Abstract: A hydraulic cement is formed from a Class C fly ash, an alkali metal activator, and citric acid. Mortar and concrete compositions can be prepared with this hydraulic cement. The cement is particularly useful in producing mortar and concrete compositions that achieve high strengths in a short time, in particular, a mortar having a strength of at least 2500 psi in 24 hours, when cured at room temperature.

Abstract: A blended hydraulic cement composition, curable at low temperatures, including temperatures below the freezing point of water, is composed of portland cement, slag, pozzolans including metakaolin, and admixtures including potassium carbonate and water reducing compositions. The cement is particularly useful in producing concrete compositions which achieve high strength in a brief period of time, and continue curing at ambient temperatures, and temperatures below the freezing point of water.

Abstract: A binder composition for Portland cement is disclosed, said composition including 100 parts by weight metakaolin and, based upon said metakaolin, from 20 to 70 parts by weight slag; from 85 to 130 parts by weight of at least 1 material selected from the class consisting of fly ash, calcined shale, and calcined clay; from 70 to 215 parts by weight finely divided silica, preferably amorphous silica; and from 55 to 145 parts by weight of a mixture of potassium silicate and potassium hydroxide, wherein at least 55 parts by weight is potassium silicate. The binder composition can be mixed with Portland cement or with a combination of Portland cement and fly ash to provide a composition curable to a material having a high early strength and a high ultimate strength.