Chert
Chert is a type of fine-grained and silica-rich sedimentary rock. It often contains microfossils and/or macrofossils, and can be found in a great variety of colours. It is often confused with flint which is a particular type of chert.
Chert occurs in geology as nodules, concretionary masses and layered deposits, and is characterised by its hardness and conchoidal fractures that create sharp edges. It was these properties that meant chert was used in early human civilisations for creating tools and weapons.
Chert is often used as an aggregate and as a material for road surfacing. It is particularly suited to road surfacing as rainwater firms and compacts it rather than making it 'muddy' like some other fill materials.
However, there can be problems when is used as an aggregate in concrete, such as the development of surface pop-outs as a result of freezing and thawing. This is due to the high porosity of weathered chert. In addition, some kinds of chert can undergo an alkali-silica reaction (ASR) when they come into contact with high-alkali cement which can lead to cracking or expansion.
[edit] Find out more
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
The restoration of the novelist’s birthplace in Eastwood.
PAC report on the Remediation of Dangerous Cladding
Recommendations on workforce, transparency, support, insurance, funding, fraud and mismanagement.
New towns, expanded settlements and housing delivery
Modular inquiry asks if new towns and expanded settlements are an effective means of delivering housing.
Building Engineering Business Survey Q1 2025
Survey shows growth remains flat as skill shortages and volatile pricing persist.
Construction contract awards remain buoyant
Infrastructure up but residential struggles.
Home builders call for suspension of Building Safety Levy
HBF with over 100 home builders write to the Chancellor.
CIOB Apprentice of the Year 2024/2025
CIOB names James Monk a quantity surveyor from Cambridge as the winner.
Warm Homes Plan and existing energy bill support policies
Breaking down what existing policies are and what they do.
Treasury responds to sector submission on Warm Homes
Trade associations call on Government to make good on manifesto pledge for the upgrading of 5 million homes.
A tour through Robotic Installation Systems for Elevators, Innovation Labs, MetaCore and PORT tech.
A dynamic brand built for impact stitched into BSRIA’s building fabric.
BS 9991:2024 and the recently published CLC advisory note
Fire safety in the design, management and use of residential buildings. Code of practice.