Breakage of waste concrete for liberation using autogenous mill

It is known that gentle breakage in autogenous (AG) milling promotes preferential breakage along the grain boundaries. Therefore, in this study, AG milling of waste concrete was conducted for a better liberation of aggregate and cement mortar. Tests involved grinding of lumps of waste concrete with/without heat treatment at various conditions and examining the degree of liberation. Because of typical breakage mechanisms of AG milling, the breakage does not follow first-order relation, and it can make a better liberation of aggregate from cement matrix. The resistance to breakage was reduced considerably when a sample was pretreated with heat prior to AG milling. The degree of liberation increased as grinding time increased and the quality of recycled aggregate satisfied the Korea 1st grade specification after 30 min grinding in laboratory scale AG milling, 10 min grinding in semi-pilot scale AG milling.