Abstract: Hardenable foam compositions comprising oxygen-releasing foaming agents, a hardener consisting of an alkali silicate solution, a fine particle solid material which reacts with said hardener, namely an oxide mixture consisting of SiO.sub.2 and Al.sub.2 O.sub.3 extracted from a filter dust, an electrofilter ash from high-temperature power plants, and calcinated bauxite or amorphous silica, to which reaction accelerators are added, are improved, firmer, faster hardening foams. Reducing agents, in particular sulphur compounds with a reducing action are preferred. Oxidizing agents or fine particle substances such as soot or color pigments are effective.

Abstract: The present invention is directed to a process for strengthening geological formations in underground mining or other operations introducing into the formation which is to be strengthened mixtures of a polyisocyanate component (a) and a polyol component (b) which react together to form polyurethanes, characterized in that the polyol component (b) is based on mixtures of (i) organic polyhydroxyl compounds having hydroxyl numbers of about 100 to 600 and (ii) dihydric alcohols having a molecular weight of 62 to about 150, component (ii) being present in an amount of about 0.01 to 20% by weight, based on the total quantity of component (b).