Presence of High Alumina Cement (HAC) in concrete

Presence of High Alumina Cement (HAC) in concrete

 As the name suggests High Alumina Cement differs from Portland Cement in as much as it is made up of calcium aluminates as opposed to calcium silicates.  This allows rapid strength gain and led to its popularity in building construction during the 1950’s to 1970’s.

However it has since been found that a further mineralogical conversion in the hardened concrete can occur over time which causes a severe reduction in strength of the concrete element, leading to structural weakness or a vulnerability to chemical attack.

Details of how to determine the possible presence of HAC are contained within document reference BRE IS 15/74.  Samples of the suspect concrete are taken by ‘knocking off’ a small amount of concrete.  Drilled samples are not considered acceptable as the heat produced may affect the result.  The concrete is then subject to a relatively quick chemical test to determine the likely presence of HAC.  If this proves positive then further confirmatory testing can be undertaken by XRF methods.

Nicholls Colton are *UKAS accredited for the rapid chemical test as detailed within BRE IS 15/74.