Concrete @ your Fingertips

In-service performance – Leaching

Concrete is a conglomerate of aggregates, cement and chemical admixtures. Concern has been raised that harmful substances may leach out from concrete into the surroundings. Leaching from hardened concrete could be of importance where concrete is in contact with drinking water and in normal structures where leaching could affect the environment.

However, concrete is a dense, low-permeability material where movement of dissolved substances is very slow.

From fresh wet material: The Portland Cement Association in America conducted tests reported in ‘An analysis of selected trace metals in cement and kiln dust’. They concluded that no samples of cement from 97 kiln systems exceeded the US RCRA (Resource Conservation and Recovery Act) limits for leaching for any of the 12 metals assessed.

From hardened material: Dutch research reported on leach testing from 81 production concretes in the hardened state. Not a single substance failed the stringent limiting values that the Dutch have set under their Building Materials Decree. Currently there are proposals to allow concrete pipes of diameter 300mm or more to be used to carry drinking water, provided the concrete’s constituents are from an approved list.

Acknowledgement: The Concrete Society