Air Entrainment was uncovered by accident within the mid-1930s.[two] At that time, cement manufacturers were being using a grinding help to improve the entire process of grinding cement. This grinding support was a combination of various chemicals, like salts of wood resin, which were being added for the cement in https://modtp-cas-no-72030-25-259369.blogolenta.com/32372614/concrete-release-colors-for-dummies