“Portland-cement” should possess distnctive properties according to the purpose, so that it's function as cement will be in full play.High durability should be the distinctive property of cement for asbestos-cement product, although it is required for cement for general contractions.Then, serious consideration must be carefully paid towards the following elements that makes portland-cement possess high durability.(1) Strength, especially strength against tension is required to be large.(2) Free from crack due to contraction of cement, as well as from change of temperature and humidity.(3) High resistance against solubility in water, as well as against abrasion.After the result of a long-standing research and experiment on strength, contraction, modulus of elasticity, and etc. in many kinds of portland-cement, it will be understood that the chemical compostion of cement that is very suitable for asbestos-cement product will be as follow.Chemical compositionH. M. Act. I. S. M. I. M. C3S. C2S. C3A. C4AF.2.15 6.4 3.06 0.9 65 18 3 12Fineness of cementResidue 88μ 7.5%-8.5%.Blaine specific surface value 2400-2700cm2/g.