Sulphate attack on asbestos cement pipes

Abstract

Asbestos cement pipes have been successfully used in many countries, including the Middle East, for construction of water distribution network. Recent studies confirmed that sulphate salts in the vicinity of the asbestos cement pipes often exceed the allowable limits. This paper presents the impact of various concentration of sulphates on asbestos cement pipe performance. A total of 500 samples were sawn from normally cured pipes: changes in length, weight and flexural strength were monitored. The specimens were intermittently exposed to sulphate solution of 0, 0.5, 2 and 5% SO 3. Accelerated exposure to sulphate for 24 hours coupled with drying in an oven at 105°C led to 500 × 10 −6 m/m expansion after only five cycles. The expansion is equivalent to that resulting from two year exposure to 5% of SO 3. It is concluded that asbestos cement pipes are vulnerable to sulphate attack. Precautions such as the use of type II cements or certain coatings are recommended whenever aggressive sulphates are encountered.