What is added to hot mixed asphalt to increase its fluidity?

To enhance the fluidity of hot mixed asphalt, asphalt cement or moisture is added. Asphalt cement is the primary binder used in asphalt mixes, giving it viscosity and the ability to adhere to aggregates while providing flexibility and durability. When combined with hot mixed asphalt, it can help achieve the desired consistency for proper mixing and application.

Moisture, in small amounts, can also be used to modify the viscosity of the asphalt and make it easier for compaction and spreading. This is particularly important in maintaining an optimal working condition during the mixing and laying processes, ensuring that the asphalt will perform effectively once cooled and set.

The other options do not effectively increase fluidity in the same way. Water can adversely affect asphalt properties if added inappropriately, leading to possible stripping and weakening of the bond. Sand can add bulk but does not inherently change the fluidity of the asphalt mix, rather affecting its stability and compaction. Granulated rubber is often utilized to enhance flexibility and reduce cracking but does not primarily serve to increase fluidity. Thus, the addition of asphalt cement or moisture is the most effective and appropriate means for increasing fluidity in hot mixed asphalt.