Settable compositions that comprise water, CKD, and microspheres, wherein the lightweight settable composition has a density less than about 13 pounds per gallon. Methods of cementing that comprise providing a lightweight settable composition having a density less than about 13 pounds per gallon, the lightweight settable composition comprising water, CKD, and microspheres, introducing the lightweight settable composition into a location to be cemented and allowing the lightweight settable composition to set therein.