A settable fluid cementitious composition which is fluid for sufficient time to be suitable for use in a flexible container to provide support in a mine said composition comprises (i) Portland cement in an amount from at least about 8% preferably 10%, (ii) a water soluble silicate in an amount from at least about 2% and (iii) water in an amount to provide a water to solids weight ratio of at lest about 1.2:1 preferably at least abou5 1.5:1 and where the % are by weight based on the combined weights of (i), (ii) and (iii). The viscosity immediately after mixing the components together is sufficiently low that additional water can be incorporated. The composition may include (iv) a pozzolan in an amount from 2 to 35% by weight based on the combined weight of (i), (ii), (iii) and (iv).