DURABILITY AND ENVIRONMENTAL IMPACT OF CEMENT MORTAR LININGS A
REVIEW OF DURABILITY

FR0220

Sept 1991

SUMMARY

I OBJECTIVES

To review critically the current state of knowledge on the durability of cement mortar linings used for the renovation and/or corrosion protection of ferrous water mains.

II REASON

Cement mortar lining activity has significantly increased to meet 'levels of service' regulatory requirements in a cost effective manner. There is a requirement to relate life expectancy to supply water quality for the purpose of asset management planning. Knowledge of durability will enable more accurate estimates of the effective lifetime of cement mortar linings.

III CONCLUSIONS

Studies to date have shown that lime may be lost from factory applied cement mortar lining surfaces at rates of up to
0.1 mm/year. Sand rich gel layers are formed, which appear to provide protection from corrosion. In certain situations the durability of the gel layer may be compromised and it is reported that high aluminium cement (HAC) mortars form gel layers with greatly enhanced durability. There is apparently no UK and little international durability data available for in situ cement mortar linings.

IV RECOMMENDATIONS

  1. The behaviour of in situ Ordinary Portland Cement (OPC) and Blast Furnace Slag (BFS) modified mortar linings should be characterised in terms of their durability, by means of suitable field trials. Degradation of the cement should be related to factors such as supply water quality, flow, age and cement composition.
  2. The effectiveness of gel layers in preventing corrosion should be further examined - particularly in exposure conditions typical of the UK.
  3. The durability of gel layers should be further studied and the use of modified or alternative cement mortars considered.
  4. Accurate durability tests should be developed for evaluation of existing and novel cement mortar lining materials and for inclusion in performance related specifications.

V RESUME OF CONTENTS

An introduction to the durability of cement mortar linings is provided. UK experiences with the durability of cement mortar linings are presented, including previously unpublished data. International experiences are also presented, with reference to data which support the theory that lime depleted linings can be effective corrosion inhibitors in certain circumstances. Recommendations for further work are made.

 

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