Construction Materials. Ceramics, Glass and reinforced concrete
Posted on December 14th, 2009 by Technology Department
All types of bricks used in construction are ceramic materials that are modelled and dried by the action of heat. The most important components of bricks are traditional clays. Clay is a natural product which has decomposed from rock within the earth’s crust for millions and millions of years. In order to get a brick, clay is mixed with additives that give the ceramic brick different properties when fired. An essential element is feldspar: feldspar is the second most important ingredient in making bricks, after clay. The great feature of Feldspar is that it does not have a strict melting point. Appropriate mixing of clay and feldspar allows us to reduce the melting point, as Feldspars are used as fluxing agents. Feldspar improves the toughness, strength, and durability of the ceramic brick.
What do we understand by Glass?
All we know is that it is a transparent , hard and brittle solid, used for many bottles or windows.
Do not worry, sugar glass doesn’t contain any glass element !
If you’ve ever seen the film Terminator 2 where a actor is thrown through a window – and you’ve wondered “how did they do that?”, Well just sugar and more sugar.
The optical and physical properties of glass make it suitable for construction applications such as flat glass for windows, thermal insulators (glass wool which fills up the space between two walls ) internal glazed partitions, etc
A wide variety of colours may be obtained by addition of dispersed particles, such as soda-lime glass for a colourless glass or iron(II) oxide (FeO) which produce a green shade. To obtain float glass, a combination of metallic oxide ( for colour ), sand and alkali is required.
It is concrete in which reinforcement bars (iron bars ) have been incorporated to strengthen the material. Remember that concrete is good at compression efforts but bad at tension efforts. Iron has a good tension efforts value so adding iron to concrete will lead to a material good at both compression and tension. Concrete has a compressive stresses of about 27.5 MPa, however, any appreciable tension (e.g. due to bending in a beam will break the beam. If steel is placed in concrete, then the reinforced concrete resists compression but also bending. In a beam element there is a tension and a compression force.
Prestressed Reinforced Concrete:
Where the concrete will experience higher tensile stress, such as in a bridge or a beam supporting the roof of a sports stadium, it is necessary to apply tension to the steel reinforcement so as to counteract the high tensile stress applied to the concrete. See next illustration.
From the top to the bottom:
1 st Rebar: a steel reinforcing bar used in concrete. It is usually formed from mild steel, and has a patterned surface for better adhesion to the concrete.
2nd These methods involve stretching the steel reinforcement bars (tendons) before the concrete hardens. 3rd In pre-tensioning the steel ¡s anchored at one end and stretched by hydraulic jacks from the other end until the required tension is achieved. The casting is then usually steam-cured for twenty-four hours to rapidly obtain a typical 28 N/mm2 compressive strength. The steel has a patterned surface, which allows the concrete to achieve a firm bond to it. 4th When the concrete has sufficiently hardened the steel projecting out at each end is cut flush with the end of the beam.
5th Prestressed reinforced concrete is finished and ready to support the load.
counteract: To oppose and mitigate the effects of a contrary action.
Patterned: a model or form of metal, used for giving the bar an extra adhesion to the concrete.
Hardens: To make hard or harder