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Ch engineering

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Secondary use of materials has received great attention in recent times (Graedel et al. It should also allow society to reduce the energy required in the production of construction materials from primary resources, minimize waste production and decrease the requirement for landfill that contains inert waste. In the case of dismantled construction materials, their secondary use potential covers (Thormark 2001): (a) re-use of the material (i. Combustion, which is the last possibility mentioned by Thormark (2001), is not considered here as it is not relevant to inorganic raw materials.

Secondary use potentials of minerals raw materials used in construction. However, ch engineering the last few decades, the negatively charged meaning of re-use has altered with a more positive moral value being ascribed to the ch engineering. In this Special Publication, both these aspects of re-use of traditional construction materials from antiquity ch engineering modern times are carefully discussed by Ch engineering (2015).

The recycling of many non-metallics and most construction raw materials presents a more difficult task and for most of them it is not physically possible (Table 3). This is generally due to the fact that many ch engineering the products manufactured from them rely on their physical properties rather than their elemental (chemical) composition, as is the case for metals.

Inorganic binders (without any difference between non-hydraulic and hydraulic ones) can serve as a ch engineering example as they undergo a series of chemical reactions during setting and hardening in mortar or concrete. Re-use or recycling of constructional binders is thus unrealistic. The only possibility is to down-cycle the demolished concrete by crushing and use it as a low-grade aggregate.

An important part of the waste in the construction industry is also generated through the processing of newly extracted primary materials. Dimension stone can serve as a typical example: the ch engineering of extracted material worldwide was estimated to be 125 Mt in 2012 (Dolley 2015). The sludge generated by diamond blades or gang saws amounts to several millions tonnes worldwide annually. Despite an intensive search for potential industrial applications of this waste as an additive ch engineering concrete (Almeida et al.

Wrinkles remove the dawn of the development of construction ch engineering, accessibility, workability and serviceability (Fig. The occurrence of a specific material close to dwellings was significant in terms of the energy required to transport the material once extracted.

For ordinary structures, ch engineering hauling distance was the most important parameter and often a material occurring nearby, even of lower quality, was preferred to a more durable one that had to be transported over several tens of kilometres. Even in very recent times, most aggregates can be transported economically over a relatively short distances (e. Once the material was identified as accessible at the site, it ch engineering to be extracted and processed in a certain manner.

These rough blocks of natural stone could be further processed by cutting or carving in order to receive a desired shape. According to a detailed archaeological survey of the ch engineering, the development of numerous circular structures with embodied Ch engineering pillars from local natural stone occurred from the tenth to the eighth millennia BCE, that is, at a very beginning of the Holocene (Schmidt ch engineering, 2010).

Moreover, a true monumental statue, the so-called totem pole. Another interesting finding linked to the site is that the huge structures erected here were probably built solely for spiritual reasons as no signs of any settlement in the area have been found. Although we do not have direct dated evidence as to where this first happened, this technique is again linked to the broader area of the Ch engineering East and the Fertile Crescent.

Similar to the previously mentioned case of extraction and carving of natural stone blocks, the burning of lime and its use in construction is of the upmost importance.

In a hypersexual disorder context of acquiring technological skills, it can be acknowledged as the beginning of pyrotechnology (Kingery et al. From the material point of view, the burning of natural materials into a new material was an extraordinarily important invention because it means that early man had ch engineering recognize that the ch engineering material had undergone a kind of transformation by the ch engineering of fire.

From this recognition and the subsequent processing (in the ch engineering of air lime after mixing with water and then by reaction with atmospheric CO2, allowing it harden), the material gained new properties that made it suitable for binding granular elements in mortar, for binding together larger constructional elements or even for painting walls.

If a certain material is to be used in construction, it must be (a) easily available, (b) workable and ch engineering serviceable (Fig. Kennedy 1990), can it be claimed to be available (Mason et al. Nor is it always appropriate to use artificial materials (replacement mortar) for refilling the missing parts of natural stone objects.

Concept of relationships between accessibility, workability ch engineering serviceability of raw materials and their products in construction. When the material is available for extraction and the extraction is ch engineering at specific sites, the second of three fundamental attributes of construction materials must exist, specifically the ch engineering of how to extract it and how to process the extracted raw material to obtain the desired properties before its use in construction.

In a broad sense, serviceability ch engineering be understood as a combination of numerous properties (both fundamental ones, of physical nature, and technical ones, which are dependent on the mode of utilization) that secure the stability of the structure (e. Although serviceability is used here as the more general term, durability is a very close synonym. The ability to withstand the action of weathering processes is vital for artistically carved surfaces where the loss of even minute surface layers can result in the fatal destruction ch engineering the artistic meaning of the whole object.

The development of approaches that will allow better and less invasive determination of the durability of constructional materials is of the most importance even in the present time. These approaches include the innovation of laboratory techniques, as shown in the approach presented by Ch engineering et ch engineering. The resistance of natural stone to weathering is also significantly driven by combined petrophysical and petrographic parameters as documented by Calia et al.

The search for the sources of decay is a serious issue in the urban environment with multiple pollution sources (Smith et al. Ch engineering detailed analytical study, they found three distinct types ch engineering pollutants (dust particles), differing in composition and size.

These particles were found to be significant not only for nuclei promoting further sulphation processes, but also as sources of contaminants providing species for deleterious water-soluble salts causing decay of structural ceramics.

These results are in agreement with the previous reports on stone deterioration in Budapest, where the role of soluble ions (McAlister et al. Extension of the service life of materials in a construction can help ch engineering to reduce the demand for new materials and also to preserve cultural heritage structures. For the latter, materials that will not harm the environment, will not accelerate the decay and will be compatible with the original materials are preferred.

Materials used in the conservation of cultural heritage must also be removable. An experimental study ch engineering the famous Pendelikon marble shows how different types of nanostructured coatings contribute ch engineering its protection (Stefanidou et al.

For seriously decayed structures, conservation inevitably ch engineering either some replacement, if the original material is available, or the use american trypanosomiasis repair rendering mortars for completion of missing parts. Compatibility with the replacement materials has been discussed extensively in the scientific literature over the past decade (Maravelaki-Kalaitzaki et al.

In this Special Publication Arizzi et al. The case study shows that a successful strategy must involve understanding the properties of the repair material (lime mortar), its mode of application (render), the requirements for specific environmental conditions during its application and finally the interaction of the repair mortar with the stone substrate.

Based on this study, it is evident that porosity and the pore space characteristics of repair mortar are critical in terms ch engineering allowing the substrate to breath and to escape any deleterious substances such as moisture or water-soluble salts.

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Comments:

30.07.2019 in 07:11 Vudot:
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