Looking for suitable material
Human beings, to meet their needs, have created materials based on natural or artificial themes. Each material has its advantages and disadvantages, and based on the latter has been built the current path from stone and wood to the current concrete and plasterboard. However, an optimal construction material has not yet been invented, so when choosing, it is necessary to prioritize.
Basic materials but techniques developed
The era of stone, copper, iron… the history of humanity is linked to the evolution of materials. In short, materials account for the needs, ways of life and knowledge of each moment.
Primitive man used easy and little worked materials: kneaded clay with roots and stone. But it was clearer than he thought and it was he who created the first prefabricated material by mixing clay and straw. The straw fibers that were added to avoid cracks during the drying of the clay and, although at present the materials have been modified, the reinforced concrete is made with the same technique.
Then, a. C. Between 8,000 and 10,000 years, ceramic technology was applied to construction to manufacture clay bricks at about 900°C. At first the bricks were glued with clay, but being permeable, they began to look for some waterproof adhesive. In Asia Minor, for example, asphalt was used as a binder.
The stone was first used for the manufacture of dolmens. The man began with stones of appropriate size and shape. However, with the development of the techniques and tools of elaboration, it began to build larger constructions that relied on pillars resting on other stones. The Greeks joined the columns with a stone of one piece, and the Romans built arches so that the light would enter more into the construction.
However, the most developed technique in the construction by Greeks and Romans was lime. Apparently, they casually discovered that lime could be useful in construction, but that discovery was not wasted.
In holes dug into the ground it was discovered that lime could be useful for construction. When heating the lime at very high temperature and mixing it with the water, they saw that in contact with the air a very hard material was obtained. But the process was long, a few months.
To solve this problem, lime was mixed with puzollage, the volcanic dust rich in silicon. Silicon reacts with lime in the presence of water and hardens without air. This technique was very well dominated by the Romans, but in 476, with the dissolution of the Roman Empire, the technique was lost.
Wood is another material that has long been used in buildings. Its main advantages are its high strength, its lightness and the existence of a reusable natural material. The disadvantages are their short duration in hostile environment and the risk of burns. At present, the first disadvantage can be corrected with the right treatments, but the second cannot be fully improved. In addition, the dimensions and shapes are limited depending on the trunk, although the union of fine wooden sheets allows obtaining very attractive shapes.
The Revolution of Steel and Concrete
XIX. From century to there, the use of steel and, subsequently, of concrete, radically modified the conception of buildings. Both materials allowed the realization of monolithic pieces of large dimensions and the union of different elements in a way that constituted a unit.
Steel is the material used in buildings that offers the best resistances, stiffness and ductility – deformed capacity or cold tense. In addition, complex parts made of steel can be easily bonded without breakage. Thus, the union of two pieces of steel is not a weak point, but an intersection with pieces of stone.
At the same time that steel was becoming the first construction material, the British Joseph Aspdin, based on lime, patented a new material as hard as the “Portland stone” cement. Cement was born in 1824 or, rather, was born. In fact, the British Parliament created cement with John Milton and J. The engineer Smeaton ordered to investigate the Roman works in 1755 and Joseph Aspdin created cement based on the lost technique.
In the beginning it was used as glue to join stones and bricks and, in the nineteenth century. From the middle of the 20th century (mixed with sand, water and pebbles), concrete emerged.
Concrete is an ideal material for high compressive strength without high costs. In addition, by introducing the liquid into the molds that give it shape, large parts are manufactured. But it splits or cracks with some ease.
The evolution of the materials has focused on the disadvantages of them, since the new materials have emerged with the intention to correct them. Thus was born the XIX. In the middle of the 20th century, reinforced concrete was the work of the Frenchman Joseph Monier.
Reinforced concrete was formed by the introduction of iron reinforcements in the manufacture of cement parts. Since then, reinforced concrete techniques have evolved a lot, especially thanks to the contributions of François Hennebique. He was the first to design the ribbed slab and use it to make a work of art in 1896. Since then, all architects, engineers and developers have learned to take advantage of the advantages of reinforced concrete. Reinforced concrete is currently used for the base of the buildings.
However, reinforced concrete, being a suitable material for construction, has also inherited a dark side. Technical advances in cement and steel allowed architects to achieve a conceptual freedom similar to that of sculptors. However, the developers have had the architects tied in short rope, being the raw material of the good price homes that were built in the 1950s and 1960s. Following industrial standards, square houses were built without aesthetics, so that the concrete acquired a negative image. It is now up to architects to work the imagination to change this image.
How to define material characteristics In the choice of construction materials you can see the price, weight, ease of adaptation, the pollution it generates or the thermal and acoustic insulation it offers. However, it can be said that one of the main characteristics of the material is resistance, without risk of error. Two types of resistance are differentiated: compression and tension. The first refers to the deformations that occur in the material depending on the force and the second to the failures or breaks that occur in the material. Normally, material characteristics are defined by a series of compression and tension tests. From these tests the curves called force deformation are performed. These tests do not take into account speed, force duration and repetition, but reliable material information is obtained. To this information we must add some non-structural characteristics of the material. For example, in the construction of bridges it is not advisable to use materials of slow resistance and of great weight, since part of the resistance is directed to support the weight of the material itself. |
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