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 Sleeper life prediction. SynopsisOur client is proactively pursuing a “back to green field site” policy, examining the rationale behind the choice of design, materials and construction methodology for all their infrastructure assets. In this context, one area of focus has been on establishing the residual life of key components so that maintenance or renewal can be planned more accurately. The client’s network includes approximately 23 single track km of ballasted track with sleepers, which have been in service for 14 years. Corus was asked to investigate and predict the residual life of twin block concrete sleepers. Key Customer IssuesTo determine the sleeper asset condition, the client needed to know the:
SolutionsA review of the possible failure mechanisms of twin block sleepers concluded that the most likely was the strength of the bond between the central tie bar and the concrete blocks. A laboratory test was therefore developed to examine the integrity of the sleepers. A comparison was made between sleepers that had been in service and those that had not. Visual examination of the sleepers also revealed that corrosion of the steel tie bar could also be an important factor on the remaining life of the sleepers. Additional sleepers were tested to determine whether corrosion significantly weakened the bond strength between the concrete block and the tie bar. The rate of corrosion was also established. Client Benefits The investigation determined that there was no deterioration in the bond strength for sleepers that had been in service from those that had not. Tie bar corrosion determines the residual life of the sleepers. Correspondingly, the client is able to:
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