Are there scholarships that are purely based on academics, without the addition of essays?

Some are! However, these scholarships are mainly offered from the university that you are attending and they are referred to as Automatic Entrance Scholarships

Only about 30% of the awards in our database demand a strong academic average. Almost all other scholarships want to get a sense of who you are as a person and your commitment to your school and community. This is the reason they ask for an essay or supplementary application!