A construction worker measures the amount of cement in a cement truck every 5 minutes as it empties what is the rate of change for the volume of cement in the truck

That's exactly what he's measuring. So we can't tell,

because you haven't told us any of his measurements.

The rate of change during any 5-minute period would be

(the difference between two of his measurements)

divided by

(5 minutes)

probably in units of [cubic yards per minute].