Under what climatic condition is it advisable to use lower penetration grade or hard asphalt?

Using a lower penetration grade or hard asphalt is advisable in hot climate conditions primarily due to the thermal properties of the material. In hotter environments, asphalt can soften significantly, which can lead to issues such as rutting and deformation on road surfaces. Hard asphalt, or those with a lower penetration grade, have a higher viscosity and are more resistant to softening under elevated temperatures.

This characteristic helps maintain the integrity of the pavement structure, reducing the risks associated with heat-induced deformation and ensuring better performance. In contrast, softer asphalt grades might not provide sufficient strength and stability, leading to premature failure of the road surface or excessive maintenance needs.

While there may be situations in cold climates where hard asphalt could also have benefits, the most critical application for using lower penetration grades revolves around managing performance in hot climates, making it the most suitable choice.