A process used on plain jointed concrete pavement (PJCP) which contains no reinforcing steel or mesh is:

The correct answer is focused on the process of cracking and seating, which is specifically utilized in the context of plain jointed concrete pavement (PJCP) that lacks reinforcing steel or mesh.

Cracking and seating involves deliberately creating cracks within the existing pavement to relieve stresses and accommodating movements, which prevents the formation of further cracks and reduces the likelihood of reflective cracking in subsequent overlaid surfaces. This method essentially prepares the concrete for a new layer by transforming the pavement into a more flexible base, enhancing the performance of the overlay material placed above.

In contrast, the other processes mentioned have different applications. Breaking and seating, while also a method for handling existing concrete, typically involves breaking the concrete into larger pieces which might provide a more substantial seating for the overlay material but is not specifically tailored for plain jointed concrete without reinforcement. Rubblizing refers to turning the existing pavement into smaller, more manageable pieces, which may not be suitable for PJCP without the presence of reinforcing materials. Sawcutting and sealing, on the other hand, is a maintenance procedure primarily used to control cracking and extend the life of existing concrete rather than preparing it for an overlay.

Thus, the essence of cracking and seating aligns with the unique characteristics of plain jointed concrete pavement,