What is the major role of moisture in pavement deterioration?

The major role of moisture in pavement deterioration is to weaken the pavement structure and accelerate the development of distresses. Moisture can infiltrate the pavement through cracks, joints, and permeable surfaces, leading to a variety of damaging effects. In asphalt pavements, moisture can cause stripping, which is the loss of adhesion between the asphalt binder and the aggregate. This weakens the asphalt mixture and makes it more susceptible to rutting and cracking. In concrete pavements, moisture can contribute to alkali-silica reaction (ASR), which is a chemical reaction between the cement and certain types of aggregates that causes the concrete to expand and crack. Moisture can also weaken the subgrade, reducing its support capacity and leading to pavement settlement and deformation. In cold climates, moisture can freeze and expand, causing frost heave, which can severely damage the pavement structure. Repeated cycles of freezing and thawing can exacerbate these effects, leading to accelerated pavement deterioration. Therefore, controlling moisture infiltration is crucial for maintaining the long-term performance of pavements.