Abstract: Discloses cementitious materials for treatment of underground or subterranean formations to reduce formation porosity for the control and of subterranean fluid flow as well as methods of applying the cementitous materials to the underground formations. The cementitious materials include both ordinary Portland cement and magnesium oxychloride cement which act co-operatively to produce a low permeability zone in the underground formation. Application methods describing injection of the cementitous materials into the underground formation to be treated are disclosed for treatment of pre-excavation formations and post excavation formations. Describes use of the cementitious materials and methods of application in relation to underground tunnel and roadway construction as well as foundation treatment of dam structures for water reservoirs.