Why are the bricks red and have holes in them?
15.09.2023
Bricks were first used in the Neolithic period in the Mediterranean Levant around 9500 B.C. Those innovative masons did it out of necessity, as there was hardly any wood or stone in that geographical area.
In the beginning, bricks were made by extracting mud from the ground, mixing it with water, kneading it and giving it a more or less rectangular shape, before leaving it to dry in the sun.
The oldest known brick courses were found at Jericho in Palestine, near the Jordan River and east of Jerusalem. The remains of two different types of bricks were found in the ruins of this city. One is similar in size to a loaf of bread and dates to a period between 8300 and 7600 BC; the other type is thinner and has been christened the reed brick.
It is curious that they were found precisely there, in Jericho, the place where the Israelites miraculously brought down their walls with the sound of trumpets.
Firing at 1,000 degrees Celsius
Those first bricks, made of mud and adobe, were replaced six thousand years later by fired bricks. The reason for this was efficiency, as it was less costly to shape a brick than to carve a stone, and firing gave similar strength. The first fired bricks appeared in Mesopotamia and were used both as decorative elements and to cover mud-brick walls.
At the present time, the main material used in brick making is clay, which is composed of alkaline materials (calcium and magnesium oxides), silica, alumina and varying amounts of iron oxides. The amalgam of these particles is capable of hygroscopically absorbing up to 70% of its weight in water.
It is precisely the ferruginous component that gives the characteristic reddish colour; when there is a high lime content in the composition, the resulting colour turns white.
Once the clay has been sufficiently hydrated, it can be moulded, followed by a hardening process by drying or firing, which gives it a remarkable solidity. Firing is usually carried out at temperatures ranging from 900 to 1000 degrees Celsius.
Fired ceramic parallelepiped bricks with perforations on the face with the largest surface area, called slabs, are used in construction. When the volume of the hollows is between 25-45%, the brick is said to be perforated, while if the volume is less than 25%, the brick is considered to be solid.
The holes in the bricks allow the final weight of the structure to be reduced, while at the same time giving it more thermal and acoustic insulation capacity. The holes also allow for better adhesion to the mortar, ensuring adequate mechanical strength and watertightness.
Before laying, dampen them.
Brick masonry uses cement mortar, which is made by mixing a certain proportion of sand and cement with water, a mixture that helps to “glue” the pieces together correctly.
If the bricks of a wall are dry when they are laid, they absorb a certain amount of moisture from the mixture, which changes their final composition, and to avoid this, the masons moisten the bricks beforehand.
*A few years ago, Kenyan engineer Nzambi Matee founded a brick factory in Nairobi, where today 1,500 bricks are produced daily. The number is certainly not very high, but it does contain a unique feature: the bricks are made of recycled plastic and come in different shapes and colours. It seems that the plastic bricks are three to four times stronger than ceramic bricks, and at the same time they are cheaper.
By Abc Diario.
