To increase compactive effort, which of the following can be done?

Increasing compactive effort in asphalt paving is essential for achieving proper density and long-lasting pavement. The correct approach in this scenario is to increase the roller's air pressure.

By increasing the roller's air pressure, you enhance the contact pressure applied to the asphalt material during rolling. This increased pressure allows for more effective compaction as it enables the roller to exert greater force on the asphalt surface, reducing air voids and achieving better density. Proper density is crucial in preventing issues like pavement rutting and premature surface distresses.

The other choices do not effectively contribute to increasing compactive effort. For instance, reducing the paver's speed may allow for better control during paving, but it does not specifically enhance compaction. Decreasing the roller's weight would reduce the force applied to the asphalt and would likely result in less effective compaction. Speeding up the vibrating mechanism could improve the initiation of compaction, but without the appropriate weight and pressure, it may not lead to the desired compaction results. Thus, increasing the roller's air pressure is the most effective action to increase compactive effort in this context.