- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 09 Sep 2020
The term 'hardcore' refers to the mass of solid materials used as a make up, formation material to raise levels, fill irregularities in excavations and create a firm and level working base onto which heavy load-bearing surfaces such as stone or concrete can be laid. The hardcore then helps evenly spread imposed loads.
A variety of graded materials can be used to make up a hardcore layer:
- Construction waste such as brick and broken tiles.
- Quarry waste.
- Crushed rock.
- Clean, graded concrete rubble.
- Blast furnace slag.
- Colliery spoil.
- Oil shale residue.
- Pulverized-fuel ash.
Materials need to be sufficiently hard as well as being capable of being compressed (rammed to form a compact base) before the upper layer is added. This removes gaps or voids which could otherwise threaten the supportive properties of the hardcore layer.
Quarry waste is a good source of hardcore material, although care should be taken not to include waste from gypsum mines. This is because such waste often contains a mixture of limestone and gypsum which can attack concrete. Similarly, concrete rubble may lead to a risk of sulphate attack if it contains gypsum plaster. Construction waste can contain timber which may deteriorate and can spread rot. Substances such as colliery spoil may contain soluble sulphate which, if it reacts with water, can infiltrate and damage cement.
The type of construction, expected load and probable stresses will determine the appropriate thickness of the hardcore layer that must be used. Typically it is laid in well-compacted layers of 100-150 mm.
 Related articles on Designing Buildings Wiki
Featured articles and news
Helping communities preserve and enhance historic environments.
Creating comfortable climates despite extreme temperatures.
Study examines how adjustable arrangements can succeed.
Government announces plans to improve accessibility.
Resource addresses pandemic-related NEC4 contract issues.
Incorporating EDI into the provision of fair access.
Government announces global innovation strategy.
An architectural biography. Book review.
The house where the future king of France lived.
The teacher, architectural technologist and mum offers her insights.
Careful planning needed as supply chain issues continue.
The sensitive conversion of a neglected Cornwall structure.