porosity structure
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Author(s):  
Krzysztof FALKOWSKI

For over a hundred years, concrete has been a well-known building material and is widely used in construction. Its properties have convinced construction engineers, architects, contractors and investors, which is why it is currently difficult to find a building completed without the use of this material. However, the influence of atmospheric conditions and other environmental influences means that over time they leave more and more visible signs of progressive destruction even on the best building material of the century. Taking into account the problems related to aeration and surface hydrophobization, the aim of the work was to demonstrate that by using an admixture in the form of an anionic bitumen emulsion and a superplasticizer based on polycarboxylate ethers, it is possible to obtain hard-to-wet concretes with a favorable porosity structure and increased resistance to environmental influences. For static calculations and dimensioning, an original calculation model of the pavement made of concrete with dispersed reinforcement in the form of fibers was used, which made it possible to eliminate the reinforcement in the form of bars. Laboratory tests with the use of concrete samples taken during concreting carried out after 28 days of maturation confirmed the high compressive strength.


2021 ◽  
Vol 14 (15) ◽  
Author(s):  
Shengze Xue ◽  
Qiang Sun ◽  
Hailiang Jia ◽  
Liwei Zhang ◽  
Shaofei Wang

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2982
Author(s):  
Maria Wesołowska ◽  
Anna Kaczmarek ◽  
Jerzy Hoła

In this paper, we analyze the state of conservation of ceramic building materials (clay masonry units) containing a large share of waste materials in the form of ash and slag from coal combustion and sawdust from wood processing, operated for several decades in facing walls of religious buildings, in external environment conditions. For the purpose of this analysis, comparative tests were carried out on the samples of ceramic materials cut out from facing walls and samples extracted from the same ceramic materials; they were stored in laboratory conditions for the entire time. The following were investigated: initial water absorption, capillary rise, and porosity structure determined with mercury intrusion porosimetry (MIP). The research has shown, among other things, that the ceramic materials exploited in the external environment are characterized by an almost twofold increase in the initial rate of water absorption and by a different size of dominant pores and a pore size distribution in comparison with ceramic materials stored in laboratory conditions. The results, obtained for ceramic building materials (clay masonry units) containing the above-mentioned waste materials in their composition, constitute a novelty. They fill a gap in the literature by establishing how decades-long operation in natural conditions affected the capillary properties and the porosity structure of the ceramics under investigation. Based on the obtained research results, conclusions of cognitive and practical significance have been formulated that relate to the possibility of the exploitation of facing walls made of investigated ceramic materials.


2021 ◽  
Author(s):  
Jinhyun Choo

<p>Many natural and engineered geomaterials have double-porosity structure where two dominant pore systems coexist. Examples include structured soils where the two pore systems are inter-aggregate pores and intra-aggregate pores, and fissured rocks where the two pore systems are fissures and matrix pores. Although such double-porosity materials are frequently observed in geosciences and geoengineering applications, it remains mostly unclear how fluid flow and solid deformation interact differently in single- and double-porosity materials. The presentation explores this question through numerical simulation of consolidation – a paradigmatic problem in poromechanics – based on a recently developed modelling framework for fluid-infiltrated, inelastic materials with double porosity. Built on a combination of continuum principles of thermodynamics and standard plasticity theory, the framework can capture deformation, flow, and their coupling that occur individually in each pore system. Simulation results using this framework suggest that double-porosity structure gives rise to a two-staged consolidation behaviour, where the second stage appears similar to secondary compression in clays. It is also found that the simulated two-staged behaviour bears a striking semblance to experimentally observed consolidation processes in shales. These findings suggest that double-porosity structure may exert dominant control over the long-term hydro-mechanical behaviour of geomaterials.</p>


2021 ◽  
Vol 274 ◽  
pp. 04009
Author(s):  
Denis Smirnov ◽  
Sergey Stepanov ◽  
Ruslan Garipov ◽  
Timur Garayev ◽  
Tagir Sungatullin

Cement-concrete pavements of roads and airfields are the most durable type of pavement. The design service life of cement-concrete pavements is 40-50 years, in Russia this period is 20-25 years, and for asphalt-concrete pavements is 10-15 years. The real, actual overhaul period of asphalt concrete pavements, is much lower than the design one (according to the Federal Road Agency of Russia «Rosavtodor», on average, 3-5 years or even less), therefore, work aimed at increasing the durability of cementconcrete pavements is of particular relevance. The main technical parameters of road concrete that characterize its durability are compressive strength, flexural tensile strength, water absorption and others. The most important parameter is the frost resistance of concrete, which is primarily influenced by the structure of the pore space. This paper shows the way of obtaining concretes based on aggregates, the frost resistance of which is lower than the frost resistance of the resulting concrete.


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