Moisture Damage Conventional Anti-stripping Agents

Since this is well established that Bituminous Pavements suffer from water damage, this damage can result in rutting, shoving, ravelling, bleeding, cracking and formation of potholes. More importantly this can also lead to loss of chippings from surface dressings (chip-sealing) and freeze-thaw damage in snow-bound area. The reason for this problem on a micro scale is loss of adhesion between the bitumen and the aggregates. There are very few types of aggregate which can resist the action of water, because the water can enter the pavement structure in a number of ways:

• Wet bitumen-aggregate interface on aggregate not dried properly.
• Rain water seepage through shoulders, cracks or pores, ground / sub-surface water exhibiting a hydrostatic action (moving inside bituminous layer).
• Capillary water sucked and expelled out from the top or subgrade.
• Water vapors formed in the subgrade due to hot weather.

The factors contributing to moisture damage of these pavements includes :

• Siliceous type and dusty aggregates.
• Presence of clay on aggregate surface.
• Bitumen with higher acidity profile.
• Mix designs with less binder and open grading of aggregates.
• Material with higher voids due to improper compaction.
• Inadequate drainage.
• Presence of water vapors between layers.