scholarly journals Analysis of strength property and pore characteristics of Taihang limestone using X-ray computed tomography at high temperatures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shi Liu ◽  
Zhe Huang
Keyword(s):  
Computed Tomography ◽  
High Temperature ◽  
Strength Property ◽  
Mechanical Test ◽  
Test Method ◽  
High Temperature Treatment ◽  
Pore Characteristics ◽  
X Ray ◽  
Limestone Sample ◽  
X Ray Computed

AbstractRising temperature will cause the changes of pore characteristics and strength property in rock. This research takes the limestone produced in Taihang Mountains as the research object, and performs high-temperature treatment within 25–1000 °C. The high-resolution X-ray computed tomography (CT) scanning test method is used to visually reconstruct the three-dimensional image of the sample, and obtain the spatial distribution status of the mesoscopic parameters of the bones, pores/cracks, etc. The results show that when the temperature exceeded 700 °C, the samples appeared milky white in appearance and as the temperature increased, the color gradually turned white, macroscopic cracks began to appear on the surface, while the meso-pores connected rapidly, reflecting a typical progressive destruction process from inside to outside. The change law of volume porosity with temperature has a consistent trend with that of the apparent morphology of the sample. Similarly, the mechanical test results suggest that 700 °C is also the turning temperature for strength deterioration and brittle-plastic transformation of sample. Based on the results of high-temperature test, CT test and mechanical test, there are enough evidences to show that, for the limestone sample, 700 °C is probably to be the mutation temperature of physical–mechanical behavior.

Effect of Fly Ash on the early Age Cracking Performance of Cement Paste

2014 ◽  
Vol 584-586 ◽  
pp. 894-898
Author(s):  
Ping Zhang ◽  
Guan Guo Liu ◽  
Chao Ming Pang ◽  
Bing Du ◽  
Hong Gen Qin
Keyword(s):  
Computed Tomography ◽  
Fly Ash ◽  
Cement Paste ◽  
Test Method ◽  
Early Age ◽  
Cement Ratio ◽  
X Ray ◽  
Cracking Performance ◽  
X Ray Computed ◽  
Ct Test

The X ray computed tomography (X-CT) was applied to test the cracking resistance of cement paste, and the hydration process was monitored to study the effect of fly ash on the early age cracking performance. The results showed that the hydration heat reduced with the increase of fly ash under the same water-cement ratio. Within 24h, the porosity increased with time. The addition of fly ash increased the proportion of large holes and then changed the internal stress state. Using X-CT test method and by comparing the number of cracks, the sample with 20% FA was found to have the most serious cracks, whereas the sample with 30% FA had the best crack resistance.

Soil pore effects on spatial patterns of extracellular enzymes: combined X-ray computed tomography and 2D zymography

2021 ◽  
Author(s):  
Archana Juyal ◽  
Andrey Guber ◽  
Alexandra Kravchenko
Keyword(s):  
Computed Tomography ◽  
Enzyme Activity ◽  
Spatial Patterns ◽  
Extracellular Enzymes ◽  
Cropping Systems ◽  
Pore Characteristics ◽  
X Ray ◽  
Preliminary Results ◽  
Computed Tomography Scanning ◽  
X Ray Computed

<p>Extracellular enzymes play an important role in soil biochemical processes as they are the key regulators of litter and soil organic matter degradation. However, understanding of the factors influencing their activity and fate in soil is still limited. In this study, we examined the relationship between soil pores and spatial patterns of extracellular enzyme activity in soils from two bioenergy cropping systems: monoculture switchgrass (Panicum virgatum L.) and restored prairie. Intact soil cores (5 cm Ø x 5 cm height) were collected at two contrasting topographical positions (depression and slope) within large topographically diverse fields where the switchgrass and prairie were grown since 2008. The cores were subjected to X-ray computed tomography scanning at 18 µm resolution. After the scanning, a switchgrass seedling was planted in these cores and allowed to grow for three months. Then the plants were terminated and the cores were rescanned. Pore characteristics were assessed using the image information, and b-glucosidase activity was characterized via 2D zymography. Preliminary results showed that soil of the prairie system had greater volumes of 60-180 mm Ø size pores compared to monoculture switchgrass system. However, enzyme activity was higher in the soil of monoculture switchgrass. Our preliminary results indicate that the soil pore size distribution and enzyme activity differ depending on the type of the bioenergy cropping system. Further analysis is conducted to determine microbial abundance, total C in soil and microbial biomass in these cropping systems to understand the effect of pores on microbial activity associated with C processes in soil.</p>

Estimating the depth of the restrictive layer of soil in a cranberry field based on CT scan images

2020 ◽  
Author(s):  
Elnaz Shahriarinia ◽  
Silvio Jose Gumiere ◽  
Christian Dupuis
Keyword(s):  
Computed Tomography ◽  
Ct Scan ◽  
Fine Particles ◽  
Pore Network ◽  
Imaging Method ◽  
Pore Characteristics ◽  
Soil Particles ◽  
X Ray ◽  
Soil Media ◽  
X Ray Computed

<p><strong>Estimating the depth of the restrictive layer of soil in a cranberry field based on CT scan images</strong></p><p> </p><p>Cranberry production is a dominant culture in Québec, Canada. In cranberry production, there is a substantial need for water whether for irrigation, harvesting, or frost control. Some farms are implementing subirrigation procedures in order to reduce water use and increase fruit yields. However, this irrigation method may impose hydraulic stresses on soil particles which results in the movement of fine particles. The accumulation of the soil particles in narrow pore throats leads to the formation of restrictive layers in soil.  In this respect, we are going to study the changes in soil media and its porosity based on X-ray computed tomography (CT) which is a non-destructive imaging method. Consequently, X-ray CT has become a great asset to analyze soil physical properties. With the analysis of the images captured by the use of X-ray computed tomography, it is possible to visualize and analyze the pore network structure in the soil media.</p><p> </p><p>This study reports the results of subirrigation experiments for four different sandy soils. These column experiments aimed to reproduce the effects of subirrigation in cranberry fields for 40 years. Seven different time steps were taken with a medical CT scanner SOMATOM Definition AS+ 128 (Siemens, Germany). The 2-D horizontal 16-bit gray-scale images were captured by an X-ray energy level of 140 KeV. For each column, we got 1677 images of 512  512 pixels with a voxel size of 0.1 × 0.1 × 0.6 mm (x, y, z). Studying our images for further analysis, we used several global and local methods to find the most reliable and efficient one to binarize our images. Results show that the methods and the image analysis neighborhood have a great impact on the accuracy of the image segmentation. We were able to reconstruct a 3-D visualization of the soil pore network for each column. We used this reconstruction to demonstrate that the variation of porosity and soil pore characteristics can be studied over time. We find that the transport of soil particles tends to be highest when there are fine sandy soil particles on top of a layer of coarse soil. These finer particles have sufficient energy to be remobilized within the pore network while coarser particles remain in place. Our results show that soil particle transport can be assessed using time-lapse imagery and thus makes it possible to approximate the depth and amount of time that will be required for these restrictive layers to form in different soil profiles. Finally, it would be possible to find the best structure of soil in construction of a cranberry field in the future.</p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p>

scholarly journals Relationship between percolation mechanism and pore characteristics of recycled permeable bricks based on X-ray computed tomography

2021 ◽  
Vol 60 (1) ◽  
pp. 207-215
Author(s):  
Songsong Lian ◽  
Tao Meng ◽  
Hongqi Song ◽  
Zhongjia Wang ◽  
Jiabin Li
Keyword(s):  
Computed Tomography ◽  
Effective Porosity ◽  
Recycled Concrete ◽  
Pore Characteristics ◽  
X Ray ◽  
Nonlinear Channels ◽  
Porosity And Permeability ◽  
Porous Permeable Material ◽  
X Ray Computed ◽  
The Relationship

Abstract The relationship between percolation mechanism and pore characteristics for recycled permeable bricks with different porosities is investigated in this study based on X-ray computed tomography (X-CT). Permeability coefficients are measured and some characteristics including size, amount, and distribution of the pore are analysed. The results show that the effective porosity and permeability coefficient of the recycled permeable bricks exhibit a linear relationship first and then a quadratic curve relationship, where the critical effective porosity is 12%. Meanwhile, we discovered that nonlinear channels in permeable bricks are larger and fewer compared with linear percolation channels, regardless of whether the percolation stage is linear or nonlinear. Additionally, when the area and number ratios of the linear and nonlinear percolation channels reached 80% and 10%, respectively, the overall percolation state of the permeable bricks changed from linear to nonlinear percolation. This research is helpful to improve the mechanical and percolation properties of recycled concrete bricks and promote the application of porous permeable material.

Agroforestry and Grass Buffer Effects on Pore Characteristics Measured by High-Resolution X-ray Computed Tomography

2008 ◽  
Vol 72 (2) ◽  
pp. 295-304 ◽  
Author(s):  
Ranjith P. Udawatta ◽  
Clark J. Gantzer ◽  
Stephen H. Anderson ◽  
Harold E. Garrett
Keyword(s):  
Computed Tomography ◽  
High Resolution ◽  
Pore Characteristics ◽  
X Ray ◽  
X Ray Computed ◽  
Grass Buffer ◽  
Buffer Effects
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