Step 1: Understanding the Question:
We need to identify the fraction of petroleum (heavy alkanes) used in road construction. Step 2: Detailed Explanation:
The heaviest non-volatile residue obtained from the fractional distillation of crude oil is asphalt (bitumen).
This residue contains very large hydrocarbon molecules, specifically alkanes with more than 35 carbon atoms (\(>\text{C}_{35} \)).
Because of their high viscosity and adhesive properties, these heavy alkanes are ideal for road surfacing. Step 3: Final Answer:
Alkanes having more than 35 carbon atoms are used for road surfacing.