Simulieren der kapillaren Wasseraufnahme von porösen Werkstoffen des Bauwesens / Modelling of the Capillary Water Absorption of Porous Building Materials

2000 ◽  
Vol 6 (3) ◽  
pp. 293-306
Author(s):  
J. Elsen ◽  
F. de Barquin
Keyword(s):  
Water Absorption ◽  
Pore Size ◽  
Building Materials ◽  
Automated Image Analysis ◽  
Invasion Percolation ◽  
Capillary Water ◽  
Capillary Suction ◽  
Capillary Water Absorption ◽  
Porous Building Materials ◽  
3D Network

Abstract Profound knowledge of the moisture transport in porous building materials is essential to understand and to improve their durability. Water flow in these materials is mainly driven by capillary forces and the capillary suction of a porous building material depends on its pore structure. We have designed a statistical model to simulate the capillary water absorption of porous building materials based on invasion percolation rules. A 3D-network with 30x30x100 sites was used and the trapping effect is included. The input for the simulated invasion percolation is a pore size distribution obtained by a stereological analysis of the results of automated image analysis measurements on SEM-BSE-images of polished sections. Pore size distributions of nine different materials have been determined experimentally by SEM and by MIP. The simulated absorption curves agree reasonably well with the experimental absorption curves.

scholarly journals POROSITY, PERMEABILITY AND MICROSTRUCTURE OF FOAMED CONCRETE THROUGH SEM IMAGES

2019 ◽  
Vol 10 (1) ◽  
pp. 22-33 ◽  
Author(s):  
P. Shawnim ◽  
F. Mohammad
Keyword(s):  
Compressive Strength ◽  
Water Absorption ◽  
Pore Size ◽  
High Porosity ◽  
Capillary Water ◽  
Sem Images ◽  
Microstructural Investigation ◽  
Capillary Water Absorption ◽  
Foamed Concrete ◽  
Percentage Ratio

This paper examined the foamed concrete (FC) for permeability of total and capillary water absorption, at 28 days of air sealed curing. The microstructure of 15 selected FC specimens was investigated to determine permeability in relation to porosity and density using Scanning Electron Microscopy (SEM) images. The FC specimens of the densities (1100, 1600, and 1800) kg/m3 were made using fine sand and brick aggregates with toner and MK inclusion as additives. The microstructural investigation of the FC revealed, porosity measure as a percentage ratio of the area under investigation to be in the range of (39.65 to 77.7) %. The pore size is in the range of (0.01 to 70) µm, depending on the type of additive, for the mixes containing toner and MK, it is in a fine range of (0.01 to 10.0) µm. For the FC specimens, the finer the pore size, the less permeable and the stronger it is. Permeability is porosity and strength dependent, whereby high porosity leads to high permeability and low compressive strength for FC mixes made with sand or brick only with no additive inclusion. Meanwhile, the FC mixes made with the inclusion of additives, such as the toner and MK20 mixes, showed an evenly spread net of independent air voids with a regular shape within their matrix, which is beneficial in decreasing permeability. Therefore, besides the porosity and strength, the fineness of the pore matrix and the shape factor of the pores are two other key factors in controlling permeability. Toner and MK20 inclusion can enhance the capillary water absorption to reach almost water tight. Besides, MK30 and MK50 inclusion displayed adverse effect on permeability. Depending on the type of filler, the additive, and the percentage ratio of the porosity of the FC matrix at (1600 and 1800) kg/m3 densities, it is possible to produce FC with compressive strength between (55.1 and 30) N/mm2.

scholarly journals Effect of Capillary Water Absorption on Electrical Resistivity of Concrete with Coal Gangue Ceramsite as Coarse Aggregates

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Dong Li ◽  
Shi Liu ◽  
Haiqing Liu
Keyword(s):  
Water Absorption ◽  
Absorption Capacity ◽  
Coal Gangue ◽  
Capillary Water ◽  
Capillary Suction ◽  
Capillary Action ◽  
Capillary Water Absorption ◽  
Coarse Aggregates ◽  
The Matrix ◽  
Water Transmission

This study intends to access the influence of the capillary action on electrical property of the concrete containing the coal gangue ceramsite. For this purpose, four kinds of concrete samples were prepared; the coal gangue ceramsite was adopted at four volume ratios of 0%, 30%, 60%, and 100%, respectively. The resistivity of the samples was explored using the two-electrode method during the capillary action. The effects of the coal gangue ceramsite contents on capillary water absorption capacity and resistivity of the matrix were verified. The variation of the resistivity of the matrix under the influence of capillary water transmission was analyzed. The results demonstrated that, for the unsaturated concrete, the resistivity of the matrix increased with the increment of the coal gangue ceramsite dosage. The electrical properties of the concrete were affected noticeably by the capillary water absorption of the matrix; the resistivity of the matrix dropped significantly under the capillary suction, which may be attributed to the formation of the new conductive channels caused by the absorbed water. The variation of the resistivity of the concrete under the capillary suction sustained the two-stage reduction curve. The ability of the capillary water absorption of concrete was enhanced with the addition of coal gangue ceramsite, compared to the traditional aggregates concrete, the initial sorptivity, and secondary sorptivity of the matrix increased by 47% and 16% with the 100% content of coal gangue ceramsite. However, during the process of the capillary suction, the resistivity of the coal gangue ceramic concrete was always greater than that of the concrete with traditional crushed aggregates.

scholarly journals Effects of Imposed Damage on the Capillary Water Absorption of Recycled Aggregate Concrete

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Qi Gao ◽  
Zhiming Ma ◽  
Jianzhuang Xiao ◽  
Fuan Li
Keyword(s):  
Absorption Coefficient ◽  
Water Absorption ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Capillary Absorption ◽  
Capillary Water ◽  
Aggregate Concrete ◽  
Capillary Water Absorption ◽  
Freeze Thaw ◽  
Loading Level

Capillary water absorption of concrete is closely related to its pore structure, permeability, and durability. This paper intensively investigates the effects of imposed damage, including freeze-thaw damage and loading damage, on the capillary water absorption of recycled aggregate concrete (RAC). Freeze-thaw cycle test, loading test, and the experiment of capillary water absorption were carried out, respectively. The results demonstrate that the addition of recycled coarse aggregate (RCA) results in the increase in the capillary absorption behavior of RAC without imposed damage, and there exists a linear correlation between the behaviors of capillary water absorption and chloride penetration of RAC. The imposed freeze-thaw damage or load damage of RAC boosts with the increase of RCA replacement percentages after suffering the same freeze-thaw cycles or loading level. The imposed freeze-thaw damage and load damage further lead to the increase in the capillary water absorption of RAC, and the capillary absorption coefficient of RAC increases linearly with the increased RCA replacement percentages, after suffering the same freeze-thaw cycles or loading level. Furthermore, capillary absorption coefficient increases linearly with the growth of imposed freeze-thaw damage or load damage degree, which can be used to estimate the capillary absorption behavior of RAC exposed to the extreme environment.

scholarly journals The Influence of 30 Years Outdoor Weathering on the Durability of Hydrophobic Agents Applied on Obernkirchener Sandstones

Buildings ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 18 ◽  
Author(s):  
Jeanette Orlowsky ◽  
Franziska Braun ◽  
Melanie Groh
Keyword(s):  
Water Absorption ◽  
Water Uptake ◽  
Capillary Water ◽  
Capillary Water Absorption ◽  
Absorption Determination ◽  
Colour Changes ◽  
Uptake Velocity ◽  
Outdoor Weathering

The durability of eleven different water repellents applied on one sandstone type was studied after a long-term weathering at seven different locations in Germany. By measuring colour changes, it could be shown that the formation of black crusts, the deposition of particles and biogenic growth caused a gradual darkening as well as significant changes in total colour over time. Additionally, the water absorption behaviour was investigated with two different methods: applying a low pressure using the pipe method and capillary water absorption measurements from a wet underlay. Afterwards, the test results were analysed with four different evaluation methods: calculation of the protection degree from pipe method and capillary water absorption, determination of the velocity of water uptake during capillary water absorption and calculation of the damaged depth of the stone surface using single-sided NMR technique. The growing damaged depth leads to an increase of the water uptake velocity and to a decrease of the protection degree of the applied hydrophobing agents. Three protective agents based on isobutyltrimethoxysilane showed already after two years of outdoor weathering a clear loss of performance, which significantly increased after 30 years of exposure.

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