The mechanical properties and durability ( mainly frost - resistance and carbonation resistance ) of fly ash-CaO-CaSO4 · 2H2O hardened paste are studied. The relationship among durability of hardened fly ash paste, the quantity and distribution of hydrates and the initial paste texture of hardened fly ash paste is presented. The mechanical properties and durability (mainly frost - resistance and carbonation resistance) of fly ash-CaO-CaSO4 · 2H2O hardened paste are studied. The relationship among durability of hardened fly ash paste, the quantity and distribution of hydrates and the initial paste texture of hardened fly ash paste is presented.