Instacrete

Instacrete is a material invented by UNSC scientists for use in combat zones. Instacrete is easy to shape and build with, incredibly strong, and dries quickly, allowing strong, permanent buildings to be hastily erected when they are needed.

Instacrete is easy to use in creating strong bunkers for defense of facilities on the ground. Quantities of this material were around Reach should they be needed, and the Spartans did use them during the Battle of Reach.