To some extent, you can also use your blog as an online commonplace book [https://en.wikipedia.org/wiki/Commonplace_book] to which you can add meta data like categories and tags. This will allow you the ability to use it for notes for research related projects.

For material and posts that you don't want to make public-facing, you can either keep them in draft form, or you can publish them privately, so that only you can see them (when logged in), or share them with a select group of colleagues or commenters by creating a password protected post.