Buried concrete can be attacked by chemicals within the soil. This can lead to a reduction in strength and a shortened lifespan of the asset. It is therefore important to determine the aggressiveness of the ground so that the concrete mix to be designed appropriately.
Much of the UK is underlain by soils that contain sulphates or sulphides (e.g. pyrite) that can oxidise to become sulphates. It is principally these substances that cause the chemical attack on buried concrete. Other substances also attack the concrete including chloride and magnesium.
We undertake a holistic assessment of a site to characterise the aggressiveness of the ground. This allows a safe design to be undertaken without being overly conservative.
Initially, we review geological maps to determine the likelihood of encountering soils containing pyrites. We also review historical maps to determine if the site has been used for industrial purposes in the past and is, therefore, a ‘brownfield’ site.
Following the initial review we undertake a ground investigation which includes sampling of the soil and laboratory testing. We analyse the results to determine a Design Sulphate Class and an ACEC (Aggressive Chemical Environment for Concrete) Class. This then allows the foundation designer to specify the correct concrete mix with additional protection measures where appropriate.