1. Performance of Slag Pavements Prepared by Peter Rufford P E E C E

2. Introduction Steel Furnace Slag is a waste product from steel making Has been used as a road base material in areas close to the steel making operations The performance has been very good over many years but this has lead to complacency

3. Slag as a road base requires careful quality control due to the presence of free calcium oxide (CaO) and magnesium oxide (MgO) which expand when hydrated Slag needs to be tested for volumetric stability (ASTM D4792) – generally a maximum expansion limit of 1% is recommended

4. A common practice is to stockpile the slag for a minimum period to weather the slag before using it as road base In the USA, the weathering period varies but is of the order of 6 months before being tested for expansion In the particular Australian case study, the supplier only stockpiled the slag for 3 months and did not test for expansion

5. The result – ridges across the pavement

7. And uplifting of the kerb

8. And discontinuity in the kerb line

9. And pushing out of the kerb

10. And upward pressure on the footpath

11. Requiring significant pavement repairs

12. Action taken Stopped using the material as a pavement material 18 months ago Assessed the extent of the problem – projects constructed over a defined period – maybe a change in the material source Started to remediate the affected areas: –Grinding off the raised pavement ridges –Trenching the driveway access to properties

13. Undertaking a number of trials to find the best way of controlling the damage –Initially thin saw cut across the pavement with compressible spacing rods and silicon seal at the surface – not successful –Thin saw cut in front of the kerb – also not successful –Thick trench across the property driveways –Wider 100mm trench in the pavement and fill with lean mix concrete (3Mpa)

14. Initial treatment – thin saw cut

15. Trench the driveway

16. Wider saw cut

18. Donnelly joint inserted

20. Issues emerging Ongoing maintenance of road pavement, kerb, footpath, drainage pits and driveways Uncertainty as to how long this type of maintenance will be required Legal action by residents to recover costs to their properties More expensive pavement designs – longer haul for traditional materials Less waste material for other uses

21. Research required Treatment options –Thin saw cuts not successful –100mm trenches filled with lean concrete (3Mpa) not yet evaluated over summer –100mm longitudinal trenches – cheaper to install as it does not impact on traffic Other issues for research –Spacing of trenches and location –Types of trench filler – polystyrene instead of lean concrete

22. Intervention Strategies Develop intervention strategies for the various types of distress and evaluate the strategies Monitor longitudinal and transverse movement over four seasons for each strategy Compare the cost of each intervention strategy and evaluate their effectiveness

23. No options for treating drainage pits, footpaths and kerbs other than replacement

24. Proposed Way Forward Guidelines for maintenance organisation –Grind off pavement ridge in first instance –100mm trench (3MPa concrete) on either side of ridge if no evidence of transverse movement –100mm longitudinal trench (3MPa concrete) in front of kerb if transverse movement evident –Insert pins in pavement to measure longitudinal, transverse and vertical movement –Take 2 samples at each site for chemical composition testing

25. Guidelines for asset owner –Measure movement of pins at each site every month for a year –Research air temperature and rainfall at each site over 12 month period –Assess cost effectiveness after 12 months Guidelines for pavement designers –Consider using slag where there is no kerbs –Specify that the material is weathered for 6 months and tested for expansion prior to use

26. –For other sites undertake a risk assessment and only use if the expansion is less than 1% and the consequences of failure are not high such as not in heavily trafficked urban areas or near: Near optic fibre trenches Near high pressure gas mains