For a spherical planet of uniform density, gravitational acceleration at the surface is proportional to both the density and to the radius; so if we want the gravitational acceleration at the surface to be some particular fixed value, then density is inversely proportional to the radius. The density of Earth is about 5.5 g/cm[sup]3[/sup], so if you wanted a super-Earth with twice the radius of Earth to have 1 g gravity, it’d have to have an average density of about 2.75 g/cm[sup]3[/sup] — which isn’t too far from the density of aluminum or of most sedimentary rocks.
So it’s not prima facie unreasonable, at least. The problem, I suspect, is that if you built a super-Earth out of such materials, the core temperatures and pressures would be far too high to the material at the center to maintain enough strength to support its own weight. The planet would then compress itself into a denser configuration, with higher surface gravity.