What is Sulphate Attack?
Sulphate attack occurs when sulphate ions (SO₄²⁻) from external sources penetrate the concrete and react with hydrated compounds in the cement.
Diagnosis of Sulphate Attack
Diagnosing sulphate attack involves a combination of visual inspection and laboratory testing:
1. Visual Inspection
- Cracking, particularly map/pattern cracking
- Surface scaling, spalling or salts
- Expansion and deformation of external low level brickwork (most commonly below DPC level)
2. Sampling and Laboratory Tests
- Chemical analysis of concrete to detect sulphate content
- Chemical analysis to establish the cement content of the concrete and therefore the base / expected sulphate levels of the concrete
Reporting on Sulphate Attack
A report would summarise both visual and laboratory testing findings and observations and provide an overall conclusion confirming whether sulphate attack has occurred or not. The report will include a copy of the laboratory testing along with a commentary as to what the results mean. Recommendations for repair will then be provided for any remedial works required.
