Insulated concrete forms (ICFs) closely match what you described. They are hollow LEGOesque foam bricks that get filled with concrete. Here is a great video (a

Insulated concrete forms (ICFs) closely match what you described. They are hollow LEGOesque foam bricks that get filled with concrete. Here is a great video (and a great channel generally) on the subject: https://youtu.be/MRipzKkeQik https://youtu.be/MRipzKkeQik