Concrete is perhaps the most widely spread building material used nowadays. Concrete is an artificial stone, made by thoroughly mixing such natural ingredients or aggregates as cement, sand and gravel or broken stone together with sufficient water to produce a mixture of the proper consistency. It has many valuable properties. It sets under water, can be poured into moulds so as to get almost any desirable form, and together with steel in reinforced concrete it has very high strength, and also resist fire. Prestressed concrete is most widely used at present while prefabricated blocks are employed on vast scale for skeleton structures.
Aggregate for concrete
By the simple definition from the dictionary “aggregates are the materials, such as sand and small stones, that are mixed with cement to form concrete.
Aggregates have three principle functions in the concrete: they provide a relatively cheap filler for the concreting material, or binder, they provide a mass of particles which are suitable for resisting the action of applied loads, of abrasion, of percolation of moisture through the mass, and of climate factors, they reduce volume changes resulting from the action of the setting and hardening of the concrete mass.
All aggregates, both natural and artificial, which nave sufficient strength and resistance to weathering, and which do not contain harmful impurities may be used for making concrete.
As aggregates such natural materials as sand, pebbles, broken stone, broken brick, gravel, slag, cinder, pumice and others can be used.
Prestressed concrete is not a new material. Its successful use has been developed rapidly during the last two decades, chiefly because steel of a more suitable character has been produced. Concrete is strong in compression but weak when used for tensile stresses.
If, therefore, we consider a beam made of plain concrete, and spanning a certain distance, it will at once be realized that the beam’s own weight will cause the beam to ‘sag’ or bend. This sagging at once puts the lower edge of the beam in tension, and if the cross-sectional are is small, causes it to break, especially if the span is relatively large.
If , on the other hand, we use the similar cross-section, but incorporate steel bars in the lower portion, the steel will resist the tensile stress derived from the sagof the beam, and thus assist in preventing it from breaking.
Bend – v сгибаться; гнуться; изгибаться
Crack – n 1.треск 2.трещина
Desire- желание; просьба, требование
Gravel - гравий
Load – n груз; нагрузка
Sag – v оседать; падать
Store – n запас; склад
Tensile – растяжимый
What is Meant by “Bioclimatic Architecture”
Bioclimatic architecture is a way of designing buildings and manipulating the environment within buildings by working with natural forces around the building rather than against them. Thus it concerns itself with climate as a major contextual generator, and with benign environments using minimal energy as its target. Bioclimatic architecture aims to protect and enhance the environment and life. It is developing on many different levels from rethinking basic concepts about our need for shelter and the function of the “city” in our lives to developing recycled or sustainable building materials.
The impact of traditional building on the environment and natural resources is enormous. However, the ideal of designing and building structures that are environmentally friendly has become fairly widespread throughout the community of architects and builders in developed nations. In many areas there is the necessity of complying with new regulations and standards aimed at protecting the environment. In addition, there are an increasing number of incentives for putting up buildings with more efficient energy consumption and that reduces the negative impacts on natural resources by using recycled or sustainable materials. While these vary around the world, there is awareness that our need for shelter must not jeopardize the environment.
There is growing interest in “green” building practice, which offer an opportunity to create environmentally sound and resource-efficient buildings by using an integrated approach to design. “Green” buildings promote resource conservation through energy efficiency, renewable energy, and water conservation features. They take into consideration the environmental impact of the building and minimize waste. Other goals are to create a healthy and comfortable, reduce operation and maintenance costs, and address issues such as historical preservation, access to public transportation and other community infrastructure systems. The entire life cycle of the building and its components is considered, as well as the economic and environmental impact and performance.