What is Sulfate Attack ?
Use of fill material in house construction first became common in mid-1940s. In the immediate post-war period, when construction materials were in short supply, solid floors, comprising a concrete floor slab over fill material, largely superseded suspended timber floors that were typically used in the 1930s. Also, waste materials, such as burnt colliery shale blastfurnace slag and red ash were promoted by government as being appropriate materials for use. Unfortunately, little or no guidance on the selection and use of suitable materials was available in the early post-war years and there was some use of deleterious materials, and particularly of materials containing sulfate. Whilst it was always standard practice for such solid floor construction to incorporate a damp-proof membrane (DPM), it was not until the 1960s that it became common to use a polythene sheet below the concrete floor slab as a DPM.
History indicates the age of properties that might have fill material with significant levels of sulfate and what measures (if any) may have been taken to minimise risk of sulfate attack. The following conclusions may be drawn:
- Domestic buildings constructed from the 1940s through to the mid-1970s may have solid floors that include fill material which has relatively high levels of sulfates, but have no protective measures that will prevent sulfate attack on concrete floor slabs or oversite concrete.
- Domestic buildings constructed from the late 1950s onwards have an increasing likelihood of incorporating precautionary measures that will minimise or prevent sulfate attack on concrete floor slabs or oversite concrete. These include more careful selection of fill material, the use of a waterproof membrane to separate fill material from concrete, and the use of sulfate-resisting concrete.
- Domestic buildings constructed from the early-1970s onwards are unlikely to have concrete floor slabs that will be affected by sulfate attack.