erzsuche.com/components/greeley/3804-iphone-6-tastensperre.php Author: Mick Wright. Unlike existing manuals on ancient building, this offers an analytic presentation and the subject matter extends across all ages and regions. The treatment of materials is set out according to a paradigm of nature, manufacture and use, so as to facilitate direct comparison between different modes of the one material, as also between different materials and between different building traditions.
This second part is published in two volumes, the first containing texts, the second more than illustrations. Add to Cart. View PDF Flyer. As with all other temples, Karnak is a paragon of symmetrical architecture which seems to rise organically from the earth toward the sky. The great difference between this structure and any other is its grand scale and the scope of the vision.
Each ruler who contributed to the building made greater advances than their predecessors but acknowledged those who had gone before. When Thutmose III built his festival hall there he may have removed monuments and buildings of earlier kings whom he then acknowledged with an inscription. Every temple symbolizes Egyptian culture and belief but Karnak does so in large letters and, quite literally, through inscriptions.
Thousands of years of history may be read on the walls and columns of the Karnak temple. Hatshepsut - BCE contributed to Karnak like every other ruler but also commissioned buildings of such beauty and splendor that later kings claimed them as their own. Among her grandest is her mortuary temple at Deir el-Bahri near Luxor which incorporates every aspect of New Kingdom temple architecture on a grand scale: a landing stage at the water's edge, flagstaffs relics of the past , pylons, forecourts, hypostyle halls, and a sanctuary.
The temple is constructed in three tiers reaching 97 feet Amenhotep III - BCE built so many monuments throughout Egypt that early scholars credited him with an exceptionally long reign. Amenhotep III commissioned over buildings, monuments, stele, and temples. His mortuary complex was guarded by the Colossi of Memnon , two figures 70 feet His palace , now known as Malkata, covered 30, square meters 30 hectares and was elaborately decorated and furnished throughout the throne rooms, apartments, kitchens, libraries, conference rooms, festival halls, and all the other rooms.
Unfortunately this is largely because he is so often equated with the unnamed pharaoh in the biblical Book of Exodus and his name has become recognizable through film adaptations of the story and the incessant repetition of the line from Exodus that Hebrew slaves built his cities of Pithom and Per-Ramesses. Long before the author of Exodus ever came up with his story, however, Ramesses II was famous for his military exploits, efficient rule, and magnificent building projects.
The temple, cut from solid rock cliffs, stands 98 feet 30 meters high and feet 35 meters long with four seated colossi flanking the entrance, two to each side, depicting Ramesses II on his throne; each one 65 feet 20 meters tall. Further statues represent his family members and various protecting gods and symbols of power. Passing between the colossi, through the central entrance, the interior of the temple is decorated with engravings showing Ramesses and Nefertari paying homage to the gods. Abu Simbel is perfectly aligned with the east so that, twice a year on 21 February and 21 October, the sun shines directly into the inner sanctum to illuminate statues of Ramesses II and the god Amun.
This is another aspect of ancient Egyptian architecture which characterizes most, if not all, of the great temples and monuments: celestial alignment. From the pyramids at Giza to the Temple of Amun at Karnak, the Egyptians oriented their buildings according to the cardinal points and in keeping with celestial events. The Egyptian name for a pyramid was Mer , meaning "Place of Ascension" the name "pyramid" comes from the Greek word pyramis meaning "wheat cake" which is what they thought the structures looked like as it was believed that the shape of the structure itself would enable the dead king to rise toward the horizon and more easily begin the next phase of his existence in the afterlife.
In this same way, temples were oriented to invite the god to the inner sanctum and also, of course, provide access for when they wanted to ascend back to their own higher realms. The New Kingdom declined as the priests of Amun at Thebes acquired greater power and wealth than the pharaoh while, at the same time, Egypt came to be ruled by weaker and weaker kings. By the time of the reign of Ramesses XI c. Alexandria became the jewel of Egypt for its magnificent architecture and grew into a great center of culture and learning. The city has magnificent public precincts and royal palaces which cover a fourth or even a third of the entire area.
For just as each of the kings would, from a love of splendour, add some ornament to the public monuments, so he would provide himself at his own expense with a residence in addition to those already standing 1. The early rulers of the Ptolemaic Dynasty continued the traditions of Egyptian architecture, blending them with their own Greek practices, to create impressive buildings, monuments, and temples.
The legacy of the Egyptian architects lives on, however, through the monuments they left behind. The imposing pyramids, temples, and monuments of Egypt continue to inspire and intrigue visitors in the present day. Imhotep and those who followed after him envisioned monuments in stone which would defy the passage of time and keep their memory alive. The enduring popularity of these structures today rewards that early vision and accomplishes their goal. Editorial Review This Article has been reviewed for accuracy, reliability and adherence to academic standards prior to publication.
We're a small non-profit organisation run by a handful of volunteers. Become a Member. Mark, J. Ancient Egyptian Architecture. Ancient History Encyclopedia. Mark, Joshua J. Last modified September 18, Ancient History Encyclopedia, 18 Sep Written by Joshua J.
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Please note that content linked from this page may have different licensing terms. Mark published on 18 September Remove Ads Advertisement. Encyclopedia of Ancient Egypt by Margaret Bunson.
Gramercy, David, R. Religon and Magic in Ancient Egypt. Penguin, Lews, J. Running Press, Nardo, D. Living in Ancient Egypt. The Oxford History of Ancient Egypt. Oxford, Strassler, R. The Landmark Herodotus. Anchor Books, Van De Mieroop, M. A History of Ancient Egypt. Wiley-Blackwell, Verner, M. The Pyramids. Grove Press, Watterson, B. The Egyptians. Wilkinson, T. The Rise and Fall of Ancient Egypt. Random House Trade Paperbacks, About the Author Joshua J. Mark has lived in Greece and Germany and traveled through Egypt.
He has taught history, writing, literature, and philosophy at the college level. Related Content Filters: All. Articles 7. The great temples and monuments of ancient Egypt continue to fascinate The ancient Egyptians had a great appreciation for life which is In modern cement kilns many advanced features are used to lower the fuel consumption per ton of clinker produced. Cement kilns are extremely large, complex, and inherently dusty industrial installations, and have emissions which must be controlled.
Of the various ingredients used to produce a given quantity of concrete, the cement is the most energetically expensive. Even complex and efficient kilns require 3. Many kilns can be fueled with difficult-to-dispose-of wastes, the most common being used tires. The extremely high temperatures and long periods of time at those temperatures allows cement kilns to efficiently and completely burn even difficult-to-use fuels.
Combining water with a cementitious material forms a cement paste by the process of hydration. The cement paste glues the aggregate together, fills voids within it, and makes it flow more freely. As stated by Abrams' law , a lower water-to-cement ratio yields a stronger, more durable concrete, whereas more water gives a freer-flowing concrete with a higher slump.
Hydration involves many different reactions, often occurring at the same time. As the reactions proceed, the products of the cement hydration process gradually bond together the individual sand and gravel particles and other components of the concrete to form a solid mass. Reaction: . Fine and coarse aggregates make up the bulk of a concrete mixture. Sand , natural gravel, and crushed stone are used mainly for this purpose. Recycled aggregates from construction, demolition, and excavation waste are increasingly used as partial replacements for natural aggregates, while a number of manufactured aggregates, including air-cooled blast furnace slag and bottom ash are also permitted.
The size distribution of the aggregate determines how much binder is required. Aggregate with a very even size distribution has the biggest gaps whereas adding aggregate with smaller particles tends to fill these gaps. The binder must fill the gaps between the aggregate as well as paste the surfaces of the aggregate together, and is typically the most expensive component. Thus, variation in sizes of the aggregate reduces the cost of concrete.
Redistribution of aggregates after compaction often creates inhomogeneity due to the influence of vibration. This can lead to strength gradients. Decorative stones such as quartzite , small river stones or crushed glass are sometimes added to the surface of concrete for a decorative "exposed aggregate" finish, popular among landscape designers. In addition to being decorative, exposed aggregate may add robustness to a concrete. Concrete is strong in compression , as the aggregate efficiently carries the compression load.
However, it is weak in tension as the cement holding the aggregate in place can crack, allowing the structure to fail. Reinforced concrete adds either steel reinforcing bars , steel fibers , glass fibers, or plastic fibers to carry tensile loads. Admixtures are materials in the form of powder or fluids that are added to the concrete to give it certain characteristics not obtainable with plain concrete mixes.
Admixtures are defined as additions "made as the concrete mix is being prepared". The common types of admixtures  are as follows:. Inorganic materials that have pozzolanic or latent hydraulic properties, these very fine-grained materials are added to the concrete mix to improve the properties of concrete mineral admixtures ,  or as a replacement for Portland cement blended cements.
Concrete production is the process of mixing together the various ingredients—water, aggregate, cement, and any additives—to produce concrete. Concrete production is time-sensitive. Once the ingredients are mixed, workers must put the concrete in place before it hardens. In modern usage, most concrete production takes place in a large type of industrial facility called a concrete plant , or often a batch plant. In general usage, concrete plants come in two main types, ready mix plants and central mix plants. A ready-mix plant mixes all the ingredients except water, while a central mix plant mixes all the ingredients including water.
A central-mix plant offers more accurate control of the concrete quality through better measurements of the amount of water added, but must be placed closer to the work site where the concrete will be used, since hydration begins at the plant. A concrete plant consists of large storage hoppers for various reactive ingredients like cement, storage for bulk ingredients like aggregate and water, mechanisms for the addition of various additives and amendments, machinery to accurately weigh, move, and mix some or all of those ingredients, and facilities to dispense the mixed concrete, often to a concrete mixer truck.
Modern concrete is usually prepared as a viscous fluid, so that it may be poured into forms, which are containers erected in the field to give the concrete its desired shape. Concrete formwork can be prepared in several ways, such as slip forming and steel plate construction.
Alternatively, concrete can be mixed into dryer, non-fluid forms and used in factory settings to manufacture precast concrete products. A wide variety of equipment is used for processing concrete, from hand tools to heavy industrial machinery. Whichever equipment builders use, however, the objective is to produce the desired building material; ingredients must be properly mixed, placed, shaped, and retained within time constraints.
Any interruption in pouring the concrete can cause the initially placed material to begin to set before the next batch is added on top. This creates a horizontal plane of weakness called a cold joint between the two batches.
During concrete preparation, various technical details may affect the quality and nature of the product. Separate paste mixing has shown that the mixing of cement and water into a paste before combining these materials with aggregates can increase the compressive strength of the resulting concrete. The cement paste premix may include admixtures such as accelerators or retarders, superplasticizers , pigments , or silica fume. The premixed paste is then blended with aggregates and any remaining batch water and final mixing is completed in conventional concrete mixing equipment.
Workability depends on water content, aggregate shape and size distribution , cementitious content and age level of hydration and can be modified by adding chemical admixtures, like superplasticizer. Raising the water content or adding chemical admixtures increases concrete workability.
Excessive water leads to increased bleeding or segregation of aggregates when the cement and aggregates start to separate , with the resulting concrete having reduced quality. The use of an aggregate blend with an undesirable gradation  can result in a very harsh mix design with a very low slump, which cannot readily be made more workable by addition of reasonable amounts of water. An undesirable gradation can mean using a large aggregate that is too large for the size of the formwork, or which has too few smaller aggregate grades to serve to fill the gaps between the larger grades, or using too little or too much sand for the same reason, or using too little water, or too much cement, or even using jagged crushed stone instead of smoother round aggregate such as pebbles.
Any combination of these factors and others may result in a mix which is too harsh, i. Workability can be measured by the concrete slump test , a simple measure of the plasticity of a fresh batch of concrete following the ASTM C or EN test standards. Slump is normally measured by filling an " Abrams cone " with a sample from a fresh batch of concrete. The cone is placed with the wide end down onto a level, non-absorptive surface.
It is then filled in three layers of equal volume, with each layer being tamped with a steel rod to consolidate the layer. When the cone is carefully lifted off, the enclosed material slumps a certain amount, owing to gravity. A relatively wet concrete sample may slump as much as eight inches. Workability can also be measured by the flow table test. Slump can be increased by addition of chemical admixtures such as plasticizer or superplasticizer without changing the water-cement ratio.
High-flow concrete, like self-consolidating concrete , is tested by other flow-measuring methods. One of these methods includes placing the cone on the narrow end and observing how the mix flows through the cone while it is gradually lifted. Concrete must be kept moist during curing in order to achieve optimal strength and durability.
This carbonation reaction, however, lowers the pH of the cement pore solution and can corrode the reinforcement bars. Hydration and hardening of concrete during the first three days is critical. Abnormally fast drying and shrinkage due to factors such as evaporation from wind during placement may lead to increased tensile stresses at a time when it has not yet gained sufficient strength, resulting in greater shrinkage cracking.
The early strength of the concrete can be increased if it is kept damp during the curing process. Minimizing stress prior to curing minimizes cracking. High-early-strength concrete is designed to hydrate faster, often by increased use of cement that increases shrinkage and cracking. The strength of concrete changes increases for up to three years. It depends on cross-section dimension of elements and conditions of structure exploitation.
Properly curing concrete leads to increased strength and lower permeability and avoids cracking where the surface dries out prematurely. Care must also be taken to avoid freezing or overheating due to the exothermic setting of cement. Improper curing can cause scaling , reduced strength, poor abrasion resistance and cracking. During the curing period, concrete is ideally maintained at controlled temperature and humidity. To ensure full hydration during curing, concrete slabs are often sprayed with "curing compounds" that create a water-retaining film over the concrete. Typical films are made of wax or related hydrophobic compounds.
After the concrete is sufficiently cured, the film is allowed to abrade from the concrete through normal use. Traditional conditions for curing involve by spraying or ponding the concrete surface with water. The adjacent picture shows one of many ways to achieve this, ponding—submerging setting concrete in water and wrapping in plastic to prevent dehydration. Additional common curing methods include wet burlap and plastic sheeting covering the fresh concrete.
For higher-strength applications, accelerated curing techniques may be applied to the concrete. A common technique involves heating the poured concrete with steam, which serves to both keep it damp and raise the temperature, so that the hydration process proceeds more quickly and more thoroughly. Pervious concrete is a mix of specially graded coarse aggregate, cement, water and little-to-no fine aggregates. This concrete is also known as "no-fines" or porous concrete. Mixing the ingredients in a carefully controlled process creates a paste that coats and bonds the aggregate particles.
The hardened concrete contains interconnected air voids totaling approximately 15 to 25 percent. Water runs through the voids in the pavement to the soil underneath. Air entrainment admixtures are often used in freeze—thaw climates to minimize the possibility of frost damage. To ensure the mixing is thorough enough to create nanoconcrete, the mixer must apply a total mixing power to the mixture of 30— watts per kilogram of the mix.
This mixing must continue long enough to yield a net specific energy expended upon the mix of at least joules per kilogram of the mix. A superplasticizer is then added to the activated mixture which can later be mixed with aggregates in a conventional concrete mixer. In the HEM process, the intense mixing of cement and water with sand provides dissipation and absorption of energy by the mixture and increases shear stresses on the surface of cement particles. As a result, the temperature of the mixture increases by 20—25 degrees Celsius.
This intense mixing serves to deepen hydration process inside the cement particles. The nano-sized colloid Calcium Silicate Hydrate C-S-H formation increased several times compared with conventional mixing. Thus, the ordinary concrete transforms to nanoconcrete. Bacteria such as Bacillus pasteurii , Bacillus pseudofirmus , Bacillus cohnii , Sporosarcina pasteuri , and Arthrobacter crystallopoietes increase the compression strength of concrete through their biomass.
Not all bacteria increase the strength of concrete significantly with their biomass. Sporosarcina pasteurii reduces water and chloride permeability. Polymer concretes are mixtures of aggregate and any of various polymers and may be reinforced. The cement is costlier than lime-based cements, but polymer concretes nevertheless have advantages; they have significant tensile strength even without reinforcement, and they are largely impervious to water.
Polymer concretes are frequently used for repair and construction of other applications, such as drains. Grinding of concrete can produce hazardous dust. Exposure to cement dust can lead to issues such as silicosis , kidney disease, skin irritation and similar effects. The U. National Institute for Occupational Safety and Health in the United States recommends attaching local exhaust ventilation shrouds to electric concrete grinders to control the spread of this dust.
That same rule went into effect 23 June for general industry, hydraulic fracturing and maritime. It should be noted, however, that the deadline was extended to 23 June for engineering controls in the hydraulic fracturing industry. Companies which fail to meet the tightened safety regulations can face financial charges and extensive penalties.
Concrete has relatively high compressive strength , but much lower tensile strength. The elasticity of concrete is relatively constant at low stress levels but starts decreasing at higher stress levels as matrix cracking develops. Concrete has a very low coefficient of thermal expansion and shrinks as it matures. All concrete structures crack to some extent, due to shrinkage and tension. Concrete that is subjected to long-duration forces is prone to creep.
Tests can be performed to ensure that the properties of concrete correspond to specifications for the application. Different mixes of concrete ingredients produce different strengths. Concrete strength values are usually specified as the lower-bound compressive strength of either a cylindrical or cubic specimen as determined by standard test procedures.
Different strengths of concrete are used for different purposes. Higher-strength concrete is often used for larger civil projects.
Bridges may use long beams of high-strength concrete to lower the number of spans required. If a structure must be very rigid, concrete of very high strength may be specified, even much stronger than is required to bear the service loads. Concrete is one of the most durable building materials. It provides superior fire resistance compared with wooden construction and gains strength over time. Structures made of concrete can have a long service life. Concrete is used more than any other artificial material in the world.
Due to cement's exothermic chemical reaction while setting up, large concrete structures such as dams , navigation locks , large mat foundations, and large breakwaters generate excessive heat during hydration and associated expansion. To mitigate these effects, post-cooling  is commonly applied during construction. An early example at Hoover Dam used a network of pipes between vertical concrete placements to circulate cooling water during the curing process to avoid damaging overheating.
Similar systems are still used; depending on volume of the pour, the concrete mix used, and ambient air temperature, the cooling process may last for many months after the concrete is placed.
Various methods also are used to pre-cool the concrete mix in mass concrete structures. Another approach to mass concrete structures that minimizes cement's thermal byproduct is the use of roller-compacted concrete , which uses a dry mix which has a much lower cooling requirement than conventional wet placement.
It is deposited in thick layers as a semi-dry material then roller compacted into a dense, strong mass. Advantage and Disadvantage of Concrete. Raw concrete surfaces tend to be porous and have a relatively uninteresting appearance. Many different finishes can be applied to improve the appearance and preserve the surface against staining, water penetration, and freezing.
Examples of improved appearance include stamped concrete where the wet concrete has a pattern impressed on the surface, to give a paved, cobbled or brick-like effect, and may be accompanied with coloration. Another popular effect for flooring and table tops is polished concrete where the concrete is polished optically flat with diamond abrasives and sealed with polymers or other sealants.
Other finishes can be achieved with chiseling, or more conventional techniques such as painting or covering it with other materials. The proper treatment of the surface of concrete, and therefore its characteristics, is an important stage in the construction and renovation of architectural structures.
Prestressed concrete is a form of reinforced concrete that builds in compressive stresses during construction to oppose tensile stresses experienced in use.
This can greatly reduce the weight of beams or slabs, by better distributing the stresses in the structure to make optimal use of the reinforcement. For example, a horizontal beam tends to sag. Prestressed reinforcement along the bottom of the beam counteracts this.
In pre-tensioned concrete, the prestressing is achieved by using steel or polymer tendons or bars that are subjected to a tensile force prior to casting, or for post-tensioned concrete, after casting.