Pilot Study of Mechanical Waves Passing through Fine-Grained Cement Composite during the Early Hydration Process

2020 ◽  
Vol 846 ◽  
pp. 243-247
Author(s):  
Michaela Hoduláková ◽  
Libor Topolář ◽  
Barbara Kucharczyková
Keyword(s):  
Internal Structure ◽  
Experimental Analysis ◽  
Cement Composite ◽  
Early Hydration ◽  
Cement Pastes ◽  
Fine Grained ◽  
University Of Technology ◽  
Mechanical Waves ◽  
Waves Propagation

The aim of this paper is to present results of an experimental analysis focused on the mechanical waves passing through fine-grained materials, prepared from the CEM I 52.5 R Portland cement and the water coefficient w/c = 0.40, during the setting and hardening phase. In the experiment differences in the wave propagation in cement pastes and mortars were investigated. After mixing, both materials were poured into a cylindrical mould with the diameter of 75.0 ± 0.3 mm. These test specimens were then used to observe, in particular, the development of the amplitude of mechanical waves using a measuring setup which was composed for this purpose from the equipment of the Brno University of Technology. The results show that the time of „critical changes" in the internal structure of the material can be determined. These changes are related to the quality of the bonds of the particles in the internal structure which are reflected in the propagation of the mechanical waves within the material. It is also expected that the experimental analysis will help extend the knowledge of mechanical waves propagation in cement-based composite materials during setting.

Study of Fine-Grained Cementitious Composites in Solidification Phase Using Acoustic Testing Technique

2020 ◽  
Vol 897 ◽  
pp. 111-116
Author(s):  
Michaela Hoduláková ◽  
Libor Topolář
Keyword(s):  
Solidification Process ◽  
Cementitious Composites ◽  
Material Structure ◽  
Early Hydration ◽  
Cement Pastes ◽  
Measuring Device ◽  
Fine Grained ◽  
Mechanical Waves ◽  
Nonintrusive Monitoring ◽  
Non Destructive

The paper deals with experimental analysis, which is focused on the use of acoustic measurement during the solidification process. As a material for monitoring was chosen fine-grained cementitious composites in the laboratory environment. For this purpose, a measuring device working on the principle of mechanical waves passing through the material was designed, assembled and verified. The experiment was conducted on cement pastes prepared from CEM I 42.5 R Portland cement with two different water coefficients (w/c = 0.40 and w/c = 0.33). The differences in the wave propagation in cement pastes were investigated. Simultaneously with this experiment, the monitoring and the saving records of the internal temperature was conducted. The results show the time of „critical changes" in the internal structure of the material can be determined. These changes are probably related to the quality of the particle’s bonds in the inner material structure, which is reflected in the propagation of mechanical waves. Overall, it is shown these experiments could be used to expand the understanding of the various processes occurring during early hydration of cement, and the application of these results to field situations (in the future) could lead to the other development of, non-destructive (and nonintrusive) monitoring techniques.

Influence of technology parameters of free-cutting steel continuous casting on the billet internal structure

2020 ◽  
Vol 76 (2) ◽  
pp. 139-142
Author(s):  
A. T. Kunakbaeva ◽  
A. M. Stolyarov ◽  
M. V. Potapova
Keyword(s):  
Regression Analysis ◽  
Continuous Casting ◽  
Internal Structure ◽  
Sulfur Content ◽  
Manganese Content ◽  
High Quality ◽  
Correlation And Regression Analysis ◽  
Cutting Steel ◽  
Continuously Cast

Free-cutting steel gains specific working properties thanks to the high content of sulfur and phosphorus. These elements, especially sulfur, have a rather high tendency to segregation. Therefore, segregation defects in free-cutting steel continuously cast billets can be significantly developed. The aim of the work was to study the influence of the chemical composition of freecutting steel and casting technological parameters on the quality of the macrostructure of continuously cast billets. A metallographic assessment of the internal structure of cast metal made of free-cutting steel and data processing by application of correlation and regression analysis were the research methods. The array of production data of 43 heats of free-cutting steel of grade A12 was studied. Steel casting on a five-strand radial type continuous casting machine was carried out by various methods of metal pouring from tundish into the molds. Metal of 19 heats was poured with an open stream, and 24 heats – by a closed stream through submerged nozzles with a vertical hole. High-quality billets had a cross-sectional size of 150×150 mm. The macrostructure of high-quality square billets made of free-cutting steel of A12 grade is characterized by the presence of central porosity, axial segregation and peripheral point contamination, the degree of development of which was in the range from 1.5 to 2.0 points, segregation cracks and strips – about 1.0 points. In the course of casting with an open stream, almost all of these defects are more developed comparing with the casting by a closed stream. As a result of correlation and regression analysis, linear dependences of the development degree of segregation cracks and strips both axial and angular on the sulfur content in steel and on the ratio of manganese content to sulfur content were established. The degree of these defects development increases with growing of sulfur content in steel of A12 grade. These defects had especially strong development when sulfur content in steel was of more than 0.10%. To improve the quality of cast metal, it is necessary to have the ratio of the manganese content to the sulfur content in the metal more than eight.

scholarly journals The Influence of Water Reducing Agents on Early Hydration Property of Ferrite Aluminate Cement Paste

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 731
Author(s):  
Chunlong Huang ◽  
Zirui Cheng ◽  
Jihui Zhao ◽  
Yiren Wang ◽  
Jie Pang
Keyword(s):  
Setting Time ◽  
Critical Role ◽  
Hydration Product ◽  
Reducing Agents ◽  
Reducing Agent ◽  
Hydration Process ◽  
Early Hydration ◽  
Cement Pastes ◽  
Hydration Rate ◽  
Aluminate Cement

The ferrite aluminate cement (FAC) could rapidly lose fluidity or workability due to its excessive hydration rate, and greatly reduce the construction performance. Chemical admixtures are commonly used to provide the workability of cement-based materials. In this study, to ensure required fluidity of FAC, chemically different water reducing agents are incorporated into the FAC pastes. The experiments are performed with aliphatic water reducing agent (AP), polycarboxylic acid water reducing agent (PC) and melamine water reducing agent (MA), respectively. Influence of the water reducing agents on fluidity, setting time, hydration process, hydration product and zeta potential of the fresh cement pastes is investigated. The results show that PC has a better dispersion capacity compared to AP and MA. Besides decreasing water dosage, PC also acts as a retarder, significantly increasing the setting times, delaying the hydration rate and leading to less ettringite in the hydration process of FAC particles. The water reducing agents molecules are adsorbed on the surface of positively charged minerals and hydration products, however, for PC, steric hindrance from the long side chain of PC plays a critical role in dispersing cement particles, whereas AP and MA acting through an electrostatic repulsion force.

scholarly journals The Effect of Process Parameters in Helical Rolling of Balls on the Quality of Products and the Forming Process

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2125 ◽  
Author(s):  
Janusz Tomczak ◽  
Zbigniew Pater ◽  
Tomasz Bulzak
Keyword(s):  
Metal Flow ◽  
Experimental Tests ◽  
Rolling Process ◽  
Helical Rolling ◽  
Forming Process ◽  
University Of Technology ◽  
Quality Of Products ◽  
Skew Rolling

This paper presents selected numerical and experimental results of a skew rolling process for producing balls using helical tools. The study investigates the effect of the billet’s initial temperature on the quality of produced balls and the rolling process itself. In addition, the effect of billet diameter on the quality of produced balls is investigated. Experimental tests were performed using a helical rolling mill available at the Lublin University of Technology. The experiments consisted of rolling 40 mm diameter balls with the use of two helical tools. To determine optimal rolling parameters ensuring the highest quality of produced balls, numerical modelling was performed using the finite element method in the Forge software. The numerical analysis involved the determination of metal flow kinematics, temperature and damage criterion distributions, as well as the measurement of variations in the force parameters. The results demonstrate that the highest quality balls are produced from billet preheated to approximately 1000 °C.

ENHANCEMENT OF SCREEN FILM MAMMOGRAM UP TO A LEVEL OF DIGITAL MAMMOGRAM: EXPERIMENTAL ANALYSIS

2013 ◽  
Vol 13 (02) ◽  
pp. 1340004
Author(s):  
APARNA NARENDRA BHALE ◽  
MANISH RATNAKAR JOSHI
Keyword(s):  
Experimental Analysis ◽  
Breast Imaging ◽  
Point Of View ◽  
Quality Analysis ◽  
Digital Mammogram ◽  
Total Recovery ◽  
Clinical Observations ◽  
Opinion Score ◽  
Better Than

Breast cancer is one of the major causes of death among women. If a cancer can be detected early, the options of treatment and the chances of total recovery will increase. From a woman's point of view, the procedure practiced (compression of breasts to record an image) to obtain a digital mammogram (DM) is exactly the same that is used to obtain a screen film mammogram (SFM). The quality of DM is undoubtedly better than SFM. However, obtaining DM is costlier and very few institutions can afford DM machines. According to the National Cancer Institute 92% of breast imaging centers in India do not have digital mammography machines and they depend on the conventional SFM. Hence in this context, one should answer "Can SFM be enhanced up to a level of DM?" In this paper, we discuss our experimental analysis in this regard. We applied elementary image enhancement techniques to obtain enhanced SFM. We performed the quality analysis of DM and enhanced SFM using standard metrics like PSNR and RMSE on more than 350 mammograms. We also used mean opinion score (MOS) analysis to evaluate enhanced SFMs. The results showed that the clarity of processed SFM is as good as DM. Furthermore, we analyzed the extent of radiation exposed during SFM and DM. We presented our literally findings and clinical observations.

scholarly journals Quality of outdoor and indoor environment during the cruise of the tall ship STS Fryderyk Chopin

2018 ◽  
Vol 49 ◽  
pp. 00024
Author(s):  
Szymon Firląg
Keyword(s):  
Relative Humidity ◽  
Ventilation System ◽  
Pm 2.5 ◽  
The North ◽  
University Of Technology ◽  
Open Sea ◽  
The North Sea ◽  
Pm 10 ◽  
The Impact

The aim of this paper is to present the results of measurements, on the quality of internal and external environment, carried out during the cruise of the tall ship STS Fryderyk Chopin. The cruise took place between 16th and 30th September 2017 as part of the scientific seminar of the Warsaw University of Technology (WUT) on the Wave, addressed to students of the WTU. After leaving the port of Edinburgh, crossing the North Sea, the Danish straits, stops in Copenhagen and Kołobrzeg, the tall ship reached Szczecin after two weeks. The measurements carried out on the deck included the temperature and relative humidity of the indoor air in three cabins and the men’s bathroom. In two cabins, the CO2 concentration was measured additionally. The outdoor temperature, relative humidity and concentration of PM 1.0, PM 2.5 and PM 10 were also measured. The obtained results allowed to assess the quality of the internal environment in accordance with the standards and to analyze the effectiveness of the mechanical ventilation system. Measurements of particulate matter have shown significant differences between outdoor air quality in the open sea and in ports or near major shipping routes. It turned out that the impact of emissions from passing ships using diesel engines is clearly visible.

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