I don't have an ashphalt driveway. Mine is concrete. I wonder how much damage a blade can do to ashphalt? If it leaves a few marks, so what? People where I live seal their ashphalt every year. Won't the sealer cover up scratches?
BYW, I have a 3 inch steel pipe on my grader blade and it works just fine on gravel and concrete. However, you need to level the gravel before it snows. If your drive isn't level, you will grab some rocks.