Spraycrete

Spraycrete is a heavy aerosol agent that reacts with particles found in common soil. It breaks down and rearranges the bonds to effectively transform dirt into a material with the strength of reinforced concrete. The reaction is nearly instantaneous, taking only seconds. Liquid spraycrete is inert; however when it is atomized and passed through an electrically charged field, the particulates "activate."

In use, spraycrete can pose severe health hazards. Contact with the skin should be avoided, and inhalation should be prevented at all costs. Fortunately, the particulates don't carry far, even in moderate wind conditions, so exposure would be limited to severe neglect of safety protocols or intentional contamination.

This mystery compound is actually a derivative of alien technologies, one of the few projects that Project Covenant researchers were able to unlock over the years. It is currently the only technology they have been able to reproduce and manufacture in mass quantities. This coupled with the excavator probes allowed for Project Covenant to secretly build bases and their underground infrastructure over the years.

In game terms, spraycrete can be used to harden some types of cover, providing more stopping power and resistance to suppressing fire. Tactically, it is deployed in hand-held canisters that look and are operated much like a small household fire extinguisher.

When spraycrete was revealed to members of the Elma resistance cell, it was given the codename "Medusa," in case they needed to speak about it in front of oustiders.

This technology has been extensively researched. It can be replicated and several application methods are available.