Building materials

Steel. There are different kinds of steel. Alloyed steel or special steel

is corrosion-resistant steel. This kind of steel is widely used in building. Stainless steel is also corrosion-resistant steel. It is used for cutlery, furnace parts, chemical plant equipment, valves, ball-bearings, etc.

Non-ferrous metals. Non-ferrous metals have the following characteristics: high electric and heat conductivity, high corrosion resistance, non-magnetic qualities, light weight.

Alumunium. This is the oldest and best known light metal. It is used in aircraft, automobile, chemical and some other industries.

+Copper. Copper is the best conductor of electricity. There are different alloys with copper. An alloy of copper and tin is called bronze. This metal is often used for making various ornaments.

Buildings of reinforced concrete may be constructed with load-bearing walls or with a skeleton frame. According to the first method, the exterior walls are designed of sufficient strength to carry the loads of the girders, beams, floors and roofs which rest on them. The interior supports may consist also of load-bearing walls or of columns, but this method does not utilize the full potentialities of concrete. By the second method, the floors and roofs rest directly on exterior and interior columns or are carried on beams and girders which, in turn, rest on the columns. The walls and partitions are simple enclosures of brick or reinforced concrete supported by the beams and girders. Most concrete buildings of any size are now designed according to this second or skeleton frame method.

One of man’s oldest building materials is finding its way into a lot of new places these days. Concrete, first discovered by the Romans, is now more widely used in construction than all other materials together.

The magic ingredient that makes concrete possible is cement, about which according to one expert more has been learnt in the past three decades than in the preceding 2000 years. Concrete is a synthetic stone which can be formed while soft into practically any shape the builder wants. Portland cement mixed with water is the paste that binds sand, gravel, clinker into an artificial rock that becomes harder as the years pass. Portland cement does not come from a place of that name; it was called Portland because Joseph Aspdin, the English builder who invented the first dependable, scientifically made cement about 1824, thought it resembled the rock excavated on the Isle of Portland on the Dorset Coast.

What’s so new about cement after all these years? Several things. One item is “squeezed” concrete known technically as pre-stressed concrete. By giving concrete a big squeeze after it has hardened, builders can increase its elasticity ten times, so that it will bend under a heavy load without breaking. This is important in building bridges, viaducts and floors of large buildings.

The simplest way to pre-stress concrete is to put steel wires or rods in the concrete when it is poured.

An unusual American use of reinforced concrete is the floating highway bridge across Lake Washington. The depth of the lake made piers too expensive, so engineers built the bridge on hollow concrete pontoons anchored in place by steel cables. It is the longest pontoon bridge structure on Earth.

Until recently the aim of engineers was to make concrete with as few bubbles as possible. Now they have come up with a new concrete that has millions microscopic bubbles per cubic foot. It is made by adding an agent which foams to form the bubbles when the concrete is mixed. This concrete doesn’t crack when freezing. The first “air bubble” roads were built many years ago. They have stood up under winter freezes so well that today this concrete is used for new road construction.

Another discovery is “soil cement”. Several years ago road builders lacking funds found that they could mix cement with soil on the site of the road, wet it and compact it, then cover it with bitumen. The first road they built is still carrying traffic. There are miles of soil-cement secondary roads and streets today. Construction goes so fast that with modern equipment a road builder can complete a mile of soil cement road in one day.

+Scientists are working on research into the behavior of cement and concrete under all kinds of conditions. Collaborating with engineers they are developing new ways of using concrete. Cement is changing the face of the Earth.

Air, water, sand, salt, coal, petroleum are familiar elements in the everyday life but these form the basic sources of the world’s fastest growing industry – plastics. The last decade has seen the plastic industry to become the fastest growing industry in the world with a total annual production already more than 9 000 000 tons.

From a purely engineering viewpoint the following characteristics of plastics explain their increasing acceptance by industries and consumers alike. These characteristics are usually shared by all plastics, but there are variations between individual materials; light weight; corrosion resistance; electrical and thermal insulation; ease of fabrication; transparency of some materials, etc.

The increasingly successful application of plastics which take advantage of these characteristics have meant that plastic material are now manufacturing materials in their own rights and not substitutes. The high strength to weight ratio of some plastics offers big field in the coming age of space travels and rockets.

+The same benefits of light weight coupled with good strength and absence of corrosion offer tremendous potential as alternatives to traditional building materials. New shapes in building are absorbing the attention of the architects. Plastics offer many of properties for these designs and their application in exotic structures is an example.