An oil-based slurry composition comprising hydratable (water-soluble) materials with improved settling properties is disclosed with the addition of a suspending agent to the slurry mixture. The suspending agent is a styrenic diblock copolymer of formula A-B. The styrenic diblock copolymer is a hydrogenated styrene-(ethylene/propylene) (S-EP) block copolymer having a molecular weight of 175-225 kg/mole and a polystyrene (PSC) content of 30-50%. The block copolymer maintains the water-soluble materials in suspension in the mixture with less than 3 wt. % free hydrocarbon solvent separation after at least 1 day standing.