C.O.N.C.R.E.T.E.

CONCRETE


Concrete is a construction material that consists of cement (commonly Portland cement) as well as other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate such as gravel limestone or granite, plus a fine aggregate such as sand or manufactured sand and water) and chemical admixtures.
Concrete solidifies and hardens after mixing and placement due to a chemical process known as hydration.The water reacts with the cement, which bonds the other components together, eventually creating a stone-like material. It is used to make pavements, architectural structures, foundations, motorways/roads, overpasses, parking structures, brick/block walls and footings for gates, fences and poles.
COMPOSITION
The composition of concrete is determined initially during mixing and finally during placing of fresh concrete. The type of structure being built as well as the method of construction determine how the concrete is placed and therefore the composition of the concrete mix (the mix design).
TYPES OF CONCRETE



Regular concrete
High-strength concrete
High-performance concrete
Self-compacting concretes
Shotcrete
Pervious concrete
Cellular concrete
Cork-cement composites
Roller-compacted concrete
Glass concrete
Asphalt concrete
Rapid strength concrete
Rubberized concrete
Polymer Concrete
HISTORY

In Serbia, remains of a hut dating from 5600 BC have been found, with a floor made of red lime, sand, and gravel. The pyramids of Shaanxi in China, built thousands of years ago, contain a mixture of lime and volcanic ash or clay.

ROBERT ANDRIOAIA - 3 D

REFRACTORY BRICKS

Refractory bricks are made out of a refractory ceramic. Its main properties are that it has a low thermal conductivity to save energy. These can support high temperatures(1650 °C) (3000 °F) so that is the main reason why it is often used in fireplace. They are weaker, but they are much lighter, easier to form, hard and insulate far better than dense bricks. People don´t usualy put the normal bricks because they cannot support the variation of temperatures easily.
They usually contain about 30-40% aluminium oxide, 50% silicon dioxide. For bricks of extreme refractory character, the aluminium oxide content can be as high as 50-80%.
This brick was invented in 1817 by William Harry, in Wales. Harry used the possibility of combining different materials with silica, this is how he invented the brick know has fire-proof brick. In 1822 its use in construction spread worldwide.

POLYMERIZATION

Last day in Technology workshop, we made a practice consisting in creating a plastic by the process called Polymerization.

Plastics are polymers, which means they are formed by smaller molecules called monomers that join each other lining up in longer chains. The monomer that we used is called Vinyl Acetate. We transformed this monomer into a polymer called Polyvinyl Acetate, using a catalyst, sodium perborate. This is the chemical substance needed to make the chemical reaction to occur.

During the practice, we were taking notes about the properties of the substances we observed.

Don't forget you have to write a report about this lesson in a word document and send it to your technology teacher.