were generally similar but more Pb-containing classes were observed for the Nottingham samples when a comparison was made between results of the same size fractions. However, difficulties with the technique arose when particles showing chemically similar weathering crusts were assigned to the same class, despite having different internal compositions. The CCSEM data therefore need to be interpreted with caution and their application limited to situations in which particle internal complexity is not an issue.

Scanning Electron Microscopy Studies of Neoformations on Stony Materials of Modern Building Works

2013 ◽  
Vol 19 (5) ◽  
pp. 1241-1247 ◽  
Author(s):  
Carlos Alves
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Urban Areas ◽  
Building Materials ◽  
Microscopy Study ◽  
Cementitious Materials ◽  
Electron Microscopy Study ◽  
Weathering Processes ◽  
Central Portugal ◽  
Scanning Electron

AbstractThe built environment is subjected to several pollutants under variable environmental conditions defined by diverse geochemical systems. These geochemical systems promote the occurrence of neoformations that can have a detrimental effect on surfaces of the building materials. Hence, the study of neoformations helps in the understanding of weathering processes that affect built structures. In the present paper we present a scanning electron microscopy study of macroscopic manifestations of neoformations detected during an extensive visual survey of several modern architectural works in urban areas of northern and central Portugal. The studies performed suggest that cementitious materials play an important role as a source of pollutants for the most common neoformations such as carbonate rich stains and coatings, as well as salt efflorescences of alkaline sulphates and carbonates. There are also indications of contributions from organic sources for alkaline nitrates and atmospheric pollution for gypsum-rich black crusts. Other less common neoformations include phosphate aggregates and silica stains that represent interesting indicators of the geochemical systems in built environments. In the case of carbonate-rich coatings, indications of recurrence related to the circulation of carbonate forming solutions relevant to the maintenance of built surfaces were detected.

scholarly journals A study on micro-morphology and impacts of curing temperature on bond strength of interfacial transition zone through scanning electron microscope

2021 ◽  
Vol 2083 (2) ◽  
pp. 022082
Author(s):  
Binbin Na ◽  
Bin Yan
Keyword(s):  
Electron Microscopy ◽  
Bond Strength ◽  
Interfacial Transition Zone ◽  
Curing Temperature ◽  
Early Age ◽  
Hydration Products ◽  
Growth Trend ◽  
Micro Morphology ◽  
Morphology Characteristics ◽  
Scanning Electron

Abstract The influence of curing temperature on the bond strength of ITZ was studied in this paper. It is found that, Increasing curing temperature can improve the bond strength of ITZ in the early age, but it will significantly decreases the growth trend of the bond strength. The micro-morphology characteristics were examined by the method of scanning electron microscopy, It was found that, the higher the curing temperature is, the more uneven the hydration products distribution of ITZ is, and also the looser the ITZ structure is.

Preparation and Study on the Performance of Glazed Hollow Beads Thermal Insulation Materials

2013 ◽  
Vol 662 ◽  
pp. 335-338
Author(s):  
Xiao Long Li ◽  
Guo Zhong Li
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Thermal Insulation ◽  
Material Properties ◽  
Cementitious Materials ◽  
Insulation Material ◽  
Action Mechanism ◽  
Molding Process ◽  
Internal Morphology ◽  
Scanning Electron

The glazed hollow beads thermal insulation board was made of glazed hollow beads and perlite by selecting cement and fly ash as cementitious materials, and adding appropriate amount of VAE emulsion and fibers, in the compression molding process. In this paper, the influence of different dosages of perlite replacing vitrified beads, VAE emulsion and fiber on the material properties were studied. Besides, the internal morphology of the sample was observed by scanning electron microscopy, and the action mechanism of the insulation material was explored.

Cluster Analysis of Automated Fine-Particle Analysis Using Scanning Electron Microscopy

1997 ◽  
Vol 3 (S2) ◽  
pp. 1071-1072
Author(s):  
C.A. O’Keefe ◽  
J.P. Hurley
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cluster Analysis ◽  
Chemical Composition ◽  
Fine Particle ◽  
Submicron Particles ◽  
Particle Analysis ◽  
Solvent Ratio ◽  
Individual Particles ◽  
Scanning Electron

Because of analytical advances, submicron particles as small as 0.2 μm can be characterized for chemical composition, size, and shape using scanning electron microscopy (SEM). Once these characteristics are determined, cluster analysis can be used to group the individual particles into categories based on size, shape, and chemical composition.Submicron particle analysis is important when characterizing the ash to provide information to help solve ash-related problems in coal combustion and gasification systems. Since a combustion system has an excess of oxygen available, the resulting ash is typically easier to characterize than ash from a gasification system. In a gasification system, the lack of oxygen results in additional categories high in Cl and P.Adequate dispersion of submicron particles for proper analysis of individual particles is required because of the analysis volume of the SEM beam. Therefore, an aliquot of an aqueous solution with a set sample-to-solvent ratio is drawn while being sonicated. A few drops of solution are placed on a vitreous carbon substrate, allowing for particle dispersion on the surface of a smooth substrate. Next, the particles are analyzed by the fine-particle technique (FPT).

The Study of Alkaline-Activated Magnesium Slag Cementitious Material

2012 ◽  
Vol 517 ◽  
pp. 363-366 ◽  
Author(s):  
Li Guang Xiao ◽  
Feng Luo ◽  
Rui Bo Li ◽  
Chang Yu Liu
Keyword(s):  
Electron Microscopy ◽  
Mechanical Property ◽  
Interaction Mechanism ◽  
Cementitious Materials ◽  
Cementitious Material ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
X Ray ◽  
Furnace Slag ◽  
Scanning Electron

Magnesium slag cementitious material was prepared successfully using the magnesium slag-furnace slag-clinker system and different activators in this paper. The effect of activator on the mechanical property of the material was studied. The hydration and microstructure of this composite cement were analyzed by X-ray diffraction and scanning electron microscopy and the interaction mechanism was researched. The results show that the activity of magnesium slag was enhanced significantly by adding a small amount of activator. Combined activators have the best effect. The hydration products of magnesium slag cementitious materials mortar were C-S-H, Aft and Ca (OH)2 and so on.

scholarly journals Fabrication of Advanced Cement Mortar for Building Anti-Bacterial Applications

2019 ◽  
Vol 15 (1) ◽  
pp. 89-96
Author(s):  
Farhad M. Othman ◽  
Alaa A. Abdul-hamead ◽  
Noor A. Hmeed
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Cement Mortar ◽  
Anatase Tio2 ◽  
Partial Replacement ◽  
Early Age ◽  
Weight Percentage ◽  
Atomic Force ◽  
Nano Material ◽  
Scanning Electron

In this research, we have added nano anatase TiO2 as a partial replacement of Portland cement by a weight percentage of (0.25 to 1%) for the development of properties for protection against bacteria. The control mix was made by using "the cement to sand" proportion about (1: 2.75) with the "water to cement" proportion of (0.5) to study the structure, porosity, water absorption, density, mechanical properties, as well as anti-bacterial behavior. Inspections have been done such as scanning electron microscopy (SEM), and atomic force microscope (AFM) for mortar. Experimental results showed that after the addition of Nano powders in cement mortar, the structural properties improved significantly with the development of hydration of cement mortar at early age, reduction of porosity and the increase of density as well as enhancement in compressive and anti-bacteria properties that make the preparation of nano material very suitable for protection against bacteria.

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