Sika® Dust Seal PH is best applied when the surface of the soil is slightly damp. If binding soil is to be added, spreading should take place shortly afterwards. Under normal conditions, best results are obtained when the road surface is watered shortly before the spreading of Sika Dust Seal. Watering should be a light sprinkling of approximately 0.5 to 1 liter of water per square meter.
Application Procedure
1. Grade the road to remove all corrugations and potholes, and to loosen the road surface material to the desired depth of penetration. Some roads work easier if a light application of Sika® Dust Seal PH is used before the first grading to soften the surface.
2. Blade most of the loose material into windrows on both sides of the road to prevent run-off of valuable Sika Dust Seal and to assure uniform penetration down into the subsurface.
3. After the windrows are formed. Sika® Dust Seal PH is applied by spraying it on the road from a tank truck. The rate of application can
be regulated by valves or truck speed with gravity flow equipment. Pressure regulated trucks can also be used. For best results, Sika Dust® Seal PH should be thoroughly mixed with the soil. For stabilisation of the top 70 – 80 mm of the road material, the following steps are commonly used to ensure good mixing:
a) Spray 1/3 to ½ of the Sika® Dust Seal PH specified for total treatment between windrows.
b) Blade windrows to the centre, spreading evenly.
c) Spray approximately 1/3 of the total specified Sika® Dust Seal PH on the surface, and blade or mechanically
mix with a grader or pulveriser. Save part of the Sika® Dust Seal PH for final top dressing treatmen
4. The road is now ready for the final forming. Since rapid surface drainage normally is important to lignin treated roads, the best
type of crown is a modified A type slope of the road. This crown is also favourable when using Sika® Dust Seal PH though it is not critical. The rounded crown commonly used is not favourable for lignin treated roads, as it allows pools of water to collect on the relatively flat centre part of the road. This standing water an increase the plasticity of the road material to the point where traffic can cause potholes to develop.
5. After the final shaping and formulation of the A type crown, a top dressing of Sika® Dust Seal PH should be used to touch up any dry spots which might have been exposed during grading. This should be a relatively light spray, especially when the soil is wet, in order to avoid excess surface plasticity and run-off of valuable binder.
6. The final step is compaction. This is best done with a multiple wheeled roller, but very satisfactory results can be obtained by letting traffic do the compaction. Compaction should be done before Sika® Dust Seal PH dries ie. while the road material is still somewhat plastic. Sika® Dust Seal PH can be used also for stabilising base courses prior to covering the bituminous or concrete wearing mat, because it adds
stability to the sub-surface and useful life to the mat. In this case it is desirable to add aggregate and stabilise the top 250 –300 mm of the road to provide a good hard wearing surface. The strength of a well graded soil is increased in direct proportion to the quantity of Sika® Dust Seal PH added.
Maximum strength improvement comes with between 2 and 3 percent by weight of Sika® Dust Seal PH in the soil.