Use soybeans to make it removable:
https://www.amazon.com/500MR-Mastic-Remover-Concrete-Quart/dp/B00U2R4AVG
You'll be able to wipe it off with paper towels. Then prime the porch, and paint it with porch/deck paint.
Pretty sure it is mastic. Some of them were asbestos containing materials, FYI.
If you wish, you can likely remove it with soybeans:
https://www.amazon.com/500MR-Mastic-Remover-Concrete-Quart/dp/B00U2R4AVG
It liquefies the mastic, allowing you to mop it with nothing more than paper towels. No asbestos gets released into the air doing this.