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What is cement and how is it made?

Cement is a complex chemical glue. When mixed with water, and any other inert durable material such as: sand & stone, it will set as hard as rock and remain extremely durable to impact, heat, abrasion and weathering. Another interesting characteristic of cement, is that it does not require air to set hard. In fact, it will go hard under water or even in space provided sufficient moisture is available to react with the cement powder.

Cement is made primarily from limestone and is fired in a kiln at very high temperatures to create a material called clinker. The clinker is finely ground and mixed with small amounts of other minerals to form OPC (Ordinary Portland Cement). 

The chemistry of the resulting cement determines its colour, strength, durability, and speed of setting. Australian Standards govern minimum standards for the manufacture and performance of various cement products.

Some History

Modern OPC (Ordinary Portland Cement) was patented in 1874 by a fellow named John Aspdin. He named it after a limestone found in Portland because of its resemblance to cement. It continues to be called OPC today.

Off course, a form of cement has been used by modern humans dating back to as early as the Romans. Many structures constructed by the Romans continue to exist today because of their knowledge and skill with “cement like” materials – a testament to the long term durability of this material. 
Bulk supply of concrete is produced using Computer controlled Production Plants in accordance with Industry and Australian Standards.

What is concrete and how is it made?

Concrete is one of the oldest building materials known to man. It is extremely strong, durable and able to be moulded into virtually any shape you can imagine. 

It is made by mixing together: 

  1. Cement (this is the glue that holds everything else together),
  2. stone (also called aggregate),
  3. sand, and
  4. water.

Other ingredients, such as: specialist chemicals, colour pigments, steel & plastic, can be added to further enhance its mechanical properties.

What can concrete be used for?

Concrete is extremely versatile and is used to construct: mass structures such as: high or low rise buildings, bridges, columns, beams, pipes, wall panels, internal and external floor surfaces. Floor surfaces made from concrete are usually the most notable structures as they often incorporate a myriad of decorative finishes that enhance their appearance. 

Coloured, Stamped, Stencilled, Acid Etched, Exposed & Polished Concrete was developed to enhance the appearance of flat concrete structures such as: internal and external floors, driveways, pathways, pool surrounds, entertainment/patio areas, to name a few. 

Can I design my own concrete?

Of course! The performance aspects of the concrete you choose are designed for you. So you don’t have to worry about strength, durability and other technical stuff. Your task is to focus on the finished appearance of your concrete.

With Midway Decorative Concrete you can choose:

  • The type of finish (exposed or polished),
  • The decorative stone (aggregate) of your choice, and
  • The colour of the surrounding paste by choosing colour from our pigment range.

How does one go about exposing concrete?

The process is relatively straight forward. All concrete is placed in a wet and malleable state (often referred to as the Plastic State). This property of concrete enables it to be formed into an endless number of shapes. 

Over a period of hours, the concrete ceases to be Plastic, and begins to firm and become hard (often referred to as the Hardened State). 

Before final set of the surface occurs, the top few millimetres of concrete are removed in order to reveal the materials embedded within it. 

The surface paste can be removed in a number of ways, but the most common is to wash the surface material away with pressurised water.

Chemicals called Surface Retardants help to keep the surface paste soft and help to ensure an even exposure of the underlying stone is ultimately achieved. 

This process of revealing, or exposing the stone (normally called: aggregate) is why the resulting finish is called: Exposed Aggregate Concrete.

How does one go about polished concrete?

The process is relatively straight forward. All concrete is placed in a wet and malleable state (often referred to as the Plastic State). This property of concrete enables it to be formed into an endless number of shapes. 

Over a period of hours, the concrete ceases to be Plastic, and begins to firm and become hard (often referred to as the Hardened State). 

After the concrete has fully hardened, the top few millimetres of concrete are removed in order to reveal the materials embedded within it. 

This process of revealing, or exposing the stone (normally called: aggregate) is achieved by first grinding and then successively polishing the surface smooth. The resulting finish is called: Polished Aggregate Concrete.

How much does decorative concrete cost?

Concrete remains one of the cheapest construction materials in use today. Without it, many well known structures would not be possible or would not be as long lasting with out constant costly maintenance.

Concrete in Australia is sold by volume and the unit of measure is: cubic metres. This is best explained by imaging a open box that is 1 metre long, 1 metre wide and 1 metre tall. Fill it with concrete, and the quantity of concrete represents 1 cubic metre.

The cost of concrete is made up of:

  • The cost of raw materials (The quarrying, crushing, processing of natural materials such as: cement, stone & sand)
  • The cost of transporting raw materials to the concrete plant
  • The cost of handling, weighing, administering, servicing, testing, and transforming the raw materials into concrete
  • The cost of loading, mixing and transporting the concrete to the construction site
  • A profit margin for all businesses involved in the supply chain.

In order to be competitive, Concrete Producers have to constantly seek out the best methods of achieving the above, whilst maintaining quality of product & service; complying with relevant Australian Standards and controls set by government and local authorities. 

What Colours are available and where do they come from?

There are an enormous range of colourising pigments available. Oxide Pigments are non-dissolving, ultrafine particles derived from non-organic minerals. Such powders are used in many different industries to alter and enhance the colour of the products manufactured. For example: ceramics, asphalt, inks, paints, cosmetics, plastics, rubber and concrete to name a few. 

Unlike dye colours derived from animal and vegetable sources which have a tendency to fade, mineral oxide pigments are derived from the earth, possess UV resistance and do not fade with the changing environment.

The principal minerals are: haematite (reds), magnetite (brown to black), goethite and lepidocrocite (yellows), cobalt (blue), ilmenite -titanium dioxide (white). The minerals are blended to produce hundreds of subtle variations in perceived colour.

Midway has simplified the vast array of available colours to a basic set of 16. 

However, if you have very specific needs, or colour matching is required, we have access to numerous Colour Suppliers capable of producing just the right blend of pigments to satisfy your needs. 

What Aggregates are available and where do they come from?

Aggregates are derived from two basic sources – Hard rock quarries, and Sand quarries. 

Hard rock quarries employ explosives and mechanical crushing plant to produce aggregate for use in concrete. The physical nature of these aggregates is that they have sharp edges as a result of the crushing process. They provide better strength properties for concrete because their angular nature provides additional mechanical interlock within the concrete – enhancing its strength.

Sand quarries employ dry and wet methods of sand extraction from ancient sand deposits. These deposits were once rivers or streams. The movement of water over millions of years produces rounded (approximately spherical) aggregate particles. Mechanical methods are used to separate the aggregates (often called pebbles) from the sand. 

The nature of natural quarried materials is that variation is inevitable over the life of the quarry and some materials may contain traces of naturally occurring iron which can lead to stains developing on the surface of the finished concrete some time after construction is complete.

There are seven basic aggregate types on offer through Midway in various sizes: 7mm, 14mm and 20mm. However, other specialist aggregates can be sourced for the right project. 

How do I protect my concrete and keep it looking good?

Once hardened, concrete is an extremely durable and long lasting construction material. However, there are things you can do to help keep it looking good.

The first thing to appreciate is that concrete is not in its self completely impermeable. Tiny holes (pores) in the concrete create a matrix of voids that allow moisture and other elements to migrate slowly through its structure. This is not a desirable quality if contaminants (particularly petroleum based products such as oils & grease) happen to drip onto the surface of concrete. The contaminant enter the void structure and become trapped within the matrix of the concrete. Cleaning becomes very difficult because although the majority of surface material is easily removed, it remains an almost impossible feat to draw out ingrained contaminants. This means that even after cleaning and scrubbing, a shadow of the contaminant usually remains. Having said this, there are many options for improving the impermeability of concrete and protecting the finished appearance.

A reduction in permeability is achieved by using higher strength concrete. Generally speaking, higher strength concretes are more dense and as a result have a smaller void structure. Other specialist cementitious based products, generally referred to as: Waterproofing Additives, can be added to standard concrete to reduce voids, increase density and improve strength.

In the context of most flatwork construction, such as: driveways & pathways, a far more cost effective means to reduce permeability and protect against staining from contaminants is to apply a simple surface coating. A surface coating (sealer) acts as a rain coat reducing the ability for water and other contaminants entering the concrete’s void structure.

Not only does a sealer provide the surface of the concrete with some protection from harsh elements, its makes the surface easier to clean, and it also helps to intensify depth of natural colours in the finished concrete that would otherwise appear dull and go unnoticed without the sealer.

For further information on the application of sealers, speak to your Concrete Contractor/Placer and get their advice. There are many products on the market and some may be more suitable for your specific project than others. 

Are Material Safety Data Sheets available?

Yes, Please contact us to obtain a MSDS.