Cement

Some people confuse concrete with cement, but cement is just the ‘glue’ which holds the other constituents of concrete together.

There are a range of different cements but these are the three you will most commonly come across:

General Purpose Cement

This is consistent, versatile and cost effective which makes it a good choice for most building works. It can be used for Domestic concrete slabs, driveways and footpaths

Trivial Fact -You may hear standard cement referred to as Portland Cement – This is because the finished concrete has an appearance similar to stone quarried from Portland in England.

Sulphate Resisting Cement

Sulfate Resisting Cement is a blended cement designed to improve the performance of concrete where the risk of sulfate attack may be present. It also provides improved durability for concrete, and the steel reinforcement, in most aggressive environments,

Although it has an additional cost it is best for:

  • Geothermal areas and soils containing sulphates
  • Saline Areas
  • Area that are frequently wet such as concrete swimming pools

Rapid Set Cement

Normally found in dry premixed concrete mixes. This is a cement with various additives that speed up the reaction to give an initial hardening within 15 minutes.

Any speeding up of the cement reaction time leads to lower final strength. This makes this product good for things like setting fence posts………… but NOT for significant structural applications.

Water Cement Ratio

One of the most important issues with cement is ensuring the ratio of water and cement is correct as this affects both the final strength and the durability. For instance:

  • Water cement ratio 0.5 (10L water to 20kg cement) is needed for high strength 35MPa.
  • Increasing the Water cement ratio to 1 (20L water to 20kg cement) will reduce the strength to 10MPa.

To ensure they don’t add too much water premix companies usually measure the water content in the sand and gravel piles and reduce the water content accordingly.
 

For more information see Concrete.

 

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