What does a stiff mix indicate about the asphalt blend?

• A. The mix is too hot.
• B. The mix is too cold or not enough binder present.
• C. The mix has too much moisture.
• D. The mix shows blue smoke.

Answer: (B)

Stiffness in an asphalt blend happens when there isn’t enough lubrication between the aggregate particles, either because the mix is too cold or the binder content is too low. The asphalt binder smooths and coats the aggregates, allowing the mix to flow and compact properly. When temperature is low, the binder thickens and the mix becomes hard to move, resisting compaction and making it feel stiff. If the binder content is insufficient, there isn’t enough film to coat and separate the particles, producing a stiff, resistant mix as well. By contrast, heating the mix makes it softer and more workable, excess moisture weakens the mix and causes other issues, and blue smoke signals overheating or burning, not stiffness. So a stiff mix mainly indicates cold conditions or not enough binder.