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CONCRETE IN THE CONSTRUCTION INDUSTRY

CONCRETE IN THE CONSTRUCTION INDUSTRY | AGORA AFRICA

By: Chanel Fos

Posted on: 15 September 2021

Concrete is used worldwide as a construction material. In fact, it is the most used construction material in the world according to statistics, where at least 20 billion tons are used yearly (and no surprise that the biggest consumer is China using over 11 billion tons).

Where did it all start?

Concrete formed naturally in Israel a few million years ago, the Egyptians used concrete to build the pyramids of Giza and the Romans perfected the whole thing (looking at the Pantheon – an unsupported concrete structure that is to today one of the most stunning structures in the world).

The Romans also named concrete; the name comes from the Latin word “concretus” which when translated means “to grow together”.

CONCRETE IN THE CONSTRUCTION INDUSTRY | AGORA AFRICA

What are the main components of concrete?

Concrete consists of mainly cement, fine aggregates and crushed stone mixed or gravel with water. Once the aggregates are mixed with water a chemical process, known as hydration, takes place where the mixture hardens and becomes solid in the mould it is poured.

Why use concrete?

Concrete has many advantages characteristics for not only the designer, but the developer and the owner too. Concrete is extremely versatile, it is readily available, its durability makes it very cost effective due to low to no maintenance required.

One of the most prominent characteristics of concrete not mentioned above, is its high compression strength. Combining concrete with rebar (steel work bent inside of concrete) makes it even more rigid and versatile. Using formwork concrete is moulded into the desired shapes as per the designs.

Concrete can take any shape and form, can be made any colour and any texture and therefor “the sky is the limit” when it comes to design. When designed correctly and placed accordingly, concrete is one of the most durable materials on earth. I mean look at Rome; it exists of concrete which was built a few thousand years ago.

Interesting fact is that the Pantheon was one of the first concrete buildings in Rome, it stands till today and is in my opinion one of the most beautiful structures I have travelled to, this structure is over 2,000 years old.

CONCRETE IN THE CONSTRUCTION INDUSTRY | AGORA AFRICA

What finishes are possible when using concrete?

Concrete can be displayed in many different textures, to name but only a few:

  • Trowelled finish (this is the most common smooth finish).
  • Stipple broom finish (this is the most common rough finish).
  • Exposed aggregate finish (use a power floater or a diamond polisher to polish the top surface of partially cured concrete, removing a few millimetres off the top, concrete is then sealed for protection).
  • Stamped concrete finish (this is when they stamp a pattern into the wet concrete).
  • Polished finish (grinding and polishing of concrete surfaces together with a penetrant chemical).
  • Coloured finish (either adding pigments to the mix prior to pouring or staining of cured concrete and finished with a sealant to protect the surface).
  • Salt finish (course rock salt is inserted into freshly poured concrete using rollers, then washed off with water once the concrete is set).

There are countless more forms of finishes, but the above summarises the most common ones used in the industry today. By listing the above one can already see how versatile concrete can be.

When selecting a finish, the purpose of the concrete should be considered, will it be exposed to weather, will it be required to be slip resistant, do you need colour of glossy look, etc.

CONCRETE IN THE CONSTRUCTION INDUSTRY | AGORA AFRICA

What different types of concrete are there?

When selecting the type of concrete, it is once again very important to determine what the purpose of the structure will be and what the nature around it will be. Below are a few different types of concrete:

  • Plain concrete (the most used form of concrete used for making pavements, dams, etc).
  • Reinforced concrete (second to plain concrete, this is used for construction of buildings etc where steel is used as reinforcement and concrete cast in formwork over the steel giving it high compressive and high tensile strength).
  • Pre-cast concrete (concrete is cast into moulds at a factory or on site and merely installed in place required after it has reached complete strength. Main uses are lintels, concrete blocks, staircase units, fence poles etc).
  • Lightweight concrete (the density of the concrete is reduced by adding additives to the mix, the most important characteristic it has is its low thermal conductivity, therefore mainly used for thermal insulation, protecting of steel structures, etc).
  • High density concrete (crushed rocks are used as coarse aggregates, mainly used in power plants to protect from radiation).
  • Prestresses concrete (steel reinforcing is installed and tensioned before the concrete is poured. This increases the compressive strength of the concrete and lowers the risk of tension cracks forming on the surfaces and is mainly used where there are long spans applicable).
  • Air entrained concrete (foaming agents are added at the mixing stage and makes up around 4% of the concrete volume mostly used where freezing and thawing is a risk).
  • Glass concrete (recycled glass is used as an aggregate in the concrete mix and provides thermal insulation and aesthetic looks).
  • Shotcrete (basically ordinary concrete placed using high air pressure nozzles, compaction takes place as it is “sprayed”).

The list goes on and on, but these are the main concrete types used in the industry. It is advised to consult with a professional before deciding on which type of concrete or type of finish you select.

From the above one can easily conclude that concrete has many benefits when it comes to its characteristics, aesthetics, textures, durability etc. and is therefore the most used construction material.

CONCRETE IN THE CONSTRUCTION INDUSTRY | AGORA AFRICA