FINAL REPORT OF WATER SOLUBLE SULPHATE INSPECTION AT , SUTTON COLDFIELD, BIRMINGHAM.
Observations:
The lounge floor was of suspended timber construction, the kitchen floor was of solid concrete construction. There was some unevenness noted to the kitchen floor surface. The kitchen floor appeared to comprise a weak 60mm layer of sand lime type concrete with a stronger 60mm layer of traditional concrete on top. The quality of the sand lime type concrete at the interface with the sub-floor infill was poor. There was no lateral slippage to the external brickwork at damp proof course level and no sulphate staining internally or externally.
Analysis:
Water soluble sulphate tests have been carried out on an infill sample recovered from beneath the kitchen floor slab of the property detailed above. Sampling was in accordance with the recent guidance issued by The Department of Communities and Local Government (February 2008). The infill sample appeared to be composed of blast furnace ash aggregate, a material which has been associated with sulphate attack of concrete in the past. The infill sample had a high water soluble sulphate content of 2.66g/l and a moisture content of 19.2% (Summary of Test Results attached). This sulphate content value corresponds with a grading of Class 3 as defined in Table C2 of BRE Special Digest 1:2005. According to the BRE Special Digest a concrete floor slab should be stable when placed in contact with a Class 3 infill provided that the concrete satisfies certain minimum depth (140mm) and cement quality requirements and the infill is dry. The concrete at the sampling point was less than this thickness, the cement quality to the lower layer was not as recommended and the infill had a high moisture content. There was no visqueen membrane beneath the concrete floor slab.
Recommendations:
Based on the recommendations of the BRE Special Digest and our previous experience of sulphate affected concrete it is considered that there is a medium risk that sulphate attack could affect the solid kitchen floor of the property in the future. At the moment the kitchen floor is showing some evidence of possible sulphate attack and this is in combination with the sulphate content and moisture content of the infill being high. We would recommend that repairs to the kitchen floor slab are considered to ensure the long term durability of the structure.
W. Templeton
W. Templeton B.Sc. (Hons), P.I. Insured
