Change of internal/pore structure in alumina green body during initial sintering

1992 ◽  
Vol 27 (24) ◽  
pp. 6609-6614 ◽  
Author(s):  
Jin-Young Kim ◽  
Masayori Miyashita ◽  
Nozomu Uchida ◽  
Keizo Uematsu
Keyword(s):  
Pore Structure ◽  
Green Body ◽  
Internal Pore Structure ◽  
Internal Pore

The Influence on the Concrete Durability in Bleed Air Performance Caused by Concrete Admixture

2013 ◽  
Vol 690-693 ◽  
pp. 767-770
Author(s):  
Yu Xian Zheng ◽  
Xun Guo Zhu
Keyword(s):  
Pore Structure ◽  
Frost Resistance ◽  
Performance Test ◽  
Concrete Durability ◽  
Air Content ◽  
Environmental Actions ◽  
Internal Pore Structure ◽  
Internal Pore

The article issued the influence on concrete durability caused by concrete admixture, based on the further study on concrete admixture bleed air performance test, and researched the influence on concrete durability caused by it. The experiments show that the admixtures of air-entraining performance improve internal pore structure of concrete and increase the compacting condition concrete. Concrete admixture also can improve the impermeability of concrete frost resistance and improve the resistance to environmental actions, and proposed concrete air content of the Dalian region suitable value.

scholarly journals Study on the Process and Characteristics of Clogging for Ceramic Permeable Brick

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zizeng Lin ◽  
Hai Yang ◽  
Huiming Chen
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Pore Structure ◽  
Size Distribution ◽  
Permeability Coefficient ◽  
Simulated Rainfall ◽  
Experimental Conditions ◽  
Internal Pore Structure ◽  
Internal Pore ◽  
Insight Into

A ceramic permeable brick was selected for study in a device that was designed to fully investigate the process and characteristics of clogging in permeable bricks. In order to evaluate the permeability influenced by clogging, a simulated rainfall was filtered through the permeable brick placed in an innovative device. The macroscopic and microscopic changes in the brick and the filtrate were all measured to fully investigate the causes and process of clogging. Then, the mechanism of clogging in the permeable brick pores was further discussed. The results showed that the clogging risk of permeable brick was extremely high, and it can result in a complete clogging in only 5–10 years under the experimental conditions. The permeability coefficient and porosity both decreased exponentially with the increase in filtrate, which was attributed to the clogging of the internal pore structure due to particle interception. The chord size distribution results stressed that the blockage mainly occurred in the upper layer pores in the range of 0.5–1.5 mm, which is relatively sensitive to clogging due to the particle size distribution in rain water. The particle size distribution of the influent and effluent indicated that the clogging process could completely remove particles larger than 88 µm but showed variable removal efficiency for particles with sizes of 20–88 µm. This research offers new insight into the clogging of permeable bricks and provides theoretical guidance for restoring the brick permeability.

Application of Low-Voltage Field-Emission SEM to the Study of Internal Pore Structures of Activated Carbon

1996 ◽  
Vol 54 ◽  
pp. 138-139
Author(s):  
J. Liu ◽  
R. L. Ornberg
Keyword(s):  
Activated Carbon ◽  
Pore Structure ◽  
Field Emission ◽  
Low Voltage ◽  
Industrial Applications ◽  
Chemical Recovery ◽  
Limited Information ◽  
Pore Structures ◽  
Internal Pore Structure ◽  
Internal Pore

Activated carbon has interesting and useful properties for industrial applications. It has been used extensively in purification, separation, chemical recovery and catalysis. To achieve a predictable performance of activated carbon materials, it is necessary to develop a comprehensive understanding of the pore structure including pore size, pore shape, and pore surface chemistry. Macropores (> 50 nm), mesopores (2-50 nm) and micropores (< 2 nm) generally coexist in activated carbon. It is thus desirable to synthesize activated carbon with controlled pore structures to optimize its performance. We previously reported the characterization of the surface pore structure of activated carbon by field emission SEM (FESEM) and the examination of the internal pore structure by HAADF/HRTEM techniques.1 However, both HAADF and HRTEM techniques give only limited information about the carbon pore structure. We report here some preliminary observation of the internal pore structure of activated carbon by high resolution low voltage FESEM technique.

scholarly journals Damage of shotcrete under freeze-thaw loading

2017 ◽  
Vol 23 (5) ◽  
pp. 583-593 ◽  
Author(s):  
Jianxun CHEN ◽  
Pengyu ZHAO ◽  
Yanbin LUO ◽  
Xianghui DENG ◽  
Qin LIU
Keyword(s):  
Computed Tomography ◽  
Mass Loss ◽  
Pore Structure ◽  
Modulus Of Elasticity ◽  
Dynamic Modulus ◽  
Cement Mortar ◽  
Ct Scanning ◽  
Freeze Thaw ◽  
Internal Pore Structure ◽  
Internal Pore

The freeze-thaw durability of shotcrete can be improved by adding an air-entraining agent in cold areas. The main focus of this paper is to investigate the changes in the internal pore structure of C25 ordinary shotcrete and shot­crete mixed with a RM-YQ air-entraining agent using computed tomography (CT) scanning technique during freeze-thaw cycles. The macroscopic tests were conducted, including mass loss, dynamic modulus of elasticity and ultrasonic wave velocity tests. Results were compared, and the freeze-thaw durability characteristics of shotcrete mixed with the air-entraining agent were revealed. Adding an air-entraining agent could reduce the number of pores largely that ranged mainly from 0.01 mm2 to 1.00 mm2 (excluding the pores or bubbles < 0.01 mm2 because of the precision of the CT scan­ning system), and could therefore improve the initial pore structure of the formed shotcrete. During first few freeze-thaw cycles, just few small pores formed. After cement mortar fragmentations appeared, the number of small pores (0.01 mm2 to 0.50 mm2) in ordinary shotcrete increased significantly. The pore structure deteriorated largely. However, this could be prevented effectively by adding an air-entraining agent. Therefore, the freeze–thaw durability of shotcrete was improved.

Effect of Carbonation on the Microstructure of Concrete Containing Fly Ash and Expansive Admixture

2011 ◽  
Vol 347-353 ◽  
pp. 4074-4080
Author(s):  
Liu Qing Tu ◽  
Zhong He Shui ◽  
Wei Chen ◽  
Wen Bing Xu ◽  
Jun Tao Ma
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Pore Structure ◽  
Hydration Product ◽  
Dsc Analysis ◽  
Accelerated Carbonation ◽  
Carbonation Reaction ◽  
Carbonation Process ◽  
Internal Pore Structure ◽  
Internal Pore

The effects of carbonation on the microstructure of concrete containing fly ash and expansive admixture are investigated in this paper. Eight mix proportions of the concrete are designed in the experiment with the different replacement levels of the Portland cement with the fly ash and the expansive admixture. The specimens cured in accelerated carbonation condition for 3 days, 7 days and 28 days are used for macro and micro tests. MIP test is used to analyze the influence on internal pore structure of concrete by carbonation reacts. The changes of Ca(OH)2 and CaCO3 contents are measured with TG/DSC analysis. The results indicate that carbonation reaction can make concrete denser. Replacing Portland cement with fly ash and expansive admixture increases the carbonation rate of concrete and fly ash blended in concrete can improve the pore structure of concrete. Apart from the reaction of Ca(OH)2 and CO2, the carbonation reaction of other hydration product also exit in the accelerated carbonation process.

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