Concrete, Implicated Portland -Chamber, Can Turn Out Either the So -Called «Hard» or not. This, as a rule, depends on the properties of the cement itself. Over Thears of Construction Practice, There Has Been a Certain Popularity Among Cement with The M-400 Labeling and the M-500 ″. This Happens Due to the Fact that Possessing the Most Necessary Qualites, They Areboth Accessible to the Vast Majority of Developers.