The paper presents the properties of a new type of alkali activated borosilicate inorganic polymers (AABSIPs) resulted by the activation of waste glass powder and fly ash with alkaline solutions. The alkali activators used in this study were mixtures of borax decahydrate with NaOH and KOH solutions. For the preparation of AABSIP mortars two types of aggregates were used i.e. sand and a waste resulted during the mechanical processing of titanium alloy ingots. The thermal treatment of these pastes and mortars determines an intumescent process i.e. significant increase of volume; consequently, these materials could be used as low-cost fire stopper blocks for passive fire protection of buildings.