DURABILITY AND ENVIRONMENTAL IMPACT OF CEMENT MORTAR LININGS
Report No FR0473
The results of this work provide a detailed understanding for the users and applicators of cement mortar linings for corrosion protection of iron water mains. It supplies information that can aid rehabilitation planning decisions and assist users in meeting regulatory requirements. The tests developed for assessing performance of cement mortar linings, provide a basis for a type test, forming part of an appropriate standard or specification.
The objective of this programme of work is to provide guidance on the use of cement mortar linings in relation to their durability, effect on water quality and disposal of associated effluents.
Laboratory test rigs provide the basis for reliable testing of the effects of cement mortar linings on water quality.
- Existing guidelines on water quality effects need to be modified when applying them to large diameter and for long retention time systems.
- In routine situations, these general guidelines should be followed:
OPC should not be used for in situ linings where the supply water bicarbonate alkalinity is less than 55 mg CaCO3/l.
BFS/OPC should not be used for in situ linings where the supply water bicarbonate alkalinity is less than 35 mg CaCO3/l.
Factory linings should not be used if the supply water bicarbonate alkalinity is less than 25 mg/l CaCO3.
- Accelerated ageing tests provide a basis for establishing the service potential of cement mortar linings.
- Characterisation of in situ cement lined pipe samples show that prior to the routine use of CCTV inspection, many linings were incorrectly applied.
- In very soft waters, in situ linings may have an asset life of 30 years. In harder waters, a life of 100 years or more, is predicted.
- The use of effluent disposal guidelines (Appendix A), alleviate the potential for pollution of water courses associated with disposal of cement mortar lining effluents.
- A recently developed settlement tank, using inclined plates, is more effective than traditional tanks, thus assisting further in reducing the risk of pollution when disposing cement lining effluents.
The detailed recommendations at the end of each section of this report for use of cement linings and disposal of the associated effluent should be adopted by users and contractors.
Findings of the first two years of the project are summarised and the work of the final year is detailed. Guidelines and research findings are provided in the areas of:
- water quality effects,
- durability in service, and
- effluent disposal issues, associated with the use of factory and in situ applied cement mortar linings for iron water mains.
Copies of the Report are available from FWR, price £35.00 less 20% to FWR Members