It's for quality assurance. You take samples of asphalt (in this case), concrete, etc. during construction and they get shipped off for analysis. I don't know what they do with the asphalt, but for concrete they do slump tests of the wet concrete and crush tests of cured samples. Probably other tests too.

I'm guessing it's pretty rare for the results to come back as "tear it all out and start over", but... you'd sure want to know if that were the case!