What is the required rate of testing for density and thickness for core samples in compacted asphalt concrete?

The required rate of testing for density and thickness in compacted asphalt concrete is structured to ensure adequate quality control and assurance throughout the paving process. Each specified rate of testing aligns with the size of the area being evaluated, which is crucial for obtaining representative samples that can accurately reflect the entire lot's properties.

In the given context, the answer encompasses all provided options, meaning that each rate of core sample testing is applicable depending on the size of the asphalted area. For areas up to 4000 square meters, one core sample is needed for every 600 square meters. As the area increases, the requirement adjusts to one core for every 900 square meters for areas between 4000 and 20,000 square meters, and further changes to one core per 1200 square meters for areas beyond 20,000 square meters.

This tiered approach ensures that as the size of the area grows, the frequency of testing is balanced against the effort and resources required, maintaining a focus on efficiency while still meeting quality standards. Hence, collectively, all these testing requirements are vital for monitoring and confirming the integrity of the asphalt concrete throughout various project scales.