Modern Building Materials

Part 2

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, also resists fire. Prestressed concrete is most widely used at present while prefabricated blocks are employed on vast scale for skeleton structures.

AGGREGATES 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”. In other words aggregates (or cushioning materials) can be defined as a mass of practically inert mineral materials, which, when surrounded and bonded together by an active binder, from the rock. This rock is denoted by the general term concrete.

Aggregates have three principal 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 have 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

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 be 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 areas is small, causes it to break, especially if the span is relatively large.

If, on the other hand, we use a beam of similar cross-section, but incorporate steel bars in the lower portion, the steel will resist the tensile stress derived from the sag of the beam, and thus assist in preventing it from breaking.

In prestressed concrete steel is not used as reinforcement, but as a means of producing a suitable compressive stress in the concrete is permanently under compression, and is consequently devoid of crack under normal loading, or so long as the “elastic limit” is not exceeded.

Prestressed concrete is not only used for beams but is now employed extensively for columns, pipes, and cylindrical water towers, storage tanks, etc.

Text 6

Design

Design - in narrow sense - creative activity which industrial purpose is definition of formal qualities products including:

-External features of a product; and it is especial-

-Structural and functional interrelations which transform a product into a single whole from the point of view of the consumer and from the point of view of the manufacturer.

Design to project. Design takes many forms in different contexts. In the applied arts, such as graphic design, industrial design, fashion design, functional art, and decorative art, design is considered a noun as it is a verb.

Design allows human beings to effectively communicate ideas and information. It cuts across a wide range of applied arts from fashion design to industrial design.

Design as a noun can refer to a drawing or a sketch. It could also be a graphic representation of a detailed plan for construction uses. It may also be described as a basic plan or pattern that could affect or control the environment. Design as a noun can also be used as an intent or purpose, a secret plot or ploy. In the context of a verb, design is the series of different processes involved in creating a plan meant for aesthetic and functional objects. These processes, or the design process, as it can be called, require significant time for deliberation, research, shaping and reshaping, adjustments, and redesign.

To design is to fashion in the mind, to create a plan in a systematic format, to execute plans, and to create designs. Our everyday lives are surrounded by the designs of people who are resourceful, creative and imaginative. We live in houses designed by architects, and ride in cars inspired by engineers. Our household items are product of a new form of art called industrial design.

The clothes we wear from shirts to jeans to underwear clothing are created by ingenious fashion designers, and the furniture pieces we install in our homes were created by the exceptional craftsmanship of their design makers.

To design entails careful evaluation of the product to be created, continuous planning, modeling and remodeling of the product, testing, and redesigning. People who are involved in design are usually creative, organized, and technology conscious.

They are committed to their craft and work well with others, because design is a process which cannot be achieved and perfected alone. This quality also helps them when they deal with clients whose ideas are different from theirs.

The design arena involve careers such as art directing, where you will be tasked to create visual concepts for a large number of products, from billboards to CD jackets.

Another occupation is that of a graphic designer, where you will design the packaging of books, magazines, catalogs, posters, and CD inserts. Industrial designers work in coordination with engineers to create and design everyday items, most of which are mass produced.

Text 7

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