Roads Department - Government of Botswana

Roads Department
LIST OF TABLES
Table 2.1 Salt Content of pavement layers (Sekoma-Kang road).............................................................................14
Table 2.2 Some salts which can contribute to salt damage of pavements.................................................................19
Table 3.1 Salt Analysis tests for materials and water in Botswana...........................................................................25
Table 4.1 Climate risk evaluation..............................................................................................................................32
Table 5.1 Suggested Maximum salt content limits for Botswana.............................................................................36
LIST OF FIGURES
Figure 1.1 Flowchart of guideline ..............................................................................................................................10
Figure 2.1 World Distribution of dry climates and occurrence of Salt Damage ........................................................11
Figure 2.2 Areas of Botswana most susceptible to salt damage.................................................................................12
Figure 2.3 Salt damage process in relation to pavement and water table and salinity ...............................................20
Figure 2.4 Solubility of some natural salts in relation to temperature .......................................................................23
Figure 4.1 Risk analysis for salt damage to bituminous surfacings ...........................................................................29
Figure 4.2 Materials risk rating-salt damage to bituminous surfacings .....................................................................30
Figure 5.1 Permissible intervals between prime and final surfacing in relation to subgrade salinity and
pavement surface salinity ......................................................................................................................... 34
Figure 5.2 Electrical conductivity readings at the surface (0-50mm) of a layer with time for various levels of
initial conductivity of the bulk material ....................................................................................................35
REFERENCES
LIST OF APPENDICES
Appendix A Maximum salt content limits worldwide..............................................................................................41
Appendix B Field Electrical Conductivity measurements of soils by the quick conductivity method. ..................43
Appendix C Risk Evaluation and determination of required preventative measures- Worked Example..................44
Appendix D Glossary of Terms.................................................................................................................................46
Appendix E Abbreviations .......................................................................................................................................47
6 Guide to the Prevention and Repair of Salt Damage to Roads and Runways