Air Entrainment was discovered accidentally within the mid-1930s.[2] At that time, cement manufacturers had been employing a grinding aid to boost the whole process of grinding cement. This grinding aid was a mixture of assorted chemicals, like salts of wood resin, which were being added on the cement throughout the https://modtpcasno72030-25-227037.jasperwiki.com/6781437/helping_the_others_realize_the_advantages_of_concrete_foaming_machine