In precast concrete elements manufacturing, steam-cured concrete incorprating 30% mineral admixtures encountered the problem of too low demoulding compressive strength. To resolve it, this paper mainly studied the influence of mineral admixtures on the compressive strength, the tensile-splitting strength and the flexural strength of the steam-cured concrete. The experimental results indicated that, compared with steam-cured concrete incorprating mineral admixtures, the later strength of steam-cured concrete incorprating 0% mineral admixtures has lower increment degree and its increment of tensile-splitting strength and flexural strength inverted to some extent. The demoulding compressive strength is too low for the high volume fly ash concrete mixtures. The problem of too low demoulding compressive strength is solved by incorprating composites of ground blast furnace slag(GBFS) and fly ash. Different varieties of mineral admixture used in the concretes can produce a certain degree of potentiation.