Understanding the difference between 'GAP' products

General All Passing or 'GAP' products are crushed rock aggregate products that are made at quarries during the quarrying process.

Blasted rock is processed through a series of 'crushers' that progressively crush rock down into smaller and smaller sizes.

Crushed rock is then separated over a series of vibrating metal screens that divides the rock based on its nominal size.

GAP65 for instance is crushed rock that is passed over a metal screen with a screen size allowing for rock material 65mm and less to pass through the screen.

Material is collected from a conveyor belt and placed into stockpiles for supply to clients.

The same process is used to produce other GAP prodcuts such as GAP40, GAP20 and GAP7.

GAP7 is typically the smallest crushed aggregate product available and represents aggregate with a 'top end' of 7mm through to fine dust or 'fines'.

The fines in the GAP products are important as they help to bind the aggregate together when it is being laid in driveways or roads. 

Having too little fines in GAP products leads to 'boney' material that doesn't bind effectively to form a firm base.

The following is a quick guide to the different types of GAP products and their uses - 

  • GAP7 - Is typically used under pavers due to its sand like quality.GAP7 holds its form when compacted and wont easily wash away in water/rain.
  • GAP20 - Used in footpaths or driveways
  • GAP40 - used on driveways and under concrete. Will compact to form a nice finish.
  • GAP65 - Used under concrete bases or on driveways to add strength (will require a layer of another aggregate like GAP20 on top for finishing if used on a driveway).

For any other questions regarding aggregate, feel free to reach out to the team at iaggregates.