Cement: know origin, importance, risks and alternatives

Cement is the main material found in civil construction works. Although essential, its manufacture poses risks to health and the environment.

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Cement is one of the most used products around the world, and it can be said that this material revolutionized the history of engineering and the way in which cities began to structure themselves. Look around you... It is present in almost every type of construction, from the simplest house to the most complex engineering work.

Basically, cement is a fine powder with binding, binding or binding properties, which hardens when it comes into contact with water. Once hardened, even if subjected to the action of water again, this material does not decompose again.

Its main raw materials are: limestone, clay, and smaller amounts of iron and aluminum oxides, used for the production of clinker - basic material for the manufacture of cement (read more in Clinker: know what it is and what are yours environmental impacts) -, gypsum (gypsum) and other additions (such as pozzolan or kiln slag).

Usually, when you talk about cement you also talk about concrete. Both are essential materials in civil construction. But would you be able to tell the difference between these two materials?

Cement is a fine powder, with binding properties, which can be used for various purposes, such as in the composition of mortar, wall plastering, in the manufacture of concrete, etc.

Concrete is a compound, widely used in civil construction, which uses cement as one of its main components, which gives it the necessary stiffness and binding properties. In addition to cement, other materials present in the composition of concrete are water, sand and stone.

In short: concrete is the structure resulting from the mixture of cement and other materials, while cement is one of the “ingredients” that are part of this recipe.

Source

Cement is a word originated from the Latin 'caementu', which designated, in ancient Rome, a kind of natural stone for boulders.

Historians assume that primitive man, from the Stone Age, already had the knowledge about a material with binding properties similar to cement. It is believed that these human beings, when lighting their fires next to the limestone and plaster stones, observed part of these stones turning into powder under the action of fire and, when the material was hydrated by the calm of the night, it was converted again in stone.

In addition, the origin and creation of cement, with a composition different from what we know today, are very old. It is estimated that they began to be used around 4,500 years ago.

Coliseum

Some ancient peoples, such as the Egyptians and Romans, already used a kind of agglomerate between the blocks of stones in the construction of their monuments. In Ancient Egypt, an alloy consisting of a mixture of calcined gypsum was already used. The great Greek and Roman works, such as the Pantheon and the Coliseum, were built using soils of volcanic origin, which had hardening properties under the action of water.

In 1756, the first step towards the development of modern cement was taken by the Englishman John Smeaton, who managed to obtain a resistant product by calcining soft and clayey limestones.

But it was only in 1824 that the English builder Joseph Aspdin burned together limestone and clay, turning them into a fine powder, very similar to modern cement. When water was added to this powder, a mixture was obtained which, after drying, became as hard as stone and did not dissolve in water. This discovery was patented under the name Portland cement, for its color and properties of durability and solidity similar to the rocks of the British Isle of Portland.

The formulation of Portland cement is the most used and widespread throughout the world to this day.

Emergence in Brazil

In Brazil, the first experiences related to the manufacture of Portland cement occurred around 1888, through Commander Antônio Proost Rodovalho, who installed a factory on his farm in Santo Antônio (SP), followed by the installation of a new factory on the island Tiriri (PB), in 1892. And, in 1912, the government of Espírito Santo founded its own factory in the city of Cachoeiro do Itapemirim.

However, these actions were no more than attempts, which culminated, in 1924, with the implantation of a factory, by the Companhia Brasileira de Cimento Portland, in Perus (SP), whose construction can be considered as the landmark of the implantation of the Brazilian cement industry. .

The first tons were produced and placed on the market in 1926. Until then, cement consumption in the country depended exclusively on the imported product. In this way, from the date mentioned, the national production was gradually increased with the implantation of new factories and the participation of imported products diminished in the following decades, until practically disappearing nowadays.

Risks to the environment and human health

The main environmental impacts are related to the cement production process. Factories of this material end up polluting the environment and are responsible for relevant impacts.

And, although the manufacturing process for this material does not directly produce solid waste, since the ash from burning fuels in cement plants is normally reused in the process itself, there is a high emission of gaseous pollutants and particulate matter.

Thus, the main impacts are caused by the emission of polluting gases from these fuels. An example is the high emission of carbon dioxide (CO2), one of the main gases that unbalance the greenhouse effect. Read more about the environmental impacts caused during cement production in the article "How does the cement production process occur and what are its environmental impacts?".

In addition to these environmental impacts, cement can also pose risks to human health. The use of cement without the use of adequate protective equipment can cause serious damage to the health of the worker who handles this material. According to a study, cement is classified as an 'irritating material', reacting when in contact with the skin, eyes and respiratory tract.

Cement reacts in contact with the skin due to moisture (body perspiration) after prolonged contact. Heat is released due to the reaction of the cement in contact with the liquid surface, causing injuries. Furthermore, it is common to observe the alkaline action of cement on, mainly, the hands and feet of construction workers. Cement exerts an abrasive effect on the stratum corneum of the skin, causing lesions such as: redness, swelling, blisters and cracks.

Care must be redoubled with the sensitivity of the eyes as cement can cause conjunctival irritations and even more serious and irreversible injuries such as blindness.

Other health risks are related to the inhalation of dust from this material. The time of exposure to dust, without the necessary safety methods, is an aggravating factor in this process. According to research, it is estimated that the period between ten to 20 years of exposure to these dusts is sufficient for the development of lung diseases. These diseases result from the accumulation, by inhalation, of solid particles in the lungs.

Over the years, the inhaled dust remains deposited in the lungs, creating a framework of fibrosis, that is, the hardening of the lung tissue, causing the lungs' elastic capacity to be compromised.

Alternatives and Innovations

The forecast is that the production and need for cement will continue to grow in the coming years, which would consequently increase the total emissions of greenhouse gases, such as CO2. To avoid, or at least minimize this situation, it is vital to think about alternatives and appropriate innovations for the production and consumption of cement, since the demand for this material is unlikely to decrease. Below, we present some alternatives and innovations:

Metallic structures

Currently there are already several constructions that use metallic structures.

If we compare the cost/benefit ratio of this type of construction with that of reinforced concrete (concrete + iron), we will obtain advantages and disadvantages, such as:

Regarding the structure, while the concrete one must be produced entirely on site, the metallic one is only assembled, having its production done in the factory, which speeds up the process.

The labor used in works with metallic structures is much smaller than that used in reinforced concrete works, although metallic structures require more specialized labor. Errors are sometimes permissible and corrected when dealing with concrete structures. However, errors in the metallic structure must be null.

The weight of the metallic structure is less than that of the reinforced concrete structure, which relieves tension on the beams and columns.

As for the strength of these structures, they are equivalent.

Regarding the deadlines for the work, the metallic structure has more advantages, as the work steps can be carried out simultaneously, unlike structures in reinforced concrete.

As for thermal insulation, reinforced concrete structures have an advantage over metal structures, as metal structures overheat in summer and cool too much in winter, unlike concrete structures, which end up being more cozy and comfortable.

Finally, concrete structures have a great advantage over metallic structures in fire protection. This fact seems to justify the still great use of reinforced concrete structures.

Use of certified wood

There are different initiatives that defend the use of certified wood in civil construction to replace structures made of concrete. There are many positive factors advocated for this practice, such as the fact that wood is a renewable resource, reduces the amount of greenhouse gases and is a resistant and easily reusable material.

Check below the animation provided by the non-governmental organization WWF-Brasil (World Wide Fund for Nature), which addresses and encourages the use of certified wood in civil construction projects.

In addition to this animation, it's interesting to check out Michael Green's TED Talks talk, 'Why we should build wooden skyscrapers'(Why should we build wooden skyscrapers). He is an architect who evaluates and proposes the possibility of constructing high-rise buildings and complex works with certified wood (carbon sink) instead of using concrete and steel. The presentation lasts 14 minutes and approaches this topic in a very innovative and interesting way. Check out the lecture here.

Bioconcrete: the concrete that 'cures' itself

The so-called bioconcrete is a discovery capable of completely revolutionizing the civil construction sector and the way human beings carry out their constructions and repairs. It was born from the hands and minds of Dutch scientists, from the University of Technology in Delft, and stands out for its ability to seal its own fissures and cracks. It would be a concrete endowed with 'self-healing' capabilities, as occurs in nature with certain living beings.

According to its creators, bioconcrete is so called because it is a 100% live product. This is due to the presence of bacteria in the material, responsible for offering it special properties. The researchers mix common concrete with calcium lactate and a colony of microorganisms (Bacillus pseudofirmus). These bacteria are able to survive for more than two centuries in buildings, even in an adverse environment.

In practice, existing cracks in buildings constructed using bioconcrete are regenerated when bacteria present in the product come into contact with water. When penetrating the cracks, they are stimulated by moisture and start to consume lactate. The final result, after the 'digestion' of these bacteria, is the production of limestone, a substance in charge of repairing the material.

Another positive aspect of bioconcrete is related to the extent of the crack that it is possible to recover, with practically no limits, being able to repair up to kilometers of cracks. However, for best operation, the break must not be wider than 8 mm. Furthermore, the savings provided by the use of bioconcrete are unimaginable, as a lot of money can be saved.

Check out the following video, in English, made available by the University of Delft, Netherlands. In it, the concept and functioning of the concrete bio are briefly explained by one of its creators.

Concrete recycling

Concrete recycling is an alternative to combat the huge volume of waste generated daily by civil construction and to help reduce the environmental impacts caused by the process of extracting and manufacturing cement and concrete. Read more about concrete recycling in 'Technique using electrical discharges to recycle concrete successfully tested'.

A major barrier to the use of recycled concrete refers to the variability and uncertainty in the properties and final quality of the recycled material and how this would affect the strength, rigidity and durability of the constructed structures.

Because of the knowledge gap so far, the use of recycled aggregates has been limited mainly to non-structural applications such as sidewalks, roads and in land leveling works, although the quality of recycled material is generally higher than required in these non-structural applications.

Thus, it is necessary to develop appropriate research and engineering methods for a greater use of recycled concrete aggregates in structural works, such as buildings.

In addition to these, there are also other alternatives that aim to help reduce the impacts caused by the cement industry. Check the articles: 'Alternative techniques mitigate environmental damage from the cement production process' and 'Clinker: know what it is and what its environmental impacts are'.

Cement, as already mentioned, is fundamental for the "construction" of the society we know today. Therefore, we should not demonize it, but look for alternatives on a large scale so that its impacts are reduced and more sustainable alternatives can be developed.


Sources: Brazilian Association of Portland Cement (ABCP) and Risks associated with the use of cement in civil construction


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